Genetic variation in nuclear and mitochondrial markers supports a large sex difference in lifetime reproductive skew in a lekking species.

Sex differences in skews of vertebrate lifetime reproductive success are difficult to measure directly. Evolutionary histories of differential skew should be detectable in the genome. For example, male-biased skew should reduce variation in the biparentally inherited genome relative to the maternally inherited genome. We tested this approach in lek-breeding ruff (Class Aves, Philomachus pugnax) by comparing genetic variation of nuclear microsatellites (θ n ; biparental) versus mitochondrial D-loop sequences (θ m ; maternal), and conversion to comparable nuclear (N e ) and female (N ef ) effective population size using published ranges of mutation rates for each marker (µ). We provide a Bayesian method to calculate N e (θ n = 4N e µ n ) and N ef (θ m = 2N ef µ m ) using 95% credible intervals (CI) of θ n and θ m as informative priors, and accounting for uncertainty in µ. In 96 male ruffs from one population, N e was 97% (79-100%) lower than expected under random mating in an ideal population, where N e :N ef = 2. This substantially lower autosomal variation represents the first genomic support of strong male reproductive skew in a lekking species.

Arctic-nesting birds find physiological relief in the face of trophic constraints.

A climate-induced phenological mismatch between the timing of reproduction and the timing of food resource peaks is one of the key hypothesized effects of climate change on wildlife. Though supported as a mechanism of population decline in birds, few studies have investigated whether the same temperature increases that drive this mismatch have the potential to decrease energetic costs of growth and compensate for the potential negative effects of reduced food availability. We generated independent indices of climate and resource availability and quantified their effects on growth of Dunlin (Calidris alpina) chicks, in the sub-arctic tundra of Churchill, Manitoba during the summers of 2010-2011 and found that when resource availability was below average, above average growth could be maintained in the presence of increasing temperatures. These results provide evidence that chicks may find physiological relief from the trophic constraints hypothesized by climate change studies.