Cahiers scientifiques de l'océan Indien occidental 5, 2014: 21-26.
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Confirmation of the presence of the fern species: Lepisorus schraderi (Mett.)
Ching in Reunion island (Polypodiales: Polypodiaceae)
YANNIS ROBERT1,2, JEAN MAURICE TAMON1 & HERMANN THOMAS1
1 - Association des naturalistes de Bourbon, 18 Rue des Capucines, 97431 La Plaine des Palmistes, île de la Réunion.
yrobert@ecologie.re
2 - Association réunionnaise d'écologie, 188 chemin nid joli, 97430 Le Tampon, île de la Réunion
reçu le 08/09/2014, accepté le 24/12/2014
ABSTRACT: Reunion Island (Mascarene Archipelago, Indian Ocean) belongs to one of the
thirty-four world biodiversity hotspots. On this island, where approximately 250 species of
Pteridophytes were recorded, the presence of Lepisorus schraderi (Mett.) Ching is confirmed for
the first time. Only, one population of this fern was located in a mountain forest near the Piton de la
Fournaise volcano. As L. schraderi could be confused with L. excavatus (Bory ex Willd.) Ching
also present on the island, this paper provides a key to identify correctly L. schraderi and L.
excavatus, using morphological characters, as well as cytologic methods.
RÉSUMÉ: La présence de Lepisorus schraderi (Mett.) Ching (Polypodiaceae) est confirmée
pour la première fois sur l'île de La Réunion. Les caractères morphologiques et cytologiques
permettant de distinguer les deux espèces réunionnaises de Lepisorus, L. schraderi et L. excavatus
(Bory ex Willd.) Ching, sont précisés.
KEYWORDS: Lepisorus schraderi, Pteridophytes, Reunion island, Mascarene, chromosome
numbers
MOTS CLÉS: Lepisorus schraderi, Ptéridophytes, La Réunion, Mascareignes, nombres
chromosomiques
INTRODUCTION
The studies on Pteridophytes species from Reunion island reveal regularly some new details.
For example, recently, ROBERT (2011) showed that Christella parasitica (L.) Lév. ex Holttum is a
new native fern. DUBUISSON et al. (2014) also described a new endemic variety: Crepidomanes
inopinatum (Pic. Serm.) J.P. Roux var tamonii Y. Robert & Dubuisson.
Lepisorus (J. Sm.) Ching is a fern genus including approximately 40 species (HENNIPAN &
al., 1990; ZINK, 1993), mainly distributed in the Sino-Himalayan region. Around six Lepisorus
species were observed in the Afro-Malagasy region including the Mascarene islands. A single one is
present in the Hawaiian archipelago. WANG et al. (2012) showed that the Afro-Malagasy species
result from a rapid radiation which began around 1.5 My ago from an ancestor native to the SouthWest of China.
There are three species in the Malagasy region (TARDIEU-BLOT, 1960; ROUX, 2009):
Lepisorus excavatus (Bory ex Willd.) Ching, Lepisosrus schraderi (Mett.) Ching and Lepisorus
perrierianus (C. Chr.) Ching. L. excavatus and L. schraderi are present in Madagascar, in tropical
and southern Africa while L. perrierianus is endemic to Madagascar. Hitherto, a single species, L.
excavatus was known on Reunion island (CORDEMOY, 1891; TARDIEU-BLOT, 1960; BADRÉ,
2008; ROUX, 2009).
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Lepisorus schraderi (Mett.) Ching in Réunion island
Y. ROBERT, J.-M. TAMON & H. THOMAS
It should be noted, however, that preliminary works conducted by the botanist Th. Cadet
mentioned the presence in Reunion island of a plant identified by F. Rakotondrainibe as L.
schraderi (Grangaud, comm. pers.). A voucher specimen (Cadet 3189) classified in Cadet’s
Herbarium is preserved at the Reunion University Herbarium (REU). Th. Cadet collected this
species in Acacia heterophylla (Lam.) Willd. forest over the « Rivière de l'Est » bottom near the
Piton de la Fournaise volcano.
This work provides the confirmation of the presence of L. schraderi on Reunion island. The
comparison between L. schraderi and L. excavatus (Tab. I), the local and worldwide distribution as
well as the cytology of L. schraderi and the threats against this fern into its environment are
described in this paper.
MATERIALS AND METHODS
A specimen of L. schraderi was collected in Acacia heterophylla forest over the « Rivière de
l'Est » bottom near the Piton de la Fournaise volcano as it was done by Th. Cadet.
