THE GEOGRAPHICAL ORIGINS AND MIGRATION HISTORY OF CREEPING SIBBALDIA, SIBBALDIA PROCUMBENS (ROSACEAE)

From: Gerry Allen & L.J. McCormick (University of Victoria) and K.L. Marr & R.J. Hebda (Royal British Columbia Museum), Victoria, British Columbia

Many arctic-alpine plants have very large geographic ranges, often extending almost completely around the Northern Hemisphere. Some of these geographic distributions are nevertheless highly discontinuous, suggesting a long history with multiple cycles of range expansion and contraction. Molecular methods have become widely used to elucidate the geographic history of such groups.

Arctic tundra habitats became widespread at the end of the Tertiary, approximately 3 million years ago (Murray 1995; Abbott & Brochmann 2003). Some arctic species date back to the late Tertiary, whereas others colonized the arctic much more recently. Phylogeographic approaches (integrating genetic analyses of DNA data with spatial information) can be used to ask questions about the geographic origins of species, the locations of Pleistocene refugia, the role of long-distance dispersal, and (in combination with other evidence, such as dated macrofossils) the timing of all these events.

To investigate these questions for a low-arctic plant with a fragmented geographic range, we examined genetic patterns (Allen et al. 2015) in the montane to arctic-alpine creeping perennial Sibbaldia procumbens. Our analyses were based on DNA sequences from three regions of the chloroplast genome (the atpI-atpH and trnL-trnF intergenic spacers and the trnL intron). We sampled Sibbaldia from 176 localities, including 168 for S. procumbens. We carried out Bayesian phylogenetic analyses and statistical parsimony analyses on the combined sequences, using these to analyze genetic diversity (based on plastid haplotype frequencies) and geographical patterns of divergence over the entire geographic range.

Sibbaldia has historically been a genus of uncertain taxonomic definition and affinities, with recent studies resulting in a much narrower circumscription (e.g., Ericksson et al. 2015, Ertter & Reveal 2015). A broader traditional circumscription is polyphyletic and consists of multiple divergent lineages. The most widespread of these lineages is the Sibbaldia procumbens clade, consisting of S. procumbens and a few closely related species (including the central to south Asian S. parviflora and S. cuneata). This clade probably originated in the vicinity of the Qinghai-Tibetan Plateau in China. We identified two highly distinct subclades within S. procumbens, one centred in Europe and the other in North America. These two subclades overlap on oceanic islands of the North Atlantic, indicating that this species has long-distance dispersal capability although its achenes lack any obvious dispersal adaptations (Coker 1966).

Similar patterns have been reported for other arctic species (e.g., Alsos et al. 2007). The North American subclade was further divided into two lineages, one restricted to California and the other widely distributed across the continent and North Atlantic. In the widespread lineage, genetic diversity was low in the north and markedly higher to the south. This suggests that following the spread of S. procumbens into North America, a mid- to late Pleistocene southward displacement of North American populations occurred, with subsequent migration northward into previously glaciated regions. Our sampling of the European subclades, though less extensive than in North America, showed that disjunct geographical regions generally harboured distinct haplotypes.

There is evidence for multiple Pleistocene refugia for Sibbaldia procumbens in both North America and Europe. North American refugia existed in California and in the southern Rocky Mountains. Beringia has long been considered to be a critically important Pleistocene refugium for arctic-alpine plants (Hultén 1937). However, in contrast with results for most widespread arctic-alpine species, we found no evidence that S. procumbens persisted in a Beringian refugium. Geographic distributions of some haplotypes suggest that cryptic refugia may have existed within the Cordilleran Ice Sheet. Episodes of range expansion and contraction and long-distance dispersal have all contributed to the genetic structure and widespread but fragmented distribution of this species.

References

Abbott, R.J. & C. Brochmann. 2003.

History and evolution of the arctic flora: in the footsteps of Eric Hultén. Molecular Ecology 12: 199-213.

Allen, G.A., K.L. Marr, L.J. McCormick & R.J. Hebda. 2015.

Geographic origins, migration patterns and refugia of Sibbaldia procumbens, an arctic-alpine plant with a fragmented range. Journal of Biogeography (published online 19 JUN 2015 | DOI: 10.1111/jbi.12543).

Alsos, I.G., P.B. Eidesen, D. Ehrich, I. Skrede, K. Westergaard, G.H. Jacobsen, J.Y. Landvik, P. Taberlet, & C. Brochmann. 2007.

Frequent long-distance plant colonization in the changing Arctic. Science 316: 1606-1609.

