Jean-Philippe Claude
UMR ESPACE DEV-BIORECA Laboratory, University of Antilles, Schœlcher, France.
DOI: 10.4236/nr.2025.1613019   PDF    HTML   XML   47 Downloads   254 Views   Citations

Abstract

The flora of the Lesser Antilles archipelago located in the Caribbean, presents a remarkable diversity of species belonging to the Rubiaceae family, with a representation of all possible forms of life. More than twenty are herbaceous plants present in the archipelago (three of which are endemic) and about fifteen in Martinique. Although several species are rather rare, others are described as ruderal, arval or ubiquitous, colonizing different types of environments. We therefore undertook to explore the ecology of herbaceous Rubiaceae of the forest edges of the island of Martinique, following a protocol distinct from that used for woody species. The results reveal that it is possible to find Rubiaceae, whatever the type of forest edge and the type of bioclimate. However, if some herbaceous Rubiaceae thrive there, probably attracting various pollinators, ensuring their ecological success, the majority of them remain rare. Yet the study shows that these forest edges support a diverse biodiversity, playing a role as transitional habitats by offering unique conditions that neither dense forests nor other open spaces provide.

Keywords

Rubiaceae, Forest Edges, Ecology, Martinique

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1. Introduction

There are over 14,000 species and approximately 580 recognized genera of the Rubiaceae family worldwide, making it the fourth largest family of flowering plants with a primarily pantropical distribution [1]. In the Caribbean, the flora of the Lesser Antilles archipelago is composed of a remarkable diversity of Rubiaceae [2]-[5]. Rubiaceae form the fifth largest plant family in the archipelago with 129 species recorded, including 89 on the island of Martinique [2]-[5]. This mountainous island occupying a central position in the archipelago, hosts all forms of life in this family (trees, shrubs, bushes, lianas, herbaceous plants, epiphytes and aquatic plants) and these species occupy a very wide range of habitats [2]-[10].

Combining the censuses of the American botanist Richard Alden Howard and the French botanist Jacques Fournet, 20.2% of Rubiaceae in the Lesser Antilles are herbaceous (i.e. 26 species divided into 10 genera), and in Martinique, 15.7% are herbaceous (i.e. 14 species divided into 6 genera) (Appendix 1) [2] [3]. Their flowering can be annual, seasonal (rainy season) or regular but absent in the event of a long drought [2] [3]. Although several species are rather rare, others are described as ruderal, arval or ubiquitous, adapted to disturbed, open or cultivated environments [2] [3] [8]. They colonize forest edges, fields, ruins and even roadsides [2]-[4] [8]. Given their ability to colonize diverse and often disturbed habitats, we hypothesize that herbaceous Rubiaceae have a specific distribution and diversity influenced by variations in ecological conditions, for example, at forest edges, particularly in terms of light availability and humidity. This study aims to answer the following question: to what extent do ecological gradients present at forest edges modulate the floristic composition and spatial distribution of herbaceous Rubiaceae in Martinique? We therefore undertook to explore the ecology of herbaceous Rubiaceae in forest edges on the island of Martinique.

2. Materials and Methods

2.1. Study Area

Martinique, a mountainous and volcanic island in the Lesser Antilles archipelago (Figure 1), is the result of subduction between the North American and Caribbean plates, a phenomenon that gives rise to its unique topography marked by massifs in the north, hills in the south and a diversity of soil types [11]-[14].

Figure 1. Location of Martinique in the Lesser Antilles archipelago, Caribbean.

This topographic and pedological diversity, influenced by orographic precipitation and altitudinal climatic variations, generates various bioclimates ranging from dry to hyper humid and various forests such as xerophilous forests at low altitude, mesophilous forests at medium altitude to submontane and montane rainforests [15]-[20].

Martinique, with its diversity of soils, reliefs, hydrography and vegetation, as well as a strong varied anthropization, offers a great heterogeneity of habitats favorable to herbaceous Rubiaceae, which disperse mainly by barochory and zoochory [4] [17] [21] [22]. Forest edges for example, transitional zones between forest and open environments, constitute habitats rich in biodiversity, in particular for pollinators, throughout the year [23]-[25]. These edges constitute ecological corridors that facilitate biological exchanges in a fragmented landscape, offering an ideal habitat for herbaceous Rubiaceae [23]-[25]. Despite its modest surface area (1128 km²), Martinique is home to a diversity of species from the Rubiaceae family, contributing to the biodiversity of the archipelago, a component of the Caribbean hotspot recognized worldwide [4] [5] [26]-[28]. Around 89 species of the family are present on the island, including 14 herbaceous species divided into 6 genera, but the majority of them remain rare (Appendix 1, Figure 2), [2]-[5]. The identification of these plants is possible with the help of floras and reference works containing in particular illustrations facilitating their determination [2] [3] [8].

Figure 2. Abundance of herbaceous Rubiaceae [2] [3].

2.2. Methods

The data were collected exclusively by non-exhaustive floristic surveys, carried out in 2020 with the help of a few members of the Association of Martinican Botanists (Figure 3). This study uses an approach aimed at analyzing the main trends, as well as the interactions between plant species within largely herbaceous communities [23] [29]-[32]. Thus, walking on the hiking trails, in various bioclimates, 29 surveys were carried out targeting the Rubiaceae encountered in the forest edges of the island (Appendix 2). One of the main difficulties was then to identify as many species of the family as possible in these very dense edges, during our only passages on each of the hiking trails. Indeed, regardless of the bioclimate, these edges proved to be extremely dense, composed largely of herbaceous plants but including other physiognomic types (shrubs, lianas, liana shrubs, etc.) and therefore constituting multiple populations of very varied surfaces.

Figure 3. Location of surveys.

Wanting to inventory and obtain a representative sample of this diversity of populations was almost impossible. We therefore chose to arbitrarily select a reference surface corresponding to the square meter. This standard methodology consisted of placing wooden sample squares of 1 meter on each side, on non-contiguous surfaces where Rubiaceae were identified (Figure 4 and Figure 5).

Figure 4. Cross-Sectional diagram illustrating the structure of the forest edges traversed.

Figure 5. Some photos to illustrate the different types of forest edges traveled and sample squares made of 1 m × 1 m. (1. Cap Macré, 2. Morne Aca, 3. Fond Baron, 4. Trace des Jésuites).

The objective of the sample squares was to provide an overview of the number of Rubiaceae, their abundances and densities per square meter, and the types of populations to which they can contribute. For each sample square, a set of ecological and floristic descriptors were systematically noted, such as the name of the species, their number of individuals, their height, their physiognomic type as well as their phenological state (flowering and fruiting periods). For lianas or seedlings (less than 10 cm), we simply noted their abundance when their identification was possible (+ very low (number 1 to 5); ++ low (number 5 to 15); +++ average (number 15 to 30); ++++ high (number 30 to 45); +++++ very high abundance (number 45 to 100 and more)). Furthermore, based on the GPS points of the surveys and the QGIS software version 3.36, the biotopes were characterized (Appendix 2). The average annual minimum and maximum temperatures, the average annual precipitation were noted using climatic data from Météo-France (French meteorological organization). The slope gradient and altitude were recovered using altimetric data from the IGN (National Geographic Institute, BDALTI 25 meters) and the soil types of the surrounding forests using pedological data from the IRD (Research Institute for Development, soil map of the Antilles at 1/20,000). The level of sunshine received on the ground was noted on site, according to two simple variables (medium (50% sunshine) or high (100% sunshine)). The data obtained were then entered into Excel software and ecological indices and indicators were used for the treatment of Rubiaceae or stations [2] [4] [15] [17] [29]-[31] [33].

