Multiple Pleistocene refugia in the widespread patagonian tree Embothrium coccineum (Proteaceae)

ROMINA VIDAL-RUSSELL, CINTIA P. SOUTO, AND ANDREA C. PREMOLI

AUSTRALIAN JOURNAL OF BOTANY

CSIRO PUBLISHING

Año: 2011 vol. 59 p. 299 - 314

0067-1924

Embothrium coccineum J.R. Forst. & G. Forst is an endemic tree of the Patagonian temperate forest. The objective of this study is to evaluate the impact of last glaciation events on the genetic structure of this widespread and ecologically tolerant species, to postulate possible refugial areas. Phylogeographic analyses were performed using chloroplast DNA sequences (trnL-trnF spacer and ndhC-trnV spacer) from individuals collected in 34 populations along the total range of the species, and these results were compared with a similiar study in Nothofagus. A total of 22 haplotypes were found, three of which were widely distributed while 13 were found at only one location. Historical demography suggests a long period of stable effective population size, decreasing gradually towards the LGM, followed by an increase in population size that stabilized 2,500 years ago. The phylogeographic analyses reflect recent events of colonization after LGM from multiple refugia. In the northern area of its distribution probably the species survived in several pockets within the Andes mountain range and in Cordillera de la Costa in Chile. While in the South, it is suggested that Embothrium survived the glacial period at the edge of the glaciers. These findings are in agreement with the fossil pollen that recorded 10,000 years old grains in the south suggesting colonization from nearby areas when ice retreated. Embothrium is a colonizer that naturally occurs as scattered individuals within mixed forests. Hence, the shallow phylogeographic structure reported here reflects a Plesitocene signature highly impacted by drift and high levels of gene flow resulting in the randomly fixation of new variants reducing the cpDNA structure.