Delayed phenology and reduced fitness associated with climate change in a wild hibernator

The most commonly reported ecological effects of climate change are shifts in phenologies, in particular of warmer spring temperatures leading to earlier timing of key events. Among animals, however, these reports have been heavily biased towards avian phenologies, whereas we still know comparatively little about other seasonal adaptations, such as mammalian hibernation. Here we show a significant delay (0.47 days per year, over a 20-year period) in the hibernation emergence date of adult females in a wild population of Columbian ground squirrels in Alberta, Canada. This finding was related to the climatic conditions at our study location: owing to within-individual phenotypic plasticity, females emerged later during years of lower spring temperature and delayed snowmelt. Although there has not been a significant annual trend in spring temperature, the date of snowmelt has become progressively later owing to an increasing prevalence of late-season snowstorms. Importantly, years of later emergence were also associated with decreased individual fitness. There has consequently been a decline in mean fitness (that is, population growth rate) across the past two decades. Our results show that plastic responses to climate change may be driven by climatic trends other than increasing temperature, and may be associated with declines in individual fitness and, hence, population viability

Kin effects on energy allocation in group-living ground squirrels

International audience1. The social environment has potent effects on individual phenotype and fitness in group-livingspecies.2. We asked whether the presence of kin might act on energy allocation, a central aspect oflife-history variation.3. Using a 22-year data set on reproductive and somatic allocations in Columbian groundsquirrels (Urocitellus columbianus), we tested the effects of co-breeding and non-breeding kinon the fitness and energy allocation balance between reproduction and personal body conditionof individual females.4. Greater numbers of co-breeding kin had a positive effect on the number of offspringweaned, through the mechanism of altering energy allocation patterns. On average, femaleswith higher numbers of co-breeding kin did not increase energy income but biased energyallocation towards reproduction.5. Co-breeding female kin ground squirrels maintain close nest burrows, likely providing asocial buffer against territorial invasions from non-kin ground squirrels. Lower aggressiveness,lower risks of infanticide from female kin and greater protection of territorial boundariesmay allow individual females to derive net fitness benefits via their energy allocationstrategies.6. We demonstrated the importance of kin effects on a fundamental life-history trade-off

A quantitative genetic analysis of hibernation emergence date in a wild population of Columbian ground squirrels

The life history schedules of wild organisms have long attracted scientific interest, and, in light of ongoing climate change, an understanding of their genetic and environmental underpinnings is increasingly becoming of applied concern. We used a multi-generation pedigree and detailed phenotypic records, spanning 18years, to estimate the quantitative genetic influences on the timing of hibernation emergence in a wild population of Columbian ground squirrels (Urocitellus columbianus). Emergence date was significantly heritable [h2=0.22±0.05 (in females) and 0.34±0.14 (in males)], and there was a positive genetic correlation (rG=0.76±0.22) between male and female emergence dates. In adult females, the heritabilities of body mass at emergence and oestrous date were h2=0.23±0.09 and h2=0.18±0.12, respectively. The date of hibernation emergence has been hypothesized to have evolved so as to synchronize subsequent reproduction with upcoming peaks in vegetation abundance. In support of this hypothesis, although levels of phenotypic variance in emergence date were higher than oestrous date, there was a highly significant genetic correlation between the two (rG=0.98±0.01). Hibernation is a prominent feature in the annual cycle of many small mammals, but our understanding of its influences lags behind that for phenological traits in many other taxa. Our results provide the first insight into its quantitative genetic influences and thus help contribute to a more general understanding of its evolutionary significance