Glacial refugia and modern genetic diversity of 22 western North American tree species

Abstract

North American tree species, subspecies and genetic varieties have primarily evolved in a landscape of extensive continental ice and restricted temperate climate environments. Here, we reconstruct the refugial history of western North American trees since the last glacial maximum using species distribution models, validated against 3571 palaeoecological records. We investigate how modern subspecies structure and genetic diversity corresponds to modelled glacial refugia, based on a meta-analysis of allelic richness and expected heterozygosity for 473 populations of 22 tree species. We find that species with strong genetic differentiation into subspecies had widespread and large glacial refugia, whereas species with restricted refugia show no differentiation among populations and little genetic diversity, despite being common over a wide range of environments today. In addition, a strong relationship between allelic richness and the size of modelled glacial refugia (r 2 ¼ 0.55) suggest that population bottlenecks during glacial periods had a pronounced effect on the presence of rare alleles.

Provenance Variation in Phenology and Frost Tolerance in Subalpine Fir (Abies lasiocarpa) Planted in Denmark and Iceland

“…The results in our trials for survival, flushing and bud set showed similar geographical groupings as those found by Hansen et al [15]. There were also similarities with the division into refugia done by Roberts and Hamann [14]. Taken together, this indicates that the selection of favorable genetic material for use in Iceland and Denmark should concentrate on geographical groups of provenances from certain refugia rather than frost hardiness in spring and autumn.…”

“…Hansen et al [15] used canonical variates analysis, based on 15 characteristics, to divide the 26 provenances into six groups. These groups show a strong relationship to the classification by Alexander et al [10] and Roberts and Hamann [14].…”

“…The present distribution area may not yet have reached equilibrium with the climatic niche of the species after the last glacial maximum. Roberts and Hamann [14] reconstructed the refugial history of western North American trees and divided subalpine fir into 6 different refugia. Each provenance might have adapted partly to the present local climate, but the opportunity for adaptation may be constrained by evolution and dispersal from these refugia as well as genetic bottlenecks.…”

Contrasting Levels of Genetic Diversity Among Populations of the Endangered Tropical Palm Euterpe Edulis Martius

“…Such event could be related to the establishment of populations with lower effective population sizes, as those determined by demographic and genetic bottlenecks and founder effects. Significance evidence on the matter has been reported for forest tree species (ROBERTS; HAMANN, 2015). However, the Wilkoxon test of the infinite allele model for bottleneck revealed no significant changes in each population size.…”

Climate and vegetation since the Last Interglacial (MIS 5e) in a putative glacial refugium, northern Idaho, USA

“…Ascaphus montanus, Plethodon idahoensis, Microtus richardsoni, Salix melanopis, T. plicata) residing within the interior mesic forests show that the LGM climate was too harsh for many of the species currently found in the region today (Carstens and Richards, 2007;Roberts and Hamann, 2015). Both vegetation (subalpine Pinus and Picea forest with high abundances of Artemisia; SM 3/2) and sediment composition records (low percent organic carbon, decreasing biogenic silica, and increasing bulk density; SM 3/2 and SM 2) support climate simulations of a cold and dry LGM (Braconnot et al, 2007).…”