THE GALAPAGOS-ISLANDS GENUS NEORYCTES ARROW (COLEOPTERA, SCARABAEIDAE, DYNASTINAE)

The endemic Galapagos' genus Neoryctes Arrow has had a confused nomenclatorial and taxonomic history. Evaluation of morphological variation in the 41 specimens now available confirms the distinctiveness of the genus and establishes the existence of four species, each restricted to a single island. The original Darwin specimen, named Oryctes galapagoensis by G.R. Waterhouse in 1845, is shown to be from Isla Santiago. Two other names are valid: N. linelli Mutchler for the population on San Cristobal and N. moreti Dechambre for the one on Santa Cruz. The population on Floreana is named as a new species, N. williamsi. Neoryctes most likely originated from a Pentodontini dynastine ancestor from lowland South or Central America. The ancestor first dispersed to Isla San Cristobal, one of the oldest islands. It is hypothesized that before hindwing reduction occurred, which is now characteristic of all members of the genus, individuals from San Cristobal spread to the other islands. Subsequently, possibly during periods of Pleistocene aridity, each population became restricted to its present range in the moist highland zone of an individual island.