Psocoptera of the Hawaiian Islands, Part IV The Endemic Genus Palistreptus (Elipsocidae): Systematics, Distribution, and Evolution

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A complex of twenty psocopteran species of the endemic elipsocid genus Palistreptus is reported from the Hawaiian Islands. A generic diagnosis is provided, and the genus is allied with the propsocines rather than the elipsocines. The species inconstans (the type species) and montanus are redescribed, and 18 species are newly described. Following an analysis of 76 characters and the application of Hennigian principles to a species-character matrix using 9 characters, 2 subgenera (Palistreptus and Strepilaptus) comprising 6 species groups are recognized on characteristics of female genitalia. Keys are given for the identification of species and species groups, and a cladogram based on apomorphies of species groups is constructed. Analysis of the distribution of the complex shows that, as with the genus Ptycta, the Kaua'i–O'ahu strait has been the greatest barrier to distribution of Palistreptus species. Two species groups are confined to Kaua'i, which, as in the case of Ptycta species, has 100% endemicity. In contrast to the Ptycta situation, however, there is no evidence that either the Maui complex of islands or the island of Hawai'i has been an important center of endemism. It is suggested that since species of Palistreptus are in general more strictly mountain insects than are those of Ptycta, they have narrower ecological tolerances as a group. This may have impeded dispersal of the genus along the island chain from the west so that the younger islands east of O'ahu have not been dynamic settings for evolution, as they have been for Ptycta.

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