Intricate patterns of phylogenetic relationships in the olive family as inferred from multi-locus plastid and nuclear DNA sequence analyses: A close-up on Chionanthus and Noronhia (Oleaceae)

Cynthia Hong-Wa; Guillaume Besnard

Ochnaceae is a pantropical family in the order Malpighiales. A recently published molecular phylogeny of the Ochnaceae identified three subfamilies, viz. Medusagynoideae, Quiinoideae and Ochnoideae. Clades within the latter are classified at tribal and subtribal level. The palaeotropical genus Campylospermum is placed in the tribe Ochneae, subtribe Ochninae, together with the genera Brackenridgea, Idertia, Ochna, Ouratea, and Rhabdophyllum. We reconstructed the phylogenetic relationships of the family using three chloroplast markers (matK, rbcL, trnLF) with intensified taxon sampling for the Ochninae, so as to focus on the relationships within this subtribe with special emphasis on the genus Campylospermum. Our Maximum likelihood and Bayesian analyses corroborate the phylogenetic backbone previously recognized while two clades could be distinguished within the genus Campylospermum. The first comprises the West/Central African Campylospermum species while the second includes the West...

Molecular Phylogenetics and Evolution 67 (2013) 367–378 Contents lists available at SciVerse ScienceDirect Molecular Phylogenetics and Evolution journal homepage: www.elsevier.com/locate/ympev Intricate patterns of phylogenetic relationships in the olive family as inferred from multi-locus plastid and nuclear DNA sequence analyses: A close-up on Chionanthus and Noronhia (Oleaceae) Cynthia Hong-Wa a,b,⇑, Guillaume Besnard c,1 a b c Department of Biology, University of Missouri – St. Louis, One University Blvd., St. Louis, MO 63121-4000, USA Missouri Botanical Garden, P.O. Box 299, St. Louis, MO 63166-0299, USA Imperial College London, Silwood Park Campus, Buckhurst Road, Ascot SL5 7PY, UK a r t i c l e i n f o Article history: Received 1 March 2012 Revised 19 October 2012 Accepted 4 February 2013 Available online 13 February 2013 Keywords: Noronhia Chionanthus Madagascar Phylogeny Cenozoic dispersal Taxonomy a b s t r a c t Noronhia represents the most successful radiation of the olive family (Oleaceae) in Madagascar with more than 40 named endemic species distributed in all ecoregions from sea level to high mountains. Its position within the subtribe Oleinae has, however, been largely unresolved and its evolutionary history has remained unexplored. In this study, we generated a dataset of plastid (trnL-F, trnT-L, trnS-G, trnK-matK) and nuclear (internal transcribed spacer [ITS]) DNA sequences to infer phylogenetic relationships within Oleinae and to examine evolutionary patterns within Noronhia. Our sample included most species of Noronhia and representatives of the ten other extant genera within the subtribe with an emphasis on Chionanthus. Bayesian inferences and maximum likelihood analyses of plastid and nuclear data indicated several instances of paraphyly and polyphyly within Oleinae, with some geographic signal. Both plastid and ITS data showed a polyphyletic Noronhia that included Indian Ocean species of Chionanthus. They also found close relationships between Noronhia and African Chionanthus. However, the plastid data showed little clear differentiation between Noronhia and the African Chionanthus whereas relationships suggested by the nuclear ITS data were more consistent with taxonomy and geography. We used molecular dating to discriminate between hybridization and lineage sorting/gene duplication as alternative explanations for these topological discordances and to infer the biogeographic history of Noronhia. Hybridization between African Chionanthus and Noronhia could not be ruled out. However, Noronhia has long been established in Madagascar after a likely Cenozoic dispersal from Africa, suggesting any hybridization between representatives of African and Malagasy taxa was ancient. In any case, the African and Indian Ocean Chionanthus and Noronhia together formed a strongly supported monophyletic clade distinct and distant from other Chionanthus, which calls for a revised and more conservative taxonomy for this group. Ó 2013 Elsevier Inc. All rights reserved. 1. Introduction Noronhia, first described as a monotypic genus by Stadman in Du Petit-Thouars (1806), comprises 45 described species and is the largest genus of the olive family (Oleaceae) in Madagascar. Examination of herbarium material, however, suggests there may be as many as ca. 70 species (C. Hong-Wa, in preparation); many new specimens having been accumulated through intensive botanical exploration in Madagascar during the last two decades. The ⇑ Corresponding author at: Missouri Botanical Garden, P.O. Box 299, St. Louis, MO 63166-0299, USA. E-mail addresses: cynthia.hong-wa@mobot.org (C. Hong-Wa), guillaume. besnard@univ-tlse3.fr (G. Besnard). 1 Address: CNRS, Université Paul Sabatier, ENFA, Laboratoire Evolution & Diversité Biologique, UMR 5174, 31062 Toulouse 4, France. 1055-7903/$ - see front matter Ó 2013 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.ympev.2013.02.003 only taxonomic treatment of the genus is that of Perrier de la Bâthie (1949), revised by the same author in 1952 for the Flore de Madagascar et des Comores series. Forty-one species were recognized at that time and four others have been described since (Bosser, 1973; Callmander et al., 2009; Labat et al., 1999). As currently circumscribed, all species of Noronhia are endemic to Madagascar, except two that are found in the Comoro Islands. Noronhia, together with 10 other extant genera, belongs to tribe Oleeae and subtribe Oleinae where its position is uncertain (Wallander and Albert, 2000). Existing molecular phylogenies of Oleaceae have included only Noronhia emarginata (Lee et al., 2007; Wallander and Albert, 2000), a species that is commonly found in tropical botanical gardens. This species has also naturalized in different regions (e.g. Florida, French Polynesia, Hawaii, Réunion and Seychelles) and is even invasive in Hawaii (PIER, 2011). Recently, Besnard et al. (2009) included, as part of the outgroup for their 368 C. Hong-Wa, G. Besnard / Molecular Phylogenetics and Evolution 67 (2013) 367–378 phylogenetic study of the genus Olea, seven species of Noronhia and provided, for the first time, some insights into the phylogenetic relationships within Noronhia. In their study, Olea ambrensis is nested within Noronhia, but the voucher specimen for O. ambrensis (Schatz,3605), wrongly identified by Green (2002), is in fact N. linocerioides. A close relationship between Noronhia and the three Malagasy Chionanthus species has long been suspected. Indeed, Perrier de la Bâthie (1949, 1952) noted only subtle morphological differences between the two genera, mainly the presence of a corona in most species of Noronhia, and suggested that the Noronhia species lacking this feature would form a transition between the two genera. The most comprehensive phylogenetic study of Noronhia to date included only two Chionanthus species and neither is from Madagascar (Besnard et al., 2009). However, relationships of these Chionanthus species reflected geography more than phylogeny: C. broomeana, from Réunion, was sister to Noronhia, and C. retusus, from China, was sister to an Asian clade of Olea (i.e. subgenus Tetrapilus). Therefore, inclusion of Chionanthus species from the Malagasy Floristic Region (MFR = Madagascar, Mascarenes, Comoros, Seychelles, Aldabra, Amirantes and surrounding small islands; Takhtajan, 1986) and Africa is clearly of considerable interest in resolving the relationship between Noronhia and Chionanthus. Phylogenetic inferences from molecular data within Oleaceae have used mainly plastid regions (Baldoni et al., 2002; Besnard et al., 2009; Guo et al., 2011; Lee et al., 2007; Wallander, 2008; Wallander and Albert, 2000; Yuan et al., 2010). The nuclear ribosomal internal transcribed spacer (ITS) has also been useful in resolving phylogenetic relationships within Oleaceae including Fraxinus (Jeandroz et al., 1997; Wallander, 2008), Ligustrum and Syringa (Li et al., 2002), Olea (Besnard et al., 2009) and Osmanthus (Yuan et al., 2010). A multi-locus approach to phylogenetic analysis can increase the strength of the phylogenetic inference (Townsend, 2007; Aguileta et al., 2008), and the use of plastid and nuclear regions together allows the detection of evolutionary events such as hybridization or incomplete lineage sorting (Brysting et al., 2011; Lihová et al., 2006; Linder and Rieseberg, 2004). In this study, we were interested in using genes that permit phylogenetic inferences within subtribe Oleinae, both at higher and lower taxonomic levels. Plastid (trnL-F, trnT-L, trnS-G and trnK-matK) and nuclear (ITS) markers were used to: (1) examine the generic relationships within the subtribe with a particular focus on the placement of Noronhia, and (2) test the monophyly of this genus and infer its evolutionary history. In light of our phylogenetic results, we propose a revised generic circumscription for Noronhia based on both molecular and morphological evidence. We also evaluate possible explanations of incongruence between gene trees. 