Print PagePhylogenetic Diversity (PD) measures the shortest spanning pathway in the phylogenetic tree for a given set of taxa. Its magnitude is influenced by both the number of component taxa and their genetic divergence. The standard plant DNA barcodes of two plastid markers (rbcL, matK) were generated for 700 species (465 genera, 122 families) of angiosperms from an 110,000 hectare terrestrial portion of Area de Conservacion Guanacaste (ACG), northwestern Costa Rica. Separate community phylogenies were derived for the species collected from three separate sub-ecosystems: Sector Santa Rosa (dry forest), Sector Rincon Rain Forest (rain forest), and Sector Cacao (cloud forest). Our goal was to evaluate the robustness of the results with either of the two barcode markers as well as the standard two locus barcode. Correlation with the species, generic, and family level richness in each particular ecosystem were compared with PD. We have used a ML (GARLI) phylogenetic analysis to reconstruct the community phylogenetic structure. The same analysis was repeated for the whole set of 700 species with rbcL sequences which allowed the inclusion the species-rich groups where sequencing success was low for matK.
Results/Conclusions
PD was not correlated with the species richness in each ecosystem. Instead it reflects the divergence time of the taxa in each ecosystem. The dry forest of Sector Santa Rosa possessed the lowest PD value in relation to the number of species reflected by the close affinities of species within big families (Fabaceae, Rubiaceae). Surprisingly, the Cloud forest of Sector Cacao showed higher PD then rain forest. It is more affected by over-dispersal assembly mechanisms where the species-rich communities represented by taxonomically distant lineages. Determinants of PD values are evaluated and discussed.
