INVESTIGADORES
FERRETTI Valentina
congresos y reuniones científicas
Título:
Historical variation in hatching success and offspring sex ratio in a moving hybrid zone of Carolina and black-capped chickadees (Poecile carolinensis and P. atricapillus)
Autor/es:
FERRETTI, VALENTINA; BAINS, ASHVEEN; LEE, RACHEL; CORNELL, KERI L.; CURRY, ROBERT
Lugar:
Venus
Reunión:
Congreso; Association of Field Ornithologists Annual Meeting; 2013
Resumen:
Moving hybrid zones, although rare, can provide a temporal window in which to study the dynamics of inter-specific mating and its fitness consequences. In particular, reduced survival and hatching success of the heterogametic sex is expected when hybridization occurs, resulting in a biased sex ratio, as proposed by Haldane (1922). Thus, populations impacted by moving hybrid zones will likely suffer changes in fitness and sex ratio of the surviving offspring over time, depending on the position of the interbreeding zone. Here, we study temporal variation in hatching success and nestling sex ratio in the leading and trailing ends of a moving hybrid zone of Carolina and black-capped chickadees (Poecile carolinensis and P. atricapillus). From 1998 to 2012 we monitored nesting activity and hatching success in artificial nests at four study sites: Hawk Mountain Sanctuary (HM), Nolde Forest (NF), Great Marsh (GM) and Tuscarora State Park (TU, all sites in southeastern Pennsylvania). At the start of our study, NF was located within the chickadee contact zone, while HM was located north of the leading edge supporting a pure Black-capped chickadee population. Towards the end of our study, however, the leading edge of the contact zone had reached HM, with NF now closer to the trailing edge (Curry et al. 2007). We found differences in hatching success across years within sites in all four sites. When individual years were used in paired comparisons (i.e., comparisons between year-blocks) we found, however, that HM was the only site for which hatching success showed a significant decline coupled with an increase in variance for this measure; while at NF hatching success improved, and the variance in this reproductive variable got smaller as years progressed. Previous studies at these same field sites in Pennsylvania have documented reduced reproductive success associated with interspecific pairing (Reudink et al. 2006). Preliminary analyses on the sex ratios of nestlings carried out over two breeding seasons (1999 and 2000) at two of our sites (GM and NF), however, showed no significant differences (53.6% and 52.1% of male nestlings respectively). We discuss these results, and those of additional analyses that are currently underway for nestlings sampled over all the other years of our study at our four sites. Our results provide partial evidence for a hybrid disadvantage in this moving hybrid zone.