2. Materials and methods 2.1. Taxon and gene sampling A total of 77 taxa were included in this study, of which 35 were named species and varieties of Noronhia, 38 represented 10 other genera within subtribe Oleinae, and four others were from tribe Oleeae (Supplementary Table S1). Whenever possible, multiple individuals per species were included, especially for Noronhia; species of the latter encompassed both the range of morphological variation within this group and its geographic distribution. Given the close relationships between Noronhia and Chionanthus, we included 13 of the ca. 18 species occurring in Africa, Madagascar and the Comoro and Mascarene Islands; five representative species from the New World and Asian-Pacific Old World were also included. Sampling for outgroups consisted of the other genera within Oleinae that were represented by a few species each except Priogymnanthus and Hesperelaea, for which adequate samples were unavailable. We also included representatives of subtribes Fraxininae and Schreberinae in the outgroups and we used the subtribe Schreberinae (Comoranthus and Schrebera) to root the trees. Total genomic DNA was extracted from silica gel-dried leaves collected in the field or from herbarium specimens using the DNeasy Plant Mini kit (Qiagen, Valencia, CA). Voucher specimens were deposited at the Missouri Botanical Garden-St. Louis (MO), Muséum National d’Histoire Naturelle-Paris (P) and Parc Botanique et Zoologique de Tsimbazaza-Antananarivo (TAN). DNA samples for some species were obtained from herbaria and botanical gardens in Geneva (G), Kew (K), Madrid (MA) and Paris (P). Plastid regions previously used for phylogenetic inferences within Oleaceae with various degrees of resolution included trnLF, rps16, rbcL, ndhF, psbA-trnH, matK, trnT-L, trnS-G, rps16-trnQ, rpl32-trnL, psbJ-petA (Baldoni et al., 2002; Besnard et al., 2009; Guo et al., 2011; Lee et al., 2007; Wallander, 2008; Wallander and Albert, 2000; Yuan et al., 2010). In general, plastid DNA sequence divergence was very low within Noronhia (0.03%), and so we used four of the most informative regions in this study (trnLF, trnT-L, trnS-G, trnK-matK). Since ITS has already been successfully used in resolving phylogenetic relationships within Oleaceae and had higher informative variation, we also used it. In addition to ITS, we surveyed low-copy nuclear genes. Indeed, such gene sequences are increasingly being used to address phylogenetic questions, especially at lower taxonomic levels (Hughes et al., 2006; Small et al., 2004). The nuclear nitrate reductase (NIA) gene has been successfully amplified in Olea, yielding two products of 900 bp and 250 bp (Hamman-Khalifa et al., 2007), but we inconsistently obtained only a small-sized product (<300 bp) for Noronhia through standard polymerase chain reaction (PCR). We successfully amplified segments of genes encoding chalcone isomerase (CHI), chalcone synthase (CHS), glyceraldehyde 3-phosphate dehydrogenase (G3PDH) and triose phosphate isomerase (TPI) (Strand et al., 1997). However, all low-copy nuclear genes were discarded for various reasons including doubtful sequence similarity, lack of informative variation and presence of multiple copies, probably stemming from the ancient allopolyploid origin of the tribe Oleeae (Taylor, 1945; Wallander and Albert, 2000). Specific primers targeting individual copies need to be designed for these gene families in order for them to be useful in addressing species-level phylogenetic studies within the subtribe Oleeae. 2.2. Laboratory protocols Amplification of the four plastid DNA regions (trnL-F, trnT-L, trnS-G, trnK-matK) followed the protocol described in Besnard et al. (2009). PCR products were cleaned and directly sequenced using the same set of primers as for amplification. Amplification of the internal transcribed spacer (ITS) region that encompasses ITS1, 5.8S and ITS2 was carried out using the primers ITSLeu1 (50 -GTC CAC TGA ACC TTA TCA TTT AG-30 ; Baum et al., 1998) and ITS4 (50 -TCC TCC GCT TAT TGA TAT GC-30 ; White et al., 1990) in 25 ll reactions containing 2 ll of undiluted DNA template, 1.5 ll of each primer and 12.5 ll of GoTaqÒ Green Master Mix (Promega). Thermal cycling parameters consisted of an initial denaturation at 97 °C for 2 min, followed by 30 cycles of 1 min at 97 °C, 1 min at 50 °C, 1 min at 72 °C and a final extension of 7 min at 72 °C. PCR products were cleaned using the QIAquick PCR purification Kit (Qiagen, Valencia, CA) and cloned using pGEM-TÒ vector (Promega). Three to eight clones were sequenced in both directions using primers T7 and SP6. 2.3. Data preparation For each plastid DNA region, one sequence was generated for each accession. Since the plastid genome is inherited as a single 369 C. Hong-Wa, G. Besnard / Molecular Phylogenetics and Evolution 67 (2013) 367–378 linked unit, DNA sequences representing the four regions were combined into a single dataset of ca. 3800 bp for subsequent analyses. For ITS, sequences with more than 80% overlap and base call accuracy P99% (Ewing et al., 1998) were assembled and edited using Seqman v4.00 (DNASTAR Inc., Madison, WI). BLAST searches were performed to confirm the authenticity of the amplified regions. Altered conserved motifs, lower GC content and higher minimum free energy (DG at 37 °C, estimated via the mFold website; Zuker, 2003) were used to assist in identification of putative pseudogenes. Multiple sequence alignments using MUSCLE (Edgar, 2004) implemented in MEGA v5 (Tamura et al., 2011), were followed by some manual adjustments where necessary. The final dataset contained only a single ITS sequence per accession. Sequence data were deposited at GenBank (GenBank: JX862563– JX863069, Supplementary Table S2). 2.4. Phylogenetic analyses We used maximum likelihood (ML) and Bayesian inference (BI) in independent analyses of the combined plastid (CP) dataset and the ITS region. Model of nucleotide substitution for each dataset was assessed with jModeltest v0.1.1 (Posada, 2008), with the best-fit model selected from among 88 possible models based on the Akaike Information Criterion (AIC). The chosen models for the different datasets were: GTR + I + G for ITS and TVM + G for CP. Because the best model selected for the CP dataset is not implemented in the phylogenetic programs we used, the next best model was instead applied (GTR + G). This is acceptable since BI is known to be robust enough to over-parameterization (Huelsenbeck and Rannala, 2004). Maximum likelihood analyses were performed with RAxML v7.2.6 (Stamatakis, 2006) using the rapid bootstrap algorithm for 1000 replicates combined with the search of the best-scoring ML tree under default parameters. Bayesian analyses were performed with MrBayes v.3.1.2 (Ronquist and Huelsenbeck, 2003) via the CIPRES portal (Miller et al., 2010). The analyses consisted of two parallel runs, each of four chains (one cold and three hot), initiated with random starting trees. Program parameters, mostly at default settings, were similar for the different datasets with the Markov chain Monte Carlo (MCMC) run for 15–20 million generations and trees sampled every 1000th generation. Preliminary analyses showed infrequent or no chain swapping under the default temperature (T = 0.2), which was then adjusted along with the number of generations for optimal mixing (Table 1). Analyses of the two datasets applied the previously determined models of substitution with model parameters unlinked across different partitions. Stationarity and convergence between runs were assessed by plotting likelihood values against the number of generations, as well as with trace plots generated in Tracer v1.5 (Rambaut and Drummond, 2009) and with correlations of split frequencies between two runs using the online application AWTY (Nylander et al., 2008). The first 20% of trees before stationarity were discarded as burn-in and a 