Department of Biology, Aarhus University, Aarhus C, Denmark.
Department of Biology, Lund University, Lund, Sweden.
J Evol Biol. 2022 Jul;35(7):1020-1026. doi: 10.1111/jeb.14032. Epub 2022 Jun 8.
Conspecific tolerance is key for maintaining group cohesion in animals. Understanding shifts from conspecific tolerance to intolerance is therefore important for understanding transitions to sociality. Subsocial species disperse to a solitary lifestyle after a gregarious juvenile phase and display conspecific intolerance as adults as a mechanism to maintain a solitary living. The development of intolerance towards group members is hypothesized to play a role in dispersal decisions in subsocial species. One hypothesis posits that dispersal is triggered by factors such as food competition with the subsequent development of conspecific intolerance, rather than conspecific intolerance developing prior to and potentially driving dispersal. Consistent with this hypothesis, we show that intolerance (inferred by inter-individual distance) developed post-dispersal in the subsocial spider Stegodyphus lineatus. The development of conspecific intolerance was delayed when maintaining spiders in groups showing plasticity in this trait, which is advantageous when trade-offs are not fixed over time. However, major evolutionary transitions, such as the transition to sociality, can permanently modify trade-offs and cause derived adaptations by the evolution of new or modified traits or evolutionary loss of traits that become redundant. Sociality in spiders has evolved repeatedly from subsocial ancestors, and social life in family groups combined with a lack of interaction with competing groups suggests relaxed selection for the development of conspecific intolerance. In the social Stegodyphus sarasinorum we found no evidence for the development of conspecific intolerance, consistent with the loss of this trait. Instead, we found evidence for conspecific attraction, which is likely to govern group cohesion.
同种容忍是动物维持群体凝聚力的关键。因此，了解同种容忍向不容忍的转变对于理解向社会性的过渡非常重要。亚社会物种在群居的幼年期后分散到独居的生活方式，并在成年时表现出同种不容忍，作为维持独居生活的一种机制。同种不容忍的发展被假设在亚社会物种的扩散决策中起作用。一种假设认为，扩散是由食物竞争等因素引发的，随后发展出同种不容忍，而不是在扩散之前发展出同种不容忍，并可能驱动扩散。与这一假设一致，我们表明，在亚社会蜘蛛 Stegodyphus lineatus 中，同种不容忍（通过个体间的距离推断）在扩散后发展。当维持表现出这种特性可塑性的群体中的蜘蛛时，同种不容忍的发展会被延迟，当权衡不是随时间固定时，这是有利的。然而，重大的进化转变，如向社会性的转变，可以永久性地改变权衡，并通过新的或改良的特征的进化或变得多余的特征的进化丧失，导致衍生适应。蜘蛛的社会性已经从亚社会性祖先中多次进化而来，而与竞争群体的缺乏相互作用的家族群体中的社会生活表明，同种不容忍的发展受到的选择压力较小。在社会性的 Stegodyphus sarasinorum 中，我们没有发现同种不容忍发展的证据，这与该特征的丧失一致。相反，我们发现了同种吸引的证据，这可能控制着群体的凝聚力。
