Department of Evolutionary Biology and Environmental Studies, University of Zurich, Winterthurerstrasse 190, CH-8057, Zurich, Switzerland.
Biol Rev Camb Philos Soc. 2019 Apr;94(2):721-736. doi: 10.1111/brv.12475. Epub 2018 Oct 24.
Dispersal is ubiquitous throughout the tree of life: factors selecting for dispersal include kin competition, inbreeding avoidance and spatiotemporal variation in resources or habitat suitability. These factors differ in whether they promote male and female dispersal equally strongly, and often selection on dispersal of one sex depends on how much the other disperses. For example, for inbreeding avoidance it can be sufficient that one sex disperses away from the natal site. Attempts to understand sex-specific dispersal evolution have created a rich body of theoretical literature, which we review here. We highlight an interesting gap between empirical and theoretical literature. The former associates different patterns of sex-biased dispersal with mating systems, such as female-biased dispersal in monogamous birds and male-biased dispersal in polygynous mammals. The predominant explanation is traceable back to Greenwood's () ideas of how successful philopatric or dispersing individuals are at gaining mates or the resources required to attract them. Theory, however, has developed surprisingly independently of these ideas: models typically track how immigration and emigration change relatedness patterns and alter competition for limiting resources. The limiting resources are often considered sexually distinct, with breeding sites and fertilizable females limiting reproductive success for females and males, respectively. We show that the link between mating system and sex-biased dispersal is far from resolved: there are studies showing that mating systems matter, but the oft-stated association between polygyny and male-biased dispersal is not a straightforward theoretical expectation. Here, an important understudied factor is the extent to which movement is interpretable as an extension of mate-searching (e.g. are matings possible en route or do they only happen after settling in new habitat - or can females perhaps move with stored sperm). We also point out other new directions for bridging the gap between empirical and theoretical studies: there is a need to build Greenwood's influential yet verbal explanation into formal models, which also includes the possibility that an individual benefits from mobility as it leads to fitness gains in more than one final breeding location (a possibility not present in models with a very rigid deme structure). The order of life-cycle events is likewise important, as this impacts whether a departing individual leaves behind important resources for its female or male kin, or perhaps both, in the case of partially overlapping resource use.
选择扩散的因素包括亲缘竞争、避免近亲繁殖和资源或栖息地适宜性的时空变化。这些因素在促进雄性和雌性扩散的程度上有所不同，并且对一种性别的扩散选择往往取决于另一种性别的扩散程度。例如，为了避免近亲繁殖，一种性别只要从出生地扩散开就足够了。试图理解性别特异性扩散进化的努力创造了丰富的理论文献，我们在此对其进行回顾。我们强调了实证文献和理论文献之间一个有趣的差距。前者将不同的性别偏向扩散模式与交配系统联系起来，例如在一夫一妻制的鸟类中雌性偏向扩散，在多配偶制的哺乳动物中雄性偏向扩散。主要的解释可以追溯到格林伍德（Greenwood）的思想，即成功的恋地或扩散个体如何获得配偶或吸引配偶所需的资源。然而，理论却令人惊讶地独立于这些思想发展：模型通常跟踪移民和移民如何改变相关模式，并改变对限制资源的竞争。这些限制资源通常被认为是有区别的，繁殖地点和可育雌性分别限制雌性和雄性的繁殖成功率。我们表明，交配系统与性别偏向扩散之间的联系远未得到解决：有研究表明交配系统很重要，但多配偶制和雄性偏向扩散之间的常规定律并不是一个直接的理论预期。在这里，一个重要的研究不足的因素是，运动是否可以解释为寻找配偶的延伸（例如，在途中是否可能交配，或者只有在新栖息地定居后才会发生交配，或者雌性是否可以带着储存的精子移动）。我们还指出了弥合实证研究和理论研究之间差距的其他新方向：需要将格林伍德有影响力但口头解释的内容构建到正式模型中，这还包括个体从流动性中受益的可能性，因为它会在多个最终繁殖地点带来适应度的提高（在具有非常严格的生境结构的模型中不存在这种可能性）。生命周期事件的顺序同样重要，因为这会影响离开的个体是否会为其雌性或雄性亲属留下重要资源，或者在资源部分重叠的情况下，可能会为两者都留下重要资源。