50% Majority-Rule Consensus Tree was generated with the remaining trees for each dataset. Trees were visualized using TreeGraph2 (Stöver and Müller, 2010). Congruence among datasets was examined using the incongruence length difference test (ILD, Farris et al., 1995) as implemented by the partition homogeneity test in PAUP 4.0b10 (Swofford, 2002). The test was applied to the CP and ITS datasets with 100 replicates. Topological congruence was also examined in a likelihood context. Site-wise log-likelihoods were obtained from RAxML for each dataset and run in CONSEL v0.1i (Shimodaira and Hasegawa, 2001) to evaluate the probability values of each alternative topology using the approximately unbiased (AU) test (Shimodaira, 2002), the Kishino–Hasegawa (KH) test (Kishino and Hasegawa, 1989) and the Shimodaira–Hasegawa (SH) test (Shimodaira and Hasegawa, 1999). Table 1 Statistics of alignments and phylogenetic analyses of the different regions analyzed: combined plastid DNA regions (CP = trnL-F, trnT-L, trnS-G, tnrK-matK) and internal transcribed spacer (ITS). PIC = parsimony-informative character; K2p = Kimura twoparameter; HI = homoplasy index; ln L = log-likelihood; ASDSF = average standard deviation of split frequencies. CP ITS Number of terminals Aligned length (bp) Variable characters PIC/percent Mean K2p sequence divergence (%) Mean GC content (%) HI 111 3818 429 212/5.55 0.8 31.23 0.35 126 765 385 297/38.82 7.2 63.25 0.68 Substitution model Alternative model ln L TVM + G [GTR + G] 10484.76 MrBayes/BEAST 15/10 0.1 0.003 GTR + I + G Number of generations Heating parameter ASDSF 10197.17 20/10 0.1 0.006 2.5. Molecular dating We obtained absolute ages for each gene tree using a reduced dataset including only a single individual per species and accessions represented in both plastid and ITS datasets. We used BEAST v1.6.1 (Drummond and Rambaut, 2007) to estimate divergence times. The molecular clock hypothesis was tested using the likelihood ratio test (LRT) in MEGA v5 and was strongly rejected for each dataset. Data for BEAST analysis were first prepared with BEAUti v1.6.1 (Drummond and Rambaut, 2007) using a relaxed clock model (Drummond et al., 2006) and an uncorrelated lognormal model of rate variation. The same nucleotide substitution models applied for the Bayesian inference were used. The tree prior was set to a birth–death process and used a randomly generated starting tree. The other priors were left at default except for prior information on clade ages. Fossil evidence suggests a divergence time older than 37 Mya for Fraxinus and Oleinae (Call and Dilcher, 1992; Suzuki, 1982). Following Besnard et al. (2009), we implemented this age as a lower bound of a normal distribution with a mean of 40 Mya and a standard deviation of 3 Mya. Given our phylogenetic results, Fraxinus was constrained to be outside Oleinae in the ITS analysis as this position has been well supported in other studies (e.g. Besnard et al., 2009; Lee et al., 2007; Wallander and Albert, 2000). Divergence of Olea sensu stricto (excluding Olea subgenus Tetrapilus, represented here by O. dioica) occurred before 23 Mya (Muller, 1981; Palamarev, 1989; Terral et al., 2004) and was also applied as a calibration using a uniform distribution constrained between 23 and 30 Mya. Results of two independent MCMC runs of 10 million generations with sampling frequency of 1000 generations were assessed with Tracer v1.5 (Rambaut and Drummond, 2009), combined with LogCombiner v1.6.1 (Drummond and Rambaut, 2007) and summarized in TreeAnnotator v1.6.1 (Drummond and Rambaut, 2007) into one Maximum Clade Credibility Tree using a burn-in of 2 million generations. The effective sample size (ESS), an indicator of effective independent draws from the posterior distribution (Drummond and Rambaut, 2007), was good (i.e. >200) for all analyses. Node ages were estimated as mean node heights in million years. Trees were visualized using FigTree v1.3.1 (Rambaut, 2006). 3. Results 3.1. Data This study analyzed a total of 136 individuals representing 77 taxa, of which 35 were named species and varieties of Noronhia, 370 C. Hong-Wa, G. Besnard / Molecular Phylogenetics and Evolution 67 (2013) 367–378 38 members of subtribe Oleinae and four other members of tribe Oleeae (Fig. 1). Statistics of the alignments and phylogenetic analyses of the two datasets (CP and ITS) are presented in Table 1. The entire molecular dataset included 4583 nucleotides. Although the CP dataset (3818 bp) had almost five times the number of nucleotides as the ITS dataset (765 bp), it had almost a similar number of variable sites, thus a much lower mean sequence divergence (Table 1). A pairwise ILD test comparing the different regions yielded p-values 6 0.01, indicating significant incongruence. Although the sensitivity of the ILD test is well-known and its use in testing data partition combinability has been discouraged (Barker and Lutzoni, 2002; Darlu and Lecointre, 2002; Yoder et al., 2001), these results and subsequent analyses nonetheless encouraged us to carry out only independent analyses of each dataset. 3.2. Phylogenetic analyses For the CP or ITS dataset, the best-scoring ML tree and the BI consensus tree exhibited largely similar topologies and were combined in TreeGraph2 for better visualization. For the sake of clarity, Fig. 1. Bayesian 50% majority-rule consensus tree inferred from analyses using (A) combined plastid (CP) DNA regions (trnL-F, trnT-L, trnS-G and trnK-matK) and (B) nuclear ribosomal DNA (ITS). Values above branches denote maximum likelihood bootstrap support (MLBS%) and those below branches are Bayesian posterior probabilities (BPP). Boldfaced values are MLBS P 85% and BPP P 0.95. Shaded areas indicate members of subtribe Oleinae. Numbers after taxon names refer to vouchers listed in Supplementary Table S1. Abbreviations are: Ch. m. = Chionanthus mannii; Ch. o. = Chionanthus obtusifolius; N = Noronhia; N. e. = Noronhia emarginata; N. l. = Noronhia luteola; O. c. = Olea capensis; O. e. = Olea europaea. C. Hong-Wa, G. Besnard / Molecular Phylogenetics and Evolution 67 (2013) 367–378 clades composed of conspecific accessions in these two trees are presented with only a single taxon name, but are shown in full with all individuals in the Supplementary material (Fig. S1). Accessions from the same species usually clustered together (Fig. S1). Accessions of Noronhia emarginata introduced outside the MFR (i.e. Hawaii and Florida) were also included to verify their affinity and were found to form a strongly supported monophyletic group with accessions of that species from Madagascar and Réunion (Fig. S1). We regard maximum likelihood bootstrap (MLBS) and Bayesian posterior probability (BPP) values of 100–85% and 1– 0.95 respectively as strong, 84–75% and 0.94–0.85 moderate, and 74–50% and 0.84–0.70 low support. 3.2.1. Plastid regions (trnL-F, trnT-L, trnS-G, trnK-matK; Fig. 1A) Both ML and BI analyses showed a strongly supported monophyletic Oleinae (MLBS = 100%, BPP = 1). Patterns of relationships within the subtribe were more structured than those shown in Wallander and Albert (2000), and several genera were found to be paraphyletic or polyphyletic, e.g. Chionanthus, Olea, Osmanthus and Phillyrea. The relationships among these genera corresponded more with geography than with taxonomy. For instance, Osmanthus americanus and Chionanthus virginicus, both North American species, and Chionanthus ramiflorus and Olea dioica, both Asian, were sister to each other respectively. Noronhia, together with Chionanthus species from Africa and Indian Ocean islands formed a strongly supported monophyletic clade, hereafter referred to as NCAIO (Noronhia and Chionanthus from Africa and Indian Ocean). Chionanthus species from the MFR were nested within Noronhia forming what we call the MFR clade. Relationships of the African Chionanthus with the MFR clade did not show a clear geographic patterning. Thus C. battiscombei, distributed in eastern and predominantly southern Africa, linked with the MFR clade together with the strictly southern African C. foveolatus and C. peglerae (Africa 2), whereas C. richardsiae, a strictly southern African species, clustered with the widely distributed central and eastern African species (C. mannii, C. mildbraedii and C. niloticus) in a separate clade (Africa 1) sister to the MFR and Africa 2 clades. Various subclades were identified within the MFR clade, usually with moderate to strong BPP but moderate to low MLBS. Relationships within these subclades showed more geographic patterning than those between the MFR clade and the African Chionanthus. For instance, apart from Noronhia comorensis, species from the Comoro Islands fell within the same clade despite belonging to different genera (e.g. N. cochleata and C. insularis). Similarly, N. buxifolia and N. myrtoides, from southwestern Madagascar, were sister to each other, as were the northern species N. linearifolia and N. longipedicellata. These relationships were also strongly supported. 