Fig 1.
Map showing the countries that surround the Mozambique Channel, with the localities cited in the text.
Fig 2.
Madagascar: (A) Trunk, in Sacaramy (Antsiranana), with a significant injury at its base. (B) Habitus of an individual, producing abundant resin in several parts, Andranotsara (Sambava). (C) Detail of the injury in A, with important resin production. (D) Leaves, Ambahy (Mananjary) (leaflet length ca. 6.5 cm). (E) Decomposed fruit showing seeds and pod resin beads (these developed as resin pockets in the pod wall) and intact fruit 4 cm in length, Ambahy (Mananjary). Observe the characteristic roughness of the external surface produced by these resin pockets, which gives the species its name.
Table 1.
Characteristics of the samples, FTIR analysis.
Fig 3.
FTIR analyses comparing the differences between resin, copal and amber produced by Hymenaea spp. and Canarium madagascariensis.
(A) FTIR analyses of the samples in order to identify the tree-resin producer of “Madagascar copal”, include (see Table 1): Canarium madagascariensis and two samples of “Madagascar copal” (CM01 and CM02), two samples of resin from H. verrucosa branches (RHvA01-R1 and RHvA02-R0). (B) Malagasy H. verrucosa analyses: FTIR analyses that show the comparison between the results of A and other resin, copal and amber produced by Hymenaea ssp. The analyses include samples of Canarium madagascariensis (RMCR-01), “Madagascar copal” (CM01), resin from H. verrucosa branch, (RHvA01-R1), resin from H. verrucosa of the Andranotsara pit Q1, found in A horizon A (CM05-Q1) and in the sub-horizon B1 (CM06-Q1), and resin pieces of H. verrucosa of the Antampolo pit Q2, found in A horizon (CM03-Q2) and in sub-horizon B1 (CM4-Q2). (C) Neotropical Hymenaea spp. resin and amber analyses: resin from “copal of Colombia”, (CCS01), Miocene Mexican amber (AMS01), Miocene Dominican amber (AD-03) and (AD-04), and Miocene Ethiopian amber (EA-01). Diterpenic resin/copal has some characteristic vibrational group frequencies: characteristic is a low intensity of absorption band at 3080 cm-1 that is absent from triterpenoid resin/copal and that corresponds to v (= C-H), intensity absorption band at 2937–2929 cm-1 corresponds to vas(C-H), CH3, CH2 (methylene group), intensity band at 2874–2844 cm-1 corresponds to vs (C-H), CH3, CH2 (methyl group), intensity bands at 1718 cm-1, 1694 cm-1, and 1644 cm-1 correspond to v (C = O), intensity band at 1446 cm-1 corresponds to δas (CH3), intensity band at 1386 cm-1 corresponds to δs (CH3), and intensity band at 888 cm-1 corresponds out of plane δ (CH2) of the exomethylene functionality C8-C20. “Madagascar copal” and “East African Copal” can be differentiated from “Western African Copal” by the linear slope of the spectra in the case of the resin/copal of West Africa and the intensity of 3411–3422 cm-1 that corresponds to v (OH) of the East African copal. It is possible to differentiate between amber and copal by observing the exocyclic methylene bands at 3048, 1642 and 887 cm-1. In the case of copal, the first two bands are not intense, but they are clearly observed, and the band of 887 cm-1 is very intense. In the case of ambers, the bands are absent or of very weak intensity.
Table 2.
Characteristics of the samples and results.
Fig 4.
Pits excavated in the Sambava region.
(A) Commencement of the Andranotsara pit Q1 (S14°38.472’—E050°12.467’). (B) Andranotsara pit Q1, showing the different horizons to the top of the sub-horizon B4 (105 cm deep). (C) Final result of the Antampolo pit Q2 (S14°43.468’—E050°12.860’), 140 cm deep. (D) Sample from the A horizon of the Andranotsara pit Q1; it includes fungi-bearing resin beads, humus-quartz aggregates, some roots, quartz grains and pellets. (E) Sample from the sub-horizon B1 of the same pit Q1, formed mainly of non-rounded quartz grains, and a small number of fungi-bearing resin beads. (F) Resin remains formed under aerial conditions, found in the Antampolo pit Q2 in the A horizon, showing the intense pulverulent surface alteration. (G) Sample from the sub-horizon B3 of the Antampolo pit Q2, formed of non-rounded quartz grains with clay. Notations: r = H. verrucosa root; O, A, B1 to B4 = horizons and sub-horizons.
Fig 5.
Pedologic logs of the pits excavated in the Sambava region.
(A) Andranotsara pit Q1, 170 cm deep, and (B) Antampolo pit Q2, 140 cm deep. The detailed explanation is in the text. For geographical locations of the pits, see Fig 4. (C) FTIR analyses of three samples to determine the origin of soil beads (= fungi-bearing resin beads) preserved in the O horizon of the forest soil. The analyses include samples of resin from: 1. soil beads from the soil surface of a different part of Antampolo; 2. soil beads from the O horizon of the Antampolo pit Q2, and 3. living H. verrucosa tree resin in Antampolo.
Fig 6.
Soils in which H. verrucosa grows.
(A) Ferralsols in Sacaramy (between Montagne d’Ambre and Antsiranana). (B) Searching for resin in the litter around an H. verrucosa trunk, rooted in a ferralsol, in Sacaramy. (C) Ferralsols in the delta of the river Antomboka, in Anamakia, next to the salt production site of Antsiranana. (D) Ferralsols in a delta plain in front of Nosy Lonjo (Andovobazaha Bay, Antsiranana). (E) Regosols/arenosols in the Pangalanes Channel margins, Ambahy (Nosy Varika, Mananjary). (F) Arenosols in a lake margin between Nosy Varika and Ambahy.
Fig 7.
Hymenaea verrucosa fungi-bearing resin beads found abundantly in some pit horizons (featured specimens from pit Q2, Antampolo) are important resin inputs.
(A–B) Fungi-bearing resin beads as organic matter isolated from the sand. (C) Fungi-bearing resin bead, sectioned to show the small spherical, organic structures purple in colour and interpreted as fungal sclerotia. (D) SEM image of the same sectioned bead. (E) SEM detail of the inner cavity containing sclerotia and inset showing a detail of their punctated external surface. (F) SEM detail of the external unaltered layer (left) and the state of preservation in the interior of the resin body of the fungi-bearing bead (right lower part), see inset indicated in D. (G) SEM detail of the resin body of the bead invaded by a fungal mycelium (see inset indicated in D), which is of the same fungus that produced the sclerotia, most probably a representative of the genus Aspergillus.
Fig 8.
Pieces of resin obtained from a tree and from the pits at several depths.
(A) Resin exuded by roots around which quartz-grain aggregates form (crusts), as found in the B horizon, Andranotsara pit Q1. (B) Thin section of the A sample; the label “root” shows the position of the H. verrucosa root; the resin (brown) when exuded by the root agglutinated the quartz sand grains (transparent). (C) Resin flow of H. verrucosa with embedded arthropods, Ambahy (Mananjary). (D) Detail of the same flow showing the original transparency, as if polished. (E) Sample of the resin found in Andranotsara pit Q1 at sub-horizon B1 between 15 cm and 30 cm depth. (F) Sample of the resin found in Antampolo pit Q2 at sub-horizon B1 between 20 cm and 30 cm depth. (G) Sample of the resin found in the same pit at sub-horizon B2 at 50 cm depth. E–G are samples dated by 14C analysis.