We distinguish:

• Species richness (number of species identified);

• Abundance (number of individuals per species);

• Frequency (presence of a Rubiaceae in a specific number of sample squares);

• Density (ratio between the number of individuals of a species and the area of the surveys), calculated according to the following equation:

$D=n/a$ . (1)

where “D” is the density, “n” is the number of individuals of a species, “a” is the area of the sample square.

• The distribution index (distribution of Rubiaceae within the surveys, expressed by the product between the frequency and the density per species), calculated according to the following equation:

$Id=F\times D$ . (2)

where “Id” is the distribution index, “F” is the frequency and “D” the density.

• Simpson’s diversity index (floristic diversity and numerical dominance of one or more species), calculated according to the following equation:

$\lambda ={\displaystyle {\sum }_{i=1}^S{\left[n_i/N\right]}^2}$ (3)

where “λ” is the Simpson index, “S” is the total number of species, “n_i” is the number of individuals of a species and “N” is the total number of individuals. The index is close to 0 when the specific diversity is high, no species dominates numerically; and close to 1 when the diversity is low and one species dominates numerically. Finally, multivariate statistical processing was carried out using XLSTAT software in order to characterize of our surveys [29] [34] [35].

3. Results

3.1. Characteristics of the Surveys Carried Out

The surveys were carried out on various sites, covering bioclimates ranging from dry subhumid to hyperhumid (Figure 3, Appendix 2 and Appendix 3). The sample squares are distributed in habitats corresponding to the edges of xerophilous, xero-mesophilous (transition zone), meso-hygrophilous (transition zone) and hygrophilous forests (Table 1). The altitudes range from 1 to 635 meters, and the slopes are gentle to moderate (Appendix 2). The hiking trails are more or less wide and of a diverse nature, ranging from secondary roads to stone and earth paths. However, the soils of the surrounding forests are mainly composed of vertisols (rarely marine alluvium) in dry subhumid bioclimates, and of red or brown montmorillonitic soils in more humid bioclimates (Appendix 2). Most of the surveys are located in semi-shaded areas, with sunlight on the ground limited by the canopy cover of the surrounding trees (Appendix 2). In total, the 29 surveys cover an area of 29 m². Approximately 2276 specimens were recorded, of very diverse physiognomic types, belonging to 96 species, divided into 79 genera and from 40 different families (Appendix 3).

Two species are invasive according to the DEAL (Directorate of the Environment, Planning and Housing in Martinique): Clerodendron paniculatum and Dichrostachys cinerea [36]. We find mostly herbaceous species but also lianas, ferns, or even seedlings or young individuals of future shrubs, trees and bushes. Among these specimens, 228 belong to 7 species, divided into 5 genera of the Rubiaceae family (Appendix 3).

Table 1. Summary table of floristic surveys carried out between August and October 2020 (Appendix 2 and Appendix 3).

Bioclimate	Dry subhumid	Ecotone (transition between dry subhumid and humid subhumid)	Ecotone (transition between humid and humid subhumid)	Hyper humid
Forest edge	Xerophilous	Xero-mesophilous	Meso-hygrophilous	Hygrophilous
Number of sample squares	8	6	6	9
Total area (square meter)	8	6	6	9
Minimum area (square meter)	1	1	1	1
Number of families (all physiognomic types included)	21	14	16	18
Number of genera (all physiognomic types included)	40	18	20	27
Number of species (all physiognomic types included)	47	19	20	31
Number of individuals (all species included, excluding seedlings, lianas and ferns)	599	164	561	952
Physiognomic types encountered	tree, shrub, herbaceous, liana.	tree, shrub, bush, herbaceous, liana.	tree, shrub, herbaceous, fern.	shrub, herbaceous, fern.
Number of genera of the Rubiaceae family (all physiognomic types included)	3	3	2	2
Number of species of the Rubiaceae family (all physiognomic types included)	3	3	2	3
Number of individuals of the Rubiaceae family (all species included)	96	20	25	87
Location of place name	Morne Aca and Cap Macré	Pointe Rouge to Pointe à Bibi hiking trail	Fond Baron	Plateau Boucher and Trace des Jésuites
Municipality	Marin	Trinité	Fort-de-France	Fonds-Saint-Denis and Morne Rouge

3.1.1. Forest Edges of Xerophilous Forests: Cap Macré

The species recorded in the sample squares of Cap Macré, present diversified physiognomic types. The flowering of some species, which is conducive to attracting pollinators, indicates an active reproductive capacity (Table 2). The overall low density and abundance of species suggest a relatively stable environment, favourable to ruderal plants able to adapt to water stress and high light. In at least three surveys, the Simpson index approaches 1, reflecting a marked abundance of several species. Only one shrub and two herbaceous plants of the Rubiaceae family are recorded, of which only Diodia ocymifolia (herbaceous) stands out for its particularly high abundance and density.

Table 2. Contents of the sample squares made at Cap Macré in Marin.

			Square 1 (S1)					Square 2 (S2)					Square 3 (S3)					Square 4 (S4)
	Simpson index		0.43867036					0.28125					0.33742198					0.44636678
No.	Species	Ph	H	A	D	Fl	F	H	A	D	Fl	F	H	A	D	Fl	F	H	A	D	Fl	F
1	Abrus precatorius	L		5+					1+										1+
2	Capraria biflora	He						40	1	0.0001
3	Cenchrus echinatus	He						60	3	0.0003	Y
4	Citharexylum spinosum	T						15	1	0.0001
5	Croton bixoides	Sh											20	3	0.0003			50	2	0.0002
6	Cuscuta americana	L		1+		Y
7	Desmodium incanum	He											20	50	0.005	Y	Y
8	Desmodium sp	He		10+
9	Dichrostachys cinerea	Sh						50	3	0.0003
10	Diodia ocymifolia	He											30	80	0.0080	Y		20	10	0.0010	Yes
11	Eleocharis flavescens	He											10	10	0.0010	Y		10	5	0.0005	Yes
12	Enicostema verticillatum	He						20	2	0.0002	Y
13	Eugenia cordata	Sh						20	1	0.0001
14	Guettarda odorata	Sh	70	1	0.0001
15	Haematoxylum campechianum	T	80	2	0.0002
16	Heliotropium ternatum	He	90	5	0.0005	Y
17	Ipomoea setifera	L		5+
18	Leptochloa filiformis	He						60	2	0.0002	Y
19	Leucaena leucocephala	T	40	30	0.0030
20	Pithecellobium unguis-cati	T											160	8	0.0008
21	Sida rhombifolia	He	10	55	0.0055			60	1	0.0001
22	Sida sp	He	10	2	0.0002
23	Spermacoce verticillata	He						20	1	0.0001	Y
24	Spigelia anthelmia	He						10	5	0.0005	Y	Y
25	Sporobolus jacquemontii	He											80	15	0.0015	Y
26	Tabebuia heterophylla	T						20	14	0.0014
27	Tragia volubilis	L		2+
28	Vernonia cinerea	He						30	30	0.0030	Y	Y

Legend. S: Survey/Ph: Physiognomic type in maximum morphogenetic development (T: Tree; Sh: Shrub; He: herbaceous; L: liana)/H: Height in cm/A: Abundance/D: Density (cm²)/Fl: Flowers (Y: yes)/F: Fruits (Y: yes).

3.1.2. Forest Edges of Xerophilous Forests: Morne Aca

The surveys of Morne Aca, also in a xerophilous zone, also present a diversity of physiognomic types (Table 3).

