DiRienzo Nicholas, Aonuma Hitoshi
Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, AZ, U.S.A.
Research Institute for Electronic Science, Hokkaido University, Sapporo, Hokkaido, Japan.
Anim Behav. 2018 Apr;138:9-17. doi: 10.1016/j.anbehav.2018.01.022. Epub 2018 Mar 20.
Many animals actively defend their offspring using a range of behaviours from calling and mobbing in birds, to physical grappling in crustaceans, and the expression of these behaviours positively scale with offspring value. While this role of behaviour in defence is well studied, very little is known about how other traits, specifically the structure of architectural constructions such as webs and nests, contribute to offspring defence. Additionally, although some tax a show consistent individual differences in offspring defence behaviour, it is completely unknown whether individuals also differ in defensive structures. We addressed these questions in the redback spider, , by measuring how a female laying an eggcase influences female behaviour and web structure, and whether those traits scale with relative reproductive investment. Our results show that females modified web structure in response to an eggcase, but only the protective elements of web structure positively scaled with the relative value of that eggcase. Finally, despite the significant correlations, fixed effects (e.g. eggcase possession/value) in the models explained only 5-23% of the variation in behaviour and web structure, while the random effect of individual identity explained 46-65% of the variation. This variation drove moderate to high repeatability estimates across all traits, suggesting that some individuals consistently invest relatively more in defence, while some invest less. These results highlight that extended phenotypic traits may be a critical component of offspring defence in some taxa. Furthermore, individual variation in these traits suggest that different reproductive strategies may exist, whereby some individuals invest more in reproduction at a cost to safety/foraging and vice versa.
许多动物会通过一系列行为积极保护它们的后代，从鸟类的鸣叫和围攻，到甲壳类动物的身体搏斗，这些行为的表现与后代的价值呈正相关。虽然行为在防御中的这种作用已得到充分研究，但对于其他特征，特别是诸如蛛网和巢穴等建筑结构的构造如何有助于后代防御，人们却知之甚少。此外，尽管一些分类群在后代防御行为上表现出一致的个体差异，但个体在防御结构上是否也存在差异却完全未知。我们以红背蜘蛛为研究对象，通过测量产卵袋的雌蛛如何影响雌蛛行为和蛛网结构，以及这些特征是否与相对繁殖投入相关，来解决这些问题。我们的结果表明，雌蛛会根据产卵袋改变蛛网结构，但只有蛛网结构的保护元素与该产卵袋的相对价值呈正相关。最后，尽管存在显著相关性，但模型中的固定效应（如拥有产卵袋/产卵袋价值）仅解释了行为和蛛网结构变异的5%-23%，而个体身份的随机效应解释了46%-65%的变异。这种变异导致所有特征的重复率估计值处于中等至较高水平，表明一些个体在防御方面的投入始终相对较多，而另一些则较少。这些结果突出表明，扩展表型特征可能是某些分类群后代防御的关键组成部分。此外，这些特征的个体差异表明可能存在不同的繁殖策略，即一些个体以牺牲安全/觅食为代价在繁殖方面投入更多，反之亦然。
