Phylogeographical patterns in the widespread arctic–alpine plant Bistorta vivipara (Polygonaceae) with emphasis on western North America

Abstract

Aim We investigated genetic variation in Bistorta vivipara, a widespread Northern Hemisphere tundra species, to infer patterns of migration and where it may have survived during the Last Glacial Maximum (LGM). Location Samples came primarily from western North America, with a few from the Arctic and Eurasia. Methods We sequenced two chloroplast DNA spacer regions, trnH–psbA and trnS–G, in individuals from 199 populations and mapped haplotype distributions and their relationships using a haplotype network. We calculated genetic and molecular diversity statistics for the seven geographical regions from which we obtained samples. Results Fifteen haplotypes were detected, with very little divergence among them. The haplotypes are separated into two main groups by the presence or absence of a 22 bp tandem duplication. Four haplotypes are common, widespread and with substantial range overlap; 11 are rare and mostly unique to one region. Two rare haplotypes were found only in British Columbia (BC). Western North America and Asia have the highest levels of genetic and molecular diversity. Northern and southern BC have different haplotype complements. Main conclusions Bistorta vivipara has relatively low genetic diversity, with much less genetic structure than we expected for such a widespread species. We expected significant geographical structure due to the combined effects of genetic drift and geographical isolation. The asexual reproductive mode of B. vivipara may facilitate relatively rapid population establishment and spread compared with sexual reproduction by seed. Bistorta vivipara probably originated in Asia and spread to North America and Europe prior to the LGM. In western North America it spread to its modern distribution from Beringia and the western USA following the LGM. Populations in northern and southern BC may have different histories, possibly related to the timing and extent of glaciation. The occurrence of two unique haplotypes within BC suggests that some individuals may have survived in full glacial refugia within BC.

Do geographic, climatic or historical ranges differentiate the performance of central versus peripheral populations?

“…For S. acaulis and P. viviparum we would therefore expect a higher genetic diversity in southern populations, declining towards areas glaciated at the LGM (Fig. ), but the latter deviates from this prediction, most probably due to its asexual mode of reproduction (Diggle et al ., ; Marr et al ., ). The nunataks present within the ice sheet at the LGM could also potentially act as refugia for boreoalpine plants and therefore alter this prediction.…”

Biogeography of plant root‐associated fungal communities in the North Atlantic region mirrors climatic variability

“…21 kya), large parts of Northern Europe were covered with ice, and as such, all of the sampling areas were completely or partially covered by ice (Clark et al, ; Landvik et al, ). Although there are little specific data on the migration route of B. vivipara in Europe after the LGM (but see: Marr, Allen, Hebda, & McCormick, ), recolonization by other plant species in these areas occurred from multiple source regions, for example, to Svalbard from Greenland, Russia and Fennoscandia (Alsos et al, ). Despite relatively close geographical proximity and physical connectivity since the LGM, the community composition in the samples from Austria was different from mainland Norway samples.…”

Geographical origins, migration patterns and refugia of Sibbaldia procumbens, an arctic–alpine plant with a fragmented range

“…It occurs in disjunct populations in southern Québec (Mont Groulx) and New England (White Mountains); macrofossil evidence of S. procumbens has been found in the Connecticut Valley of New Hampshire at approximately 11,500 14 C yr bp (Miller & Thompson, ) and in the Great Lakes region at 12,200 14 C yr bp (Maher et al ., ), indicating that the species extended farther south at the end of the LGM than at present. However, we found no support for a northern (Bering‐ian) refugium during the LGM, in strong contrast with evidence for other arctic–alpine plants (Alsos et al ., ; Eidesen et al ., ,b; Skrede et al ., ; Allen et al ., ; Marr et al ., ; Guest & Allen, ). Thus, S. procumbens is a notable exception to the generally well‐supported hypothesis of Hultén () that Beringia was a critically important refugium for arctic–alpine species.…”

“…Cooper, ), and biogeographical evidence suggests that some areas along the Pacific margin of the Cordilleran Ice Sheet in British Columbia escaped glaciation (Ogilvie & Ceska, ; Hebda et al ., ; Reimchen & Byun, ). Recent genetic evidence from tundra species, in the form of unique haplotypes in both coastal and inland British Columbia, suggests cryptic LGM refugia (Shafer et al ., ; Allen et al ., ; Marr et al ., ; Guest & Allen, ). No unique haplotypes of S .…”