D. K., B. | bioRxiv Science

bioRxiv2022

Range restricted old and young lineages show the southern Western Ghats to be both museum and cradle of diversity for woody plants

The Western Ghats (WG) mountain chain is a global biodiversity hotspot with high diversity and endemicity of woody plants. The latitudinal breadth of the WG offers an opportunity to determine the evolutionary drivers of latitudinal diversity patterns. We examined the spatial patterns of evolutionary diversity using complementary phylogenetic diversity and endemism measures. To examine if different regions of the WG serve as a museum or cradle of evolutionary diversity, we examined the distribution of 470 species based on distribution modelling and occurrence locations across the entire region. In accordance with the expectation, we found that the southern WG is both a museum and cradle of woody plant evolutionary diversity, as a higher proportion of both old and young evolutionary lineages are restricted to the southern WG. The diversity gradient is likely driven by high geo-climatic stability in the south and phylogenetic niche conservatism for moist and aseasonal sites. This is corroborated by persistent lineage nestedness at almost all evolutionary depths (10-135 million years), and a strong correlation of evolutionary diversity with drought seasonality, precipitation and topographic heterogeneity. Our results highlight the global value of the WG, demonstrating, in particular, the importance of protecting the southern WG - an engine of plant diversification and persistence.

evolutionary biology↗

bioRxiv2020

Spatial patterns of phylogenetic diversity and endemism in the Western Ghats, India: a case study using ancient predatory arthropods

Abstract and keywordsO_ST_ABSAimC_ST_ABSTo study patterns of phylogenetic diversity, endemism and turnover in a community of ancient arthropods across a biodiversity hotspot. Our specific aims were to understand diversity gradients, identify hotspots of endemism and conservation importance, and highlight poorly-studied areas with unique biodiversity. LocationThe Western Ghats (WG), India MethodsWe compiled a location data-set for 19 scolopendrid centipedes species which was used to predict areas of habitat suitability using bioclimatic and geomorphological variables in Maxent. We used predicted distributions and time-calibrated species phylogeny to calculate taxonomic and phylogenetic indices of diversity, endemism and turnover. ResultsWe observed a decreasing gradient in Taxonomic and Phylogenetic Diversity (TD/PD) from the southern to northern WG and high Phylogenetic Endemism (PE) in the southern and northern WG. Southern WG had the highest diversity and was represented by lineages with long branch lengths and short ranges as observed from Relative Phylogenetic Diversity/Endemism (RPD and RPE). Despite having low PD, the northern WG had high values of PE represented by distinct lineages as inferred from RPE. Sites across the Palghat Gap grouped separately in comparisons of species turnover along the WG. Main conclusionsOur findings support expectations from the latitudinal diversity gradient in the WG and the southern WG refuge hypotheses. The high diversity and endemism along with the presence of ancient lineages in the southern WG is consistent with in-situ speciation. Climatic differences or dispersal barriers might have retained this diversity locally. High phylogenetic endemism in lateritic plateaus of the northern WG, albeit with low phylogenetic diversity, indicates the presence of distinct evolutionary lineages that might be adapted to life in these landscapes characterized by poor soil conditions and seasonal ephemeral habitats. Our results from soil arthropods highlight the need to use phylogeny and distribution data while assessing diversity and endemism patterns in the WG.

evolutionary biology↗