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Dryad

Unilateral exclusion of three leaf beetle species due resource competition for oviposition sites

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Mar 01, 2025 version files 4.98 MB

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Abstract

Resource competition is a key factor in shaping community structure. However, exclusion due to resource competition likely occurs only in immobile herbivorous insects such as scale insects, because free-living insects mitigate competition by moving to alternative resources. Given that eggs are immobile, their placement is critical for larval survival and development, especially in terms of optimal resource consumption, making oviposition site selection a crucial factor for females. Therefore, competition for oviposition sites may lead to exclusion if resources are scarce. This study examined the competitive relationships among three leaf beetle species (Coleoptera: Chrysomelidae): Aspidimorpha difformis, Aspidimorpha transparipennis, and Laccoptera nepalensis. Competitive dynamics were assessed using field surveys, experiments, and simulations. Results revealed that habitats for both Aspidimorpha species were less than half the size of L. nepalensis habitats. Additionally, both Aspidimorpha species avoided oviposition on leaves with the oothecae of other species, with A. difformis showing a reduction of up to 0% of ootheca number. Simulation results indicated that only A. difformis, which experienced oviposition site reductions due to other species, faced certain extinction under conditions mimicking natural condition of mortality. Our findings suggest that even free-living herbivorous insect experiences unilateral exclusion due to resource competition for oviposition sites, as observed in the field.Thus, based on our findings, even free-living herbivorous insects can be excluded due to interference competition during their immobile stage, such as eggs.