Growth and developmental performance of the milfoil weevil on distinct lineages of Eurasian watermilfoil and a northern x Eurasian hybrid

摘要

Recent identification of two genetically distinct lineages of Eurasian watermilfoil (Myriophyllum spicatum L.) and hybrid M. sptkatum x M. sibiricum Kom. populations in Ontario, Canada has lead to emerging concerns surrounding the efficacy the milfoilweevil [Euhrychiopsis lecontei (Deitz)] as a biological control agent. In the summer of 2011 we conducted an experiment in a climate controlled growth chamber to determine the growth and developmental performance of E. kontei on two distinct M. spicatumlineages (EWM1, EWM2) an Kspkatum xM. sibiricum hybrid (HYB) and M. sibiricum (NWM). We observed an increased overall survivorship of E. lecontei on HYB in comparison to EWM2 and NWM. Additionally, greater mass at emergence and shorter larval stage duration was observed for E. lecontei reared on HYB and EWM1 in comparison to NWM. Although not statistically significant, an increased survivorship of￡. lecontei was observed on HYB in comparison to EWM1. This suggests a dominance or hybrid susceptibilityto herbivory for HYB in comparison to its parental congeners rather than an additive or intermediate relationship observed in previous studies. This may be due in part to increased nutritional quality; HYB had a higher shoot tissue N and P content than all other milfoil types. E. lecontei reared on EWM2 showed poor development including low overall survivorship and larval stage duration which may have been greatly influenced by poor plant response to growth in the environmental chamber. The results of this experiment expand current knowledge surrounding the influence of host plant preference and host plant quality on the growth and development of herbivorous insects and can be used to inform future biological control applications.