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

Abstract

The Western Ghats (WG) mountain chain in peninsular India is a global biodiversity hotspot, one in which patterns of phylogenetic diversity and endemism remain to be documented across taxa. We used a well-characterized community of ancient soil predatory arthropods from the WG to understand diversity gradients, identify hotspots of endemism and conservation importance, and highlight poorly studied areas with unique biodiversity. We compiled an occurrence dataset for 19 species of scolopendrid centipedes, which was used to predict areas of habitat suitability using bioclimatic and geomorphological variables in Maxent. We used predicted distributions and a time-calibrated species phylogeny to calculate taxonomic and phylogenetic indices of diversity, endemism, and turnover. We observed a decreasing latitudinal gradient in taxonomic and phylogenetic diversity in the WG, which supports expectations from the latitudinal diversity gradient. The southern WG had the highest phylogenetic diversity and endemism, and was represented by lineages with long branch lengths as observed from relative phylogenetic diversity/endemism. These results indicate the persistence of lineages over evolutionary time in the southern WG and are consistent with predictions from the southern WG refuge hypothesis.The northern WG, despite having low phylogenetic diversity, had high values of phylogenetic endemism represented by distinct lineages as inferred from relative phylogenetic endemism. The distinct endemic lineages in this subregion might be adapted to life in lateritic plateaus characterized by poor soil conditions and high seasonality.Sites across an important biogeographic break, the Palghat Gap, broadly grouped separately in comparisons of species turnover along the WG. The southern WG and Nilgiris, adjoining the Palghat Gap, harbor unique centipede communities, where the causal role of climate or dispersal barriers in shaping diversity remains to be investigated. Our results highlight the need to use phylogeny and distribution data while assessing diversity and endemism patterns in the WG.

New species of Cocalus C.L. Koch, 1846 and Habrocestum Simon, 1876 (Araneae: Salticidae) from the South Western Ghats of India

“…Of them, 42 species (46%) are endemics [Sen, Sureshan, 2020;Caleb, Sankaran, 2022]. Compared to few vertebrate [Vijaykumar et al, 2016] and invertebrate groups [Bharti et al, 2021;Johnson et al, 2022] whose diversity has been fairly studied, the salticid taxonomy and diversity in the WG is yet to be fully explored. Therefore, extensive surveys and studies are required to discover a real diversity of the salticids occurring in the WG.…”

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

“…The code for the SDMs was modified from Bharti et al . [46] (). Spatial data were processed using the packages ‘rgeos’ [47], ‘raster’ [48], ‘sf’ [49], ‘sp’ [50], and Maxent models were run using the package ‘ENMeval’ [51] and ‘dismo’ [52] in R 4.1.1 [53].…”

“…However, we decided to focus on the former to get a conservative estimate of species distributions [45]. The code for the SDMs was modified from Bharti et al [46] (https://github.com/bhartidk/centipede_diversity_endemism). Spatial data were processed using the packages 'rgeos' [47], 'raster' [48], 'sf' [49], 'sp' [50], and Maxent models were run using the package 'ENMeval' [51] and 'dismo' [52] in R 4.1.1 [53].…”

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

“…However, we decided to focus on the former to get a conservative estimate of species distributions [45]. The code for the SDMs was modified from Bharti et al [46] (https://github.com/bhartidk/centipede_diversity_endemism). Spatial data were processed using the packages “rgeos” [47], “raster” [48], “sf” [49], “sp” [50], and Maxent models were run using the package “ENMeval” [51] and “dismo” [52] in R 4.1.1 [53].…”

“…The raw data used for the study is available on request to the respective authors, Dr. Navendu Page, Dr. Ramanathan Krishnamani and Dr. Ajith Kumar. The dataset provided by Ramesh et al 2010, is accessible at https://esajournals.onlinelibrary.wiley.com/doi/abs/10.1890/10-0133.1 The scripts for running the SDMs were modified using the code from [46]: https://github.com/bhartidk/centipede_diversity_endemism. The supporting figures and tables, and the processed data are available in Appendix S1, S2, and S3 respectively.…”