Centre for Integrative Ecology, Deakin University, Geelong, VIC, Australia.
School of Biology, Aristotle University of Thessaloniki, Thessaloniki, Greece.
Adv Mar Biol. 2018;79:1-31. doi: 10.1016/bs.amb.2017.09.004. Epub 2017 Nov 2.
Why females would mate with multiple partners and have multiple fathers for clutches or litters is a long-standing enigma. There is a broad dichotomy in hypotheses ranging from polyandry having benefits to simply being an unavoidable consequence of a high incidence of male-female encounters. If females simply give in to mating when it is too costly to avoid being harassed by males (convenience polyandry), then there should be a higher rate of mating as density increases. However, if females actively seek males because they benefit from multiple mating, then mating frequency, and consequently the incidence of multiple paternity of clutches, should be high throughout. To explore these competing explanations, here we review the incidence of multiple paternity for sea turtles nesting around the World. Across 30 rookeries, including all 7 species of sea turtle, the incidence of multiple paternity was only weakly linked to rookery size (r=0.14). However, using high resolution at-sea GPS tracking we show that the specifics of movement patterns play a key role in driving packing density and hence the likely rate of male-female encounters. When individuals use the same focal areas, packing density could be 100× greater than when assuming individuals move independently. Once the extent of adult movements in the breeding season was considered so that movements and abundance could be combined to produce a measure of density, then across rookeries we found a very tight relationship (r=0.96) between packing density and the incidence of multiple paternity. These findings suggest that multiple paternity in sea turtles may have no benefit, but is simply a consequence of the incidence of male-female encounters.
为什么雌性会与多个伴侣交配，并为其卵或幼崽拥有多个父亲，这是一个长期存在的谜。关于这个问题的假设存在广泛的二分法，从多配偶制有好处到仅仅是雄性与雌性相遇频率高的不可避免的后果。如果雌性只是在避免被雄性骚扰的代价太高时（方便的多配偶制）屈服于交配，那么随着密度的增加，交配的频率应该会更高。然而，如果雌性主动寻找雄性，因为她们从多次交配中受益，那么交配频率，以及因此卵的多父系发生率，应该在整个过程中都很高。为了探索这些相互竞争的解释，我们在这里回顾了世界各地海龟筑巢时多父系的发生率。在 30 个筑巢地中，包括所有 7 种海龟，多父系的发生率与筑巢地的大小只有微弱的联系（r=0.14）。然而，我们利用高分辨率的海上 GPS 跟踪，表明运动模式的具体细节在驱动包装密度方面起着关键作用，从而可能影响雄性与雌性的相遇率。当个体使用相同的焦点区域时，包装密度可能比假设个体独立移动时高出 100 倍。一旦考虑到繁殖季节成年个体的运动范围，以便将运动和丰度结合起来产生密度的度量，那么在整个筑巢地中，我们发现包装密度与多父系发生率之间存在非常紧密的关系（r=0.96）。这些发现表明，海龟的多父系可能没有好处，而是雄性与雌性相遇频率高的必然结果。