A specimen of L. excavatus was collected in Jean Maurice Tamon’s garden, located at the
Plaine des Palmistes .
The collected samples allowed to determine the chromosome number of both L. schraderi and
L. excavatus by using GIBBY method (1985) which has been adapted by ROBERT (2014).
MATERIAL EXAMINED:
REUNION ISLAND: Commune de Sainte Rose, rempart de la rivière de l'Est near the Piton
de la Fournaise volcano, alt. 1 900 m, 26/03/1971, Cadet 3189 (REU).
NOMENCLATURAL ASPECT:
– Lepisorus schraderi (Mett.) Ching in Bulletin of the Fan Memorial Institute of Biology 4, 3:
51. 1933b.
– Polypodium schraderi Mett. in Abhandlungen herausgegeben von der Senckenbergischen
Naturforschenden Gesellschaft 2, 1: 98, pl. 2, fig. 11. 1856b. Type: "Prom. b. spei", C. H. F.
Hesse s. n. (LE. holo.).
– Niphobolus schraderi (Mett.) Keyserl., Polypodiaceae et Cyatheaceae herbarii bungeani:
39. 1873.
– Polypodium lineare Thunb. var schraderi (Mett.) Sim, Handbook of the ferns of Kaffraria:
52, pl. LVI. 1891, nom. nov. for Polypodium elongatum Schrad. (1818: 915).
– Pleopeltis schraderi (Mett.) Tardieu in Flore de Madagascar et des Comores, 5 ème FamillePolypodiacées (sensu lato) [5(11) Blechnacées-5(14) Polypodiacées (sensu stricto)]: 110.
1960a.
– Polypodium elongatum Schrad. in Göttingische Gelehrte Anzeigen (1818: 915), non Aiton
(1789: 465), nom. superfl. [McNeill et al. (2006) Art. 53. 1]. Type: South Africa,
Grahamstown, C. H. F. Hesse s. n. (LE. holo.).
– Phymatodes elongata (Schrad.) Pappe & Rawson, Synopsis filicum Africae australis: 41.
1858, nom illeg. [MacNeill et al. (2006) Art. 53.1], non (Kaulf.) C. Presl. (1836: 196).
– Polypodium gueinzii Mett. in Abhandlungen herausgegeben von der Senckenbergischen
Naturforschenden Gesellschaft 2, 1: 91, pl. 3, figs 18, 19. 1856b, as "gueintzii". Type: "Ad
portum Natalensem lectum", W. Gueinzius s. n. (LZ, Holo. B, S, ? iso.).
– Polypodium lineare Thunb. var gueinzii (Mett.) C. Chr., Index filicum: (540: 1906). - L.
gueinzii (Mett.) Ching in Bulletin of the Fan Memorial Institute of Biology 4, 3: 51 1933b,
as "gueintzii".
Cahiers scientifiques de l'océan Indien occidental 5, 2014: 21-26.
23
LIST OF EXSICCATA FROM REUNION ISLAND (IN YANNIS ROBERT PRIVATE HERBARIUM):
Lepisorus schraderi: Sainte Rose, rempart de la Rivière de l'Est near the Piton de la Fournaise
volcano, 13/05/2014, Robert 1701.
Lepisorus excavatus: Plaine des Palmistes, Jardin de Jean Maurice Tamon, 11/07/2014,
Robert 1779.
RESULTS
L. schraderi was found in the « Rivière de l'Est » bottom near the Piton de la Fournaise
volcano at an altitude of 1 700 to 1 900 m. It grows among the native vegetation on the rim over the
excavation where the river begins. This fern is an epiphyte growing on several trees or shrubs such
as Acacia heterophylla, Sophora denudata Bory, Claoxylon glandulosum Boivin ex Baill.,
Dombeya ficulnea Baill. It is usually found with two other Polypodiaceae: L. excavatus and
Pleopeltis macrocarpa (Bory ex Willd.) Kaulf. Its presence closer to these last two species could
explain why this new species was not detected earlier because of the possible confusion. Moreover,
a broad similarity with a fourth species belonging to the same family: Belvisia spicata (L. f.) Copel
could also noted. The confusion is more likely when, under bad water conditions, B. spicata has not
its fertil ear. Indeed, L. schraderi and B. spicata can withstand water stress by keeping a strong
desiccation during drought period and can be revitalized when rains return.
Our countings gave for L. excavatus n = 36 (Fig. 1a) and for L. schraderi n = 72 (Fig. 1b) this
last result constitutes a first record. Thus, L. excavatus would be diploid while L. schraderi would
be tetraploid by taking as basic chromosome number x = 36 in accordance with WANG et al.
