Performance of leaf beetle larvae on sympatric host and non-host plants

Studies asking the ability of insects to utilize novel host plants often us e novel hosts that are allopatric with the insect population under investig ation. However, since the outcomes of species interactions are often site-s pecific, such studies cannot tell us whether a plant would actually be used by a given insect population if the plant grew sympatrically with it. We t herefore performed a quantitative genetics experiment to analyse the perfor mance of larvae of the leaf beetle Oreina elongata Suffrian (Coleoptera: Ch rysomelidae, Chrysomelinae) on two host and three non-host plants, collecte d from a site where insects and plants co-occur in the Western Alps. When r aised on the non-host Petasites albus (L.), larvae were able to survive equ ally well as on the two hosts, Adenostyles alliariae (Gouan) and Cirsium sp inosissimum (L.), whereas they did not survive on the two other non-hosts, Peucedanum ostruthium (L.) and Rumex alpinus L. On P. albus, growth rate wa s slightly lower and development time slightly longer than on the two hosts . We found a genotype by environment interaction only for growth rate but n ot for development time and survival. However, the shape of the reaction no rms of growth rates suggests that it is unlikely that selection could favou r the inclusion of P. albus into the host range of the study population.