Tocco Claudia, Dacke Marie, Byrne Marcus
Lund Vision Group Department of Biology Lund University Lund Sweden.
School of Animal, Plant and Environmental Sciences University of the Witwatersrand Wits, Johannesburg South Africa.
Ecol Evol. 2021 Oct 27;11(22):15947-15960. doi: 10.1002/ece3.8264. eCollection 2021 Nov.
In nature, nothing is wasted, not even waste. Dung, composed of metabolic trash and leftovers of food, is a high-quality resource and the object of fierce competition. Over 800 dung beetle species (Scarabaeinae) compete in the South African dung habitat and more than 100 species can colonize a single dung pat. To coexist in the same space, using the same food, beetles divide the day between them. However, detailed diel activity periods and associated morphological adaptations have been largely overlooked in these dung-loving insects. To address this, we used a high-frequency trapping design to establish the diel activity period of 44 dung beetle species in their South Africa communities. This allowed us to conclude that the dung beetles show a highly refined temporal partitioning strategy, with differences in peak of activity even within the diurnal, crepuscular, and nocturnal guilds, independent of nesting behavior and taxonomic classification. We further analyzed differences in eye and body size of our 44 model species and describe their variability in external eye morphology. In general, nocturnal species are bigger than crepuscular and diurnal species, and as expected, the absolute and relative eye size is greatest in nocturnal species, followed by crepuscular and then diurnal species. A more surprising finding was that corneal structure (smooth or facetted) is influenced by the activity period of the species, appearing flat in the nocturnal species and highly curved in the diurnal species. The role of the canthus-a cuticular structure that partially or completely divides the dung beetle eye into dorsal and ventral parts-remains a mystery, but the large number of species investigated in this study nevertheless allowed us to reject any correlation between its presence and the nesting behavior or time of activity of the beetles.
在自然界中，没有什么是被浪费的，甚至连废物也不例外。粪便由代谢废物和食物残渣组成，是一种优质资源，也是激烈竞争的对象。超过800种蜣螂（金龟子亚科）在南非的粪便栖息地展开竞争，而且100多种蜣螂可以在单个粪堆上繁衍。为了在同一空间、利用相同食物共存，蜣螂在它们之间划分了白天的时间。然而，这些喜爱粪便的昆虫详细的昼夜活动时间以及相关的形态适应在很大程度上被忽视了。为了解决这个问题，我们采用了高频诱捕设计来确定南非群落中44种蜣螂的昼夜活动时间。这使我们能够得出结论，蜣螂表现出一种高度精细的时间分配策略，即使在昼行性、晨昏性和夜行性类群中，活动高峰期也存在差异，且与筑巢行为和分类学分类无关。我们进一步分析了我们的44个模型物种的眼睛和身体大小差异，并描述了它们外部眼睛形态的变异性。一般来说，夜行性物种比晨昏性和昼行性物种体型更大，正如预期的那样，夜行性物种的绝对和相对眼睛大小最大，其次是晨昏性物种，然后是昼行性物种。一个更令人惊讶的发现是，角膜结构（光滑或有小平面）受物种活动时间的影响，在夜行性物种中呈扁平状，在昼行性物种中则高度弯曲。眼角（一种将蜣螂眼睛部分或完全分为背侧和腹侧部分的表皮结构）的作用仍然是个谜，但本研究中调查的大量物种使我们能够排除其存在与蜣螂筑巢行为或活动时间之间的任何关联。
