The impact of Pleistocene climate change on an ancient arctic–alpine plant: multiple lineages of disparate history in Oxyria digyna

Abstract

The ranges of arctic–alpine species have shifted extensively with Pleistocene climate changes and glaciations. Using sequence data from the trnH-psbA and trnT-trnL chloroplast DNA spacer regions, we investigated the phylogeography of the widespread, ancient (>3 million years) arctic–alpine plant Oxyria digyna (Polygonaceae). We identified 45 haplotypes and six highly divergent major lineages; estimated ages of these lineages (time to most recent common ancestor, TMRCA) ranged from ∼0.5 to 2.5 million years. One lineage is widespread in the arctic, a second is restricted to the southern Rocky Mountains of the western United States, and a third was found only in the Himalayan and Altai regions of Asia. Three other lineages are widespread in western North America, where they overlap extensively. The high genetic diversity and the presence of divergent major cpDNA lineages within Oxyria digyna reflect its age and suggest that it was widespread during much of its history. The distributions of individual lineages indicate repeated spread of Oxyria digyna through North America over multiple glacial cycles. During the Last Glacial Maximum it persisted in multiple refugia in western North America, including Beringia, south of the continental ice, and within the northern limits of the Cordilleran ice sheet. Our data contribute to a growing body of evidence that arctic–alpine species have migrated from different source regions over multiple glacial cycles and that cryptic refugia contributed to persistence through the Last Glacial Maximum.

Persistent history of the bird-dispersed arctic–alpine plant Vaccinium vitis-idaea L. (Ericaceae) in Japan

“…Long-term isolation will usually lead to strong genetic differentiation and accumulation of unique genotypes in marginal populations. Some studies have detected unique genetic diversity in southern marginal populations, suggesting isolation and long-term persistence; e.g., in western North America (Albach et al 2006;Allen et al 2012;Alsos et al 2005), the Carpathians (García et al 2012;Ronikier et al 2012), central Asia (Allen et al 2012;García et al 2012;Skrede et al 2006) and the central part of the Japanese Archipelago (central Japan) (Ikeda et al 2008a(Ikeda et al , 2009. However, given the high long-distance dispersal ability demonstrated for many arctic-alpine plants Eidesen et al 2007;Popp et al 2011;Westergaard et al 2011), it is also possible that their marginal populations on high mountains at lower latitudes may have resulted from southward colonization during the last glacial period when suitable habitat was more widespread or via postglacial long-distance dispersal.…”

Integrating environmental, molecular, and morphological data to unravel an ice‐age radiation of arctic‐alpine Campanula in western North America

“…Many recent studies (reviewed in Shafer et al 2010) support a multiple refugia hypothesis for the region. Oxyria digyna (L.) Hill (Allen et al 2012), for example, not only provided support for multiple refugia, but also the possibility of cryptic refugia in north British Columbia. Likewise, the persistence of Orthilia secunda (L.) House in multiple western refugia led to the emergence of endemic haplotypes (Beatty and Provan 2010).…”

“…Several potential glacial refugia have been identified in the west, including Beringia, Haida Gwaii, Vancouver Island, the Olympic Peninsula, the Southern Cascades (including the Columbia Gorge and the Klamath region), and the Northern and Southern Rocky Mountains (Hultén 1937; Soltis et al 1997; Swenson and Howard 2005; Shafer et al 2010). Furthermore, the north–south running cordillera provided opportunities for the persistence of arctic-alpine plants during cold and warm climatic periods (Allen et al 2012; DeChaine et al 2013a,b; Marr et al 2013). In general, during interglacials, populations expanded from refugia, but along a chain of sky islands that reduced the connectedness among alpine populations and potentially led to local extinction through habitat reduction.…”

Relationships of North American members ofRhodiola(Crassulaceae)

“…These glaciations would have formed potentially suitable habitats for multiple Rhodiola species near their margins, and would have formed corridors for potential east-west migration of arctic and alpine species. Given these potential habitats and the complex range shifts in arctic and alpine species that have been documented for the Pleistocene (Brochmann and Brysting 2008;Allen et al 2012), overlap in R. rhodantha (2n = 7 II ) and R. rosea (2n = 11 II ) ranges could have occurred to produce R. integrifolia (2n = 18 II ). Our estimated divergence dates for the North American Rhodiola species, and the glaciation patterns of the Pleistocene thus support the assertion of Hermsmeier et al (2012), based on their nuclear genetic data, that R. integrifolia is the result of a R. rhodantha -R. rosea hybridization event.…”