Behavioral Heterochrony and the Evolution of Birds' Helping at the Nest: An Unselected Consequences of Communal Breeding?
Behavioral Heterochrony and the Evolution of Birds' Helping at the Nest: An Unselected Consequences of Communal Breeding?
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DOI：
10.1086/284925
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发表时间：
1989-03
期刊：
影响因子：
--
通讯作者：
I. Jamieson
中科院分区：
文献类型：
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作者：
I. Jamieson
大多数研究人员认为，群体或合作繁殖者的帮助行为是自然选择的直接结果。因此，在不同的公共物种背景下，帮助是根据其对帮助者的适应性或功能意义来解释的。非繁殖辅助性提供行为的表达是群体繁殖进化的非选择结果的假设被提出作为功能假设的替代。首先，我认为非繁殖者哺育后代的功能意义与这种行为的进化起源无关，因为哺育后代是当今许多鸟类的约束，包括那些有帮手的鸟类。我提出了一个模型，该模型将非繁殖辅助物的供给描述为生命史模式转变（即繁殖分散和亲代耐受性减少）导致的个体发育异时变化的表达。因为非繁殖期鸟类提供食物的成本可能低于（正常）亲代提供食物的收益，“帮助”的选择压力可能可以忽略不计。然而，进一步的证据表明，即使成本很高，发展区分引起提供反应的刺激背景的能力也很困难。此外，尽管群体繁殖的发生与帮助者的发生几乎完全相关，但对包容性适合度的估计不能用来证明帮助者有（单独的）选择来提供食物。出现这个问题是因为研究人员未能区分自然选择的原因和结果。“非选择假说”被认为比各种功能假说具有更强的解释力，因为它为群落繁殖者的亲缘和非亲缘提供了一个单一的解释，也为非群落物种中亲本以外的个体提供了一个罕见的解释。
Helping behavior in communal or cooperative breeders is presumed by most researchers to have evolved as a direct result of natural selection. Hence, helping in different communal-species contexts is explained in terms of its adaptive or functional significance for the helper. The hypothesis that the expression of provisioning behavior by nonbreeding auxiliaries is an unselected consequence of the evolution of communal breeding is presented as an alternative to the functional hypotheses. First, I argue that the functional significance of nonbreeders' feeding offspring is irrelevant with respect to the evolutionary origin of the behavior because provisioning offspring is a constraint of many present-day species of birds, including those with helpers at the nest. I present a model that depicts provisioning by nonbreeding auxiliaries as an expression of a heterochronic change in ontogeny brought about as a result of a shift in life-history pattern (i.e., reduced breeding dispersal and parental tolerance). Because the cost to nonbreeding birds of exhibiting provisioning may be low relative to the benefits of (normal) parental provisioning, selection pressure on "helping" may be negligible. However, further evidence suggests that even if the costs were high, evolving the ability to discriminate between the contexts of the stimuli evoking the provision response would be difficult. Furthermore, even though the occurrence of communal breeding correlates almost perfectly with the occurrence of helping, estimates of inclusive fitness cannot be used to argue that there has been (separate) selection for provisioning by helpers. This problem arises because researchers have failed to distinguish between the causes and effects of natural selection. The "unselected hypothesis" is considered to have greater explanatory power than the various functional hypotheses because it provides a single explanation for provisioning by kin and non-kin in communal breeders and for the infrequent incidents of provisioning by individuals other than parents in non-communal species.