Table 3. Contents of the sample squares made at Morne Aca in Marin.

			Square 1 (S5)					Square 2 (S6)					Square 3 (S7)					Square 4 (S8)
	Simpson index		0.20199446					0.11005917					0.12755102					0.09157025
No.	Species	Ph	H	A	D	Fl	F	H	A	D	Fl	F	H	A	D	Fl	F	H	A	D	Fl	F
1	Bidens sp	He											15	2	0.0002
2	Bursera simaruba	T																10	1	0.0001
3	Cenchrus echinatus	He						20	1	0.0001	Y		10	1	0.0001
4	Centrosema virginianum	L												3+
5	Chamaecrista glandulosa var schwarzii	B	80	16	0.0016	Y
6	Chamaecrista nictitans	B						30	9	0.0009	Y		30	3	0.0003	Y		20	20	0.0020	Y
7	Chamaecrista obcordata	B						30	8	0.0008			30	3	0.0003	Y		20	1	0.0001	Y
8	Chamaesyce hirta	He						20	1	0.0001	Y	Y
9	Desmodium heterocarpum	He	20	18	0.0018		Y						10	8	0.0008
10	Desmodium incanum	He	30	5	0.0005	Y		30	1	0.0001	Y		30	8	0.0008	Y		20	1	0.0001	Y
11	Eriochloa polystachya	He						15	8	0.0008
12	Leucaena leucocephala	T	110	30	0.0030
13	Lonchocarpus punctatus	T																10	1	0.0001
14	Ocimum gratissimum	He						10	5	0.0005	Y
15	Oxalis barrelieri	He						20	6	0.0006	Y		10	2	0.0002	Y		15	2	0.0002	Y
16	Paspalum conjugatum	He											50	3	0.0003	Y
17	Sida acuta	He	30	14	0.0014	Y	Y	10	10	0.0010		Y	50	7	0.0007		Y	20	10	0.0010	Y	Y
18	Spermacoce verticillata	He	40	1	0.0001	Y		20	1	0.0001	Y		20	1	0.0001	Y		10	1	0.0001	Y
19	Spigelia anthelmia	He						10	1	0.0001	Y
20	Sporobolus jacquemontii	He						70	5	0.0005	Y
21	Stachytarpheta jamaicensis	He	40	11	0.0011	Y		20	8	0.0008	Y							20	12	0.0012	Y
22	Stachytarpheta sp	He											20	4	0.0004
23	Synedrella nodiflora	He						15	1	0.0001								20	5	0.0005
24	Urena lobata	B																20	1	0.0001
25	Urvillea ulmacea	L																	1+

Legend. S: Survey/Ph: Physiognomic type in maximum morphogenetic development (T: Tree; B: Bush; He: herbaceous; L: liana)/H: Height in cm/A: Abundance/D: Density (cm²)/Fl: Flowers (Y: yes)/F: Fruits (Y: yes).

The abundance of flowering plants indicates an environment favorable to ecological interactions, such as pollination, despite the water stress conditions. The abundance of these species is low but the low values of the Simpson index confirm the presence of a diversity of species in the sample squares.

None of them dominate numerically and the densities are therefore very low, which also characterizes these environments as relatively stable for ruderal plants. We also note the presence of a single Rubiaceae, Spermacoce verticillata, with a single individual and therefore a low density in all the sample squares.

3.1.3. Xero-Mesophilic Forest Edges (Ecotone): Pointe Rouge to Pointe À Bibi Hiking Trail

In these surveys of xero-mesophilic edges, we observe a transition towards a slightly more humid environment, with a very marked presence of trees such as Cassipourea guianensis, Garcinia humilis and Pisonia fragans (Table 4 and Table 5).

Table 4. Contents of the first three sample squares made on the trail from Pointe Rouge to Pointe à Bibi, in Trinité.

			Square 1 (S9)					Square 2 (S10)					Square 3 (S11)
	Simpson index		0.727810651					0.401920439					0.533163265
No.	Species	Ph	H	A	D	Fl	F	H	A	D	Fl	F	H	A	D	Fl	F
1	Cassipourea guianensis	T											10	1	0.0001
2	Cordia collococca	T						40	1	0.0001
3	Erythroxylum havanense	Sh	20	1	0.0001			15	1	0.0001			20	2	0.0002
4	Eugenia monticola	B						10	1	0.0001
5	Garcinia humilis	T	20	11	0.0011			50	8	0.0008			20	3	0.0003
6	Geophila repens	He		3+		Y	Y		3+			Y		3+
7	Macfadyena unguis-cati	L		1+
8	Paullinia cururu	L							1+					3+
9	Pisonia fragans	T	15	1	0.0001			30	15	0.0015			20	20	0.0020
10	Securidaca diversifolia	L							1+
11	Spondias mombin	T						10	1	0.0001			10	2	0.0002

Legend. S: Survey/Ph: Physiognomic type in maximum morphogenetic development (T: Tree; Sh: Shrub; B: Bush; He: herbaceous; L: liana)/H: Height in cm/A: Abundance/D: Density (cm²)/Fl: Flowers (Y: yes)/F: Fruits (Y: yes).

We note the presence of numerous lianas, shrubs and small trees. The few herbaceous plants present are mainly Rubiaceae, often in flower, indicating a good adaptation to the conditions of the ecotone. The diversity of physiognomic types shows an ecological complexity favorable to pollination and seed dispersal. These plant compositions are however characterized by a low diversity of species as shown by the high values of the Simpson index in the majority of sample squares. Floristic diversity is often low and species also have low abundances and densities, probably linked to a response to the very moderate humidity and light conditions of these sites.

Table 5. Contents of the last three sample squares made on the trail from Pointe Rouge to Pointe à Bibi, in Trinité.

			Square 4 (S12)					Square 5 (S13)					Square 6 (S14)
	Simpson index		0.50059453					0.26					0.223761157
No.	Species	Ph	H	A	D	Fl	F	H	A	D	Fl	F	H	A	D	Fl	F
1	Cassipourea guianensis	T	10	20	0.0020								10	10	0.0010
2	Erythroxylum havanense	Sh											20	1	0.0001
3	Eugenia ligustrina	Sh						10	2	0.0002			20	20	0.0020
4	Garcinia humilis	T	10	2	0.0002
5	Geophila repens	He		4+					3+
6	Guettarda odorata	Sh											10	10	0.0010
7	Inga laurina	T	10	2	0.0002
8	Myrcia citrifolia	Sh						50	3	0.0003			10	5	0.0005
9	Ocotea coriacea	T											20	1	0.0001
10	Oxalis frutescens	He						20	3	0.0003	Y
11	Pisonia fragans	T	15	3	0.0003			10	2	0.0002
12	Spermacoce assurgens	He											30	10	0.0010	Y
13	Tabebuia heterophylla	T	5	2	0.0002
14	Cassipourea guianensis	T	10	20	0.0020								10	10	0.0010
15	Erythroxylum havanense	Sh											20	1	0.0001
16	Eugenia ligustrina	Sh						10	2	0.0002			20	20	0.0020
17	Garcinia humilis	T	10	2	0.0002
18	Geophila repens	He		4+					3+
19	Guettarda odorata	Sh											10	10	0.0010

Legend. S: Survey/Ph: Physiognomic type in maximum morphogenetic development (T: Tree; Sh: Shrub; He: herbaceous)/H: Height in cm/A: Abundance/D: Density (cm²)/Fl: Flowers (Y: yes)/F: Fruits (Y: yes).

