Meeting Abstract

P3.11  Friday, Jan. 6  Evolution of photorefractoriness in the Cardueline finches. HAHN, T. P.*; HAIMAN, A. N.; BRAZEAL, K. R.; DE CASTRO, D. M.; GENDI, K. M.; BOMZE, L. M.; WATTS, H. E.; Univ. of California, Davis; Univ. of California, Davis; Univ. of California, Davis; California State Univ. East Bay; Univ. of California, Davis; Univ. of California, Davis; Loyola Marymount Univ.

Photorefractoriness in birds is defined as reproductive insensitivity to the stimulatory effects of long days. It is characterized by spontaneous termination of reproductive competence despite continued long days, and complete unresponsiveness even to constant light once the gonads have collapsed. Among songbirds, taxa that breed on temporally opportunistic schedules (e.g., crossbills, zebra finches) tend to lack refractoriness, whereas seasonally-breeding taxa consistently display refractoriness as part of their annual cycles. Within the Cardueline tribe of finches (Fringillidae), the only taxa that have been found to lack refractoriness are the crossbills (Loxia spp.), a group of archetypal temporal opportunists that specialize on unpredictably-distributed seeds of conifers. This study extended existing among-species comparisons of photorefractoriness by testing for photorefractoriness in two relatively basally-derived cardueline lineages, genus Leucosticte (rosy-finches) and genus Coccothraustes (hawfinches/evening grosbeaks). Both gray-crowned rosy-finches (L. tephrocotis) and evening grosbeaks (C. vespertinus) collapsed the gonads spontaneously when held on constant long days after the summer solstice, consistent with the hypothesis that photorefractoriness is the ancestral trait within the cardueline finches. This finding lends further support to the inference that the absence of photorefractoriness in the crossbills represents a recently-evolved adaptation facilitating temporal reproductive flexibility.