Phylogeographical evidence of gene flow among Common Crossbill (Loxia curvirostra, Aves, Fringillidae) populations at the continental level

Common Crossbill subspecies have been described according to morphological traits, vocalizations and geographical distribution. In this study, we have tried to determine whether the subspecies correspond to clear-cut mitochon drial DNA lineages, by sequencing 717 bp of the control region from individ uals taken at several sampling locations in North America and the Western P alaearctic. We find 22 haplotypes from the 37 sampled individuals with a me an divergence of 0.0118 +/- 0.0069 (mean +/- SD). We find a mixing of the m itochondrial haplotypes at the continental level among the different types or subspecies previously described. Morphological differentiation (in bill size and shape essentially) shows the possibility of rapid local adaptation to fluctuating resources (coniferous seeds), without necessarily promoting the development of reproductive barriers between morphs.