Marked genetic divergence among sky island populations ofSedum lanceolatum(Crassulaceae) in the Rocky Mountains

Abstract

Climate change during the Quaternary played an important role in the differentiation and evolution of plants. A prevailing hypothesis is that alpine and arctic species survived glacial periods in refugia at the periphery of glaciers. Though the Rocky Mountains, south of the southernmost extent of continental ice, served as an important glacial refuge, little is known about how climate cycles influenced populations within this region. We inferred the phylogeography of Sedum lanceolatum (Crassulaceae) within the Rocky Mountain refugium to assess how this high-elevation plant responded to glacial cycles. We sequenced 884 base pairs (bp) of cpDNA intergenic spacers (tRNA-L to tRNA-F and tRNA-S to tRNA-G) for 333 individuals from 18 alpine populations. Our highly variable markers allowed us to infer that populations persisted across the latitudinal range throughout the climate cycles, exhibited significant genetic structure, and experienced cycles of range expansion and fragmentation. Genetic differentiation in S. lanceolatum was most likely a product of short-distance elevational migration in response to climate change, low seed dispersal, and vegetative reproduction. To the extent that Sedum is a good model system, paleoclimatic cycles were probably a major factor preserving genetic variation and promoting divergence in high-elevation flora of the Rocky Mountains.

Genetic Structure of the Carnivorous Plant Pinguicula moranensis (Lentibulariaceae) on the Transvolcanic Mexican Belt

“…First, populations of montane or subalpine species are exposed to unsuitable habitats occurring between the mountaintops and tend to experience an insular-like effect. The montane distribution is frequently correlated with a marked genetic differentiation (Gaudeul et al 2001;DeChaine and Martin 2005;Ge et al 2005;Zheng et al 2008;Wang et al 2008). This seems to be the case for P. moranensis, because most of its populations in Mexico are restricted to north-oriented wet rocky walls and cliffs at altitudes of 2,000-3,200 m (Zamudio 2001).…”

Range shifts of Potentilla fruticosa on the Qinghai-Tibetan Plateau during glacial and interglacial periods revealed by chloroplast DNA sequence variation

“…However, genetic patterns of alpine plants in temperate and tropical regions are complex, and it is difficult to detect clear range shifts because alpine habitats are highly fragmented, having never been connected during glacial or interglacial periods. High-elevation populations may have mainly migrated upslope and downslope, thus remaining isolated throughout the palaeoclimatic cycles, with the result that there was little opportunity for inter-population gene flow (DeChaine and Martin, 2005). Moreover, stochastic demographic events, including extinction, population isolation and long-distance dispersal, can have more noticeable effects in fragmented habitats than in connected habitats, further obscuring geographic genetic patterns.…”

Relationships of North American members ofRhodiola(Crassulaceae)

“…3) suggest that populations of an ancestral R. integrifolia lineage became separated into two refugia during one of the Early or Middle Pleistocene glacial maxima. One of the refugia might have been in the central or southern Rocky Mountains and the other in Beringia (Duk-Rodkin et al 2004;DeChaine and Martin 2005). The patterns of sequence variation evident in Guest's analysis and in our data set suggest that Leedy's roseroot and the Harney Peak (South Dakota), Canadian, Alaskan, and Siberian R. integrifolia populations originate from the Beringian refugium.…”