Centre for Biological Diversity, Harold Mitchell Building, University of St Andrews, St Andrews, KY16 9TH, U.K.
Biol Rev Camb Philos Soc. 2022 Aug;97(4):1389-1407. doi: 10.1111/brv.12847. Epub 2022 Feb 26.
Behavioural traits are often noted to persist after relaxation or removal of associated selection pressure, whereas it has been observed that morphological traits under similar conditions appear to decay more rapidly. Despite this, persistent non-adaptive, 'vestigial' behavioural variation has received little research scrutiny. Here we review published examples of vestigial behavioural traits, highlighting their surprising prevalence, and argue that their further study can reveal insights about the widely debated role of behaviour in evolution. Some vestigial behaviours incur fitness costs, so may act as a drag on adaptive evolution when that adaptation occurs via trait loss or reversal. In other cases, vestigial behaviours can contribute to future evolutionary trajectories, for example by preserving genetic and phenotypic variation which is later co-opted by selection during adaptive evolution or diversification, or through re-emergence after ancestral selection pressures are restored. We explore why vestigial behaviours appear prone to persistence. Behavioural lag may be a general phenomenon arising from relatively high levels of non-genetic variation in behavioural expression, and pleiotropic constraint. Long-term persistence of non-adaptive behavioural traits could also result when their expression is associated with morphological features which might be more rapidly lost or reduced. We propose that vestigial behaviours could provide a substrate for co-option by novel selective forces, and advocate further study of the fate of behavioural traits following relaxed and reversed selection. Vestigial behaviours have been relatively well studied in the context of antipredator behaviours, but they are far from restricted to this ecological context, and so deserve broader consideration. They also have practical importance, with mixed evidence, for example, as to whether predator/parasite-avoidance behaviours are rapidly lost in wildlife refuges and captivity. We identify important areas for future research to help determine whether vestigial behaviours essentially represent a form of evolutionary lag, or whether they have more meaningful evolutionary consequences distinct from those of other vestigial and behavioural traits.
行为特征通常在相关选择压力放松或消除后仍会持续存在，而在类似条件下观察到的形态特征似乎会更快地衰减。尽管如此，持续的非适应性、“退化”的行为变异受到的研究关注很少。在这里，我们回顾了已发表的退化行为特征的例子，强调了它们令人惊讶的普遍性，并认为进一步研究可以揭示行为在进化中广泛争论的作用。一些退化行为会产生适应度成本，因此当适应是通过特征丢失或反转发生时，可能会对适应性进化产生阻碍。在其他情况下，退化行为可以为未来的进化轨迹做出贡献，例如通过保留后来在适应性进化或多样化过程中被选择利用的遗传和表型变异，或者在祖先选择压力恢复后重新出现。我们探讨了为什么退化行为似乎容易持续存在。行为滞后可能是一种普遍现象，源于行为表达中相对较高水平的非遗传变异和多效性约束。如果非适应性行为特征的表达与形态特征相关，而这些特征可能会更快地丢失或减少，那么这些特征的长期持续存在也可能导致行为特征的长期持续存在。我们提出，退化行为可能为新的选择压力提供被选择的基础，并主张进一步研究放松和反转选择后行为特征的命运。在防御捕食者的行为背景下，退化行为已经得到了相对较好的研究，但它们远不限于这种生态背景，因此值得更广泛的考虑。它们也具有实际意义，例如，在野生动物保护区和圈养环境中，是否会迅速失去逃避捕食者/寄生虫的行为，这方面的证据存在混合情况。我们确定了未来研究的重要领域，以帮助确定退化行为是否本质上代表一种进化滞后的形式，或者它们是否具有与其他退化和行为特征不同的更有意义的进化后果。
