Replicated radiations of the alpine genusAndrosace(Primulaceae) driven by range expansion and convergent key innovations.
OBJECTIVE
We still have limited understanding of the contingent and deterministic factors that have fostered the evolutionary success of some species lineages over others. We investigated how the interplay of intercontinental migration and key innovations promoted diversification of the genusAndrosace.


METHODS
Mountain ranges and cold steppes of the Northern Hemisphere.


METHODS
We reconstructed ancestral biogeographical ranges at regional and continental scales by means of a dispersal-extinction-cladogenesis analysis using dated Bayesian phylogenies and contrasting two migration scenarios. Based on diversification analyses under two frameworks, we tested the influence of life form on speciation rates and whether diversification has been diversity-dependent.


RESULTS
We found that three radiations occurred in this genus, at different periods and on different continents, and that life form played a critical role in the history ofAndrosace. Short-lived ancestors first facilitated the expansion of the genus' range from Asia to Europe, while cushions, which appeared independently in Asia and Europe, enhanced species diversification in alpine regions. One long-distance dispersal event from Europe to North America led to the diversification of the nested genusDouglasia. We found support for a model in which speciation of the North American-European clade is diversity-dependent and close to its carrying capacity, and that the diversification dynamics of the North American subclade are uncoupled from this and follow a pure birth process.


CONCLUSIONS
The contingency of past biogeographical connections combined with the evolutionary determinism of convergent key innovations may have led to replicated radiations ofAndrosacein three mountain regions of the world. The repeated emergence of the cushion life form was a convergent key innovation that fostered radiation into alpine habitats. Given the large ecological similarity ofAndrosacespecies, allopatry may have been the main mode of speciation.
Laboratoire d'Écologie Alpine, CNRS UMR 5553, Université Joseph Fourier - Grenoble 1, Grenoble, France.
Cristina
C
Roquet
Laboratoire d'Écologie Alpine, CNRS UMR 5553, Université Joseph Fourier - Grenoble 1, Grenoble, France.
Florian C
FC
Boucher
Laboratoire d'Écologie Alpine, CNRS UMR 5553, Université Joseph Fourier - Grenoble 1, Grenoble, France.
Wilfried
W
Thuiller
Laboratoire d'Écologie Alpine, CNRS UMR 5553, Université Joseph Fourier - Grenoble 1, Grenoble, France.
Sébastien
S
Lavergne
Allopatry; Androsace; biogeography; cushion plants; diversification; evolutionary determinism; historical contingency; long-distance dispersal; speciation rates