Furthermore, we note the presence of three Rubiaceae including Geophila repens, an herbaceous plant very widespread in the sample squares, forming fairly dense carpets whose individuals were difficult to differentiate and count. The species nevertheless seems very adapted to this ecotone, with an average to high abundance of individuals depending on the squares. Spermacoce assurgens is another herbaceous Rubiaceae present in a single square but with a relatively notable abundance and density. Its individuals were in flower when we visited. Finally, the shrub Guettarda odorata is also present in a single square with a relatively notable abundance and density.

3.1.4. Meso-Hygrophilous Forest Edges (Ecotone): Fond Baron

In the first surveys of this meso-hygrophilous ecotone, herbaceous plants predominate, with species such as Diodia ocymifolia and Hyptis atrorubens, often in flower. Plant diversity, both in terms of species and heights, is notable, even if the Simpson index values reveal high population abundances of the species Hyptis atrorubens or Wedelia trilobata. Many species were in flower during our visit, ensuring a strong attraction for pollinators and good seed dispersal. These transition zones with a moderate water supply allow species to adapt to humidity variations. The low density of plants seems to promote a balance between competition and survival in this partially shaded habitat (Table 6).

Table 6. Contents of the first three sample squares made at Fond Baron, in Fort-de-France.

			Square 1 (S15)					Square 2 (S16)					Square 3 (S17)
	Simpson index		0.58490566					0.514609765					0.516711111
No.	Species	Ph	H	A	D	Fl	F	H	A	D	Fl	F	H	A	D	Fl	F
1	Centella asiatica	He							2+
2	Commelina diffusa	He											30	40	0.0040
3	Desmodium incanum	He		3+										2+		Y
4	Diodia ocymifolia	He	70	1	0.0001	Y		70	6	0.0006	Y		30	2	0.0002	Y
5	Hyptis atrorubens	He	40	2	0.0002	Y		30	70	0.0070	Y		70	100	0.0100	Y
6	Leptochloa filiformis	He						20	1	0.0001	Y		20	3	0.0003	Y
7	Nautilocalyx melittifolius	He	30	3	0.0003
8	Nephrolepis multiflora	F							4+
9	Piper dilatatum	Sh	60	2	0.0002								15	3	0.0003
10	Pseudelephantopus spicatus	He						80	1	0.0001
11	Scleria pterota	He	70	5	0.0005	Y		50	4	0.0004
12	Vigna luteola	He							2+
13	Wedelia trilobata	He	50	40	0.0040	Y		30	20	0.0020	Y		80	2	0.0002	Y

Legend. S: Survey/Ph: Physiognomic type in maximum morphogenetic development (Sh: Shrub; He: herbaceous; F: Fern)/H: Height in cm/A: Abundance/D: Density (cm²)/Fl: Flowers (Y: yes)/F: Fruits (Y: yes).

The last sample squares at Fond Baron also show a diversified vegetation of mainly herbaceous species and mostly in flower (Table 7). The low values of the Simpson index confirm this floristic diversity and that no species dominates numerically with the exception of the high population abundance of Desmodium incanum in square 6 (Survey 20). The density of species is low, but the majority of these plants thrive in this humid environment, with a high production of flowers and fruits favoring reproduction. We note the presence of two Rubiaceae: Diodia ocymifolia (herbaceous) and Gonzalagunia hirsuta (shrub) whose abundances and densities are low. Diodia ocymifolia is nevertheless better distributed in the squares than Gonzalagunia hirsuta.

Table 7. Contents of the last three sample squares made at Fond Baron, in Fort-de-France.

			Square 4 (S18)					Square 5 (S19)					Square 6 (S20)
	Simpson index		0.2288					0.120661157					0.389010847
No.	Species	Ph	H	A	D	Fl	F	H	A	D	Fl	F	H	A	D	Fl	F
1	Boehmeria nivea	He	50	7	0.0007	Y
2	Centella asiatica	He		1+
3	Clerodendron paniculatum	He											40	2	0.0002
4	Commelina diffusa	He	20	2	0.0002	Y		20	5	0.0005			10	20	0.0020
5	Cyperus luzulae	He											50	3	0.0003	Y
6	Desmodium incanum	He						30	10	0.0010	Y		50	100	0.0100	Y
7	Diodia ocymifolia	He	50	7	0.0007	Y		40	3	0.0003	Y		50	2	0.0002	Y
8	Gonzalagunia hirsuta	Sh						50	4	0.0004
9	Hyptis atrorubens	He						30	10	0.0010	Y
10	Impatiens hawkeri	He											50	2	0.0002	Y
11	Leptochloa filiformis	He						30	5	0.0005			30	2	0.0002	Y
12	Nautilocalyx melittifolius	He	50	6	0.0006	Y		10	2	0.0002
13	Ocotea coriacea	T	20	1	0.0001
14	Piper dilatatum	Sh											30	5	0.0005
15	Scleria pterota	He						30	6	0.0006	Y
16	Sida rhombifolia	He						50	5	0.0005	Y
17	Vigna luteola	He												2+
18	Wedelia trilobata	He	30	2	0.0002	Y		30	5	0.0005	Y		40	40	0.0040	Y
19	Boehmeria nivea	He	50	7	0.0007	Y
20	Centella asiatica	He		1+

Legend. S: Survey/Ph: Physiognomic type in maximum morphogenetic development (T: Tree; Sh: Shrub; He: herbaceous)/H: Height in cm/A: Abundance/D: Density (cm²)/Fl: Flowers (Y: yes)/F: Fruits (Y: yes).

3.1.5. Hygrophilous Forest Edges: Boucher Plateau

Surveys conducted on the Plateau Boucher, in a hyper-humid bioclimate, reveal a hygrophilous environment that is particularly favorable to the development of herbaceous plants, characterized by abundant flowering (Table 8). Some species sometimes display high population density and abundance, while overall floristic diversity remains significant, as shown by the Simpson index. This illustrates the strong resilience and adaptability of species to wetlands. The production of flowers and fruits observed in many plants highlights the essential role of these edges as reproduction and dispersal habitats. In addition, the presence of two herbaceous Rubiaceae is noted. The first, Diodia ocymifolia is well distributed in all the squares but its abundances and densities are low. The second, Spermacoce sp. was difficult to determine and only has one individual, present in a single square.

Table 8. Contents of the sample squares made at Plateau Boucher, in Fonds-Saint-Denis.

			Square 1 (S21)				Square 2 (S22)				Square 3 (S23)				Square 4 (S24)				Square 5 (S25)
	Simpson index		0.374818338				0.444079474				0.289550781				0.235				0.273483948
No.	Species	Ph	H	A	D	Fl	H	A	D	Fl	H	A	D	Fl	H	A	D	Fl	H	A	D	Fl	F
1	Ageratum houstonianum	He					80	7	0.0007	Y
2	Boehmeria nivea	He																	70	1	0.0001	Y
3	Chloris inflata	He	90	50	0.0050	Y
4	Commelina diffusa	He													60	15	0.0015	Y
5	Cyperus surinamensis	He													30	2	0.0002	Y	60	1	0.0001	Y
6	Diodia ocymifolia	He	70	2	0.0002	Y	80	4	0.0004	Y	60	10	0.0010	Y	100	9	0.0009	Y	60	10	0.0010	Y
7	Hyptis atrorubens	He	50	5	0.0005		60	100	0.0100	Y					60	50	0.0050		60	20	0.0020
8	Kyllinga erecta var polyphylla	He													50	20	0.0020	Y	60	1	0.0001	Y
9	Leptochloa filiformis	He	50	3	0.0003	Y	60	4	0.0004	Y					20	6	0.0006	Y
10	Ludwigia octovalvis	He					80	1	0.0001						30	1	0.0001		100	1	0.0001	Y	Y
11	Nephrolepis multiflora	F		3+								3+				2+				3+
12	Oxalis barrelieri	He	70	8	0.0008	Y					30	7	0.0007	Y	40	1	0.0001
13	Phyllanthus urinaria	He																	60	4	0.0004		Y
14	Pseudelephantopus spicatus	He													40	6	0.0006
15	Rhynchospora polyphylla	He					60	10	0.0010
16	Rubus rosifolius	B									20	1	0.0001
17	Scleria pterota	He					90	2	0.0002		60	10	0.0010	Y
18	Sida rhombifolia	He									70	6	0.0006	Y
19	Spermacoce sp	He	40	1	0.0001
20	Vigna luteola	He	70	3	0.0003	Y		3+				2+				2+
21	Wedelia trilobata	He	60	15	0.0015		50	30	0.0030	Y	30	30	0.0030	Y	60	10	0.0010	Y	60	20	0.0020	Y

