Putative role of learning and genetics in host range shift in Manduca sexta

Larvae of the Six-Spotted Hawkmoth Manduca sexta are specialist herbivores on members of the Solanaceae; but some populations in Arizona and North Carolina have recently been observed to oviposit on and her offspring subsequently consume an unrelated novel host of the genus Proboscidea. This project investigates whether host preference in M. sexta can be induced in larvae and maintained following metamorphosis. Commercially purchased M. sexta were reared on artificial diet alone or supplemented with aqueous extract of solanaceous host Datura wrightii or Proboscidea parviflora, both native the American Southwest. Adult females will be presented with males from either the Datura or Proboscidea experimental group, and then mated females will be presented with both species for oviposition to detect host plant and mate preference. Ongoing behavioral experiments investigating diet preference in larvae indicate they prefer their natal host to a novel host when presented with both extracts. To investigate whether genetic factors are currently mediating a host range shift, the experiment will be repeated with wild-type M. sexta. If a strong genetic component to host preference emerges, this may represent incipient host race formation in M. sexta.