Hybridization in natural populations may be an adaptive response to shifting climatic regimes, but understanding this can be limited by the timing of sampling effort and confident identification of hybrids. On the Galapagos Islands, Darwin’s finches regularly hybridize; the islands also show extreme annual variation in rainfall, but the effect of annual rainfall on the frequency of finch hybridization is little known. Across a 20-year period on Floreana Island, we compare patterns of hybridization in sympatric Darwin’s tree finches (N = 425; Camaryhnchus spp.) and test for an effect of annual rainfall on (1) the frequency of hybrids (C. pauper × C. parvulus) and (2) the percentage of male hybrid birds produced per year (hybrid recruitment). Annual rainfall correlated with recruitment positively for hybrids, negatively for C. parvulus and not at all for C. pauper. Furthermore, the percentage of hybrids (range: 12–56%) and C. parvulus did not change with sampling year, but the critically endangered C. pauper declined. Our findings indicate that hybrid recruitment is recurring and variable according to annual rainfall in Camarhynchus Darwin’s finches.

中文翻译：

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达尔文树雀的杂交过程随降雨而波动

自然种群中的杂交可能是对不断变化的气候状况的适应性反应，但了解这一点可能会受到抽样工作的时间安排和对杂交种的确定性的限制。在加拉帕戈斯群岛上，达尔文的雀科经常杂交。这些岛屿还显示出极端的年度降雨变化，但是年度降雨对雀科杂交频率的影响鲜为人知。在Floreana岛的20年期间中，我们比较了同胞达尔文的树雀（N  = 425；Camaryhnchus spp。）的杂交方式，并测试了年降水量对（1）杂交频率（C. pauper  × 小花茶）和（2）每年繁殖的雄​​性杂种鸟的百分比（杂交募集）。年降水量与招聘呈正相关的杂交种，为负C. parvulus，而不是在所有的C.穷光蛋。此外，混合动力车的百分比（范围：12-56％）和C. parvulus没有取样一年改变，但极度濒危C.穷光蛋下降。我们的研究结果表明，根据Camarhynchus Darwin雀科的年降雨量，杂种猎物的重复发生和变化。