Phylogenetic diversity, structure and diversification patterns of endemic plants along the elevational gradient in the Eastern Himalaya

ABSTRACT

Background: Several studies have documented the variation in species diversity patterns along elevational gradients in the Himalaya, but few have reported the evolutionary and biogeographic processes behind these patterns.

Aims: To understand whether evolutionary history and phylogeny have any role in structuring plant species communities along an elevational gradient in the Sikkim Himalaya.

Methods: We used data on endemic plant species occurrence from primary and secondary sources to construct family-level phylogenetic supertrees for different growth forms with the help of Phylomatic tool of Phylocom. These phylogenetic supertrees were used as a base for testing phylogenetic diversity (PD), niche conservatism, diversification time patterns and phylogenetic structure of various plant growth forms along an elevational gradient.

Results: PD was the highest at mid-elevations for all growth forms and PD had a significant positive correlation with endemic species richness. Species at mid-elevations were dominated by the ancestral/primitive taxa. There was phylogenetic clustering at higher elevations and phylogenetic overdispersion at lower and mid-elevations for the majority of the growth forms.

Conclusions: Time-for-speciation effect and niche conservatism along elevation (retention of niche-related ancestral elevational distribution over evolutionary time scale by species) together determine plant species diversity patterns in the Himalaya.

KEYWORDS:

• Biodiversity
• elevational gradient
• endemic species
• Himalaya
• phylogeny

Acknowledgements

The authors thank the University of Delhi for providing necessary logistic and financial support.

Disclosure statement

No potential conflict of interest was reported by the authors.

Supplementary material

Supplementary material can be accessed for this article here.

Additional information

Funding

This work was supported by the DST INSPIRE Research Fellowship, Government of India [grant number DST/INSPIRE Fellowship/2012/432 to KM] and DU-DST-PURSE grant [to MKP].

Notes on contributors

Kumar Manish

Kumar Manish is an assistant professor. His research interests include Himalayan plant ecology and evolution, biodiversity patterns and climate change.

Maharaj K. Pandit

Maharaj K. Pandit is a professor. His research interests include plant systematics, speciation, ecological genomics, invasion ecology, climate change and conservation biology.