Gibbs H Lisle, Grant Peter R
Museum of Zoology and Department of Biology, The University of Michigan, Ann Arbor, MI, 48109-1079.
Department of Biology, Princeton University, Princeton, NJ, 08544-1008.
Evolution. 1989 Sep;43(6):1273-1284. doi: 10.1111/j.1558-5646.1989.tb02574.x.
We studied the frequency and causes of inbreeding and its effect on reproductive success in a population of Darwin's Medium Ground Finches (Geospiza fortis) on Isla Daphne Major, Galápagos, during four breeding seasons (1981, 1983, 1984, and 1987). Pedigree analysis showed that levels of inbreeding were low but comparable with those observed in other passerine birds. For pairs with at least half of their grandparents known, approximately 20% of all pairings were between detectably related birds. The frequency of pairings between closely related birds (coefficient of kinship [φ] ≥ 0.250) among all pairs was 0.6%. We detected no effect of inbreeding on reproductive success, although sample sizes were small. The observed reproductive output of related pairs was not significantly different from the output of unrelated pairs, and there was no correlation between a pair's kinship coefficient and an estimate of the potential magnitude of inbreeding depression. Comparisons with a study of Great Tits (Parus major) by van Noordwijk and Scharloo (1981) suggest that, even if present, the fitness costs of inbreeding in this population of G. fortis would be low. Observed levels of inbreeding in each breeding episode were accurately predicted by simulations of random mating in which relatedness had no influence on pairing between individuals. This result suggests that levels of inbreeding in this population are determined more by demographic factors than by behavioral avoidance of mating with kin.
在四个繁殖季节（1981年、1983年、1984年和1987年），我们对加拉帕戈斯群岛达芙妮主岛上达尔文中型地雀（Geospiza fortis）种群的近亲繁殖频率、原因及其对繁殖成功率的影响进行了研究。谱系分析表明，近亲繁殖水平较低，但与在其他雀形目鸟类中观察到的水平相当。对于至少有一半祖父母已知的配对，所有配对中约20%是可检测到的亲缘关系鸟类之间的配对。在所有配对中，亲缘关系密切的鸟类（亲缘系数[φ]≥0.250）之间的配对频率为0.6%。尽管样本量较小，但我们未检测到近亲繁殖对繁殖成功率有影响。观察到的亲缘关系配对的繁殖产出与非亲缘关系配对的产出没有显著差异，并且配对的亲缘系数与近亲繁殖衰退潜在程度的估计值之间没有相关性。与范诺德维克和沙尔洛（1981年）对大山雀（Parus major）的研究比较表明，即使存在，该中型地雀种群中近亲繁殖的适合度代价也会很低。通过模拟随机交配准确预测了每个繁殖期观察到的近亲繁殖水平，在随机交配中亲缘关系对个体间配对没有影响。这一结果表明，该种群中的近亲繁殖水平更多地由人口统计学因素决定，而非由避免与亲属交配的行为决定。
