Abstract
BackgroundDiversification patterns in the Himalayas have been important to our understanding of global biodiversity. Despite recent broad-scale studies, the most diverse angiosperm genus of the temperate zone—Carex L. (Cyperaceae), with ca. 2100 species worldwide—has not yet been studied in the Himalayas, which contains 189 Carex species. Here the timing and phylogenetic pattern of lineage and ecological diversification were inferred in this ecologically significant genus. We particularly investigated whether priority, adaptation to ecological conditions, or both explain the highly successful radiation of the Kobresia clade (ca. 60 species, of which around 40 are present in the Himalayas) of Himalayan Carex.MethodsPhylogenetic relationships were inferred using maximum likelihood analysis of two nuclear ribosomal DNA (nrDNA) regions (ITS and ETS) and one plastid gene (matK); the resulting tree was time-calibrated using penalized likelihood and a fossil calibration at the root of the tree. Biogeographical reconstruction for estimation of historical events and ancestral ranges was performed using the dispersal-extinction-cladogenesis (DEC) model, and reciprocal effects between biogeography and diversification were inferred using the geographic state speciation and extinction (GeoSSE) model. Climatic envelopes for all species for which mapped specimen data available were estimated using climatic data from WORLDCLIM, and climatic niche evolution was inferred using a combination of Ornstein-Uhlenbeck models of shifting adaptive optima and maximum likelihood inference of ancestral character states under a Brownian motion model.ResultsThe Himalayan Carex flora represents three of the five major Carex clades, each represented by multiple origins within the Himalayas. The oldest Carex radiation in the region, dating to ca. 20 Ma, near the time of Himalayan orogeny, gave rise to the now abundant Kobresia clade via long-distance dispersal from the Nearctic. The Himalayan Carex flora comprises a heterogeneous sample of diversifications drawn from throughout the cosmopolitan, but mostly temperate, Carex radiation. Most radiations are relatively recent, but the widespread and diverse Himalayan Kobresia radiation arose at the early Miocene. The timing and predominance of Kobresia in high-elevation Himalayan meadows suggests that Kobresia may have excluded other Carex lineages: the success of Kobresia in the Himalayas, in other words, appears to be a consequence largely of priority, competitive exclusion and historical contingency.
Highlights
The habitat and topographic diversity of mountains make them important centers of biodiversity and rare species endemism (Hughes & Atchison, 2015; Luo et al, 2016; Myers et al, 2000; Xie et al, 2014; Xing & Ree, 2017; Yu et al, 2015; Zhang et al, 2014)
Our topology may be poorly supported in some clades, but the groups and branching we retrieved was fully compatible with the Global Carex Group (2016) tree, where the clades retrieved were more strongly supported
Our analyses demonstrate that Himalayan diversification in the core Unispicate clade has contributed significantly to global sedge diversity
Summary
The habitat and topographic diversity of mountains make them important centers of biodiversity and rare species endemism (Hughes & Atchison, 2015; Luo et al, 2016; Myers et al, 2000; Xie et al, 2014; Xing & Ree, 2017; Yu et al, 2015; Zhang et al, 2014). High-alpine lineages often have only long-distance dispersal and adaptation as options for responding to climate change. Recent studies have reported long-distance dispersals among mountains to be more frequent than formerly assumed (Heaney, 2007; Levin, 2006; Schaefer, Heibl & Renner, 2009; Villaverde et al, 2015a). As global warming threatens to drive many cold-adapted species upslope toward extinction (Chen et al, 2009; Thomas et al, 2004; Morueta-Holme et al, 2015; though see Crimmins et al, 2011 for an alternative to this traditional climate change scenario), research on the dynamics of species diversification in mountain systems is increasingly relevant. The timing and phylogenetic pattern of lineage and ecological diversification were inferred in this ecologically significant genus. 20 Ma, near the time of Himalayan orogeny, gave rise to the abundant Kobresia clade via long-distance dispersal from the Nearctic. The timing and predominance of Kobresia in high-elevation Himalayan meadows suggests that Kobresia may have excluded other
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
