@ARTICLE{TreeBASE2Ref23593, author = {Nicolai M. N?rk and Simon Uribe-Convers and Berit Gehrke and David C Tank and Frank R. Blattner}, title = {Oligocene niche shift, Miocene diversification ? cold tolerance and accelerated speciation rates in St. John?s Worts (Hypericum, Hypericaceae)}, year = {2014}, keywords = {age estimation, climate change, cold tolerance, diversification rate shifts, historical biogeography, Hypericum (St. John?s wort, Hypericaceae), phylogenetic niche conservatism (PNC), temperate climate}, doi = {}, url = {}, pmid = {}, journal = {BMC Evolutionary Biology}, volume = {}, number = {}, pages = {}, abstract = {Our aim is to understand the evolution of species-rich plant groups that shifted from tropical into cold/temperate biomes. It is well known that climate affects evolutionary processes, such as how fast species diversify, species range shifts, and species distributions. Many plant lineages became extinct in the Northern Hemisphere due to climate cooling starting with the Late Eocene, whilst only few tropical lineages evolved cold tolerance and adapted to temperate conditions. One of them is the hyper-diverse and geographically widespread genus Hypericum. To investigate the effect of macroecological niche shifts on evolutionary success we combine historical biogeography with diversification rate and bioclimatic niche analyses in a phylogenetic framework. Hypericum evolved cold tolerance 30?40 million years ago, and successfully colonized all ice-free continents, where today ~500 species exist. The other members of Hypericaceae stayed in their tropical habitats and evolved into ~120 species. We identified a 15?20 million year lag between the initial change in temperature preference in Hypericum and later diversification rate shifts in the Miocene. The initial niche shift into colder climates appears to be a precondition, but not directly related to increased diversification rates. Major events of mountain formation and further climate cooling can explain distribution patterns and species-richness in Hypericum. Contrary to the dramatic niche shift early in the evolution of Hypericum, niche conservatism was found, as most extant species occur in temperate climates including high altitudes in the tropics. These findings exemplify patterns of plant evolution during large-scale global climate change.} }

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