3.2.2. ITS (Fig. 1B) In general, relationships obtained from the ITS dataset were not strongly supported. In contrast to previous studies (Besnard et al., 2009; Wallander and Albert, 2000) and our own CP tree, Fraxinus (subtribe Fraxininae) was nested within (instead of sister to) subtribe Oleinae but this topology received weak support (MLBS = 63%, BPP = 0.93). This shift in position has also been found elsewhere but with plastid markers, in which case Fraxinus was sister to the clade Schreberinae–Oleinae (Lee et al., 2007). Several genera (e.g. Chionanthus, Olea and Osmanthus) again appeared to be polyphyletic and showed the same geographic patterning in their relationships as found with the CP data. The NCAIO clade was again recovered as strongly monophyletic with MLBS = 100% and BPP = 1, with the African Chionanthus species forming a monophyletic, albeit moderately supported, clade (MLBS = 77%, BPP = 0.9), sister to a monophyletic MFR clade (MLBS = 73%, BPP = 0.98). Within the NCAIO clade, subclades could 371 be distinguished that also showed a geographic signature, but mostly they had support from BI only. In particular, the African and MFR clades were well separated, and within the African clade, southern mesic African species (C. battiscombei, C. foveolatus, C. peglerae and C. richardsiae) also formed a strongly supported clade sister to the central and eastern tropical African species (C. mannii, C. mildbraedii and C. niloticus). Relationships within the MFR clade were largely unresolved. Any subclades that could be distinguished were weakly supported. Also, contrary to the CP topology, no strong geographic signal was observed. Indeed, species from the Comoro Islands or from southwest Madagascar did not cluster. Instead, clustering of species showing morphological resemblance was recovered (see Section 3.3). 3.3. Comparison of topologies The ML and BI analyses of the CP and ITS datasets agreed in showing that Noronhia formed a strongly supported monophyletic clade with the African and Indian Ocean Chionanthus (Fig. 1A and B). They also found largely unresolved relationships in the backbone of subtribe Oleinae as well as within Noronhia, although, the CP region resolved more well-supported nodes (MLBS P 85% and/or BPP P 0.95) than did ITS (Fig. 1A and B). However, inconsistencies were also apparent between the CP and ITS topologies. Incongruence patterns supported by MLBS P 85% and/or BPP P 0.95 (Fig. 1A and B) were considered hard incongruence. Conflicting relationships that were weakly supported in both CP and ITS trees, or strongly supported in one tree (usually in the CP tree) but dissolved into polytomies or conflicted only weakly in the other tree (usually in the ITS tree), were considered soft incongruence. Discordances within Noronhia were mostly soft incongruence. Noteworthy examples include N. emarginata and N. crassiramosa, both having very coriaceous leaf blades and relatively large fruit with a thick hard endocarp; they are sister to each other in the ITS but not in the CP phylogeny. Similarly, N. humbertiana and the morphologically similar N. seyrigii and C. tropophyllus, all pubescent species formed a monophyletic clade in the ITS phylogeny but not in the CP tree. Likewise, N. ovalifolia, N. densiflora and N. boivini formed a strongly supported clade, characterized by reddish flowers, in the ITS tree, but were part of polytomies in the CP tree. Lastly, the clade formed by the species N. decaryana to N. gracilipes is characterized by the absence of the corona, although not all species without a corona clustered in that clade. Relationships in the ITS topology also correlated with ecogeographic features: N. emarginata and N. crassiramosa, N. ovalifolia, N. densiflora and N. boivini, and N. decaryana and the clade including it occur in humid areas of East or North Madagascar whereas the trio N. humbertiana, N. seyrigii and C. tropophyllus are species of dry areas of the West; these relationships are not present in the CP tree. In general, there is greater correspondence between the ITS phylogeny and morphology or ecogeography than the CP phylogeny, however, it should be remembered that these incongruences are soft. The only case of hard incongruence observed here concerns N. myrtoides, which is sister to N. buxifolia in the CP tree (MLBS = 96% and BPP = 1) but sister to N. boinensis in the ITS tree (MLBS = 99% and BPP = 1). Major conflicts appeared in the placement of Fraxinus and some members of subtribe Oleinae (e.g. Forestiera neomexicana, Olea paniculata, African Chionanthus). For instance, Olea paniculata clustered with other Olea sensu stricto in the CP tree but not with ITS. The CP tree also showed two separate clades of African species that were not observed in the ITS topology (Fig. 1A and B). Even if relationships between African Chionanthus and MFR species were not significantly resolved in the ML topology of the ITS dataset, its BI counterpart showed that African Chionanthus species were clearly separated 372 C. Hong-Wa, G. Besnard / Molecular Phylogenetics and Evolution 67 (2013) 367–378 from the MFR taxa. Given the high support values (MLBS and/or BPP) for these inconsistent relationships, we considered these to be incongruence rather than a lack of phylogenetic signal. Likelihoodbased tests comparing the best-scoring CP and ITS trees and using constraints in both directions mostly supported these conflicts as statistically significant (Table 2). Most constraints were rejected, although the SH test was more conservative by suggesting fewer conflicts (Table 2). In any case, the topology of the best-scoring CP and ITS trees were reciprocally rejected by each dataset with high confidence (Table 2), suggesting complex evolutionary histories. 3.4. Divergence times (Fig. 2) For the CP data, both ML and BI suggested a migration from Africa to Madagascar. The reconstructed phylogeny in BEAST showed a topology similar to that obtained from ML and BI analyses except for a deeper placement of the second clade of African Chionanthus, which also suggested a possible migration from Madagascar back to Africa although two independent colonization events of Madagascar cannot be excluded. Divergence time estimates indicated that the NCAIO clade split from the remaining Oleinae around 36.17 Mya with a 95% HPD (highest posterior density) ranging from 30.28 to 42.65 Mya, and the separation of the first clade of African Chionanthus species (Africa 1) and the remaining NCAIO occurred around 26.7 Mya (95% HPD = 21.06–32.47 Mya). Divergence between the second clade of African Chionanthus (Africa 2) and the MFR clade happened around 21.8 Mya (95% HPD = 18.61– 29.08 Mya). For ITS, the BEAST phylogeny was topologically identical to the ML and BI trees except where constraints were enforced for calibration. Indeed, Fraxinus was constrained to be outside Oleinae since this topology has been well supported in other studies (Besnard et al., 2009; Lee et al., 2007; Wallander and Albert, 2000). This constraint also resulted in the placement of O. paniculata together with African Olea (i.e. Olea subgenus Olea). The BEAST topology also suggested a migration from Africa to Madagascar although this pattern is not clear since the inverse could be true. Age estimations, with the position of Fraxinus constrained to be basal, indicated a separation of the NCAIO clade from the remaining Oleinae at about 33.74 Mya (this node is not supported and lacks 95% HPD) and a divergence time of 19.51 Mya (95% HPD = 14.06– 25.27 Mya) between the African Chionanthus and the MFR clade. 4. Discussion 4.1. Phylogenetic utility of the plastid and nuclear DNA markers In this study, we used plastid and nuclear genes to examine generic relationships within subtribe Oleinae, to infer the phylogenetic position of Noronhia and to test its monophyly and the hypothesis of its close relationship with Malagasy Chionanthus suggested by Perrier de la Bâthie (1949, 1952). The ITS gene had the highest percentage of informative characters (Table 1), as in other studies in Oleaceae (Besnard et al., 2009; Wallander, 2008), but in the analyses here it did not perform better than the CP region both within Oleinae and within Noronhia. This might be accounted for by its high level of homoplasy (Table 1), which may cause poor phylogenetic resolution (Levin et al., 2009). The low phylogenetic signal at the species level may not be surprising given the low CP mutation rate found within Noronhia and other members of Oleaceae (Besnard et al., 2009, 2011; Heuertz et al., 2004) and/or if rapid diversification or other evolutionary events are involved. 