Lis Natalia, Mądra-Bielewicz Anna, Wydra Jędrzej, Matuszewski Szymon
Department of Animal Taxonomy and Ecology, Adam Mickiewicz University, Poznań, Poland.
Laboratory of Criminalistics, Adam Mickiewicz University, Poznań, Poland.
Insect Sci. 2024 Dec;31(6):1918-1929. doi: 10.1111/1744-7917.13353. Epub 2024 Mar 13.
Aggregations of juveniles are dominant forms of social life in some insect groups. Larval societies are shaped by competitive and cooperative interactions of the larvae, in parallel with parental effects. Colonies of necrophagous larvae are excellent systems to study these relationships. Necrodes littoralis (Staphylinidae: Silphinae), a carrion beetle that colonizes cadavers of large vertebrates, forms massive juvenile aggregations. By spreading over carrion anal and oral exudates, the beetles form the feeding matrix, in which the heat is produced and by which adults presumably affect the fitness of the larvae. We predict that exploitative competition shapes the behavior of N. littoralis larvae in their aggregations. However, cooperative interactions may also operate in these systems due mainly to the benefits of collective exodigestion. Moreover, indirect parental effects (i.e., formation of the feeding matrix) probably modulate larval interactions within the aggregations. By manipulating parental effects (present/absent) and larval density (0.02-1.9 larvae/g of meat), we found a strong negative group-size effect on fitness components of N. littoralis, in colonies with parental effects over almost the entire density range, and in colonies without parental effects for densities larger than 0.5 larva/g. This was accompanied by positive group-size effects in terms of development time (it shortened with larval density) and thermogenesis (it increased with larval density). A pronounced positive group-size effect on juvenile fitness was found only in colonies without parental effects and only in the low-density range. These results support the hypothesis that larval societies of N. littoralis are shaped by exploitation competition.
在一些昆虫群体中，幼虫聚集是社会生活的主要形式。幼虫群体由幼虫之间的竞争与合作互动以及亲代效应共同塑造。食腐幼虫群体是研究这些关系的绝佳系统。海滨葬甲（葬甲科：埋葬虫亚科）是一种寄生于大型脊椎动物尸体的腐食性甲虫，会形成大量的幼虫聚集。通过在腐肉上散布肛门和口腔分泌物，这些甲虫形成了进食基质，热量在其中产生，成虫可能借此影响幼虫的健康状况。我们预测，剥削性竞争塑造了海滨葬甲幼虫在聚集时的行为。然而，合作互动也可能在这些系统中发挥作用，主要是因为集体体外消化的益处。此外，间接亲代效应（即进食基质的形成）可能会调节聚集内幼虫之间的相互作用。通过控制亲代效应（存在/不存在）和幼虫密度（0.02 - 1.9只幼虫/克肉），我们发现，在几乎整个密度范围内有亲代效应的群体以及密度大于0.5只幼虫/克时无亲代效应的群体中，群体大小对海滨葬甲的健康组成部分有强烈的负面影响。这伴随着发育时间（随幼虫密度缩短）和产热（随幼虫密度增加）方面的正向群体大小效应。仅在无亲代效应且处于低密度范围的群体中，发现了对幼虫健康有显著的正向群体大小效应。这些结果支持了这样的假设，即海滨葬甲的幼虫群体是由剥削性竞争塑造的。
