Rönn J L, Katvala M, Arnqvist G
Evolutionary Biology Centre, Department of Animal Ecology, Uppsala University, Sweden.
J Evol Biol. 2008 Mar;21(2):461-70. doi: 10.1111/j.1420-9101.2007.01493.x. Epub 2008 Jan 17.
When ejaculates are costly to produce, males are expected to allocate their ejaculate resources over successive matings in a manner that optimizes their reproductive success and this may have important consequences for their mates. In seed beetles (Coleoptera; Bruchidae), ejaculates vary in size across species from weighing less than 1%, up to as much as 8%, of male body weight. Ejaculates contain not only sperm but also a range of additional substances and females in some species gain benefits from receiving large ejaculates. Male ejaculate allocation may thus affect female fitness. Here, we first characterized the pattern of male ejaculate allocation over successive matings in seven-seed beetle species. We then assessed how this allocation affected female fitness in each species. Although females generally benefited from receiving large ejaculates, the interspecific variation observed both in ejaculate allocation patterns and in their effects on female fitness was remarkably large considering that the species studied are closely related. Our analyses suggest that variation in ejaculate composition is the key, both within and across species. We discuss possible causes for this variation and conclude that coevolution between male ejaculates and female utilization of ejaculate substances has apparently been rapid in this clade.
当产生射精成本较高时，预计雄性会以优化其繁殖成功率的方式在连续交配中分配其射精资源，而这可能会对其配偶产生重要影响。在豆象（鞘翅目；豆象科）中，不同物种的射精量差异很大，从不到雄性体重的1%到高达8%不等。射精不仅包含精子，还包含一系列其他物质，并且在某些物种中，雌性从接受大量射精中获得益处。因此，雄性射精分配可能会影响雌性的适应性。在这里，我们首先描述了七种豆象物种在连续交配中雄性射精分配的模式。然后，我们评估了这种分配如何影响每个物种中雌性的适应性。尽管雌性通常从接受大量射精中受益，但考虑到所研究的物种关系密切，在射精分配模式及其对雌性适应性的影响方面观察到的种间差异非常大。我们的分析表明，射精组成的差异是物种内部和物种之间的关键因素。我们讨论了这种差异的可能原因，并得出结论，在这个进化枝中，雄性射精与雌性对射精物质的利用之间的共同进化显然很快。
