Intraspecific competition along different life stages can stabilize coexistence among dragonflies and damselflies

Biodiversity is sustained by stabilizing mechanisms of coexistence that inhibit species of competitive exclusion. Yet, in organisms with complex life cycles competitive dynamics may vary according to the life stage. Dragonflies are optimal organisms to test these ideas, as aquatic larvae are generalists in their feeding behavior, but adults have a wide variety of sexual behaviors. In this way, we aimed to understand how intra and interspecific interference may vary according to the life stage in tropical Odonata species. We hypothesized that competition in the larvae stage is mostly neutral, i.e. independent of species identities but responsive to total densities, while in adults, intraspecific interference may be more intense due to sexual selection mechanisms operating as deterministic stabilizing processes. Therefore, the study integrated two approaches, focusing on: 1. Laboratory experiments, where larvae of Acanthagrion (Zygoptera, Coenagrionidae) and Erythrodiplax (Anisoptera, Libellulidae) were allocated to four different treatments, with variation in total abundance and dominance of species; 2. Field observations, where we assessed adult co-occurrences and species interactions. Our results suggested a stronger intraspecific interference in both life stages. We found a spatial segregation in the larval stage decreasing interspecific interference and increasing cannibalism. Whereas adults were spatially segregated at fine scale, increasing the frequency of intraspecific interactions, especially in species with prominent territoriality. This study provided novel results on how coexistence mechanisms could be consistent along ontogenetic development broadening our understanding of processes sustaining biodiversity in tropical ecosystems.