4.2. Potential explanations for plastid and nuclear incongruence Putting aside possible conflicts within Oleinae such as the placement of Fraxinus, Forestiera or Olea paniculata as well as those at shallower nodes within Noronhia that were mostly considered as soft incongruence, we focus on the relationships between the African Chionanthus and the MFR clade. Indeed, the ITS topology showed a clear separation of the African species from the MFR ones, even though the likelihood and Bayesian procedures resolved this relationship slightly differently (Figs. 1B and 2B), rather than an ambiguous placement among them as in the CP tree (Figs. 1A and 2A). Statistically significant supports for this inconsistency suggest various potential causes. 4.2.1. Technical and statistical causes Various technical causes, including taxon sampling, sample contamination or mix-up, PCR recombination, can affect phylogenetic inferences and result in conflicting topologies (Rautenberg et al., 2008; Wendel and Doyle, 1998). Thus, great care was taken (e.g. repeated PCRs, inclusion of multiple accessions, recombination test, etc.) to ensure good quality data. In addition, our datasets included all but two Chionanthus species from the African continent; the existence of more Chionanthus from this region remains to be documented. And even though the present analyses included only the currently described species of Noronhia, inclusion of ca. 20 as yet undescribed species gave a topology similar to that presented here (data not shown), but with the denser sampling, there were more infrageneric polytomies. Therefore, focusing exclusively on the described species of Noronhia does not affect our interpretation. Moreover, the topologies were largely robust to different analytical procedures (e.g. likelihood, Bayesian and distance methods). Finally, the incongruence tests and the high support values also rejected the possibility that statistical uncertainties caused these inconsistencies (Figs. 1A and B; Table 2). Table 2 P-values obtained from the approximately unbiased (AU), Kishino–Hasegawa (KH) and Shimodaira–Hasegawa (SH) tests for alternative topologies based on combined plastid (CP) and nuclear (ITS) datasets. Dln L = difference in log-likelihood. Boldfaced values indicate rejection of the corresponding alternative topology. Dataset and constraints Dln L AU KH SH CP Best ML tree (unconstrained) Fraxinus nested within Oleinae Olea s. str. polyphyletic (excluding O. paniculata) African Chionanthus monophyletic Topology mirroring ITS tree 0 30.83 69.39 97.54 246.28 0.995 0.007 0.000 0.000 0.000 0.981 0.010 0.001 0.003 0.000 0.998 0.472 0.136 0.034 0.000 ITS Best ML tree (unconstrained) Fraxinus sister to Oleinae Olea s. str. monophyletic (including O. paniculata) African Chionanthus polyphyletic Topology mirroring CP tree but with monophyletic African Chionanthus Topology mirroring CP tree 0 17.53 25.00 33.5 210.41 391.67 0.987 0.028 0.025 0.057 0.000 0.000 0.963 0.037 0.025 0.061 0.000 0.000 0.997 0.547 0.411 0.061 0.000 0.000 C. Hong-Wa, G. Besnard / Molecular Phylogenetics and Evolution 67 (2013) 367–378 373 Fig. 2. Schematic diagrams showing the estimated divergence times within Oleinae obtained from analyses of (A) CP and (B) ITS datasets. Boldfaced values below branches refer to mean ages in million years of the nodes after the numbers. Values above branches are posterior probabilities. Mid-branch dots with associated ages and support values indicate the start of diversification within a clade. MFR = Malagasy Floristic Region (comprising Madagascar, Comoros and Mascarenes). 4.2.2. Biological explanations Several evolutionary processes can account for discordances between gene trees and include – but are not limited to - rapid diversification, gene duplication/loss, hybridization, polyploidization and lineage sorting (Degnan and Rosenberg, 2009; Wendel and Doyle, 1998). Rapid diversification, characterized by the phenomenon of ‘‘short interior branches’’ can lead to phylogenetic incongruence (Seelanan et al., 1997; Wendel and Doyle, 1998). Within the MFR clade, rapid diversification likely accounts for most inconsistencies given the occurrence of both short interior branches and lack of statistical support, although hybridization cannot be entirely excluded (e.g. the case of N. myrtoides). However, alternative resolutions of relationships between African Chionanthus and the MFR clade displayed short internodes that were strongly supported (Supplementary Fig. S2) and were consequently inconsistent with the soft incongruence expected under the rapid diversification scenario. Instead, this incongruence is probably best explained by other evolutionary processes, three of which are discussed below. First, in the absence of any other evolutionary process and with maternal inheritance, hybridization and introgression would result in the placement of taxa unrelated in their nuclear genomes close to each other in plastid-based phylogenies (Wendel and Doyle, 1998). In fact, other studies have found that relationships suggested by plastid genes tend to be more consistent with geography while nuclear genes provided better reflection of species relationships (McKinnon et al., 1999; Rautenberg et al., 2010; Zhang et al., 2010). Our CP topology, however, failed to show a clear geographic patterning consistent with these findings, although the three African Chionanthus species that fell with the MFR clade came from the southern part of the continent, thus closer to Madagascar (Fig. 1A; Supplementary Table S1). Second, gene duplication/loss and lineage sorting, both producing the same pattern despite being completely different processes, may also explain this incongruence (Wendel and Doyle, 1998). In these cases, stochastic survivorship and/or differential sampling of duplicated copies would result in different placements of individual taxa in nuclear-based phylogenies. The separation of African and MFR taxa into two distinct clades in the ITS topology, contrary to the CP tree, showed better correspondence with taxonomy and geography (Fig. 1B). It is possible that different ITS copies were maintained in and/or sampled for these two groups, although homoplasy and concerted evolution could also obscure their true history (Álvarez and Wendel, 2003). Lastly, polyploidization can also account for incongruence between gene trees (Blöch et al., 2009; Lihová et al., 2006; Weiss-Schneeweiss et al., 2012). The occurrence of polyploids has been documented within tribe Oleeae, particularly in Fraxinus, Olea and Osmanthus (Besnard et al., 2008; Taylor, 1945; Wallander, 2008). Since Olea and Osmanthus, as well as Chionanthus, are widely scattered in our phylogenies (Figs. 1 and 2), it is therefore reasonable to assume polyploidy also occurs elsewhere within the tribe. However, our current data do not allow us to explore this possibility further. The contribution of gene duplication/lineage sorting and hybridization as causes of incongruence can be assessed computationally through relative dating under the expectations of the coalescent theory (Frajman et al., 2009; Pelser et al., 2010; Rautenberg et al., 2008, 2010; Roos et al., 2011; Willyard et al., 2011). For 95% of nuclear loci in diploid organisms, it takes 9–12Ng to reach reciprocal monophyly (Hudson and Coyne, 2002), N being effective population size and g generation time; for a haploid organelle gene, the effective population size is half that obtained from nuclear genes in hermaphroditic diploid organisms. Setting effective population size at 10,000 (although field observations suggest this could be high especially for tree species in fragmented habitats) and mean generation time of 10 years (reasonable, given that Noronhia and Chionanthus species are shrubs or trees), the conservative 374 C. Hong-Wa, G. Besnard / Molecular Phylogenetics and Evolution 67 (2013) 367–378 coalescence time (CT) is estimated to be CTN = 900,000– 1,200,000 years for nuclear loci and CTCP = 450,000–600,000 years for plastid genes. Hybridization is the most