Kendrick L. Marr

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

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.

Vicariance, long‐distance dispersal, and regional extinction–recolonization dynamics explain the disjunct circumpolar distribution of the arctic‐alpine plant Silene acaulis

PREMISE OF THE STUDY Many arctic-alpine species have vast geographic ranges, but these may encompass substantial gaps whose origins are poorly understood. Here we address the phylogeographic history of Silene acaulis, a perennial cushion plant with a circumpolar distribution except for a large gap in Siberia. METHODS We assessed genetic variation in a range-wide sample of 103 populations using plastid DNA (pDNA) sequences and AFLPs (amplified fragment length polymorphisms). We constructed a haplotype network and performed Bayesian phylogenetic analyses based on plastid sequences. We visualized AFLP patterns using principal coordinate analysis, identified genetic groups using the program structure, and estimated genetic diversity and rarity indices by geographic region. KEY RESULTS The history of the main pDNA lineages was estimated to span several glaciations. AFLP data revealed a distinct division between Beringia/North America and Europe/East Greenland. These two regions shared only one of 17 pDNA haplotypes. Populations on opposite sides of the Siberian range gap (Ural Mountains and Chukotka) were genetically distinct and appear to have resulted from postglacial leading-edge colonizations. We inferred two refugia in North America (Beringia and the southern Rocky Mountains) and two in Europe (central-southern Europe and northern Europe/East Greenland). Patterns in the East Atlantic region suggested transoceanic long-distance dispersal events. CONCLUSIONS Silene acaulis has a highly dynamic history characterized by vicariance, regional extinction, and recolonization, with persistence in at least four refugia. Long-distance dispersal explains patterns across the Atlantic Ocean, but we found no evidence of dispersal across the Siberian range gap.

Distributional and Morphological Differences between Native and Introduced Common Reed (Phragmites australis, Poaceae) in Western Canada

Phragmites australis (common reed) is a widespread perennial grass of wetland habitats, with cryptic native and introduced subspecies in North America. We determined the relative abundance of the subspecies and the distributions of plastid DNA haplotypes throughout British Columbia, Canada, at the northwestern distribution limit of common reed in North America. Of 203 specimens assigned to subspecies using molecular markers, we identified only 9 plants as the introduced ssp. australis; all remaining samples were the native ssp. americanus. The two subspecies co-occurred at only one locality. We identified four native haplotypes (one widespread in British Columbia and three others more localized) and two introduced haplotypes. Using plants of known haplotype, we assessed the utility of different morphological traits and trait combinations for distinguishing native and introduced subspecies in this geographic region. No single morphological trait was diagnostic, but principal components analysis and identification indices based on combinations of traits consistently separated the native and introduced subspecies in our sample. Two- or three-trait combinations of ligule length, lemma length and stem anthocyanic coloration gave the best separation. These indices could reduce the need for confirmation of the introduced subspecies using molecular tools, facilitating efforts to monitor and control this invasive plant.

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

Abstract The taxonomically difficult and ecologically and phytogeographically important genus, Calamagrostis, was examined for British Columbia (BC). Morphological characters were analyzed by Principal Components Analysis (PCA) to characterize taxa and to aid in the development of a new key. Eight native species (Calamagrostis canadensis, C. lapponica, C. montanensis, C. nutkaensis, C. purpurascens, C. rubescens, C. sesquiflora, and C. stricta) are confirmed to occur in British Columbia, of which C. montanensis, C. nutkaensis, C. purpurascens, C. rubescens, and C. sesquiflora are reliably distinguishable. Comparison of species distribution to regional climatic and vegetation history suggests that Calamagrostis nutkaensis and C. sesquiflora likely survived in coastal refugia during late Wisconsin glaciations. Calamagrostis purpurascens likely persisted beyond the glacial limits or within nunataks and then spread into previously glaciated sites. Two interior continental species, C. montanensis and C. rubescens, probably spread north and west from the unglaciated zone south of the Cordilleran and Laurentide ice sheets. Calamagrostis lapponica likely persisted north of the ice sheets, and then spread southward into high-elevation sites in northern and eastern BC. Calamagrostis canadensis and C. stricta probably survived south and north of the ice sheets, and then spread into the previously glaciated terrain.

CALAMAGROSTIS TACOMENSIS (POACEAE): A NEW SPECIES FROM WASHINGTON AND OREGON

ABSTRACT We used PCA of morphological characters to confirm the presence of an undescribed Calamagrostis species in Washington and Oregon that has historically been attributed to Calamagrostis vaseyi. We propose to name this grass Calamagrostis tacomensis. It is most similar to C. foliosa although it has often been confused with C. purpurascens and C. sesquiflora all of which have similar lemma awn characteristics (i.e., the awn relatively long, exserted, and bent). Calamagrostis tacomensis has been collected at high elevations (490–2170 m) in the Washington Cascades, the Olympic Peninsula and the Steens Mountains of Oregon. The name C. vaseyi has been misapplied to our new species. The description of C. vaseyi is similar to C. rubescens. We have studied the specimen that has been attributed to be the type of C. vaseyi and it is C. purpurascens. We lectotypify C. vaseyi.