Maternal effects mediate host expansion in a seed-feeding beetle

Texas ebony (Chloroleucon ebano) has recently been introduced as an ornamen tal tree in the Phoenix metropolitan area of Arizona (USA). It has since be en colonized by the seed beetle Stator limbatus (Coleoptera: Bruchidae), an d seeds of Texas ebony support the development of beetles to reproductive m aturity in nature and in the laboratory. Egg size affects the larval surviv orship of beetles on seeds of Texas ebony. Females of S. limbatus exhibit e gg-size plasticity in response to native host plants; they lay small eggs i f they encounter seeds of catclaw acacia (Acacia greggii) and lay large egg s if they encounter seeds of the blue paloverde (Cercidium floridum). We te sted the hypothesis that oviposition experiences of female S. limbatus on n ative plants affects the ability of their larvae to develop on seeds of the nonnative Texas ebony. We demonstrate that females that encounter the nati ve C. floridum while they are maturing their eggs produce progeny that have survivorship 10 times higher on seeds of the introduced Texas ebony than t hat of progeny produced by females that do not encounter C. floridum during egg maturation. However, this result cannot be explained entirely by egg-s ize plasticity; survivorship of larvae differed among treatments even in th e range of egg sizes that overlapped between treatments. These results thus indicate that females exhibit plasticity in egg size and egg composition, and that this plasticity facilitates the expansion of S. limbatus onto seed s of a nonnative plant. Our study thus demonstrates that maternal effects c an influence species interactions within communities, and that we should co nsider these maternal effects when predicting the ecological and evolutiona ry consequences of changing species distributions.