Timing and ecological priority shaped the diversification of sedges in the Himalayas.

Background: Diversification 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- L. (Cyperaceae), with ca. 2100 species worldwide-has not yet been studied in the Himalayas, which contains 189 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

Methods: Phylogenetic relationships were inferred using maximum likelihood analysis of two nuclear ribosomal DNA (nrDNA) regions (ITS and ETS) and one plastid gene (K); 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.

Results: The Himalayan flora represents three of the five major clades, each represented by multiple origins within the Himalayas. The oldest 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 flora comprises a heterogeneous sample of diversifications drawn from throughout the cosmopolitan, but mostly temperate, radiation. Most radiations are relatively recent, but the widespread and diverse Himalayan radiation arose at the early Miocene. The timing and predominance of in high-elevation Himalayan meadows suggests that may have excluded other lineages: the success of in the Himalayas, in other words, appears to be a consequence largely of priority, competitive exclusion and historical contingency.