Glacier Ice Worms Distribution
Where glacier ice worms are:
Glacier ice worms inhabit glaciers in Alaska, British Columbia, Washington State, and Oregon.
To download a list of survey sites from present and previous work, click here.
Where glacier ice worms are not:
Glacier ice worms do not occur in the Rocky Mountains of British Columbia, Alberta, and Montana. They do not occur south of the Sisters Range in Central Oregon, nor north of the southern coast of Alaska. They do not occur in the glaciers of Kamchatka (Shiro Kohshima, personal communication), Greenland or the Arctic Archipelago of Greenland (Bent Christiansen, personal communication).
Possible dispersal mechanisms
Is glacier ice worm distribution limited by where ice worms can crawl directly, and does the extent of the Cordilleran ice sheet explain the limits of their distribution? Glacier ice worms are not found on all glaciers within the area previously occupied by the Cordilleran ice sheet, but this absence could be explained by local extinctions.
On the other hand, even if there was a pan-Cordilleran glacier ice worm population, this origin would not explain the origin of the Sisters Range populations in central Oregon, well south of the maximum extent of the Cordilleran ice sheet. Phylogenetic analysis of glacier ice worm populations (Hartzell et. al., n.d.) tells us that the Oregon populations are a more recent branch off of the Washington populations; therefore, it is unlikely that they arose during a pre-Cordilleran period as well.
Some other possible mechanisms of glacier ice worm dispersal are: (1) wind, (2) humans, and (3) birds. Wind-blown cocoons are known as a mechanism of dispersal for arctic terrestrial worms; however, wind dispersal of cocoons seems less likely in an environment where water tension would make wind dispersal difficult. If the branching event was recent enough -- which future study may tell us -- human mountain climbers could have carried ice worms, inadvertantly or purposefully, from Washington or Oregon. If that was the case, however, they would have had to do this for multiple glaciers on multiple peaks. That seems unlikely.
The grey-crowned rosy finch (Leucostricte tephrocotis (Swainson)) frequently feed in singles, pairs, and small flocks, on glaciers during the spring and summer, when they are also nesting in the alpine. These birds travel short distances, but do not migrate long distances. They appear to be the most likely candidate for ice worm dispersal between glaciers. Hartzell is currently working on a manuscript discussing this topic.