Patterns of seed dispersal and pollen flow inQuercus garryana(Fagaceae) following post‐glacial climatic changes

Abstract

Aim We examined the genetic structure of Quercus garryana to infer post-glacial patterns of seed dispersal and pollen flow to test the hypotheses that (1) peripheral populations are genetically distinct from core populations and from one another; (2) genetic diversity declines towards the poleward edge of the species' range; and (3) genetic diversity in the chloroplast genome, a direct measure of seed dispersal patterns, declines more sharply with increasing latitude than diversity in the nuclear genome. We address our findings in the context of known historical oak distribution from pollen core data derived from previously published research.Location Oak-savanna ecosystems from southern Oregon, USA (core populations/non-glaciated range) northward to Vancouver Island, British Columbia, Canada (peripheral populations/glaciated range).Methods We genotyped 378 trees from 22 sites with five chloroplast and seven nuclear microsatellite loci. For both sets of markers, we estimated genetic diversity and differentiation using an analysis of molecular variance and generated Mantel correlograms to detect genetic and geographical distance correlations. For the nuclear markers, we also used a Bayesian approach to infer population substructure.Results There was a large degree of population differentiation revealed by six chloroplast haplotypes, with little (£ 3) or no haplotype diversity within sites. Peripheral island locations shared the same, maternally inherited chloroplast haplotype, whereas locations in mainland Washington had greater haplotype diversity. In contrast, genetic diversity of the nuclear markers was high at all locations sampled. Populations clustered into two groups and were significantly positively correlated over large spatial scales (£ 200 km), although allele richness decreased significantly with latitude. Population substructure was observed between core and peripheral populations because rare alleles were absent in peripheral localities and common allele frequencies differed. Main conclusionsThe observed pattern of chloroplast haplotype loss at the northern periphery suggests restricted seed dispersal events from mainland sites to peripheral islands. This pattern was unexpected, however, as refugial oak populations remained near the current post-glacial range even during the Last Glacial Maximum. Using nuclear markers, we found high within-population diversity and population differentiation only over large spatial scales, suggesting that pollen flow is relatively high among populations.

Genetic Diversity in Relict and Fragmented Populations of Ulmus glabra Hudson in the Central System of the Iberian Peninsula

“…In general, signs of population isolation and low gene flow were detected throughout the Central System (F ST = 0.239) compared to that reported for some other wind-pollinated temperate forest species: F ST = 0.049 in Quercus garryana Douglas ex Hook [64], F ST = 0.052 in Populus euphratica Olivier [65], Φ ST = 0.013 in Fraxinus excelsior L. [66], and F ST = 0.074 in Castanea sativa Mill. [67].…”

Oak canopy arthropod communities: which factors shape its structure?

“…Similar results were reported by Castagneyrol et al (2012), who found that the genetic attributes of the host plant (genetic diversity, kinship, and genetic identity) had no significant effect on the community of phytophagous insects (endophagous and ectophagous) associated with the canopy of Q. robur in France. The absence of a response by the canopy communities associated with Q. robur in Europe is probably due to the lower levels of genetic diversity of European species (whose populations were affected by glaciations) compared to the diversity reported for Mexican oak species (i.e., Magri et al 2007;Marsico et al 2009). Vakkari et al (2006) reported very low levels of genetic diversity (He = 0.162) of Q. robur in Finland.…”

Phylogeography and climate-associated morphological variation in the endemic white oakQuercus deserticola(Fagaceae) along the Trans-Mexican Volcanic Belt

“…Most previous studies of oak species using cpDNA markers have found similar high differentiation levels and a clear geographic segregation of haplotypes lineages, which are usually explained by the historical migration patterns of the populations and the very low dispersal capacity of acorns (Magni et al 2005;Grivet et al 2006;Magri et al 2007;Marsico et al 2009). However, in Q. deserticola the distribution of haplotypes was rather patchy, displaying strong local genetic structure but without obvious phylogeographic breaks, contrasting with some previous studies in the TMVB that have found a west-east LGM, and the MIROC model suggested a modest eastwards expansion from the LGM to the present along the TMVB.…”