Abstract

Avian social and genetic mating systems are influenced by parental care roles as well as by reproductive opportunities. Alternative reproductive tactics, including conspecific brood parasitism and extra-pair mating, are predicted to be most common when females have access to potential host nests and when adults have access to potential mating partners, respectively. We tested these predictions in the facultatively colonial Hispaniolan woodpecker (Melanerpes striatus), a socially monogamous species with biparental care. Up to 12 pairs may nest concurrently in the same tree or, less frequently, two adjacent trees, potentially facilitating both conspecific brood parasitism and extra-pair mating. Contrary to our predictions, genotyping with single-nucleotide polymorphisms (SNPs) revealed no evidence of extra-pair paternity in either solitary or colonial nests: all 307 nestlings in 101 broods were matched to their social parents. Two instances of apparent conspecific brood parasitism were detected via changes in clutch size, but these could not be confirmed genetically since none of the apparently parasitic eggs survived to hatching. Therefore, if conspecific brood parasitism did occur, it was not a successful route to reproduction: parents fledged only their genetic offspring. These results suggest that reproductive opportunities alone are insufficient to favor alternative reproductive tactics, and that genetic monogamy can persist despite locally high densities of breeding pairs. Other life-history traits, including high levels of nest attendance and male parental care, may constrain parasitism and extra-pair mating in this long-lived tropical species.

Significance statement

High breeding density, a feature of colonial nesting, should increase opportunities for infidelity and conspecific brood parasitism because of the close proximity of potential extra-pair mates and parasitic females. Yet, we found that Hispaniolan woodpeckers, which nest both solitarily and colonially (two or more pairs in the same tree) in the same population, were genetically monogamous and lacked successful brood parasitism. Colonial nesting is exceptionally rare in the woodpecker family, which is also characterized by high investment in male parental care, including nocturnal incubation. The essential role of paternal care for successful reproduction in the Hispaniolan woodpecker might have selected against extra-pair mating and conspecific brood parasitism despite the apparent ample opportunities provided by nesting so close to others.

中文翻译：

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机会不是一切：殖民地啄木鸟的遗传一夫一妻制和有限的寄生寄生

摘要

鸟类的社会和遗传交配系统受到父母照顾角色以及繁殖机会的影响。预计当雌性可以使用潜在的寄主巢穴和成年人可以使用潜在的交配伙伴时，替代繁殖策略，包括同种繁殖寄生和额外配对交配是最常见的。我们在兼性殖民地伊斯帕尼奥拉啄木鸟（ Melanerpes striatus）中测试了这些预测)，一种社会一夫一妻制的物种，有双亲照顾。多达 12 对可以同时在同一棵树上筑巢，或者在较少见的情况下，在两棵相邻的树上筑巢，这可能有助于同种育雏寄生和额外配对交配。与我们的预测相反，单核苷酸多态性 (SNP) 的基因分型显示，无论是单独的巢穴还是殖民地的巢穴，都没有证据表明存在额外配对亲子关系：101 个巢穴中的所有 307 只雏鸟都与其社会父母相匹配。通过离合器大小的变化检测到两个明显的同种育雏寄生实例，但由于没有一个明显的寄生卵存活到孵化，因此无法从基因上得到证实。因此，如果确实发生了同种的育雏寄生，那它就不是一条成功的繁殖途径：父母只培育出他们的遗传后代。这些结果表明，仅靠生殖机会不足以支持替代的生殖策略，并且尽管当地的繁殖对密度很高，但遗传一夫一妻制仍然可以持续存在。其他生活史特征，包括高水平的巢穴出勤率和雄性父母的照顾，可能会限制这种长寿热带物种的寄生和超配对交配。

意义陈述

高繁殖密度是殖民地筑巢的一个特征，由于潜在的外对配偶和寄生雌性非常接近，应该会增加不忠和同种寄生的机会。然而，我们发现伊斯帕尼奥拉啄木鸟在同一种群中单独和群居地筑巢（两对或多对在同一棵树上），在遗传上是一夫一妻制的，缺乏成功的寄生寄生。在啄木鸟家族中，殖民地筑巢极为罕见，其特点还在于对雄性父母照顾的高投入，包括夜间孵化。尽管与其他啄木鸟如此接近地筑巢提供了明显的充足机会，但父亲照顾对西班牙啄木鸟成功繁殖的重要作用可能选择了反对外对交配和同种育雏寄生。