Nestling sex ratios in a population of Bluethroats Luscinia svecica inferred from AFLP (TM) analysis
Résumé
We studied the sex ratio of Bluethroat Luscinia svecica broods using AFLPs. Our aim was to test whether there is a bias towards males that could be explained by sexual selection thee-tries, or conversely, a bias towards females that could help explain the female-biased sex ratio among juveniles observed at a wintering site. The AFLP technique was reliable in sexing the nestlings from even small initial DNA quantities. Given the large number of polymorphic markers that can be obtained for each primer combination, the probability of detecting a W-chromosome-linked fragment is reasonably high. As a consequence, this method could be used in other species far sex-ratio studies and for other genetic purposes. Among 246 nestlings. we found an overall proportion of males of 50.8% at hatching and the sex-ratio variation using broods as independent units was not significantly different from expectation under a binomial distribution. None of the parental and environmental variables tested changed significantly the deviance to the model. Thus, sex determination in the Bluethroat seems to match the classical Mendelian model of a 1:1 sex ratio and cannot explain the biased sex ratio towards juvenile females found at the wintering site.