1. Adaptive evolution is a major driver of organism diversification but the links between phenotypic traits and environmental niche remains little documented in tropical trees. Moreover, trait-niche relationships are complex because a correlation between the traits and environmental niches displayed by a sample of species may result from (1) convergent evolution if different environmental conditions have selected different sets of traits, and/or (2) phylogenetic inertia if niche and morphological differences between species are simply function of their phylogenetic divergence, in which case the trait-niche correlation does not imply any direct causal link. Here, we aim to assess the respective roles of phylogenetic inertia and convergent evolution in shaping the differences of botanical traits and environmental niches among congeneric African tree species that evolved in different biomes.
2. This issue was addressed with the tree genus Guibourtia Benn. (Leguminosae, Detarioideae) which contains 13 African species occupying various forest habitat types, from rain forest to dry woodlands, with different climate and soil conditions. To this end, we combined morphological data with ecological niche modelling and used a highly resolved plastid phylogeny of the 13 African Guibourtia species.
3. First, we demonstrated phylogenetic signals in both morphological traits (Mantel test between phylogenetic and morphological distances between species: r=0.24, p=0.031) and environmental niches (Mantel test between phylogenetic and niche distances between species: r=0.23, p=0.025). Second, we found a significant correlation between morphology and niche, at least between some of their respective dimensions (Mantel’s r=0.32, p=0.013), even after accounting for phylogenetic inertia (Phylogenetic Independent Contrast: r=0.69, p=0.018). This correlation occurred between some leaflet and flower traits and solar radiation, relative humidity, precipitations and temperature range.
4. Our results demonstrate the convergent evolution of some morphological traits in response to climatic factors in congeneric tree species and highlight the action of selective forces, along with neutral ones, in shaping the divergence between congeneric tropical plants.

Information contained in the attached files

det.img - etp.img - PH1.img - prc.img - rhu.img - shr.img - temp.img - wnd.img : Climate (temperature range (°C); Potential evapotranspiration (mm); precipitation (mm); relative humidity (%); solar radiation (w/m²); temperature (°C) and wind speed (m/s)) and soil (pH) data were extracted from the Climatic Research Unit (CRU) of the University of East Anglia (New et al., 1999; Mitchell and Jones, 2005) and “FAO Digital Soil Map of the World, version 3.6”

guibourtia_data_401_sp.txt : occurrence points of the 13 Guibourtia species were used to model the species environmental niches.

data_morpho.xls : morphological database used in this paper. A total of 281 georeferenced herbarium samples were used for the morphological analyses

Env_281_data.txt: geographical coordinate and climate and soil data for each herbarium samples