Contrasting patterns of host selection and performance of insect seed predators on three sympatric host plant species

Abstract

Characterising host selection mechanisms and the performance of seed‐predating insects on different hosts has broad implications for ecology and applied entomology. We assessed host selection and performance of endophagous seed‐predating insects on three species of Copaifera, testing two hypotheses: (i) large‐sized trees produce larger seeds and have higher levels of seed predation than their smaller congeneric relatives, and (ii) endophagous seed‐predating insects that develop in larger‐seeded trees exhibit higher body mass, lipid content, and muscle mass as they obtain higher amount of food resources. Unpredated seeds of the large‐sized Copaifera langsdorffii showed greater mass than their smaller congeneric relatives C. arenicola and C. oblongifolia. Two species of endophagous seed‐predating beetles (Rhinochenus brevicollis and Apion sp.) were found attacking seeds of the three Copaifera species. Rhinochenus brevicollis preyed on a higher percentage of seeds than Apion sp. The shrub C. oblongifolia had the highest percentage of seed predation, contradicting our original hypothesis that larger species have a higher percentage of seed predation. Rhinochenus brevicollis preyed on a higher percentage of seeds of larger‐sized species than Apion sp. The higher dispersal ability of R. brevicollis associated with different patterns of plant species distribution may be the mechanism driving differential seed predation among Copaifera species. Adult insects that emerged from C. langsdorffii seeds showed higher body mass and lipidic content. It is likely that insects developing in larger seeds obtain a higher amount of food resources during their development. Finally, we observed a positive relationship between body weight and lipidic content in adults of R. brevicollis. We suggest that studies shedding light onto insect performance in different host‐sized seeds are necessary to understand host selection by beetles.