Coker, P.D. 1966.

Sibbaldia procumbens L. Journal of Ecology 54: 823-831.

Eriksson, T., Lundberg, M., Töpel, M., Östensson, P. & Smedmark, J.E.E. 2015.

Sibbaldia: a molecular phylogenetic study of a remarkably polyphyletic genus in Rosaceae. Plant Systematics and Evolution 301: 171-184.

Ertter, B., & J. L. Reveal. 2015 [2014].

Sibbaldia. In: Flora of North America Editorial Committee, eds. 1993+. Flora of North America North of Mexico. 18+ vols. New York and Oxford. 9: 297-299.

Hultén, E. 1937.

Outline of the history of arctic and boreal biota during the Quaternary Period. Lehre J. Cramer, New York.

Murray, D.F. 1995.

Causes of arctic plant diversity. Pp. 21-32 in R.S. Chapin III, R.S. & C. Körner.[Eds.]. Arctic and alpine diversity: patterns, causes and ecosystem consequences. Springer, Heidelberg.

COMPANY IN CANADIAN ENVIRONMENTAL DISASTER OPENS MINE ON ALASKA-BOUND RIVER

The British Columbia government has approved full operating permits for a controversial gold and copper mine in the Stikine-Iskut River system, which rises in Canada, runs downstream into Alaska and supports a major salmon fishery.

The Red Chris mine is operated by Imperial Metals, which saw a major environmental disaster in interior B.C. last summer. And that has Alaska's fisheries industry worried.

A tailings dam at Imperial's Mount Polley mine collapsed and sent millions of gallons of contaminated water down a creek into Quesnel Lake - just as 2 million sockeye salmon were headed up the Fraser River to spawn in the area.

But nothing can dampen British Columbia's love of the mining industry, a romance fueled by major contributions to Premier Christy Clark and the province's ruling political party. The majority stockholder at Imperial Metals feted Clark at a pricey Calgary fundraiser before B.C.'s last election.

B.C. Mines Minister Bill Bennett has been lead cheerleader for the Red Chris project. "It is a totally different design in terms of the tailings storage facility itself," he recently told CBC News. The Red Chris mine will, however, produce totally different tailings, as found in an independent review of its tailings impoundment.

The mine tailings and contaminated water released by the Mount Polley mine were - by mining standards - relatively benign. The tailings at the Red Chris mine site are more acidic, and have the potential to leach toxic metals into the environment. The Iskut River is the major tributary of the Stikine River, one of North America's great rivers. The Stikine crosses the border near the Alaskan towns of Petersburg and Wrangell.

"It's astonishing to me how B.C. is dead set on getting these transboundary mines operating at all costs - even when their own experts say that current mining technology will fail," said Rob Sanderson, Jr., co-chair of the United Tribal Transboundary Mining Working Group.

"As I've said before, the B.C. government is ignoring the rights and concerns of those of us who live in Southeast Alaska. This is not O.K. and we will continue to fight," he told Alaska Native News.

In British Columbia last summer, the Tahltan First Nation blockaded the road leading to Red Chris, demanding an independent assessment of its safety features. The Tahltans have since entered into an agreement to co-manage the mine.

Bennett is relentlessly boosterish. At one point, he compared the collapse of the tailings dam to a spring avalanche in the mountains.

The Mount Polley disaster was caused by a faultily constructed tailings dam. The British Columbia government has, as well, cut back on inspections at mines in recent years.

In Bennett's words, however, "The same people in Alaska are saying they don't have these kinds of mines in the state. They do. They've got the Fort Knox gold mine. They've got the Red Dog zinc mine.

"They've got a number of mines with exactly the same open pit mining method and exactly the same earthen dams and tailings storage facilities."

Yes, but these mines are not located on major transboundary salmon rivers. British Columbia is plotting new projects on the Unuk River near Ketchikan - a major Chinook salmon stream - and the Taku River near Juneau, where an old mine site continues to leach pollutants into the river.

Alaskans, even the state's pro-development congressional delegation, have asked U.S. Secretary of State John Kerry to activate the International Joint Commission (IJC) to review mine developments in the transboundary region and their potential impacts on Alaska's waters and fisheries.

The record of the British Columbia government does not elicit trust.

[Editorial Note: Opinions expressed by the BEN contributors do not necessarily reflect those of the BEN editor.]

Subscriptions: http://victoria.tc.ca/mailman/listinfo/ben-l.
Send submissions to aceska@telus.net

BEN is archived at http://www.ou.edu/cas/botany-micro/ben/