Differing effects of parental and natal hosts on the preference and performance of the stored product pests Callosobruchus maculatus and C. analis

Bean beetles (Bruchinae) are a taxon of seed predators and several species are economically significant stored product pests. Seed quality may affect adult life history traits, with consequences for their population dynamics. We investigated if variation in host quality (poor quality: lentil; high quality: mung bean) as experienced by the parental (i.e. the individuals ovipositing) generation and the natal (i.e. the study individuals emerging from the host) generation influenced the preference and performance of Callosobruchus maculatus and C. analis. Both species preferred ovipositing on mung bean regardless of experience. Emergence rate was high for all treatments except for C. maculatus reared on mung, whose offspring did poorly when developing in lentil. The sex ratio of emerging offspring was 1:1 except for C. analis emerging from lentil, which was female biased if the parents were reared on lentil, but male biased if reared on mung. In C. analis, lentil parental host resulted in larger offspring irrespective of natal host, while in C. maculatus larger offspring emerged from mung as natal host. Overall, males emerging from lentils obtained more matings, except with C. maculatus where females had emerged from mung, where there was no preference. Development time for beetles was increased for those with parents reared on mung and for those with lentil natal hosts. For C. analis there was no difference in survival time for those where the parental host was lentil, but when the parental host was mung, then there was a significant reduction in survival time for those whose natal host was also mung, compared to those emerging from lentils. This work shows that predicting the effect of host quality on traits requires more than single-species, single-generation studies, as transgenerational effects can influence the performance and preference of closely related stored product pest species in quite different ways.