Smith H G, Härdling R
Department of Animal Ecology, Lund University, S-223 62 Lund, Sweden.
Proc Biol Sci. 2000 Nov 7;267(1458):2163-70. doi: 10.1098/rspb.2000.1264.
Models of optimal clutch size often implicitly assume a situation with uniparental care. However, the evolutionary conflict between males and females over the division of parental care will have a major influence on the evolution of clutch size. Since clutch size is a female trait, a male has little possibility of directly influencing it. However, the optimal clutch size from a female's perspective will depend on the amount of paternal care her mate is expected to provide. The sexual conflict over parental care will in its turn be affected by clutch size, since a larger clutch makes male care more valuable. Hence, there will be joint evolution of mating system and clutch size. In this paper, we demonstrate that this joint evolution will tend to stabilize the mating system. In a situation with conventional sex roles, this joint evolution might result in either increased clutch size and biparental care or reduced clutch size and uniparental female care. Under some circumstances the initial conditions might determine which will be the outcome. These results demonstrate that it may be difficult to deduce whether biparental care evolved because of few opportunities for breeding males increasing their fitness by attracting additional mates or because of the importance of male care for offspring fitness by studying prevailing mating systems using, for example, male removals or manipulation of males' opportunities for finding additional mates. In general terms, we demonstrate that models of life-history evolution have to consider the social context in which they evolve.
最优窝卵数模型通常隐含地假设了单亲抚育的情况。然而，雄性和雌性在亲代抚育分工上的进化冲突将对窝卵数的进化产生重大影响。由于窝卵数是雌性的一个特征，雄性直接影响它的可能性很小。然而，从雌性的角度来看，最优窝卵数将取决于其配偶预期提供的父性抚育量。亲代抚育方面的性冲突反过来又会受到窝卵数的影响，因为更大的窝卵数会使雄性抚育更有价值。因此，交配系统和窝卵数将共同进化。在本文中，我们证明这种共同进化将倾向于使交配系统稳定。在传统性别角色的情况下，这种共同进化可能导致窝卵数增加和双亲抚育，或者窝卵数减少和单亲雌性抚育。在某些情况下初始条件可能决定结果会是哪一种。这些结果表明，通过例如移除雄性或操纵雄性寻找额外配偶的机会来研究现存交配系统，可能很难推断双亲抚育的进化是因为繁殖雄性通过吸引额外配偶来提高其适合度的机会很少，还是因为雄性抚育对后代适合度的重要性。一般来说，我们证明生活史进化模型必须考虑它们进化所处的社会背景。