Legend. S: Survey/Ph: Physiognomic type in maximum morphogenetic development (B: Bush; He: herbaceous; F: Fern)/H: Height in cm/A: Abundance/D: Density (cm²)/Fl: Flowers (Y: yes)/F: Fruits (Y: yes).

3.1.6. Hygrophilous Forest Edges: Trace Des Jésuites

In the hygrophilous edges of the Trace des Jésuites, herbaceous species, particularly Hyptis atrorubens, largely dominate (Table 9). The Simpson index highlights a numerical dominance of certain species, moderately reducing floristic diversity. Despite an overall low density, the abundant flowering promotes the attraction of pollinators and the dispersal of seeds, demonstrating a balance between competition and survival in this shaded and very humid habitat. This plant diversity contributes to the ecological richness of these edges, which play a key role in maintaining biodiversity in a humid tropical environment. Among the species present, we regularly note Diodia ocymifolia and Spermacoce assurgens, whose densities and abundances generally remain low, although they can be locally high.

Table 9. Contents of the sample squares made at the Trace des Jésuites, in Morne Rouge.

			Square 1 (S26)					Square 2 (S27)					Square 3 (S28)					Square 4 (S29)
	Simpson index		0.43174876					0.91342448					0.414141414					0.50786808
No.	Species	Ph	H	A	D	Fl	F	H	A	D	Fl	F	H	A	D	Fl	F	H	A	D	Fl	F
1	Ageratum conyzoides	He	30	1	0.0001	Y												30	1	0.0001
2	Bidens pilosa	He	30	1	0.0001	Y
3	Cuphea carthagenensis	He	30	1	0.0001	Y												50	20	0.0020
4	Desmodium incanum	He	30	100	0.0100	Y		30	1	0.0001	Y		40	20	0.0020	Y
5	Diodia ocymifolia	He	30	10	0.0010	Y												50	30	0.0030	Y
6	Hyptis atrorubens	He	50	150	0.0150	Y		60	150	0.0150	Y							70	150	0.0150	Y
7	Kyllinga sp	He											30	2	0.0002
8	Oxalis barrelieri	He											30	3	0.0003	Y		30	3	0.0003	Y
9	Polygala paniculata	He											30	1	0.0001	Y
10	Pseudelephantopus spicatus	He	50	1	0.0001			25	3	0.0003
11	Pterolepis glomerata	He	15	1	0.0001													40	1	0.0001
12	Rhynchospora nervosa	He	30	6	0.0006
13	Sauvagesia erecta	He						30	1	0.0001	Y		30	1	0.0001	Y
14	Scleria pterota	He	50	3	0.0003													50	10	0.0010
15	Spermacoce assurgens	He	30	1	0.0001	Y		30	2	0.0002	Y		40	6	0.0006	Y		30	2	0.0002	Y

Legend. S: Survey/Ph: Physiognomic type in maximum morphogenetic development (He: herbaceous)/H: Height in cm/A: Abundance/D: Density (cm²)/Fl: Flowers (Y: yes)/F: Fruits (Y: yes).

3.2. Global Data Analysis Using CAH, AFC and ACP

3.2.1. Ascending Hierarchical Classification (HAC)

A hierarchical ascending classification (HAC) was carried out using a presence/absence table of all species. It is composed of 96 columns (species of all families, all physiognomic types included) and 29 rows (surveys or sample squares), (Appendix 3). The general dissimilarity and the “complete link” aggregation method offered the possibility of showing the differences in floristic compositions between our surveys, in the form of distinct groups or classes. The dendrograms obtained thus show five main groups or classes (Figure 6 and Table 10). These groups demonstrate a great heterogeneity of floristic compositions. While the majority of our edge surveys reflect the typical vegetation of adjacent forests, some have particularities that distinguish them from this general model (Table 10). The surveys of groups or classes 3 and 5, initially different in their location, nevertheless show a convergence of their floristic composition. Among the species that compose them, a significant number could be described as “erratic”, reflecting an ecological flexibility that could be linked to the dynamic conditions of these edges.

Figure 6. Dendrogram of dissimilarity of the 29 surveys according to their floristic composition.

Table 10. Typology of stations according to their floristic compositions.

No.	Intra-class variance	Surveys	Corresponding bioclimate type	Corresponding forest type	Floristic composition
CLASS 1	0000	S1	Dry Subhumid	Xerophilous	Diversity of physiognomic types of species (tree, shrub, herbaceous, liana). Relatively low floristic diversity. Presence of two Rubiaceae Diodia ocymifolia and Spermacoce verticillata.
CLASS 2	0000	S2	Dry Subhumid	Xerophilous	Diversity of physiognomic types of species (tree, shrub, herbaceous, liana). Relatively high floristic diversity. Presence of only one Rubiaceae: Spermacoce verticillata.
CLASS 3	4911	S3; S4; S9; S10; S11; S12; S13; S14; S27; S28.	Dry Subhumid/ Ecotone (dry subhumid to humid subhumid)/ Hyper humid	Xerophilous/ Xero-mesophilous/ Hygrophilous	Mixed composition of several types of edges. Diversity of physiognomic types of species (tree, shrub, herbaceous, liana). Low to high floristic diversity. Regular presence of several Rubiaceae: Diodia ocymifolia, Geophila repens, Guettarda odorata, Spermacoce assurgens.
CLASS 4	5750	S5; S6; S7; S8.	Dry Subhumid	Xerophilous	Diversity of physiognomic types of species (tree, shrub, bush, herbaceous, liana). Relatively high floristic diversity. Presence of only one Rubiaceae: Spermacoce verticillata.
CLASS 5	5308	S15; S16; S17; S18; S19; S20; S21; S22; S23; S24; S25; S26; S29.	Ecotone (humid to humid subhumid)/Hyper humid	Meso-hygrophilous/Hygrophilous	Mixed composition of several types of edges exclusively from humid bioclimates. Diversity of physiognomic types of species (tree, shrub, herbaceous, ferns). Moderate to high floristic diversity. Regular presence of several Rubiaceae: Diodia ocymifolia, Gonzalagunia hirsuta, Spermacoce assurgens. Spermacoce sp.

This analysis suggests that forest edges play a role as transitional habitats, serving as intermediate zones between forest ecosystems and other types of environments. They thus shelter a diverse set of species with varied ecological profiles. These areas could therefore contribute to regional diversity by supporting populations of species with varied ecological needs, some of which do not find favorable conditions in dense forests or adjacent open spaces.