likely explanation if difference in divergence times is larger than the estimated conservative coalescence time, whereas an explanation of gene duplication/lineage sorting is preferred if difference in divergence times is smaller than the estimated conservative coalescence time (Frajman et al., 2009; Rautenberg et al., 2008, 2010; Willyard et al., 2011). The time difference between the divergence of the African Chionanthus and the MFR clade and the divergence of the MFR clade in the ITS tree is far greater than the estimated conservative coalescence time for the plastid gene (3.7 My > CTCP). Likewise, the time difference between the separation of the first clade of African Chionanthus (Africa 1) and the Malagasy Noronhia and Chionanthus in the CP tree (3.1 My > CTN) as well as between the second clade (Africa 2) and the remaining MFR species (1.6 My > CTN) is also much greater than the estimated conservative coalescence time for the nuclear gene. The large differences in divergence times in the CP and ITS trees relative to the conservative coalescence times suggest that each gene had plenty of time to reach monophyly and would provide congruent phylogenetic patterns. A lack of monophyly would be assumed if differences in divergence times were smaller than the conservative coalescence times. Thus, gene duplication and lineage sorting are the least likely explanations for the incongruent placement of the African Chionanthus with regard to the MFR clade in the CP and ITS topologies. Instead, hybridization appeared to have played a major role, even when coalescence times are estimated with different values of effective population sizes and generation times. However, given the geologic history of the Malagasy region and the biology of these genera (see below, Section 4.3), any hybridization event between African Chionanthus and the MFR species (and not between Noronhia and Indian Ocean Chionanthus) must have been ancient. 4.3. Biogeographic implications Our molecular dating was based on a few calibration points, and may suffer from stochastic errors given the low statistical support in some nodes; however, it yielded age estimates fairly consistent with those of other studies (Besnard et al., 2009; Lee et al., 2007). It also allowed a preliminary look into the biogeographic history of the MFR clade (Figs. 1 and 2). In particular, different colonization scenarios of the MFR are suggested. While both the CP and ITS topologies implied the existence of a common ancestor from which the MFR clade and the African Chionanthus diverged, the CP topology indicated a colonization of Madagascar between 26–23 Mya (95% HPD = [32–21] [29–18] Mya). This was followed by a radiation of the clade within Madagascar starting around 23 Mya, a dispersal event back to Africa around 21 Mya or eventually a second independent migration to Madagascar, and later to the Indian Ocean islands. However, the node suggesting a migration back to Africa is not statistically supported (Fig. 2A); in fact, this second clade of African species is basal to Noronhia in the standard phylogenetic analyses (Fig. 1A). A scenario of migration back to Africa, although possible, is more difficult to reconcile with geological accounts and past water and wind circulations (Ali and Huber, 2010; McCall, 1997), which would have prevented westward and southbound migration from Madagascar before mid-to-late Miocene. Furthermore, species of Noronhia are predominantly dispersed by various kinds of lemurs (e.g. Eulemur, Lemur, Microcebus, Varecia, etc.; Andriamaharoa et al., 2010; Birkinshaw, 1999, 2001; Donati et al., 1999; Martinez, 2010; Radespiel, 2007; Simmen et al., 2006; Thorén, 2011) making a lemur-mediated dispersal back to Africa unlikely for this time frame. Finally, most extant Malagasy migratory birds are not frugivorous (Langrand, 1990). So, a more plausible scenario would be a separation of African Chionanthus into two distinct, tropical and southern clades, with subsequent migration to Madagascar giving rise to the MFR clade. The ITS topology suggested a clear separation between the African Chionanthus and the MFR clade and a dispersal to Madagascar between 19–15 Mya (95% HPD = [25–14] [20–11] Mya). The direction of the dispersal is rather equivocal but again we favor a migration from Africa based on the geological characteristics and water and wind circulations of this region at that time. Diversification of the MFR clade started at about 15 Mya, the clade subsequently expanding towards the Indian Ocean islands. The younger ages obtained from the ITS dataset compared to those derived from the CP data can be explained by concerted evolution, which tends to homogenize different sequences and leads to an underestimation of divergence times (Teshima and Innan, 2004), or by the constraint on the position of Fraxinus, the first calibration point. Nevertheless, the timing of dispersal to Madagascar suggested by both the CP and ITS topologies overlaps the lower margin of the time frame of the Mozambique Channel land bridge [45– 26 Mya] (McCall, 1997) or the eastward Mozambique palaeocurrent [Palaeogene period] (Ali and Huber, 2010) during which there were a number of major colonization events of Madagascar from Africa (Kuntner and Agnarsson, 2011; Russel et al., 2008; Yoder and Nowak, 2006). Colonization of other smaller Indian Ocean islands from Madagascar is also consistent with previous findings involving, e.g. spiders, dombeyoid Malvaceae, angraecoid orchids, chameleons and Indian Ocean Psiadia (Kuntner and Agnarsson, 2011; Le Péchon et al., 2010; Micheneau et al., 2008; Raxworthy et al., 2002; Strijk et al., 2012). 4.4. Taxonomic recommendations and revised classification Traditional generic circumscriptions within tribe Oleeae, in particular, are largely artificial. This is probably because of the lack of distinctive morphologies in the clade itself. Data other than from macromorphology are still largely lacking and may not be available soon, hampering efforts in elucidating the taxonomy of members of this group. Indeed, most species of Chionanthus, for instance, were initially described in one of at least six genera. In particular, there has been much contention over the placement of the African Chionanthus species, which used to be included in genera such as Linociera, Mayepea and Olea (Stearn, 1980). Their placement in Chionanthus by Stearn (1976, 1980) was based largely on external morphology. Such taxonomic instability reflects the difficulty in interpreting convergent or homoplastic morphologies. Moreover, recent phylogenetic studies highlight the complexity of morphology-based taxonomy within Oleaceae in general by showing extensive cases of polyphyly and paraphyly of conventional genera (Besnard et al., 2009; Guo et al., 2011; Lee et al., 2007; Li et al., 2002; Wallander and Albert, 2000; Yuan et al., 2010). However, wood anatomy suggests the existence of two geographically structured groups (temperate and tropical) within Chionanthus, with perhaps three additional subgroups in the tropics: Neotropics and Africa, Asia–Pacific and S.E. Asia–Malesia (Baas et al., 1988). Our data agree with this anatomical study in finding a comparable number of geographic clades, but with a slightly different geographic distribution: Africa–Indian Ocean, Central America, North America and Asia–Pacific. Despite the absence of distinctive morphological characters within Chionanthus, other lines of evidence may support these anatomical and molecular results; in any case, we recommend restrictions in the use of the generic epithet ‘‘Chionanthus’’. None of the type specimens of the previously used names subsumed under Chionanthus sensu lato occur in the Old World: Chionanthus (type Chionanthus virginicus L. [1753], USA), Linociera (type Linociera ligustrina Sw. [1797], Jamaica), and Mayepea (type Mayepea guianensis Aubl. [1775], French Guiana). These names would thus be available for other species previously called Chionanthus C. Hong-Wa, G. Besnard / Molecular Phylogenetics and Evolution 67 (2013) 367–378 that occur in other clades. Instead we opted to apply the generic name ‘‘Noronhia sensu lato’’ to all species distributed in Africa and the MFR currently recognized as Chionanthus as well as species of Noronhia itself, despite the possible lack of robust morphological synapomorphies. Indeed, the datasets used in this study all very strongly support the monophyly of the NCAIO clade (i.e. Noronhia and Chionanthus from Africa and Indian Ocean islands) and the placement of Chionanthus species from the MFR deep within Noronhia sensu stricto. Recognition of several genera within this clade would not solve the problem of the absence of synapomorphies. Nevertheless, the extended Noronhia is characterized, with some degree of variation, by coriaceous evergreen foliage, woody petioles, and small flowers with a partially fused and fleshy corolla. These features distinguish members of this group from temperate and New World Chionanthus, e.g. C. virginicus and L. ligustrina. However, they are found in some tropical Asian representatives, in particular those from West Malesia, which have not yet been sampled and which lack separate generic names. The revised nomenclature applied to the African and Indian Ocean species of Chionanthus is presented in Appendix A; further extension of Noronhia is a possibility. 