Abstract:
Phenological shifts are the most commonly reported ecological
responses to climate change and can be produced rapidly by phenotypic
plasticity. However, both the limits of plasticity and whether it
will be sufficient to maintain local adaptation (or even lead to maladaptation)
are less clear. Increased winter precipitation has been shown to
lead to phenological delays and corresponding annual decreases in fitness
in Columbian ground squirrels (Urocitellus columbianus).Wetook
advantage of natural phenological variation (across elevations) in this
species to better assess the extent of phenotypic plasticity in emergence
dates and the relationships between emergence dates and individual annual
fitness. We coupled a reciprocal translocation experiment with
natural monitoring across two populations separated by ∼500 m in elevation.
Individuals in both populations responded plastically to both
spring temperature and winter precipitation. Translocated individuals
adjusted their emergence dates to approach those of individuals in their
adoptive populations but did differ significantly in their emergence
dates fromresidents. There were no differences in annual fitness among
treatment groups nor selection on emergence date within a year. Phenotypic
plasticity is thus sufficient to allow individuals to respond to
broad environmental gradients, but the influence of variation in emergence
dates on annual fitness requires further investigation.