3.2.2. Factorial Correspondence Analysis (FCA)

A factorial correspondence analysis (FCA) was performed using the same species presence/absence table, composed of 96 columns (species from all families, all physiognomic types included) and 29 rows (surveys or sample squares). Only the Hellinger distance allows to obtain a link between rows and columns, with the p-value (1.000) almost similar to the alpha significance level (0.9999), but the F1 and F2 axes support more than 30% of the information and give the best possible quality of data representation (Figure 7).

These axes demonstrate that the floristic compositions of our surveys are very heterogeneous (Figure 7, Table 10). While the floristic composition of the majority of our surveys reflects the adjacent forest type, some surveys are exceptions.

Figure 7. Factorial correspondence analysis (Appendix 2 and Appendix 3).

Survey 28 carried out in a hyper-humid bioclimate at the Trace des Jésuites, for example, stands out from other surveys of the same bioclimate, and the surveys of the dry subhumid bioclimate, xerophilous forests, are split into two distinct groups (Figure 7). Forest edges therefore appear to constitute transitional habitats, sheltering large pools of species with different ecological profiles, including a significant number of so-called “erratic” species.

3.2.3. Principal Component Analysis (PCA)

A principal component analysis (PCA) was also carried out, this time using a cross-tabulation of data, composed of 29 rows (surveys or sample squares) and 7 columns (eco-climatic factors), (Appendix 2).

The eco-climatic factors that we took into account were as follows: altitude (meter), slope (%), annual rainfall (mm), average minimum annual temperature (˚C), average maximum annual temperature (˚C), soil type and level of sunshine. For these last two parameters, we had to assign numerical values to each variable in order to be able to take them into account. Thus, the numerical variables are as follows for the types of soils: Marine alluvium (1), Vertisols (2), Fersiallitic soils (3), Red or brown montmorillonitic soils (4). The numerical variables are as follows for the level of sunshine: medium (1), high (2). The links between the variables are very well taken into account, because the F1 and F2 axes of the PCA obtained using the Person Coefficient, support more than 90% of the information and give an excellent quality of their representation (Figure 8).

Figure 8 shows four groups of coherent surveys according to the ecological differences between the areas studied. Axis F1 organizes the surveys mainly according to humidity, altitude and shade gradients. It contrasts areas adapted to dry and open environments (edges of xerophilous and xero-mesophilous forests)

Figure 8. Principal component analysis of the eco-climatic factor matrix (Appendix 2). Legend. T_min = Average annual minimum temperatures, T_max = Average annual maximum temperatures.

with areas adapted to humid and shaded environments (edges of meso-hygrophilous and hygrophilous forests). Axis F2, on the other hand, allows us to single out the surveys of ecotones (transition zones). This PCA attests to the plurality of forest edges inventoried in various bioclimates.

4. Discussion

Finally, five species of herbaceous Rubiaceae divided into three genera were recorded at forest edges: Diodia ocymifolia, Geophila repens, Spermacoce assurgens, Spermacoce verticillata and an undetermined species, Spermacoce sp. Two shrubby Rubiaceae, Gonzalagunia hirsuta and Guettarda odorata, were also observed. This low number of species confirms the rarity of herbaceous Rubiaceae, although additional inventories are necessary (Table 11) [2] [3] [8].

Table 11. Contents of the sample squares made at Plateau Boucher, in Fonds-Saint-Denis.

Bioclimate			Dry subhumid				Ecotone (transition between dry subhumid and humid subhumid)				Ecotone (subhumid humid to hyperhumid)				Hyper humid
Forest edge			Xerophilous				Xero-mesophilous				Meso-hygrophilous				Hygrophilous
No.	Species	Ph	A	D	F	Id	A	D	F	Id	A	D	F	Id	A	D	F	Id
1	Diodia ocymifolia	He	90	11.25	2	2.81					21	4	6	3.5	75	8	7	6.48
2	Geophila repens	He					3+		5
3	Gonzalagunia hirsuta	Sh									4	1	1	0.11
4	Guettarda odorata	Sh	1	0.125	1	0.01	10	2	1	0.27
5	Spermacoce assurgens	He													11	1	4	0.54
6	Spermacoce sp	He													1	0	1	0.01
7	Spermacoce verticillata	He	5	0.625	5	0.39	10	2	1	0.27

Legend. Ph: Physiognomic type in maximum morphogenetic development (Sh: Shrub; He: herbaceous)/A: Abundance/D: Density (cm²)/F: Frequency/Id: Distribution index.

Among these species, Diodia ocymifolia stands out for its high frequency, high density and wide distribution in various types of edges, demonstrating tolerance to humidity variations and notable competitiveness. Geophila repens forms dense mats in xero-mesophilic ecotones, while Spermacoce assurgens prefers wetter edges, where its distribution is notable but its abundance low. Spermacoce verticillata, on the other hand, is confined to xerophilous and xero-mesophilous edges, with a more marked presence in dry environments, while Spermacoce sp. is limited to a single individual recorded. The observed herbaceous Rubiaceae, except Diodia ocymifolia, show specific ecological preferences, limiting their distribution. These observations highlight the importance of forest edges as intermediate habitats hosting a variety of species, ranging from plants tolerant to fluctuating conditions to specialized species [23]-[25]. Some edges, particularly in humid bioclimates, display relatively high diversity, while those dominated by pioneer species such as Diodia ocymifolia display more restricted diversity. These variations reflect the influence of environmental conditions on the structure of plant communities [15]-[20]. These observations made on the island of Martinique find parallels in other tropical regions where certain species of Rubiaceae show great tolerance to environmental variations.

Studies conducted in Forest Guinea reveal, for example, that Rubiaceae are among the most represented families, illustrating their adaptation to varied ecological conditions [37]. Forest edges, located at the interface between open environments and forests, undoubtedly play a key role in the conservation of regional biodiversity in Martinique, by providing refuges and ecological corridors between different habitats [23]-[25].

5. Conclusion

At the end of a campaign of 29 floristic surveys carried out in the forest edges of the island of Martinique, our results confirm the influence of ecological variations, particularly in terms of light availability and humidity, on the distribution and floristic composition of herbaceous Rubiaceae. Although they represent a small proportion of the Rubiaceae present on the island, these plants show a great capacity to adapt to environmental gradients, allowing certain species, such as Diodia ocymifolia, to occupy both xerophilous and humid areas. Other species have a more restricted distribution, suggesting specific ecological preferences. These observations highlight the importance of forest edges as dynamic ecological corridors, offering a diversity of niches conducive to the cohabitation of species with varied ecological needs. By promoting pollination and seed dispersal, these transitional habitats play a crucial role in the resilience of plant communities. This study therefore highlights the need to preserve these areas in order to maintain the floristic and functional biodiversity of the island forest ecosystems of Martinique.

Acknowledgements

The floristic inventories were carried out with the help of several members of the Association of Martinican Botanists (ABM) between 2015 and 2020: Mr Patrick Rancelli, Ms Martine Despointes, Ms Geneviève Baral, Ms Catherine Blanchard, Ms Ghislaine Volny-Anne, Ms Karine Jaffory, Ms Monique Duval and Ms Josette Brival. Several eco-climatic and administrative data, usable in GIS software, were collected from public institutions: Météo-France (French meteorological organization), IRD (Research Institute for Development), IGN (National Geographic Institute). Sincere thanks to the University Professor, head of the UMR ESPACE DEV-BIORECA research group at the University of the Antilles, Mr. Philippe JOSEPH for proofreading the text.

