Data from: Habitat saturation promotes delayed dispersal in a social reptile

When and where offspring disperse has important implications for the evolutionary emergence and maintenance of group living. In non-cooperative breeders, direct benefits of delayed dispersal are relatively limited, suggesting that decisions regarding whether or not to remain in the parental territory are largely driven by the availability of suitable habitat in which to settle. While there is ample evidence of correlations between habitat saturation and delayed dispersal, experimental tests are rare, particularly for species with facultative group formation. We manipulated the density of conspecifics in enclosed populations of a family living reptile to experimentally evaluate the influence of habitat saturation on the tendency to delay dispersal. Habitat saturation did not influence whether or not offspring explored their surroundings. However, when conspecific density was high, more offspring delayed dispersal and those that did settle in high-density enclosures had reduced survival. These patterns appear to be due to increased dispersal costs imposed by conspecific aggression; offspring that explored high-density enclosures had reduced body condition and a greater risk of mortality. We discuss these results in the context of the evolutionary origins of family living.

后代扩散的时机与空间位置，对群居生活的演化起源与维持具有重要学术意义。在非协作繁育类群（non-cooperative breeders）中，延迟扩散所能带来的直接收益相对有限，这意味着个体是否选择留在亲代领地的决策，主要受限于可用于定居的适宜栖息地的可获得性。尽管已有大量研究证实栖息地饱和与延迟扩散之间存在相关性，但相关实验验证仍较为匮乏，尤其是针对具备兼性集群形成能力的物种。本研究以一种营家庭群居习性的爬行动物的封闭种群为实验对象，通过调控同种个体（conspecifics）的种群密度，实验性地评估栖息地饱和对后代延迟扩散倾向的影响。实验结果显示，栖息地饱和并未对后代的周围环境探索行为产生显著影响。然而，当同种个体密度较高时，选择延迟扩散的后代比例更高，且定居于高密度封闭种群中的个体存活率有所降低。上述模式似乎源于同种个体间的攻击行为所导致的扩散成本上升：在高密度封闭种群中进行探索的后代，其身体状况会出现下降，且死亡风险显著升高。本研究最后结合家庭群居习性的演化起源这一背景，对上述实验结果展开了讨论。