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

Abstract

During the Quaternary, southern South American temperate forests were confined to small and isolated refugia. Recolonization could be related not only with location of refugia but also with postglacial phenomena like volcanism, which could have interrupted the expansion of the forests. The aim of this study was to analyze the local effect of volcanism during the postglacial migration of Nothofagus nervosa in a particular region of Argentina were convergence of two migratory routes was suggested. The main question is whether admixture occurred or not and if the current populations are connected by pollen or seed gene flow. Two populations separated by a 3-kmwidth lava flow were sampled. Buds from 30 individuals of each of the two populations and from a total of 142 juveniles were analyzed. Genetic variation was detected through maternally inherited chloroplast deoxyribonucleic acid (cpDNA; polymerase chain reaction restriction fragment length polymorphisms of two fragments) and nuclear markers like isozymes (six loci) and simple sequence repeats (three loci). Population genetic parameters were estimated and the existence of a genetic structure was tested with an analysis of molecular variance. Historical gene flow was estimated through the indirect method of the genetic differentiation (F ST ). Chloroplast DNA revealed a total genetic differentiation between the two populations indicating completely isolation respecting seed gene flow. On the contrary, the degree of genetic differentiation for the nuclear markers was significantly lower, and moderate levels of historical gene flow through pollen were inferred. The results suggest that in this area, volcanism has played an important local role during the expansion of N. nervosa maintaining these two populations separated.

Population genetic structure, genetic diversity, and natural history of the South American species of Nothofagus subgenus Lophozonia (Nothofagaceae) inferred from nuclear microsatellite data

“…For nuclear microsatellite loci, values for genetic diversity ( H E = 0.452–0.496) and number of alleles per locus ( A = 3.7–4.4) for Nothofagus in Argentina (Milleron et al. ; Azpilicueta et al. ; Mathiasen and Premoli ) and for species of the related genera Fagus and Quercus (0.597–0.864 for H E , 4.9–14.9 for A ) from the Northern Hemisphere are similar to those found in our study ( H E = 0.50–0.66, A = 4.5–6.2).…”

“…The high levels of nuclear microsatellite genetic variation in these species of Nothofagus are consistent with results for other related, large-sized, long-lived, outcrossing, wind-pollinated trees (Table 1) loci, values for genetic diversity (H E = 0.452-0.496) and number of alleles per locus (A = 3.7-4.4) for Nothofagus in Argentina (Milleron et al 2008;Azpilicueta et al 2013;Mathiasen and Premoli 2013) and for species of the related genera Fagus and Quercus (0.597-0.864 for H E , 4.9-14.9 for A) from the Northern Hemisphere are similar to those found in our study (H E = 0.50-0.66, A = 4.5-6.2). However, our values are higher than those reported for Nothofagus in Argentina and fall in the lower end of the ranges for Fagus and Quercus.…”

The effect of different glaciation patterns over the current genetic structure of the southern beech Nothofagus antarctica

“…Latitudinal variation in the distribution of haplotype variants and low levels of polymorphisms were also observed in other Nothofagus species (Marchelli and Gallo 2006;Millerón et al 2008;Azpilicueta et al, submitted) suggesting a general trend in these forests. The low levels of cpDNA variation observed for the Nothofagus species analysed so far contrast with those of other forest trees where several haplotypes were usually identified (see review in Petit et al 2005).…”

Phylogeographically concordant chloroplast DNA divergence in sympatric Nothofagus s.s. How deep can it be?

“…, 1990; Hill, 1991) and its extinction outside South America is suggested to have occurred as a result of a decline in catastrophic disturbances in these areas (Hill, 1991). Therefore, gene pools of such widespread lineages have been shaped by disturbance (Premoli & Kitzberger, 2005; Millerón et al. , 2008; Premoli & Steinke, 2008; Mathiasen, 2010).…”