Data Availability

There is no data available, made available to readers. On the other hand, data for woody Rubiaceae are available from the thesis conducted on Rubiaceae in Martinique, accessible online (https://theses.fr/2020ANTI0548).

Appendix 1. List of Herbaceous Rubiaceae in the Lesser Antilles [2] [3] [10]

No.	Scientific name	Synonymy	Presence in Martinique	Flowering period	Estimation of abundance	Endemism	Threat status in Martinique (INPN)
1	Diodia ocymifolia	Spermacoce ocymifolia	Yes	Almost all year round.	Common		Not rated
2	Diodia rigida	Hexasepalum apiculatum	Yes		Rare
3	Géophila repens		Yes		Quite rare		Not rated
4	Hedyotis callitrichoides	Oldenlandiopsis callitrichoides		During the rainy season.	Rare
5	Hedyotis corymbosa	Oldenlandia corymbosa	Yes	Almost all year round.	Quite rare		Not rated
6	Hedyotis lancifolia	Oldenlandia lancifolia	Yes		Quite rare		Not rated
7	Hoffmannia pedunculata				Very rare	Possibly endemic to Jamaica.
8	Mitracarpus hirtus		Yes	Almost all year round, intermittently.	Quite common		Not rated
9	Mitracarpus polycladus
10	Pentodon pentandrus			All year round, except for exceptional drought.	Quite rare
11	Psychotria discolor	Notopleura discolor	Yes	All year round.	Quite rare		Not rated
12	Psychotria gardenioides		Yes		Very rare
13	Serissa foetida				Very rare
14	Sipanea pratensis				Very rare
15	Spermacoce assurgens	Spermacoce remota	Yes	All year round.	Very common		Not rated
16	Spermacoce berteroana				Rare	Lesser Antilles
17	Spermacoce confusa		Yes	Almost all year round.	Quite rare		Not rated
18	Spermacoce densiflora		Yes		Rare		Not rated
19	Spermacoce dussii			Almost all year round, except during long droughts.	Quite rare	Guadeloupe
20	Spermacoce eryngioides		Yes	Almost all year round.	Common		Not rated
21	Spermacoce ernstii
22	Spermacoce latifolia			All year round.	Quite common
23	Spermacoce prostrata		Yes	Almost all year round.	Common		Not rated
24	Spermacoce riparia	Spermacoce laevis			Quite common
25	Spermacoce tetraquetra
26	Spermacoce verticillata		Yes		Quite rare		Not rated

Appendix 2. List of the 29 Floristic Surveys

No.	Location	Latitude	Longitude	Tmin	Tmax	Annual Rainfall	Level of sunshine	Altitude	Slope	Soil
S1	Cap Macré	1601537.462	735661.077	23.6	29	1641	high	1	0%	Marine alluvium
S2	Cap Macré	1601600.46	734691.971	23.4	28.8	1685	high	3	1%	Vertisols
S3	Cap Macré	1601524.257	734636.176	23.4	28.8	1685	high	5	8.9%	Vertisols
S4	Cap Macré	1601518.844	734630.42	23.4	28.8	1685	high	5	8.9%	Vertisols
S5	Morne Aca	1599875.254	726377.855	22.6	28.4	1697	high	224	12%	Vertisols
S6	Morne Aca	1599786.339	726327.511	22.6	28.4	1697	high	214	3%	Vertisols
S7	Morne Aca	1599757.151	726323.398	22.6	28.4	1697	high	213	17.7	Vertisols
S8	Morne Aca	1599751.683	726320.491	22.6	28.4	1697	high	213	17.7%	Vertisols
S9	Pointe Rouge to Pointe à Bibi	1632851.888	723003.514	23.8	30.6	1945	medium	18	18%	Fersiallitic soils
S10	Pointe Rouge to Pointe à Bibi	1632881.348	723004.832	23.8	30.6	1945	medium	13	16.7%	Fersiallitic soils
S11	Pointe Rouge to Pointe à Bibi	1632882.75	723002.278	23.8	30.6	1945	medium	13	16.7%	Fersiallitic soils
S12	Pointe Rouge to Pointe à Bibi	1632860.584	722994.881	23.8	30.6	1994	medium	18	18%	Fersiallitic soils
S13	Pointe Rouge to Pointe à Bibi	1632866.9	722995.6	23.8	30.6	1994	medium	13	16.7%	Fersiallitic soils
S14	Pointe Rouge to Pointe à Bibi	1632889.671	722745.591	23.8	30.6	1994	medium	58	30.5%	Fersiallitic soils
S15	Fond Baron	1623498.353	705354.726	20.2	26.8	2613	medium	433	31%	Red or brown montmorillonitic soils
S16	Fond Baron	1623495.12	705339.001	20.2	26.8	2613	medium	433	31%	Red or brown montmo-rillonitic soils
S17	Fond Baron	1623560.645	705379.985	20.2	26.8	2613	medium	427	19.8%	Red or brown montmo-rillonitic soils
S18	Fond Baron	1623545.479	705429.188	20.2	26.8	2613	medium	420	31.7%	Red or brown montmo-rillonitic soils
S19	Fond Baron	1623539.652	705417.459	20.2	26.8	2613	medium	420	31.7%	Red or brown montmo-rillonitic soils
S20	Fond Baron	1623568.246	705489.718	20.2	26.8	2613	medium	407	49%	Red or brown montmo-rillonitic soils
S21	Plateau Boucher	1628052.279	704912.979	18.6	25.6	5088	medium	635	20.5%	Red or brown montmo-rillonitic soils
S22	Plateau Boucher	1628047.851	704955.099	18.6	25.6	5088	medium	635	18.8%	Red or brown montmo-rillonitic soils
S23	Plateau Boucher	1628046.581	704977.844	18.6	25.6	5088	medium	635	17.6%	Red or brown montmo-rillonitic soils
S24	Plateau Boucher	1627971.113	705070.648	19.6	26.6	4532	medium	615	17.5%	Red or brown montmo-rillonitic soils
S25	Plateau Boucher	1627899.66	705114.617	19.6	26.6	4532	medium	619	30.4%	Red or brown montmo-rillonitic soils
S26	Trace des Jésuites	1630489.461	704634.000	18.9	25.8	5343	medium	550	25.7%	Red or brown montmo-rillonitic soils
S27	Trace des Jésuites	1630538.9	704623.0	18.9	25.8	5343	medium	546	14.9%	Red or brown montmo-rillonitic soils
S28	Trace des Jésuites	1630570.1	704619.1	18.9	25.8	5343	medium	540	35.4%	Red or brown montmo-rillonitic soils
S29	Trace des Jésuites	1630613.0	704602.7	18.9	25.8	5343	medium	542	37%	Red or brown montmo-rillonitic soils

