An evolutionary explanation of the aggregation model of species coexistence

Abstract

In ecology, the 'aggregation model of coexistence' provides a powerful concept to explain the unexpectedly high species richness of insects on ephemeral resources like dung pats, fruits, etc. It suggests that females aggregate their eggs across resource patches, which leads to an increased intraspecific competition within occupied patches and a relatively large number of patches that remain unoccupied. This provides competitor-free patches for heterospecifics, facilitating species coexistence. At first glance, deliberately causing competition among the females' own offspring and leaving resources to heterospecific competitors seems altruistic and incompatible with individual fitness maximization, raising the question of how natural selection operates in favour of egg aggregation on ephemeral resource patches. Allee effects that lead to fitness maxima at intermediate egg densities have been suggested, but not yet detected. Using drosophilid flies on decaying fruits as a study system, we demonstrate a humpshaped relationship between egg density and individual survival probability, with maximum survivorship at intermediate densities. This pattern clearly selects for egg aggregation and resolves the possible conflict between the ecological concept of species coexistence on ephemeral resources and evolutionary theory.

Ecology of information: social transmission dynamics within groups of non-social insects

“…However, for a trained fly, increasing social interactions would increase information transfer but decrease its own information level. Transferring information about oviposition sites could be adaptive for a trained fly, as larval survival depends on a balance between resource exploitation and larval competition [29][30][31]. When few larvae feed on a natural resource such as decaying fruit, they cannot optimally exploit the medium, and thus fail to challenge the development of bacterial and fungal competitors.…”

Edge Effects on Morphometrics and Body Mass in Two Sympatric Species of Mouse Lemurs in Madagascar

“…Although originally designed for modelling the unexpectedly high species richness of female insects laying their eggs on ephemeral resources (e.g. animal dung, fruit), the aggregation model of coexistence holds that spatially clumped individuals, such as those in edge habitat bordered by matrix (non-habitat), that exploit ephemeral resources, such as seasonally available insects and fruit, may have limited population growth [Rohlfs and Hoffmeister, 2003]. The result of this novel pattern of population dynamics is that there should be unexploited resources available to a competitively inferior species or individual.…”

Attraction to and learning from social cues in fruitfly larvae

“…One can imagine some benefits from being in a small group, including suppressing mould, enhancing the growth of preferred species of yeast and bacteria, and improved ability to dig into the substrate [45][46][47][48][49]. Such benefits, however, may not be important in our laboratory settings, where we provide larvae with a diet containing yeast and a mould inhibitor.…”