Department of Animal Ecology and Evolution, Faculty of Biology, University of Freiburg, Freiburg, Germany.
Mol Ecol. 2013 Apr;22(7):2011-27. doi: 10.1111/mec.12219. Epub 2013 Feb 11.
In cooperative species, helping behaviour and reproductive success can be correlated, but understanding this correlation is often impaired by the difficulty to correctly infer causation. While helpers can incur costs by participating in brood care, it is yet unclear if their help depends on their individual quality. We address these questions in the previously unknown cooperative breeding system of the endangered El Oro parakeet (Pyrrhura orcesi). Specifically, we ask (i) whether breeders benefit directly from helpers by an enhanced reproductive success and if so, (ii) whether the amount of this potential benefit is regulated by the quality of contributing group members. Groups consist of a dominant breeding pair accompanied by helpers, but cooperation is not obligate. Microsatellite heterozygosity was used to assess individual quality; its suitability as indicator of quality was reflected in the positive relationship between offspring heterozygosity and recruitment into the population. The reproductive success of breeding pairs depended on helper (genetic) quality and the number of helpers. This relationship occurred on two different levels: clutch size and fledging success, indicating (i) that females profit from high-quality helpers and probably adjust clutch size accordingly and (ii) that the helpers increase fledging success. Congruently, we found that offspring body condition is positively affected by helper quality, which is most probably explained by the increased feeding rates when helpers are present. We suggest a causal link between cooperation and reproductive success in this frugivorous, endangered parakeet. Further, helper (genetic) quality can be a relevant factor for determining reproductive fitness in cooperative species, particularly in small and bottlenecked populations.
在合作物种中，帮助行为和繁殖成功可以相关，但理解这种相关性往往因难以正确推断因果关系而受到阻碍。虽然帮手在参与育雏过程中可能会付出代价，但他们的帮助是否取决于个体的质量还不清楚。我们在濒危的厄瓜多尔长尾鹦鹉（Pyrrhura orcesi）以前未知的合作繁殖系统中解决了这些问题。具体来说，我们问：（i） 繁殖者是否通过增强繁殖成功而直接受益于助手，如果是，（ii） 这种潜在利益的数量是否受到贡献群体成员质量的调节。群体由一对占主导地位的繁殖对伴以助手组成，但合作并非强制性的。微卫星杂合度用于评估个体质量；其作为质量指标的适宜性反映在后代杂合度与进入种群的招募之间的正相关关系中。繁殖对的繁殖成功取决于助手（遗传）质量和助手的数量。这种关系发生在两个不同的水平上：卵的大小和育雏成功率，表明（i） 雌性从高质量的助手受益，并可能相应地调整卵的大小，（ii） 助手提高育雏成功率。一致地，我们发现，助手的质量对后代的身体状况有积极影响，这很可能是由于助手存在时增加了喂养率。我们在这种食果的濒危长尾鹦鹉中提出了合作与繁殖成功之间的因果关系。此外，助手（遗传）质量可以成为决定合作物种生殖适应性的相关因素，特别是在小而瓶颈化的种群中。
