SPECIATION AND PHYLOGEOGRAPHY OF HAWAIIAN TERRESTRIAL ARTHROPODS

The Hawaiian archipelago is arguably the world's finest natural labora tory for the study of evolution and patterns of speciation. Arthropods comprise over 75% of the endemic biota of the Hawaiian Islands and a large proportion belongs to species radiations. We classify patterns o f speciation within Hawaiian arthropod lineages into three categories: (i) single representatives of a lineage throughout the islands; (ii) species radiations with either (a) single endemic species on different volcanoes or islands, or (b) multiple species on each volcano or isla nd; and (iii) single widespread species within a radiation of species that exhibits local endemism. A common pattern of phylogeography is th at of repeated colonization of new island groups, such that lineages p rogress down the island chain, with the most ancestral groups (populat ions or species) on the oldest islands. While great dispersal ability and its subsequent loss are features of many of these taxa, there are a number of mechanisms that underlie diversification. These mechanisms may be genetic, including repeated founder events, hybridization, and sexual selection, or ecological, including shifts in habitat and/or h ost affiliation. The majority of studies reviewed suggest that natural selection is a primary force of change during the initial diversifica tion of taxa.