Peter Wimberger
Updated: August 2009
I am an evolutionary and conservation biologist. The general goals of my research are to increase our understanding of the patterns and processes of evolution. I am particularly interested in using evolutionary trees to examine the relationship between ecology and evolutionary change and to assess population structure within single species. I am also interested in research that uses museum specimens to test evolutionary and ecological hypotheses. My two primary projects right now are looking at ice worm phylogenetics and evolution and examining wing whistling in sea ducks.
Ice worm evolution
Ice worms are annelids that live only in glaciers. They probably feed on bacteria, algae and detritus that lands on the ice. They are small (20 mm x 1.5 mm), pigmented worms that are a bit like miniature earthworms. Ice worms can be found from central Oregon (Sisters volcanoes) to south central Alaska. Previous work identified two primary evolutionary lineages – one from Alaska and the other from the Cascades and southern British Columbia. A few years ago, a Biology student, Ben Lee, looking for a way to spend the summer in the mountains and still do thesis research, proposed doing some kind of population genetic study on ice worms. No one had looked at how worms in the Olympic Mountains and on Vancouver Island fit into the overall evolutionary picture. Our prediction was that the worms in the Olympics and on Vancouver Island would be most closely related to worms from the Cascades.
As often happens when one does science, the answer to the question was much more interesting than we expected. We used DNA sequence data from the mitochondrial gene cytochrome oxidase 1 and the nuclear gene 28s ribosomal RNA to estimate relationships. Worms from the Vancouver Island and majority of the Olympic populations were descendants of the Alaska evolutionary lineage. It was only when we looked at the highest glaciers in the Olympics that we found representatives of the Cascade lineage. However, these worms coexisted on the glaciers with worms from the Alaska evolutionary lineage!
How do we explain this surprising and intriguing pattern? Usually evolutionary biologists use geology to help make inferences about geographic population patterns. The primary mode of worm dispersal is likely glacial movement. Worms are transported from place to place on glaciers. The presence of worms in alpine glaciers is likely the result of continental glaciers moving the worms from farther north. The most recent incarnation of glaciers in the northern hemisphere was probably about 3 mya. There have been numerous “ice ages” over the past 2.5 mya, meaning that continental glaciers made their way south like the recent one that departed only ~11,000 years ago. The problem with each glacial event is that it wipes out records of previous ones. Most of the worms, based on amounts of DNA divergence clearly made it here prior to the last glacial event, some long before. I think that the phylogeography of ice worms actually allows us a window to earlier glacial events not accessible via traditional geology.
Our explanation of the pattern we see in the Olympics and Cascades is this… A continental glaciation perhaps 2 mya or older left worms in the Cascades and Olympics. In subsequent interglacials all of the alpine glaciers in the Cascades melted and all but the highest glaciers in the Olympics melted leaving Cascade lineage worms in refugia on those high Olympic peaks and somewhere in north-central British Columbia. A more recent glacial event recolonized the Cascades, with the source of the continental ice (and Cascade lineage ice worms) in the Cascades from that BC refuge. Continental ice from somewhere in north BC or Alaska (and Alaska lineage ice worms) made its way down the coast, through the Straits of Georgia, into the Strait of Juan de Fuca and Hood Canal carrying Alaska lineage worms that connected with the lower alpine glaciers of the Olympics. These glaciers from further north that travelled the coastal route are now the source of the worms we now find on Vancouver Island and the majority of Olympic Mountain glaciers. Data suggest that a subsequent interglacial melted most of the glaciers in the Cascade with the exception of a few high peaks like Rainier.
What are we doing with ice worms now? Ali Garel is finishing up the phylogeographic story and has begun looking at the phenology and ecology of ice worms on glaciers. Lan Luong is looking at the molecular evolution of some metabolically important genes – a promising avenue of research because ice worms are strange - unlike most animals they increase their ATP production as they get colder. And Jordan Carelli has proposed examining the biochemistry of cold adaptation in ice worms. I hope to begin looking at more genetic variation in populations in more detail using microsatellites. These would hopefully allow us a finer resolution look at population history than DNA sequences. Finally I would like to examine more populations from central BC to find out where the split between Alaskan and Cascade worms lies to think about where the refuge for the Cascade lineage worms was.
Whistling Wings in Sea Ducks
Informal discussions in the Slater Museum led us to wonder if it’s both sexes of ducks like Goldeneyes and Surf Scoters that whistle when they fly. Remarkably, something not noted in the literature, was the fact that only males of these species whistle when they fly. Eric Doran examined the morphological correlates of wing whistling in sea ducks. Using museum spread wing specimens, Eric found that the outer wing feather (primary 10) is more attenuated in the males than females of whistling species and also more attenuated than in males of closely related non-whistlers. Eric also observed that feather width is related to pitch and observed that in some species juvenile male feathers are female-like (presumably they don’t whistle) while in others they are male-like (and we know these species whistle). These interesting observations leave us with a host of hypotheses to test and questions to answer ranging from proximate – how do the birds generate the whistling sound (is it on the upbeat or downbeat? Is it the result of turbulence over a hole or feather vibration?) to ultimate – how is whistling used in mate attraction and does it signal something about male quality to females? Some interesting potential projects would involve high speed filming and recording of different species, behavioral observations of courtship and, of course, more museum related studies of feather morphology.
