Afrotropical mistletoe butterflies: Larval food plant relationships of Mylothris Hubner (Lepidoptera: Pieridae)

Abstract

A detailed list of larval food plants of Mylothris based on review of published records in the literature is presented. Food plants have been reported for some 23 species (40%), although in only eight species (14%) of butterflies have plants been identified to species level. The food plants represent two unrelated orders, Santalales and Polygonales, although nearly all records (93%) are from four closely related families in the former group. Within the Santalales, the family Loranthaceae, a diverse group of aerial stem-parasitic shrubs (mistletoes), is most frequently exploited. Only two species of Mylothris, M. bernice (Hewitson) and M. rubricosta (Mabille), which are closely related and possibly comprise a single species, are associated with Polygonaceae (Polygonales). Comparison of the morphology of the early stages of M. bernice, and other evidence, clearly indicates that M. bernice/ rubricosta belong to Mylothris and do not represent a separate genus or sister group. Comments are made on these diverse food plant relationships within the context of a modern phylogeny of the Santalales and the evolution of parasitic plant feeding in butterflies in general. It is suggested that Mylothris had its major period of evolution and adaptive radiation on the Loranthaceae, probably sometime after the differentiation of most of the families or lineages in the Santalales (rather than on an earlier ancestral branch at or near the root of the Santalales evolutionary tree), and that this association has facilitated host switching multiple times. While more field data are clearly needed to ascertain the full extent of host specificity and range of mistletoe species exploited by Mylothris, this is unlikely to significantly change the patterns of food plant utilization seen at the higher taxonomic (ordinal and familial) levels. Mylothris represents one of only a few diverse groups of Lepidoptera, and insects in general, known to feed predominantly on African mistletoes.