Phylogeographic Patterns and High Levels of Chloroplast Dna Diversity in Four Packera (Asteraceae) Species in Southwestern Alberta

Abstract

Abstract. Chloroplast DNA (cpDNA) haplotype variation is compared among alpine and prairie/montane species of Packera from a region in southwestern Alberta that straddles the boundary of Pleistocene glaciation. The phylogeny of the 15 haplotypes identified reveals the presence of two groups: one generally found in coastal and northern species and the other from species in drier habitats. The presence of both groups in all four species and most populations from southwestern Alberta is evidence of past hybridization involving species or lineages that may no longer be present in the region. With the exception of the alpine P. subnuda (⌽ ST ϭ 1.0), interpopulational subdivision of haplotype variation is low (⌽ ST Ͻ 0.350), suggesting that interpopulational gene flow is high. However, based on haplotype distribution patterns, we propose that Pleistocene hybridization and incomplete lineage sorting have resulted in reduced subdivision of interpopulational variation so that gene flow may not be as high as indicated. Drift has been more important in the alpine species populations, especially P. subnuda.

Evidence for Historical Introgression Along a Contact Zone Between Two Species of Char (Pisces: Salmonidae) in Northwestern North America

“…The congruence in pattern between char and plants suggests that historical processes have strongly impacted not only the phylogeographic distribution of intraspecific lineages in diverse taxa, but also evolutionary interactions between species such as introgression. In particular, these analogous situations highlight the potential role of the dynamic geological history of northwestern North America in initiating vicariance and influencing dispersal patterns and subsequent evolutionary interactions between species (see also Latta and Mitton 1999;Golden and Bain 2000). Phillips et al (1999) showed (with rDNA sequences) that Dolly Varden were paraphyletic with respect to Arctic char.…”

Introgressive Hybridization inPinus montezumaeLamb andPinus pseudostrobusLindl. (Pinaceae): Morphological and Molecular (cpSSR) Evidence

“…This area has also been cited as a core region for the hybrid origin of some pine species and varieties (Styles 1993). In this scenario, it is also expected that we will find similar chloroplasts in closely related species because of hybridization and/or the retention of ancestral polymorphisms (Golden and Bain 2000). These two phenomena could be in some instances dissociated through the analysis of the geographic distribution of the putative hybrids and their position in a haplotype network.…”

Glacial refugia and reticulate evolution: the case of the Tasmanian eucalypts

“…In others, earlier hybridization during glacial periods has been inferred. For instance, cpDNA diversity in northern populations of Packera pseudaurea (Asteraceae) in Alberta suggests former hybridization with other Packera species that migrated southwards during periods of glaciation (Yates et al 1999;Golden & Bain 2000). In southeast Spain, species of Armeria (Plumbaginaceae), which now occur at different altitudes, may have hybridized during Quaternary compressions of vegetation within massifs (Larena et al 2002).…”