5. Conclusion In all, the plastid and nuclear DNA markers used in this study provided us with new insights into relationships at various taxonomic levels within Oleinae. The most important of these is an extensive generic polyphyly, and in particular the distinctive geographic patterning within the polyphyletic Chionanthus, in which species from different continents are phylogenetically close to other genera of Oleaceae on those continents. We also gained new insights into the evolutionary history of Noronhia, for which a close relationship with African and Indian Ocean Chionanthus and a late Cenozoic dispersal from Africa to Madagascar have been found. However, within Noronhia as well as within Oleinae, some uncertainties remained and new questions arose. Additional molecular data (e.g. more nuclear markers), different approaches (e.g. next-generation genome sequencing, population genetic studies), and other types of data (e.g. anatomy, morphology) need to be used to further address these uncertainties and questions. Chromosomal and genomic studies would also contribute greatly to the understanding of the evolution of these groups. Finally, more botanical explorations and taxonomic studies are needed to document the potential existence of additional species related to Noronhia in Africa. Acknowledgments We thank E.A. Kellogg, A.J. Miller, P.F. Stevens and A.E. Zanne for insightful comments. We also acknowledge the following herbaria and botanical gardens for providing leaf samples and for making their collections available: G, K, MA, MO, P, TAN and TEF. Special thanks as well to T. Andriamihajarivo, C. Birkinshaw, R. Letsara, P. Lowry, F. Rakotonasolo, R. Randrianaivo, A. Randrianasolo, F. Ratovoson, S. Razafimandimbison, A. Razanatsima, G. Schatz and S. Trigui for leaf material. This study was supported by grants from US National Science Foundation (NSF DEB 1011208), the Garden Club of America and the Harris World Ecology Center at UMSL to C.H.W. and the Intra-European fellowship (PIEF-GA-2008220813) to G.B. The Kellogg Lab at UMSL, the EDB Lab of the ‘‘Laboratoire d’Excellence (LABEX)’’ TULIP (ANR-10-LABX-41), Missouri Botanical Garden-St. Louis and Madagascar Program, Madagascar National Parks, Ministère des Eaux et Forêts de Madagascar, Rio Tinto Madagascar (QMM) and Idea Wild provided administrative, financial, logistic or material support. 375 Appendix A. Appendix The following presents the nomenclatural changes needed for species of Chionanthus from Africa and the Malagasy Floristic Region based on the results we obtained. Noronhia africana (Knoblauch) Hong-Wa & Besnard, comb. nov. Mayepea africana Knoblauch, Botanische Jahrbücher, 17: 529 (1893); Hiern, Catalogue of African Plants collected by Dr.Friedrich Welwitsch in 1853–1861, 1: 658 (1898). – Chionanthus africanus Welw. ex Knoblauch, Botanische Jahrbücher, 17: 529 pro syn. – Linociera africana (Knoblauch) Knoblauch, Beihefte zum Botanischer Centralblatt, 61: 129 (1895); Gilg & Schellenb., Botanische Jahrbücher, 51: 69 (1913); Green in Hutch. & Dalziel, Flora of West Tropical Africa, 2nd ed. 2: 48 (1963); Liben, Flore d’Afrique Centrale, Oleaceae: 29 (1973). – Linociera angolensis Baker, Flora of Tropical Africa, 4: 20 (1902). – Chionanthus africanus (Knoblauch) Stearn, Botanical Journal of the Linnean Society, 80: 197 (1980). – Type: Angola, Pungo Andongo, Welwitsch 941. Linociera johnsonii Baker, Flora of Tropical Africa, 4: 20 (1902); Eggeling & Dale, Indigenous Trees of Uganda: 285 (1952); Turrill, Flora of East Tropical Africa, Oleaceae 12, fig. 13 (1952). – Type: Ghana, Aburi Hills, Johnson 453. Linociera mildbraedii Gilg & Schellenb. in Mildbraed, Wissenschaftliche Ergebnisse der Deutschen Zentral Afrika-Expedition,1907– 1908, 2 (Bot.): 527 (1913); Gilg & Schellenb., Botanische Jahrbücher, 51: 70 (1913). – Type: Congo, Beni, Mildbraed 2734. Linociera fragrans Gilg & Schellenb., Botanische Jahrbücher, 51: 70 (1913). – Type: Ghana, Aburi Hills, Johnson 234. Linociera dasyantha Gilg & Schellenb. in Mildbraed, Wissenschaftliche Ergebnisse der Deutschen Zentral Afrika-Expedition,1907–1908, 2 (Bot.): 527 (1913). – Type: Congo, Beni, Mildbraed 2286. Linociera oreophila Gilg & Schellenb., Botanische Jahrbücher, 51: 70 (1913). – Type: Cameroon, Deistel 89. Noronhia ayresii (A.J. Scott) Hong-Wa & Besnard, comb. nov. Olea obovata Baker, Flora of Mauritius and the Seychelles: 219 (1877), non C. obovata Rafin. (1836). – Chionanthus ayresii A.J. Scott nom. nov., Kew Bulletin, 33: 570 (1979). – Type: Mauritius, Ayres s.n. Noronhia battiscombei (Hutch.) Hong-Wa & Besnard, comb. nov. Dekindtia africana Gilg, Botanische Jahrbücher, 32: 139 (1902); Turrill, Flora of Tropical East Africa, Oleaceae, 15, fig. 5 (1952); non Mayepea africana Knoblauch (1893). – Type: Malawi, Nyasaland, Buchanan 283. Linociera battiscombei Hutch., Bulletin of Miscellaneous Information, Royal Botanic Gardens, Kew: 17 (1914); Verdoorn, Bothalia, 6: 600, t. 26 (1956), Flora of Southern Africa, 26: 124, fig. 13 n. 4 (1963); Dale & Greenway, Kenya Trees & Shrubs: 346 (1961). – Chionanthus battiscombei (Hutch.) Stearn, Botanical Journal of the Linnean Society, 80: 197 (1980). – Type: Kenya, K4, Nairobi Dist. Nairobi Forests, Battiscombe 517. Noronhia boutonii (A.J. Scott) Hong-Wa & Besnard, comb. nov. Olea macrophylla Baker, Flora of Mauritius and the Seychelles: 219 (1877), non C. macrophylla (Wall. ex G. Don) Blume (1876). – Linociera macrophylla (Baker) H.Perrier, Flore de Madagascar famille 166 (Oléacées): 9 (1952), in adnot., non L. macrophylla Wall. ex G. Don (1837). – Chionanthus boutonii A.J. Scott nom. nov., Kew Bulletin, 33: 570 (1979). – Type: Mauritius, Bouton s.n. Noronhia broomeana Horne ex Oliver in Hooker’s Icones Plantarum, 14, t. 1365 (1881). – Chionanthus broomeana (Horne ex Oliver) A.J. Scott, Kew Bulletin, 33: 570 (1979). – Type: Mauritius, Horne s.n. Linociera verrucosa Solereder, Botanisches Centralblatt, 45: 399 (1891), 46: 17 (1891). – Mayepea verrucosa (Solereder) Knoblauch, Naturlichen Pflanzenfamilien, 4: 10 (1892), Botanische Jahrbücher, 376 C. Hong-Wa, G. Besnard / Molecular Phylogenetics and Evolution 67 (2013) 367–378 17: 527 (1893). – Linociera broomeana (Horne ex Oliver) Knoblauch, Notizblatt des Königlichen Botanischen Gartens und Museums zu Berlin-Dahlem, 11: 1028 (1934). – Type: Mauritius, Sieber 125. Linociera coriacea Cordem., Flore de l’île de la Réunion: 458 (1895), non L. coriacea Vidal (1886). – Type: Réunion, Cordemoy s.n. Linociera obscura Cordem., Flore de l’île de la Réunion: 457 (1895). – Type: Réunion, Cordemoy s.n. var. cordemoyana (Knoblauch) Hong-Wa & Besnard, comb. nov. Linociera cordemoyana Knoblauch, Notizblatt des Königlichen Botanischen Gartens und Museums zu Berlin-Dahlem, 11: 1031 (1934). – Chionanthus broomeana var. cordemoyana (Knoblauch) A.J. Scott, Kew Bulletin, 33: 570 (1979). – Type: Réunion, Cordemoy s.n. var. cyanocarpa (Cordem.) Hong-Wa & Besnard, comb. nov. Linociera cyanocarpa Cordem., Flore de l’île de la Réunion: 456 (1895). – Chionanthus broomeana var. cyanocarpa (Cordem.) A.J. Scott, Kew Bulletin, 33: 570 (1979). Type: Réunion, Cordemoy s.n. Noronhia camptoneura (Gilg & Schellenb.) Hong-Wa & Besnard, comb. nov. Linociera camptoneura Gilg & Schellenb., Botanische Jahrbücher, 51: 68 (1913). – Chionanthus camptoneurus (Gilg & Schellenb.) Stearn, Botanical Journal of the Linnean Society, 80: 198 (1980). – Type: Cameroon, Bipinde, Urwaldgebiet, Zenker 3149. Noronhia cordifolia (Labat, M. Pignal & O. Pascal) Hong-Wa & Besnard, comb. nov. Chionanthus cordifolius Labat, M. Pignal & O. Pascal, Novon, 9: 68 (1999). – Type: Mayotte, Mlima Choungi, Pascal 288. Noronhia foveolata (E. Meyer) Hong-Wa & Besnard, comb. nov. Olea foveolata E. Meyer, Commentariorum de