Wind-dispersed pollen mediates postglacial gene flow among refugia

Abstract

A long-term genetic legacy of refugial isolation has been postulated and was demonstrated for maternal refugial lineages for numerous plant and animal species. The lineages were assumed to have remained separated from each other for several glacial periods. The conifer Abies alba Miller, silver fir, is an excellent model to test whether pollen-mediated gene flow may eliminate the genetic imprints of Pleistocene refugial isolation. Two DNA markers with contrasting modes of inheritance were applied to 100 populations covering the entire range of silver fir in Europe. The markers exhibited each two highly conserved alleles based on an insertion͞deletion of 80 bp in the fourth intron of the mitochondrial nad5 gene and on a synonymous substitution in the chloroplast psbC gene. The geographical distribution of the maternally inherited mitochondrial variation supported the existence of at least two refugia with two recolonizing maternal lineages remaining largely separated throughout the range. The cline of the nad5 allele frequencies was much steeper than the one of the two psbC alleles. The psbC cline was as wide as the whole range of the species. Our results provide striking evidence that even a species with very long generation times and heavy pollen grains was able to establish a highly efficient pollen-mediated gene flow between refugia. Therefore we postulate that an exchange of genetic information between refugia by range-wide paternal introgression is possible in wind-pollinated plant species.

Species delimitation and biogeography of two fir species (Abies) in central China: cytoplasmic DNA variation

“…In agreement with results from several previous studies on conifers (Liepelt et al, 2002;Du et al, 2009), we recorded low levels of mtDNA polymorphism in the two fir species, A. chensiensis and A. fargesii, which have overlapping distributions in the Tsinling and adjacent mountains of central China. Of the four mitotypes identified, three were shared between both species, with variation distributed mainly between populations rather than within populations or between species.…”

“…The biogeography and delimitation of fir species outside China have been explored previously using mtDNA and ptDNA markers (for example, see Tsumura and Suyama, 1998;Liepelt et al, 2002Liepelt et al, , 2010JaramilloCorrea et al, 2008). These studies have revealed different phylogeographic structures and/or inconsistent patterns of species delimitation for the two markers, with mtDNA variation tending to reveal stronger intraspecific genetic structure and weaker resolution of species boundaries when compared with ptDNA.…”

Genetic analysis of silver-fir populations in the North Carpathian and Sudeten Mountains

“…This hypothesis was discredited in the early isozymes studies on the genetic structure of the silver-fir population (Mejnartowicz 1979). Populations of the species exhibited great genetic variation and diversity, with values comparable with those described in pine populations, and even higher than in spruce populations (Bergmann et al 1990; Breitenbach-Dorfer et al 1997; Konnert et al Berg-mann 1995;Lewandowski et al 2001;Liepelt et al 2002;Mejnartowicz 1979aMejnartowicz , 1996Mejnartowicz , 2000Schroeder 1989). …”

Wetland-Dryland Vegetational Dynamics in the Pennsylvanian Ice Age Tropics

“…Studies of modern wind-pollinated plants subject to isolation in fragmented landscapes suggest high levels of gene flow created by pollen dispersal. Documentation of this pattern in conifers (Jørgensen et al 2002;Liepelt et al 2002;O'Connell et al 2007) may have the most applicability to the late Paleozoic, where the two dominant groups in seasonally dry habitats, cordaitaleans and conifers, are both coniferophytes in a broad evolutionary sense (Hernandez-Castillo et al 2001b;Rothwell et al 2005;Looy 2007). High gene flow might be expected to have kept speciation rates low in these groups, regardless of fluctuating climates.…”