The effect of volcanism on postglacial migration and seed dispersal. A case study in southern South America

MILLERÓN, M.; GALLO LA; MARCHELLI, P.

TREE GENETICS & GENOMES

SPRINGER HEIDELBERG

Lugar: HEIDELBERG; Año: 2008 vol. 4 p. 435 - 443

1614-2942

During the Quaternary, southern South Americantemperate forests were confined to small and isolatedrefugia. Recolonization could be related not only withlocation of refugia but also with postglacial phenomena likevolcanism, which could have interrupted the expansion ofthe forests. The aim of this study was to analyze the localeffect of volcanism during the postglacial migration ofNothofagus nervosa in a particular region of Argentinawere convergence of two migratory routes was suggested.The main question is whether admixture occurred or notand if the current populations are connected by pollen orseed gene flow. Two populations separated by a 3-kmwidthlava flow were sampled. Buds from 30 individuals ofeach of the two populations and from a total of 142juveniles were analyzed. Genetic variation was detectedthrough maternally inherited chloroplast deoxyribonucleicacid (cpDNA; polymerase chain reaction restriction fragmentlength polymorphisms of two fragments) and nuclearmarkers like isozymes (six loci) and simple sequencerepeats (three loci). Population genetic parameters wereestimated and the existence of a genetic structure was testedwith an analysis of molecular variance. Historical gene flowwas estimated through the indirect method of the geneticdifferentiation (FST). Chloroplast DNA revealed a totalgenetic differentiation between the two populations indicatingcompletely isolation respecting seed gene flow. Onthe contrary, the degree of genetic differentiation for thenuclear markers was significantly lower, and moderate levels of historical gene flow through pollen were inferred.The results suggest that in this area, volcanism has playedan important local role during the expansion of N. nervosamaintaining these two populations separated