LTREB: Evaluating population cycles and spatial synchrony using long-term demographic and genetic data on snowshoe hares

University Of Montana, Missoula MT

Investigators

Abstract

Snowshoe hares provide the classical textbook example of cyclical, synchronous fluctuations in population size. Hare cycles in Canada and Alaska are legendary for their 8-11 year regularity and their 20- to 50-fold amplitude difference between peak and low population densities. Equally as remarkable, population fluctuations are synchronized across much of this range. Cyclic dynamics and spatial synchrony appear to break down in the southern parts of the hare's range, where habitats for snowshoe hares are more fragmented and movements among populations more difficult. The factors responsible for population synchrony and for the breakdown of synchrony, remain speculative. By extending a unique, spatially extensive time series of hare dynamics in the continguous US, PI Mills proposes to test long-held hypotheses accounting for a latitudinal gradient in hare dynamics and the role of population connectivity in generating these geographic patterns. Nine years of preliminary data suggest that southern populations exhibit greater temporal fluctuations than previously recognized, and that these populations are more distinct genetically than are northern populations spanning a similar spatial extent. Understanding patterns and causes of hare dynamics will advance the basic understanding of factors that influence large-scale population processes, with implications for conserving and managing many ecological systems. Population cycles and synchronous dynamics, though famously exemplified by snowshoe hares, occur in many taxa, including various insects, fish, oaks, viruses, grouse, and large mammals including caribou and muskox. Of particular conservation concern is the possibility that population synchrony and connectivity may directly affect the long-term persistence of a species. An additional application of this research to conservation arises because Canada lynx, which feed almost exclusively on snowshoe hares, are federally threatened in the U.S. outside of Alaska. The PI has established a formal program for undergraduate mentoring, and plans to involve a host of graduate and undergraduate students in this field project. Finally, all data collected will be available to the general public within 1.5 years of their collection.