Systematics and phylogenetics of the endemic genus Scotorythra (Lepidoptera: Geometridae) in the Hawaiian Islands

The Hawaiian archipelago hosts a remarkable diversity of Lepidoptera despite its extreme isolation from any mainland region. The genus Scotorythra (Geometridae: Ennominae), with 43 species, may be the most diverse group of macrolepidoptera within the archipelago. Although never evaluated within a phylogenetic framework, and despite considerable morphological diversity, all species have been considered part of a single radiation. In order to establish whether the radiation is the result of a single colonization and to provide an evolutionary hypothesis for a systematic treatment of Scotorythra, 605 base pairs of COI and 39 morphological characters were used to reconstruct a phylogeny. Three species of Cleora from the Society and Austral islands were used as outgroups in order to test the assumption of monophyly. Primarily, genitalic characters are used for species delimitation because wing are variable in many species. However, several characters of the wings, legs, abdomen, and head are useful for distinguishing species groups. Closely allied species are often endemic on different islands which sometimes can be used as an aid in identification. Host-plant records for this group have previously been either unknown or unconfirmed. Both Bayesian and Maximum Parsimony analyses, support a hypothesis of a single colonization event. Species defined on the basis of genitalic features are well supported by the molecular data. The results present a hypothesis for allopatric speciation. Male secondary sexual characteristics involved with pheromone dispersal appear to have evolved multiple times throughout the group suggesting an adaptive role for these structures. Through rearing and surveys of private and museum collections, host associations for twenty-two species are now confirmed and presented here and 14 new species are described.