Variances and covariances of phenological traits in a wild mammal population

Abstract

In a seasonal environment, there are multiple aspects of timing, or phenology, that contribute to an individual's fitness. Several studies have shown a genetic basis to variation between individuals in breeding time, but we know little about the heritability of other phenological traits in wild populations. Furthermore, the presence of genetic correlations between phenological variables could act to constrain or promote any response to selection, but less is known of the multivariate genetic relationships underlying phenological traits in the wild. Here, we use data from a wild population of red deer on the Isle of Rum, Scotland, to investigate covariances between eight phenological traits. Variation was characterized at the level of the phenotype, genotype, and year, and traits measured in different sexes enabled us to test for cross-sex genetic correlations. Phenotypic correlations were broadly strong and positive, as were correlations between traits expressed in the same year. We found evidence of significant additive genetic variation in five of the eight phenological traits studied. However there was little evidence of genetic correlations between traits, implying that much of the observed phenotypic correlation was environmentally induced. Our results suggest that different phenological traits may be free to move along independent evolutionary trajectories.