Rodrigues António M M, Riehl Christina
Department of Integrative Biology, University of California, Berkeley, CA 94720, USA.
Department of Ecology and Conservation Biology, Texas A&M University, College Station, TX 77843, USA.
Philos Trans R Soc Lond B Biol Sci. 2025 Mar 20;380(1922):20230275. doi: 10.1098/rstb.2023.0275.
Cooperatively breeding vertebrates typically live in family groups in which some offspring delay breeding and remain on the natal territory to help rear younger siblings. However, field studies find that helpers can have a neutral or even negative effect on the survival of their relatives. Why, then, do helpers remain, and why do parents tolerate them? Here, we use a kin selection approach to model the conditions under which tolerating helpers is adaptive to parents. Unlike previous models, we consider scenarios in which relatives compete for breeding opportunities in a saturated habitat. We show that kin competition is sufficient to favour tolerance of helpers, even when helpers decrease parental survival or fecundity. Helping is additionally favoured when delaying dispersal benefits the helper (either by decreasing the costs of dispersal or by increasing the chance of territory inheritance). This suggests that the division of reproduction in cooperative family groups can emerge for reasons unrelated to the effects of help itself, but the resulting society sets the stage for more elaborate forms of division of labour. Kin-based helping may therefore be adaptive not only because helpers are related to the brood whom they help, but also because delayed breeding reduces reproductive conflict among siblings.This article is part of the theme issue 'Division of labour as a key driver of social evolution'.
合作繁殖的脊椎动物通常生活在家族群体中，其中一些后代会推迟繁殖，并留在出生地帮助抚养年幼的兄弟姐妹。然而，野外研究发现，帮手对其亲属的生存可能产生中性甚至负面影响。那么，为什么帮手会留下来，父母又为什么会容忍他们呢？在这里，我们采用亲缘选择方法来模拟容忍帮手对父母来说是适应性行为的条件。与之前的模型不同，我们考虑了亲属在饱和栖息地中竞争繁殖机会的情况。我们表明，即使帮手会降低父母的生存能力或繁殖力，亲缘竞争也足以促使父母容忍帮手。当延迟扩散对帮手有利时（要么通过降低扩散成本，要么通过增加继承领地的机会），帮助行为会更受青睐。这表明，合作家族群体中的繁殖分工可能出于与帮助本身的影响无关的原因而出现，但由此产生的社会为更精细的分工形式奠定了基础。因此，基于亲缘关系的帮助行为可能具有适应性，不仅是因为帮手与他们所帮助的幼崽有亲缘关系，还因为延迟繁殖减少了兄弟姐妹之间的生殖冲突。本文是主题为“分工是社会进化的关键驱动力”的一部分。
