Repeated upslope biome shifts in Saxifraga during late-Cenozoic climate cooling.

Mountains are among the most biodiverse places on Earth, and plant lineages that inhabit them have some of the highest speciation rates ever recorded. Plant diversity within the alpine zone - the elevation above which trees cannot grow—contributes significantly to overall diversity within mountain systems, but the origins of alpine plant diversity are poorly understood. Here, we quantify the processes that generate alpine plant diversity and their changing dynamics through time in (Saxifragaceae), an angiosperm genus that occurs predominantly in mountain systems. We present a time-calibrated molecular phylogenetic tree for the genus that is inferred from 329 low-copy nuclear loci and incorporates 73% (407) of known species. We show that upslope biome shifts into the alpine zone are considerably more prevalent than dispersal of alpine specialists between regions, and that the rate of upslope biome shifts increased markedly in the last 5 Myr, a timeframe concordant with a cooling and fluctuating climate that is likely to have increased the extent of the alpine zone. Furthermore, alpine zone specialists have lower speciation rates than generalists that occur inside and outside the alpine zone, and major speciation rate increases within significantly pre-date increased rates of upslope biome shifts. Specialisation to the alpine zone is not therefore associated with speciation rate increases. Taken together, this study presents a quantified and broad scale perspective of processes underpinning alpine plant diversity.

Project(s)

Priority 4: Accelerated Taxonomy

Plant and Fungal Trees of Life (PAFTOL) Project

Funder

Funder name	Awards
Aarhus Universitets Forskningsfond, Denmark	Grant AUFF-E-2017-7-19
Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung, Switzerland	Grant 310030_185251
David and Claudia Harding Foundation, United Kingdom	Harding Alpine Programme
Calleva Foundation, United Kingdom	Plant and Fungal Trees of Life (PAFTOL) Project
National Science Foundation, United States	Grant NSF DBI-1523667
Deutsche Forschungsgemeinschaft, Germany	Grant MU 2934/3-1