Past influences present: Mammalian species from different biogeographic pools sort environmentally in the Indian subcontinent

Abstract

Diversity-environment relationships are distinct across species pools, and as a result species from different biogeographic pools have different environmental preferences. Regional communities are drawn from available biogeographic pools, subject to environmental and dispersal constraints. Does shared biogeographic history of taxa lead to similar relationships with the environment? We test this idea in the Indian subcontinent, which is at the confluence of multiple biogeographic regions resulting in species from multiple biogeographic pools being distributed here. Species were classified as belonging to four biogeographic affinities based on their geographic distributions: eastern, northern, western and endemic. We investigated spatial patterns of species richness for all mammals (over 1° x 1° grid cells), for each biogeographic group and for 5 major mammalian orders. Generalized Additive Models (GAM) were used to investigate environment-diversity relationship for all mammals, each biogeographic group, and for major mammalian orders in the Indian subcontinent. Species richness of all mammals was found to be highest in the montane regions of the Eastern Himalayas and the Western Ghats. Species richness of each biogeographic group was highest at the border it shared with Asia, in the direction of immigration from Asia. Environment and spatial variables were both correlated with species richness in the Indian subcontinent and each biogeographic group showed a distinct richness-environment relationship. Additionally, biogeographic groups sorted along environmental space, in keeping with our predictions based on their global distributions. Finally, analyses across mammalian orders had low predictive value, suggesting that shared phylogenetic history is relatively less important than biogeographic ancestry in determining relationships to environment. We conclude that historical factors such as immigration and the distinct evolutionary histories of species impact species richness patterns in the Indian subcontinent. Our results provide insights into drivers of regional community assembly in transition zones where multiple biogeographic species pools co-exist.

The role of geography, environment, and genetic divergence on the distribution of pikas in the Himalaya

“…Geographic isolation of recently diverged species with similar niche relationships has been observed in other herbaceous plants (Boucher, Zimmermann, & Conti, 2016). Since immigration has been identified as the major driver of Himalayan faunal diversity (Tamma, Marathe, & Ramakrishnan, 2016), the question of whether niche divergence occurred insitu or during immigration between the two recently diverged congeners remains unclear. Another close relative of these two pikas species is a trans-Himalayan species, O. curzoniae.…”

Cryptic diversity of Rhinolophus lepidus in South Asia and differentiation across a biogeographic barrier

“…South Asia encompasses several distinct biogeographic zones and biodiversity hotspots (Myers et al 2000, Tamma et al 2016. While much mammalian diversity is concentrated in the hotspots of northeastern India and the Western Ghats, mammalian endemism is largely concentrated in peninsular India, specifically the Western Ghats (Tamma et al 2016).…”

“…South Asia encompasses several distinct biogeographic zones and biodiversity hotspots (Myers et al 2000, Tamma et al 2016. While much mammalian diversity is concentrated in the hotspots of northeastern India and the Western Ghats, mammalian endemism is largely concentrated in peninsular India, specifically the Western Ghats (Tamma et al 2016). Although bats follow these general mammalian trends, much of their endemism in peninsular India is currently considered to be at the subspecific level, and often as part of large, polytypic super-species composites that may contain high degrees of cryptic specieslevel diversity (Bates and Harrison 1997, Chattopadhyay et al 2012, Chattopadhyay et al 2016.…”