Appendix 3. List of the 96 Species Recorded

No.	Family	Name Species	Synonymy	Physiognomy in maximum morphogenetic development	Invasive in Martinique according to DEAL	Abbreviations
1	Fabaceae	Abrus precatorius		Liana		ABPRE
2	Asteraceae	Ageratum conyzoides		Herbaceous		AGCON
3	Asteraceae	Ageratum houstonianum		Herbaceous		AGHOU
4	Asteraceae	Bidens pilosa		Herbaceous		BIDPIL
5	Asteraceae	Bidens sp		Herbaceous		BIDSP
6	Urticaceae	Boehmeria nivea		Herbaceous		BOEHIV
7	Burseraceae	Bursera simaruba		Tree		BURSIM
8	Scrophulariaceae	Capraria biflora		Herbaceous		CAPBIF
9	Rhizophoraceae	Cassipourea guianensis		Tree		CASGUI
10	Poaceae	Cenchrus echinatus		Herbaceous		CENECH
11	Apiaceae	Centella asiatica		Herbaceous		CENASI
12	Fabaceae	Centrosema virginianum		Liana		CEVIR
13	Caesalpiniaceae	Chamaecrista glandulosa var schwarzii		Shrub		CHAGLAN
14	Caesalpiniaceae	Chamaecrista nictitans		Shrub		CHANIC
15	Caesalpiniaceae	Chamaecrista obcordata		Shrub		CHAOB
16	Euphorbiaceae	Chamaesyce hirta	Euphorbia hirta	Herbaceous		CHAHIR
17	Poaceae	Chloris inflata	Chloris barbata	Herbaceous		CHINF
18	Verbenaceae	Citharexylum spinosum		Tree		CITSPI
19	Verbenaceae	Clerodendron paniculatum		Herbaceous	Yes	CLERPAN
20	Commelinaceae	Commelina diffusa		Herbaceous		COMDIF
21	Boraginaceae	Cordia collococca		Tree		CORDCOL
22	Euphorbiaceae	Croton bixoides		Shrub		CROBIX
23	Lythraceae	Cuphea carthagenensis		Herbaceous		CUPCAR
24	Convolvulaceae	Cuscuta americana		Liana		CUSAME
25	Cyperaceae	Cyperus luzulae		Herbaceous		CYPLUZ
26	Cyperaceae	Cyperus surinamensis		Herbaceous		CYPSUR
27	Fabaceae	Desmodium heterocarpum		Herbaceous		DESHET
28	Fabaceae	Desmodium incanum		Herbaceous		DESINC
29	Fabaceae	Desmodium sp		Herbaceous		DESSP
30	Mimosaceae	Dichrostachys cinerea		Shrub	Yes	DICCIN
31	Rubiaceae	Diodia ocymifolia	Spermacoce ocymifolia	Herbaceous		DIOCY
32	Cyperaceae	Eleocharis flavescens		Herbaceous		ELEOFLA
33	Gentianaceae	Enicostema verticillatum		Herbaceous		ENVER
34	Poaceae	Eriochloa polystachya		Herbaceous		ERPOL
35	Erythroxylaceae	Erythroxylum havanense		Shrub		ERYTHAV
36	Myrtaceae	Eugenia cordata		Shrub		EUCOR
37	Myrtaceae	Eugenia ligustrina		Shrub		EULIG
38	Myrtaceae	Eugenia monticola		Bush		EUMON
39	Clusiaceae	Garcinia humilis		Tree		GARCHUM
40	Rubiaceae	Geophila repens		Herbaceous		GEOREP
41	Rubiaceae	Gonzalagunia hirsuta		Shrub		GONHIR
42	Rubiaceae	Guettarda odorata		Shrub		GUETODO
43	Caesalpiniaceae	Haematoxylum campechianum		Tree		HAECAM
44	Boraginaceae	Heliotropium ternatum	Euploca ternata	Herbaceous		HELTER
45	Lamiaceae	Hyptis atrorubens		Herbaceous		HYPATR
46	Balsaminaceae	Impatiens hawkeri		Herbaceous		IMPHAW
47	Mimosaceae	Inga laurina		Tree		INGLAU
48	Convolvulaceae	Ipomoea setifera		Liana		IPOSET
49	Cyperaceae	Kyllinga erecta var polyphylla		Herbaceous		KYLPOL
50	Cyperaceae	Kyllinga sp		Herbaceous		KYLSP
51	Poaceae	Leptochloa filiformis		Herbaceous		LEPFIL
52	Mimosaceae	Leucaena leucocephala		Tree		LEULEU
53	Fabaceae	Lonchocarpus punctatus		Tree		LONPUN
54	Onagraceae	Ludwigia octovalvis		Herbaceous		LUDOCT
55	Bignoniaceae	Macfadyena unguis-cati	Dolichandra unguis-cati	Liana		MACUNG
56	Myrtaceae	Myrcia citrifolia		Shrub		MYRCIT
57	Gesneriaceae	Nautilocalyx melittifolius	Chrysothemis melittifolia	Herbaceous		NAUMEL
58	Nephrolepidaceae	Nephrolepis multiflora		Fern		NEPMUT
59	Lamiaceae	Ocimum gratissimum		Herbaceous		OCIGRA
60	Lauraceae	Ocotea coriacea	Damburneya coriacea	Tree		OCOCOR
61	Oxalidaceae	Oxalis barrelieri		Herbaceous		OXABAR
62	Oxalidaceae	Oxalis frutescens		Herbaceous		OXAFRUT
63	Poaceae	Paspalum conjugatum		Herbaceous		PASPCON
64	Sapindaceae	Paullinia cururu		Liana		PAULCUR
65	Euphorbiaceae	Phyllanthus urinaria	Emblica urinaria	Herbaceous		PHYLURI
66	Piperaceae	Piper dilatatum		Shrub		PIPDIL
67	Nyctaginaceae	Pisonia fragans		Tree		PISFRA
68	Mimosaceae	Pithecellobium unguis-cati		Tree		PITUNG
69	Polygalaceae	Polygala paniculata		Herbaceous		POLPAN
70	Asteraceae	Pseudelephantopus spicatus		Herbaceous		PSEUSPI
71	Melastomataceae	Pterolepis glomerata		Herbaceous		PTERGLO
72	Cyperaceae	Rhynchospora nervosa		Herbaceous		RHYNER
73	Cyperaceae	Rhynchospora polyphylla		Herbaceous		RHYNPOL
74	Rosaceae	Rubus rosifolius		Bush		RUBROS
75	Ochnaceae	Sauvagesia erecta		Herbaceous		SAUEREC
76	Cyperaceae	Scleria pterota	Scleria melaleuca	Herbaceous		SCLERPTER
77	Polygalaceae	Securidaca diversifolia		Liana		SECUDIV
78	Malvaceae	Sida acuta		Herbaceous		SIDACU
79	Malvaceae	Sida rhombifolia		Herbaceous		SIDARHO
80	Malvaceae	Sida sp		Herbaceous		SIDASP
81	Rubiaceae	Spermacoce assurgens	Spermacoce remota	Herbaceous		SPERASU
82	Rubiaceae	Spermacoce sp		Herbaceous		SPERSP
83	Rubiaceae	Spermacoce verticillata		Herbaceous		SPERVER
84	Loganiaceae	Spigelia anthelmia		Herbaceous		SPIGANT
85	Anacardiaceae	Spondias mombin		Tree		SPONMON
86	Poaceae	Sporobolus jacquemontii		Herbaceous		SPORJAC
87	Verbenaceae	Stachytarpheta jamaicensis		Herbaceous		STACJAM
88	Verbenaceae	Stachytarpheta sp		Herbaceous		STACSP
89	Asteraceae	Synedrella nodiflora		Herbaceous		SYNNOD
90	Bignoniaceae	Tabebuia heterophylla		Tree		TABHET
91	Euphorbiaceae	Tragia volubilis		Liana		TRAGVOL
92	Malvaceae	Urena lobata		Bush		URELOB
93	Sapindaceae	Urvillea ulmacea		Liana		URVULM
94	Asteraceae	Vernonia cinerea	Cyanthillium cinereum	Herbaceous		VERCIN
95	Fabaceae	Vigna luteola		Herbaceous		VIGLUT
96	Asteraceae	Wedelia trilobata	Sphagneticola trilobata	Herbaceous		WEDTRI