文獻來源：ML Forister, CC Nice, JA Fordyce, Z Gompert. 2009. Host range evolution is not driven by the optimization of larval performance: the case of Lycaeides melissa (Lepidoptera: Lycaenidae) and the colonization of alfalfa. Oecologia 160:551–561
Herbivorous insects that have recently incorporated novel hosts into their diet provide unique opportunities for understanding factors that promote or constrain the evolution of niche breadth. Lycaeides melissa has colonized both cultivated and feral alfalfa (Medicago sativa) throughout much of North America within the past 200 years. We investigated the quality of the novel host as a resource for juvenile development, and asked if the novel host is a preferred host for oviposition relative to a native host (Astragalus canadensis). Larval-performance and oviposition-preference were examined using L. melissa individuals from a population associated with both M. sativa and A. canadensis, and oviposition-preference was also examined in another population associated exclusively with M. sativa. In addition, we investigated the eVects of M. sativa and A. canadensis flowers on both preference and performance. Only one of the hosts, M. sativa, has flowers that are accessible to nectaring butterXies, and we hypothesized that the presence of flowers could aVect female behavior. We Wnd that the novel host is a relatively poor larval resource: adults that were reared as larvae on M. sativa were roughly one-third the size of adults that were reared on the native host, A. canadensis. The native host, Astragalus canadensis, is the preferred host in choice experiments involving only foliage. However, when flowers were included in preference assays, the native and novel hosts received similar numbers of eggs. Thus, the presence of flowers on hosts in the Weld might inXuence the utilization of a novel and inferior larval resource. These results are consistent with a model in which host shifts are driven by adult behavior that does not directly optimize larval performance.
Keywords Niche breadth · Niche shift · Preference ·Performance · Specialization