Refugia in the Cordilleran ice sheet of western North America: chloroplast DNA diversity in the Arctic–alpine plant Oxyria digyna

Abstract

Aim Late Pleistocene ice sheets are thought to have covered most of western Canada, including all of British Columbia (BC). We examine patterns of genetic variation in an Arctic–alpine plant to evaluate the possibility of full glacial refugia within the area covered by the Cordilleran ice sheet (CIS) and to uncover post‐glacial migration routes.Location Western North America.Methods We sampled 1030 individuals of the Arctic–alpine plant Oxyria digyna from 117 populations distributed over much of its range in western and northern North America. DNA haplotypes were identified using restriction site analysis of two chloroplast DNA intergene spacer regions, psbA‐trnH and trnT‐L. We examined the geographical distribution of haplotype diversity in relation to latitude, and also compared various indices of diversity in putatively glaciated and unglaciated regions. Patterns of migration were inferred using nested clade analysis.Results We detected a total of 20 haplotypes. High haplotype diversity was found in Beringia, in unglaciated western USA, and in northern BC at 57–59° N, well within the accepted limits of the CIS. Ancestral haplotypes were also centred in northern BC.Main conclusions High genetic diversity of Oxyria digyna is expected in unglaciated regions, but unexpected in northern BC if British Columbia was entirely covered by ice during the late Pleistocene. Our observations suggest the presence of unglaciated areas providing late Pleistocene refugia in northern BC. Such refugia would have important implications for the origins and migrations of many plant and animal species in north‐western North America.

Inter-simple sequence repeat (ISSR) and morphological variation in the western North American range ofChrysosplenium tetrandrum(Saxifragaceae)

“…Generally, low levels of genetic diversity and differentiation would characterize a scenario of recent range expansion, however, if populations in these areas are derived from separate refugia, they may exhibit comparatively high levels of differentiation (Hewitt 1996;Marr et al 2008). In fact, the results are consistent with both explanations.…”

“…Additional, smaller refugia existed along the coasts of British Columbia and southern Alaska, as well as possibly in the southern Canadian Rocky Mountains (Heusser 1960;Loehr et al 2006). The use of molecular data to determine the role of these North American refugia has become commonplace (e.g., Tremblay and Schoen 1999;Eidesen et al 2007;Marr et al 2008), and this accumulating information provides the basis for further formulation of genetic predictions, given specific historical scenarios. In the following, we discuss the putative roles (i.e., glacial refuge or area of recolonization) of sampled geographic regions as determined by patterns of genetic variation.…”

Different phylogeographic patterns in two Japanese Silpha species (Coleoptera: Silphidae) affected by climatic gradients and topography

“…However, different phylogeographic patterns have also been found in North America (e.g. Maroja et al, 2007;Marr, Allen & Hebda, 2008). Thus, in order to interpret the phylogeographic pattern of a species, we must consider the interaction of biology, geography and climatic gradients (Hewitt, 2000).…”

Morphological Analysis and Phytogeography of Native Calamagrostis (Poaceae) from British Columbia, Canada and Adjacent Regions

“…We examine the phytogeography of the genus in northwestern North America and discuss it in the context of current understandings of the regions glacial, environmental and climatic history (Hebda 1995(Hebda , 1997Byun et al 1997;Whitlock and Bartlein 1997;Heusser et al 1999;Heinrichs et al 2002). The results presented here are the basis for the measurements and a portion of the key presented in the Flora of North America treatment for those Calamagrostis species that occur in British Columbia (Marr et al 2007). …”

“…A description of the genus can be found in Marr et al (2007). Multiple chromosome counts have been reported for the species that occur in BC (Nygren 1954;Kawano 1965;Moss 1983;Greene 1984): C. canadensis (2n 5 42, 45, 48, 49, 51, 56, 62, 65); C. lapponica (2n 5 28, 42, 49-140); C. montanensis ( 2n 5 28); C. nutkaensis (2n 5 28); C. purpurascens (2n 5 40-42, 47-49, 50, 53, 56, 54, 84); C. rubescens (2n 5 28, 42, 56); C. sesquiflora (2n 5 28); C. stricta (2n 5 28, 56, 70, 84, ca.…”