Past climate and species ecology drive nested species richness patterns along an east‐west axis in the Himalaya

Abstract

Aim Although global species richness patterns appear consistent across taxa and continents, patterns are elusive at smaller spatial scales. At regional/subcontinental scales, climatic, environmental and taxon‐specific contingencies are likely to interact to modify general richness patterns. We develop a biogeographical paradigm for the Himalayan range as representative of regions at similar spatial scales, and where historical climate fluctuations might interact with species ecology to drive species richness patterns. Location Himalayan range, Asia Methods We obtained a cell × species presence–absence matrix for babblers and murid rodents in 1° latitude × 1° longitude cells in the Himalayan range. We investigated nestedness in species richness patterns in these taxa along a distance gradient from the species‐rich eastern towards the relatively depauperate west. We also investigated the relationship between species autecology and westward extent along the Himalaya. Climate data were obtained from published sources. Results Himalayan babbler and murid assemblages are nested along an east–west axis, with assemblages in westward cells tending to be subsets of assemblages immediately to the east. Distance westward from the eastern Himalaya was related positively to altitudinal mobility of babbler assemblages, while body size increased with distance westward for murid assemblages. Main conclusions The eastern Himalaya, which was not glaciated over during glacial maxima, was a potential refugium for babbler and murid species. Following glacial retreat, species could have recolonized the Himalaya westwards to different extents based on ecological traits (size, altitudinal migration) determining ability to deal with the more seasonal west. This produces both (1) a nested species richness pattern, and (2) correlations between ‘filtering’ autecological traits and distance. Such patterns should be replicated in other regions with historical climatic refugia; investigating nestedness along distance gradients from refugia would be a powerful tool in mapping biogeographical history, especially in separating historical effects from currently proposed energy‐productivity relationships.

Species delimitation of the white‐tailed rubythroat Calliope pectoralis complex (Aves, Muscicapidae) using an integrative taxonomic approach

“…The latter area is also called the Sino-Himalayan region, which is feasible that the divergence between C. p. tschebaiewi and the remaining taxa of C. pectoralis was associated with allopatric divergence due to long-term geographical fragmentation between Himalayan and south-central Chinese mountain chains. In the west, the lineage diversification of three Tian Shan-Himalayan subspecies of C. pectoralis might be a consequence of in situ diversification within the Himalayas (Päckert et al 2012), or range expansion to the Western Himalayas and Tian Shan mountains from a source population in a single refuge in the eastern Himalayas (Srinivasan et al 2014). In the west, the lineage diversification of three Tian Shan-Himalayan subspecies of C. pectoralis might be a consequence of in situ diversification within the Himalayas (Päckert et al 2012), or range expansion to the Western Himalayas and Tian Shan mountains from a source population in a single refuge in the eastern Himalayas (Srinivasan et al 2014).…”

Annual temperature variation influences the vulnerability of montane bird communities to land‐use change

“…1). A majority of the species in the Himalayas have a common evolutionary and biogeographic history, having colonized the Himalayas from the east towards the west (Srinivasan et al 2014). Despite similarities in their biogeographic origins, bird communities at the two ends of the Himalayas show significant differences in thermal tolerances.…”

Isolation drives taxonomic and functional nestedness in tropical reef fish faunas

“…A variety of processes, deterministic or stochastic, have been proposed to cause nested patterns of species assemblages (Ulrich et al ). These processes include differential colonization and extinction driven by species‐specific traits, such as dispersal ability (Patterson and Atmar , , Srinivasan et al ) and habitat heterogeneity or quality associated with species varying in their degree of specialization (Wright and Reeves ). The level of nestedness regulates the extent to which large areas contain the diversity of species hosted in smaller areas and has implications in conservation science (Patterson and Atmar , , Ulrich et al ).…”