Translocation experiment reveals capacity for mountain pine beetle persistence under climate warming

Predicting species response to climate change is a central challenge in
ecology, particularly for species that inhabit large geographic areas. The
mountain pine beetle (MPB) is a significant tree mortality agent in
western North America with a distribution limited by climate. Recent
warming has caused large-scale MPB population outbreaks within its
historical distribution, in addition to migration northward in western
Canada. The relative roles of genetic and environmental sources of
variation governing MPB capacity to persist-in-place in a changing
climate, and the migratory potential at its southern range edge in the
United States, have not been investigated. We reciprocally translocated
MPB populations taken from the core and southern edge of their range, and
simultaneously translocated both populations to a warmer, low-elevation
site near the southern range boundary where MPB activity has historically
been absent despite suitable hosts. We found genetic variability and
extensive plasticity in multiple fitness traits that would allow both
populations to persist in a warming climate that resembles the thermal
regime of our low-elevation site. We demonstrate, for the first time, that
supercooling points in MPBs are influenced both by genetic and
environmental factors. Both populations reproduced with seasonally
appropriate univoltine generation times at all translocated sites, and
bivoltinism was not observed. The highest reproductive success occurred at
the warmest, out-of-range low-elevation site, suggesting that southward
migration may not be temperature-limited.