(2011).
1a
1b
Figure 1. – Lepisorus spp. : 1a) L. excavatus, YR 1779: Microphotography and drawing of meiosis showing 36
bivalents; 1b) L. schraderi YR 1701: Microphotography and drawing of meiosis showing 72 bivalents.
Scale bar = 10 µm
DESCRIPTION OF L. SCHRADERI (FIG. 2).
Rhizome shortly creeping, 2-3 mm in diameter, bearing black scales, peltate, lanceolate to
ovate, acuminate. Frond tufted, evergreen. Stipe short, glabrous or sometimes with few scattered
scales (Fig. 2a). Lamina narrowly lanceolate, gradually attenuate towards the acute apex, base
deccurent on the very short stipe, simple, texture thick and fleshy, both sides glabrous at maturity,
margins entire. Sorus round, arranged in two rows in distal third to half of the lamina (Fig. 2b); with
small peltate paraphyse when young.
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Lepisorus schraderi (Mett.) Ching in Réunion island
Y. ROBERT, J.-M. TAMON & H. THOMAS
Table I. – Comparison between L. schraderi and L. excavatus
Plant parts
Rhizome :
- Diameter
- Scales
- Waxy coating
Lamina
- Texture
- Abaxial side
Cytology
L. schraderi
L. excavatus
2 - 3 mm
black
none
More than 5 mm
brown
present
fleshy
glabrous or with few scattered scales
Tetraploid (n = 2x = 72)
membranous
glabrous
Diploid (n = x = 36)
2a
2b
Figure 2. – Lepisorus schraderi, 2a) Short stipe with scattered scales on costa; 2b) Whole plant showing sorus in the
distal third part of the frond (photographed by Fred Henze). Scale bar = 1 cm
DISCUSSION
L. Schraderi was observed only in the hygrophilous mountain forests [Code Hab. : 49.31],
located over the « Rivière de l’Est » bottom near the Piton de la Fournaise volcano at an altitude of
1 900 m, exactly in the Acacia heterophylla forest [Code Hab. : 49.314]. WANG et al. (2012)
related a sample collected in Bébour forest by Ronnald Viane (RV8253) in 1999, identified as L.
schraderi. However, Ronnald Viane (comm. pers.) confirmed that a part of his collection, realized
in 1999, preserved in its personal herbarium, corresponds to L. excavatus. In the paper of WANG et
al. (2012), that would be probably, either a misidentification, or a confusion with a sample from
another country.
L. schraderi is present in Madagascar, in Southern and tropical Africa: Ethiopia, Kenya,
Malawi, Mozambique, Rwanda, South Africa, Swaziland, Tanzania, Uganda, Zambia and
Zimbabwe. In those areas, L. schraderi is found in high altitude such as in Reunion island.
CROUCH et al. (2011) specify that in South Africa at the Cape Province, this species can be found
until to 2 300 m of altitude. It is then much smaller, lithophyt and can easily be confused with
Grammitis poeppigiana (Mett.) Pic. Serm. which is another Polypodiaceae present in this region.
In Reunion island, L. schraderi would be present only in the A. heterophylla forest located at
the « Rivière de l’Est » bottom near the Piton de la Fournaise volcano. This forest offers an
important floral diversity with numerous protected or endangered species. But, this particular
vegetation is submitted to fire risks in relation with human activities (Fig. 3a), and to the occurrence
of cattle in this part of the Reunion National Park (Fig. 3b). Thus, precautionary measures are
needed for the protection of L. schraderi and more generally of the whole local vegetation.
Cahiers scientifiques de l'océan Indien occidental 5, 2014: 21-26.
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CONCLUSION
The substantial prospecting work realized by Th. Cadet continues today to serve as the basis
of the studies on Pteridophytes flora in the Mascarene Islands. The present work allowed to add L.
schraderi to the other ferns from Reunion island. However, real threats exist about both the single
population of this taxon and the Reunion highlands which are yet well known as rich biodiversity
reservoirs. Local authorities have to control the human activities in order to preserve this
exceptional habitat in a sustainable way.
3a
3b
Figure 3. – 3a) Photography of a volcano area after fire; 3b) Photography showing predation of Polypodiaceae by cattle
in the area of L. schraderi. Scale bar = 10 cm
ACKNOWLEDGEMENTS
We wish to express our sincerest thanks to Pr. J. Smadja and Pr. A. Bialeki for their help to translate
this paper from French to English.
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