Haydock Joseph, Koenig Walter D
Department of Biology, Gonzaga University, Spokane, Washington 99258, USA.
Am Nat. 2003 Sep;162(3):277-89. doi: 10.1086/376888. Epub 2003 Jul 18.
We compared observed levels of reproductive skew in the cooperatively breeding acorn woodpecker (Melanerpes formicivorus) with those predicted by two alternative transactional models. "Concession" models predict the degree to which parentage is shared assuming that a single dominant is in complete control of reproduction. Alternatively, "restraint" models predict reproductive sharing assuming that the dominant controls only whether subordinates remain in the group but does not control its share of reproduction. Reproductive skew is high among males: on average, the most successful male sires more than three times as many offspring as the next most successful male. Females share parentage equally and have lower constraints on dispersal and lower survival rates compared with males, which is consistent with predictions from the concessions model. Also as predicted by the concessions model, yearly variation in opportunities for dispersal before the breeding season correlates positively with skew. However, in contrast to concessions but consistent with the restraint model, skew decreases with relatedness. Thus, neither model consistently predicts patterns of reproductive skew in this species. We suggest that models of reproductive skew will need to include competitive interactions among potential breeders and mate choice before they will adequately predict patterns of reproductive partitioning in most vertebrate societies.
我们将合作繁殖的橡树啄木鸟（Melanerpes formicivorus）中观察到的繁殖偏斜水平与两种替代交易模型预测的水平进行了比较。“让步”模型预测了亲子关系共享的程度，假设单个优势个体完全控制繁殖。或者，“克制”模型预测繁殖共享，假设优势个体仅控制从属个体是否留在群体中，但不控制其繁殖份额。雄性之间的繁殖偏斜程度很高：平均而言，最成功的雄性所产的后代数量是第二成功的雄性的三倍多。雌性平等地共享亲子关系，与雄性相比，它们在扩散方面的限制较低，存活率也较低，这与让步模型的预测一致。同样如让步模型所预测的，繁殖季节前扩散机会的年度变化与偏斜呈正相关。然而，与让步模型相反但与克制模型一致的是，偏斜程度随着亲缘关系的增加而降低。因此，这两种模型都不能始终如一地预测该物种的繁殖偏斜模式。我们认为，繁殖偏斜模型需要纳入潜在繁殖者之间的竞争相互作用和配偶选择，才能充分预测大多数脊椎动物社会中的繁殖分配模式。
