On speciation and hybridization among closely related species: establishing an experimental breeding lineage between two species of Automeris Hübner moths (Lepidoptera: Saturniidae)and implications for taxonomy

Abstract

Many species of plants and a few species of animals are believed to have resulted from hybridization of parental species, and the ability of species to occasionally hybridize in captivity and in nature is even more widespread. In the present study, we describe a hybridization experiment conducted in the laboratory between the sexually dimorphic Automeris io (Fabricius), a widespread, variable species ranging from Canada to Costa Rica, and its congener A. louisiana (Ferguson and Brou), a more local, sexually monomorphic species (Lepidoptera: Saturniidae). The A. louisiana populations occur in a highly specialized habitat—the coastal marshland along the Gulf of Mexico in Louisiana and Texas and is nested inside the broad distribution of A. io, demonstrating strong differences from the latter in its ecology and morphology. No natural hybridization between the two species has been described. While the separate species status of A. io and A. louisiana is supported by morphology and ecology of their populations, we were able to create a hybrid lineage in the laboratory and maintained it for three generations. The hybrids were phenotypically intermediate between the parental species. Under a stricter reading of the biological species concept, such an ability to hybridize would be interpreted by some as a sign of conspecificity. Our experiments once again demonstrate the complexity of ‘species’ as a concept, which may need major redefinition in the popular interpretation of sciences.