Coexistence of Insect Species Competing for a Pulsed Resource: Toward a Unified Theory of Biodiversity in Fluctuating Environments

One major challenge in understanding how biodiversity is organized is finding out whether communities of competing species are shaped exclusively by species-level differences in ecological traits (niche theory), exclusively by random processes (neutral theory of biodiversity), or by both processes simultaneously. Communities of species competing for a pulsed resource are a suitable system for testing these theories: due to marked fluctuations in resource availability, the theories yield very different predictions about the timing of resource use and the synchronization of the population dynamics between the competing species. Accordingly, we explored mechanisms that might promote the local coexistence of phytophagous insects (four sister species of the genus Curculio) competing for oak acorns, a pulsed resource.We analyzed the time partitioning of the exploitation of oak acorns by the four weevil species in two independent communities, and we assessed the level of synchronization in their population dynamics. In accordance with the niche theory, overall these species exhibited marked time partitioning of resource use, both within a given year and between different years owing to different dormancy strategies between species, as well as distinct demographic patterns. Two of the four weevil species, however, consistently exploited the resource during the same period of the year, exhibited a similar dormancy pattern, and did not show any significant difference in their population dynamics.The marked time partitioning of the resource use appears as a keystone of the coexistence of these competing insect species, except for two of them which are demographically nearly equivalent. Communities of consumers of pulsed resources thus seem to offer a promising avenue for developing a unifying theory of biodiversity in fluctuating environments which might predict the co-occurrence, within the same community, of species that are ecologically either very similar, or very different

Determining the instar of a weevil larva (Coleoptera: Curculionidae) using a parsimonious method

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Mate-guarding strategies and male competitive ability: results from a field study in an orb-weaving spider

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Body mass-dependent cost of web-building behaviour in an orb weaving spider Zygiella x-notata

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Revisiting the link between breeding effort and oxidative balance through field evaluation of two sympatric sibling insect species

International audienceThe idea that oxidative stress could be a major force governing evolutionary trade-offs has recently been challenged by exper- imental approaches in laboratory conditions, triggering extensive debates centered on theoretical and methodological issues. Here, we revisited the link between oxidative stress and reproduction by measuring multiple antioxidant and oxidative dam- ages in wild-caught females of two sibling weevil species (Curculio elephas, C. glandium). The strength of our study arised from (1) studied species that were sympatric and exploited similar resource, but displayed contrasting reproductive strategies and (2) individuals were sampled throughout adult life so as to relate oxidative status to breeding effort. We found that the short-lived C. elephas sacrifices red-ox homeostasis for immediate reproduction upon emergence as characterized by low antioxidant defenses and elevated oxidative damage. Comparatively, C. glandium massively invests in antioxidant and maintains low oxidative damage, which may contribute to their extended prereproductive period. Intriguingly, we also reveal, for the first time in a field study, an unexpected reactivation of antioxidant defenses with the onset of reproduction. Our results thus support the existence of a strong, but complex relationship between oxidative stress and life-history evolution and highlight the need for a finer-scale picture of antioxidant strategies

Data from: Revisiting the link between breeding effort and oxidative balance through field evaluation of two sympatric sibling insect species

The idea that oxidative stress could be a major force governing evolutionary trade-offs has recently been challenged by experimental approaches in laboratory conditions triggering extensive debates centered on theoretical and methodological issues. Here, we revisited the link between oxidative stress and reproduction by measuring multiple antioxidant and oxidative damages in wild-caught females of two sibling weevil species (Curculio elephas, C. glandium). The strength of our study arises from: (1) studied species are sympatric and exploit similar resource but display contrasting reproductive strategies and (2) individuals were sampled throughout adult life so as to relate oxidative status to breeding effort. We found that the short-lived C. elephas sacrifices red-ox homeostasis for immediate reproduction upon emergence as characterized by low antioxidant defenses and elevated oxidative damage. Comparatively, C. glandium massively invests in antioxidant and maintains low oxidative damage, which may contribute to their extended pre-reproductive period. Intriguingly, we also reveal, for the first time in a field study, an unexpected reactivation of antioxidant defenses with the onset of reproduction. Our results thus support the existence of a strong but complex relationship between oxidative stress and life history evolution and highlight the need for a finer-scale picture of antioxidant strategies

antioxidant and oxidative stress markers in C. elephas and C. glandium

This file contain measures of antioxidant defences (total antioxidant:TEAC; superoxide dismutase: SOD; and catalase: CAT activities) and oxidative damage (malondialdehyde: MDA) expressed per mg of body mass and per mg of protein