Precipitation rather than temperature influenced the phylogeography of the endemic shrub Anarthrophyllum desideratum in the Patagonian steppe

COSACOV, A.; JOHNSON, L.; PAIARO, V.; COCUCCI A. A.; CÓRDOBA F. E.; SÉRSIC A.N.

JOURNAL OF BIOGEOGRAPHY

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2012

0305-0270

Aim In order to assess the impact of precipitation changes during Pleistoceneglaciations on plant species of the Patagonian steppe, a phylogeographical studyof the endemic shrub Anarthrophyllum desideratum was performed.Location Southern Patagonia: Argentina and Chile.Methods Chloroplast intergenic spacers trnS?trnG and rpoB?trnC weresequenced for 264 individuals from 33 localities spanning the entire distribu-tion of A. desideratum. Phylogenetic (statistical parsimony, maximum likeli-hood and Bayesian inference) and population genetic analyses (spatial analysesof molecular variance, mismatch distributions, neutrality tests and Bayesianskyline plot) were performed. Divergence time estimates using a calibratedmolecular clock were also conducted. Niche modelling was used to reconstructthe palaeodistribution to validate phylogeographical patterns.Results Thirty haplotypes were identified that clustered into two main lin-eages, revealing a significant latitudinal phylogeographical break north andsouth of the Deseado River (c.47°S). Infra-specific diversification began in thelate Miocene, with northern and southern lineages separating c. 3 Ma, after theeastern Patagonian lowlands started to become increasingly arid. Three areas ofhigh molecular diversity were identified: one in southern and two in northernPatagonia where niche modelling indicates that the species may have survivedduring the Last Glacial Maximum. These putative refugia received more mois-ture than much of the steppe during glaciation-associated aridization. Thesouth-western refugium is the more likely source for eastward range expansionduring post-glacial humidification.Main conclusions Anarthrophyllum desideratum responded differently to his-torical processes north and south of the Deseado River. In the north this spe-cies survived in situ in fragmented populations, whereas in the south itsurvived in localized refugia that presumably avoided extreme aridization, andfrom which it expanded eastwards. For southern Patagonia, our results supporta new historical scenario affected more by precipitation regimes than by tem-perature changes associated with glacial cycles. This hypothesis should be con-sidered in future plant phylogeographical studies from the Patagonian steppe