Less Pollen-Mediated Gene Flow for More Signatures of Glacial Lineages: Congruent Evidence from Balsam Fir cpDNA and mtDNA for Multiple Refugia in Eastern and Central North America

Abstract

The phylogeographic structure and postglacial history of balsam fir (Abies balsamea), a transcontinental North American boreal conifer, was inferred using mitochondrial DNA (mtDNA) and chloroplast DNA (cpDNA) markers. Genetic structure among 107 populations (mtDNA data) and 75 populations (cpDNA data) was analyzed using Bayesian and genetic distance approaches. Population differentiation was high for mtDNA (dispersed by seeds only), but also for cpDNA (dispersed by seeds and pollen), indicating that pollen gene flow is more restricted in balsam fir than in other boreal conifers. Low cpDNA gene flow in balsam fir may relate to low pollen production due to the inherent biology of the species and populations being decimated by recurrent spruce budworm epidemics, and/or to low dispersal of pollen grains due to their peculiar structural properties. Accordingly, a phylogeographic structure was detected using both mtDNA and cpDNA markers and population structure analyses supported the existence of at least five genetically distinct glacial lineages in central and eastern North America. Four of these would originate from glacial refugia located south of the Laurentide ice sheet, while the last one would have persisted in the northern Labrador region. As expected due to reduced pollen-mediated gene flow, congruence between the geographic distribution of mtDNA and cpDNA lineages was higher than in other North American conifers. However, concordance was not complete, reflecting that restricted but nonetheless detectable cpDNA gene flow among glacial lineages occurred during the Holocene. As a result, new cpDNA and mtDNA genome combinations indicative of cytoplasmic genome capture were observed.

Continent‐wide population genomic structure and phylogeography of North America’s most destructive conifer defoliator, the spruce budworm (Choristoneura fumiferana)

“…Several recent studies have focused on the phylogeography and population genetic structure of spruce and fir species (Cinget, Gérardi, Beaulieu, & Bousquet, 2015;de Lafontaine, Turgeon, & Payette, 2010;Jaramillo-Correa, Beaulieu, Khasa, & Bousquet, 2009 and references therein; Potter, Frampton, Josserand, & Nelson, 2010). Yet, we have limited knowledge of spruce budworm phylogeography and population genetic structure, or how phylogeographic patterns compare with those of its host plants.…”

Integrating phylogeography and paleoecology to investigate the origin and dynamics of hybrid zones: insights from two widespreadNorthAmerican firs

“…The four A. balsamea populations were also fixed for variant T1 of the trn F‐ trn L cpDNA locus (as well as in a majority of eastern Canada populations; Cinget et al . ). The four A. lasiocarpa populations carried the remaining variants (T2–T6) at various frequencies (Fig.…”

“…By contrast, balsam fir was sampled within a single postglacial lineage (see Cinget et al . ) originating from a putative refugium located south of the Great Lakes. It should also be noted that broad‐scale phylogeographic surveys of many transcontinental boreal conifers have reported typically low genetic diversity within such central Canada lineages compared to lineages from eastern Canada (Jaramillo‐Correa et al .…”

“…Loci were amplified in a PTC‐225 thermal cycler (Bio‐Rad) following PCR protocols of Cinget et al . (), Taberlet et al . () and Vendramin et al .…”

“…The mtDNA primer set nad 5‐4 Ab , which has already revealed a sequence polymorphism in A. balsamea (out of 43 assays, see Cinget et al . ), was used to survey mtDNA variation in the Abies complex. A set of 20 chloroplast microsatellite (cpSSR) primers (Vendramin et al .…”