Parental Host Plant Affects Offspring Life Histories in a Seed Beetle

Abstract

Non—genetic effects of maternal environment often have large influences on offspring phenotypes. Some maternal effects may be adaptive in heterogeneous environments, whereby mothers can program a developmental switch in their offspring in response to a predictive environmental cue. For herbivorous insets, maternal rearing hosts (i.e., maternal environment) may have large effects on offspring, including adaptive effects on patterns of host suitability. For example, if maternal rearing host is predictive of local host availability, then it is advantageous for mothers reared on one host to produce offspring that are physiologically 'acclimated' to that host. Previous research has demonstrated that seed beetles, Stator limbatus, collected from Cercidium floridum survived better and developed faster on this host than beetles collected from Acacia greggii or C. microphyllum at either the same site or from a different locality. These results indicate either within— and among—population host—associated genetic differentiation or a non—genetic maternal host effect, in which offspring survive better and develop faster on the host their mother was reared on. We examine the influence of maternal and paternal rearing hosts on the survivorship, development time, and body size in offspring in S. limbatus. We find no evidence that beetles are acclimated to perform better on the host their mother was reared on via non—genetic maternal effects. However, maternal rearing host did affect offspring in other ways; mothers reared on C. floridum produced larger offspring that developed faster than offspring of mothers reared on A. greggii, due to a non—genetic maternal effect (paternal rearing host had no effect). In addition, both maternal and paternal host had a large effect on offspring survivorship; offspring of parents reared on C. floridum survived better than those of parents reared on A. greggii. The symmetry between the maternal and paternal host effects on survivorship suggests that they represent a response to intense selection during the experiment, and suggest the potential for rapid adaptation to this host. Alternatively, non—genetic effects of both maternal and paternal rearing host may simultaneously influence survivorship of S. limbatus offspring. Although paternal effects are generally disregarded as an important source of environmental variation, they are potentially important for S. limbatus; non—genetic paternal effects were detected in this experiment for development time of offspring: fathers reared on C. floridum produced offspring that developed slower on C. floridum, and offspring that developed faster on A. greggii, than fathers reared on A. greggii.