plantis Africae australioris: 176 (1837); Wright, Flora Capensis, 4.i: 485 (1907). – Linociera foveolata (E. Meyer) Knoblauch, Repertorium Specierum Novarum Regni Vegetabilis, 41: 151 (1936); Verdoorn, Bothalia, 6: 591, t. 21–24 (1956), Flora of Southern Africa, 26: 120 (1963); Palmer & Pitman, Trees of Southern Africa, 3: 1832 (1972). – Chionanthus foveolatus (Meyer) Stearn, Botanical Journal of the Linnean Society, 80: 198–199 (1980). – Type: South Africa, Drège s.n. Linociera marlothii Knoblauch, Repertorium Specierum Novarum Regni Vegetabilis, 41: 151 (1936). – Type: South Africa, KwazuluNatal, Rudatis 1416. subsp. tomentella (Verdoorn) Hong-Wa & Besnard, comb. nov. Linociera foveolatasubsp. tomentella Verdoorn, Bothalia, 6: 597, t. 23 (1956), Flora of Southern Africa, 26: 122, fig. 13 n. 1 (1963). – Chionanthus foveolatus subsp. tomentellus (Verdoorn) Stearn, Botanical Journal of the Linnean Society, 80: 199 (1980). – Type: South Africa, Burchell 5539. subsp. major (Verdoorn) Hong-Wa & Besnard, comb. nov. Linociera foveolata subsp. major Verdoorn, Bothalia, 6: 598, t. 24 (1956), Flora of Southern Africa, 26: 122, fig. 13 n. 3 (1963). – Chionanthus foveolatus subsp. major (Verdoorn) Stearn, Botanical Journal of the Linnean Society, 80: 199 (1980). – Type: South Africa, Graskop, Marieskop Forest, Urry 28568. Noronhia incurvifolia (H.Perrier) Hong-Wa & Besnard, comb. nov. Linociera incurvifolia H.Perrier, Mémoires de l’Institut Scientifique de Madagascar, Série. B, 2: 280 (1949), Flore de Madagascar famille 166 (Oléacées): 12, fig. 3 n. 4 (1952). – Chionanthus incurvifolius (H.Perrier) Stearn, Botanical Journal of the Linnean Society, 80: 199 (1980). – Type: Madagascar, Ankarana, Humbert 18912. var. planifolia (H.Perrier) Hong-Wa & Besnard, comb. nov. Linociera incurvifolia var. planifolia H.Perrier, Mémoires de l’Institut Scientifique de Madagascar, Série. B, 2: 280 (1949), Flore de Madagascar famille 166 (Oléacées): 14 (1952). – Type: Madagascar, Ankarana, Humbert 18966. Noronhia insularis (Labat, M. Pignal & O. Pascal) Hong-Wa & Besnard, comb. nov. Chionanthus insularis Labat, M. Pignal & O. Pascal, Novon, 9: 69 (1999). – Type: Mayotte, Bénara, Pascal 713. Noronhia mannii (Solereder) Hong-Wa & Besnard, comb. nov. subsp. mannii (Solereder) Hong-Wa & Besnard, comb. nov. Linociera mannii Solereder, Botanisches Centralblatt, 46: 17 (1891); Baker, Flora of Tropical Africa, 4: 19 (1902); Gilg & Schellenb., Botanische Jahrbücher, 51: 70 (1913); Green in Hutchinson & Dalziel, Flora of West Tropical Africa, 2nd ed., 2: 48 (1963). – Mayepea mannii (Solereder) Knoblauch, Botanische Jahrbücher, 17: 529 (1893). – Chionanthus mannii (Solereder) Stearn, Botanical Journal of the Linnean Society, 80: 199 (1980). – Type: Gabon, Gaboon River, Mann 949. Linociera lingelsheimiana Gilg & Schellenb., Botanische Jahrbücher, 51: 72 (1913). – Type: Sierra Leone, Scarcies River, Scott-Elliott 4717. Linociera macroura Gilg & Schellenb., Botanische Jahrbücher, 51: 72 (1913). – Type: Cameroon, Preuss 1282a. subsp. congesta (Baker) Hong-Wa & Besnard, comb. nov. Linociera congesta Baker, Flora of Tropical Africa, 4: 20 (1902), quoad Mann, 1747; excl. Mann, 2214; Gilg & Schellenb., Botanische Jahrbücher, 51: 72 (1913); Green in Hutchinson & Daziel, Flora of West Tropical Africa, 2nd ed., 2: 48 (1963); Liben, Bulletin du Jardin Botanique National de Belgique, 43: 358 (1973), Flore d’Afrique Centrale, Oleaceae, 31, t. 8 (1973). – Chionanthus mannii subsp. congestus (Baker) Stearn, Botanical Journal of the Linnean Society, 80: 201 (1980). – Type: Gabon, Muni, Mann 1747. Noronhia mayottensis (H.Perrier) Hong-Wa & Besnard, comb. nov. Linociera? mayottensis H.Perrier, Mémoires de l’Institut Scientifique de Madagascar, Série B, 2: 280 (1949), Flore de Madagascar famille 166 (Oléacées): 12, fig. 3 n. 4 (1952). – Type: Mayotte, Boivin 3196. Noronhia mildbraedii (Gilg & Schellenb.) Hong-Wa & Besnard, comb. nov. Campanolea mildbraedii Gilg & Schellenb., Botanische Jahrbücher, 51: 74 (1913); non Olea mildbraedii Gilg & Schellenb. (1913). – Olea mildbraedii (Gilg & Schellenb.) Knoblauch, Notizblatt des Königlichen Botanischen Gartens und Museums zuBerlin–Dahlem, 11: 673 (1932); Turrill, Flora of Tropical East Africa, Oleaceae: 8 (1952). – Chionanthus mildbraedii(Gilg & Schellenb.) Stearn, Botanical Journal of the Linnean Society, 80: 202 (1980). – Type: Cameroon, Mildbraed 4409. Linociera giordani Chiovenda, Atti della Reale Accademia Italiana Memorie della Classe di Scienze, 11.ii.50 (1940); Friis, Kew Bulletin, 30: 16 (1975) as L. giordanoi. – Type: Ethiopia, Giordano 2396 bis. Linociera latipetala Taylor, Bulletin of Miscellaneous Informations, Royal Botanical Gardens, Kew, 54 (1940); Eggeling & Dale, Indigenous Trees of Uganda: 285 (1952); Liben, Bulletin du Jardin Botanique National de Belgique, 43: 357 (1973), Flore d’Afrique Centrale, Oleaceae, 28, t. 7 (1973). – Type: Uganda, Lake Lutoto West of Ankole, Eggeling 3186. Noronhia nilotica (Oliver) Hong-Wa & Besnard, comb. nov. Linociera nilotica Oliver, Transactions of the Linnean Society of London, 29: 106, t. 117 (1875); Baker, Flora of Tropical Africa, 4: 19 (1902); Gilg & Schellenb., Botanische Jahrbücher, 51: 12 (1913); Eggeling & Dale, Indigenous Trees of Uganda: 285 (1952); Turrill, Flora of Tropical East Africa: 12 (1952); Dale & Greenway, Kenya Trees & Shrubs: 346 (1961); Green in Hutchinson & Daziel, Flora of West Tropical Africa, 2nd ed., 2: 48 (1963); Liben, Flore d’Afrique Centrale, Oleaceae: 30 (1973). – Mayepea nilotica (Oliver) Knoblauch, Botanische Jahrbücher, 17: 528 (1893). – Chionanthus niloticus (Oliver) Stearn, Botanical Journal of the Linnean Society, 80: 202 (1980). – Type: Cameroon, Briar, Mildbraed 9431. Noronhia obtusifolia (Lam.) Hong-Wa & Besnard, comb. nov. Olea obtusifolia Lam., Tableau encyclopédique et méthodique, 1: 28 (1791), Encyclopédie Méthodique Botanique, 4: 543 (1798). – Linociera obtusifolia (Lam.) H.Perrier, Mémoires de l’Institut Scientifique de Madagascar, Série B, 2: 279 (1949), Flore de Madagascar famille 166 (Oléacées): 9, fig. 3 n. 1–3 (1952). – Chionanthus obtusifolius C. Hong-Wa, G. Besnard / Molecular Phylogenetics and Evolution 67 (2013) 367–378 (Lam.) Stearn, Botanical Journal of the Linnean Society, 80: 203 (1980). – Type: Madagascar, Commerson s.n. var. minoriflora (H.Perrier) Hong-Wa & Besnard, comb. nov. Linociera obtusifolia var. minoriflora H.Perrier, Mémoires de l’Institut Scientifique de Madagascar, Série B, 2: 279 (1949), Flore de Madagascar famille 166 (Oléacées): 10 (1952). – Type: Madagascar, Tampina, Louvel 126. var. thouarsii (H.Perrier) Hong-Wa & Besnard, comb. nov. Linociera obtusifolia var. thouarsii H.Perrier, Mémoires de l’Institut Scientifique de Madagascar, Série B, 2: 279 (1949), Flore de Madagascar famille 166 (Oléacées): 10 (1952). – Type: Madagascar, Thouars s.n. Noronhia peglerae (C.H. Wright) Hong-Wa & Besnard, comb. nov. Olea peglerae C.H. Wright, Flora Capensis, 4.i: 485 (1907), as O. pegleri. – Linociera peglerae (C.H. Wright) Gilg & Schellenb, Botanische Jahrbücher, 51: 71 (1913); Verdoorn, Bothalia, 6: 599, t. 25 (1956), Flora of Southern Africa, 26: 22 (1963); Palmer & Pitman, Trees of Southern Africa, 3: 1833 (1972). – Chionanthus peglerae (C.H. Wright) Stearn, Botanical Journal of the Linnean Society, 80: 203 (1980). – Type: South Africa, Kentani, Pegler 819. Noronhia richardsiae (Stearn) Hong-Wa & Besnard, comb. nov. Chionanthus richardsiae Stearn, Botanical Journal of the Linnean Society, 80: 204 (1980). – Type: Zambia, Richards 4144. Noronhia tropophylla (H.Perrier) Hong-Wa & Besnard, comb. nov. Linociera tropophylla H.Perrier, Mémoires de l’Institut Scientifique de Madagascar, Série B, 2: 280 (1949), Flore de Madagascar famille 166 (Oléacées): 14, fig. 3 n. 4 (1952). – Chionanthus tropophyllus (H.Perrier) Stearn, Botanical Journal of the Linnean Society, 80: 205 (1980). – Type: Madagascar, Boina, Perrier 12340 (here designated). var. angustata (H.Perrier) Hong-Wa & Besnard, comb. nov. Linociera tropophylla var. angustata H.Perrier, Mémoires de l’Institut Scientifique de Madagascar, Série B, 2: 281 (1949), Flore de Madagascar famille 166 (Oléacées): 15 (1952). – Type: Madagascar, Ankarafantsika, Service Forestier 49 (here designated). Appendix B. Supplementary material Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/j.ympev.2013.02. 003. References Aguileta, G., Marthey, S., Chiapello, H., Lebrun, M.-H., Rodolphe, F., Fournier, E., Gendrault-Jacquemard, A., Giraud, T., 2008. 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