Systematics and Range Fragmentation of the Nearctic Genus Errhomus (Rhynchota: Homoptera: Cicadellidae)

Abstract

Biogeographic analysis of flightless leafhoppers of the genus Errhomus (47 known taxa) indicates remarkable genetic stability, populations of 5 taxa having attained at most only subspecific status although separated by huge canyons > 1.5 million years old. Modern distributions appear to have stabilized long ago; many retain configurations laid down by the ancestral Columbia River canyon of at least 6 million years ago and some may be traced to events of 12 million years ago. Three subspecies are morphologically distinct and are raised to specific level, whereas evidence of introgression reduces 6 species to subspecific status and 3 other subspecies to hybrid swarms, leaving 23 species in 2 subgenera, Errhomus sensu stricto (12 species) and Erronus new subgenus (11 species). Twelve new taxa are described: E. lincatus cordatus, E. variabilis erratus, and E. variabilis mimicus from Idaho; E. bracatus, E. camensis, and E. vivalis from Montana; E. affinis attenuatus and E. variabilis gracilis from Oregon; E. naomi from Utah: E. praedictus, E. picturatus, and E. serratus obliteratus from Washington. Only 4 species are common and widespread; 10 others are known from only 1 or 2 sites. The study is based on 6,000 specimens representing 153 populations of Errhomus (including 7 new state records and 22 new county records) in addition to the 15,000 specimens of 212 populations recorded in 1987. The genus belongs to subtribe Bathysmatophorina (subfamily Cicadellinae) that encompasses Eurasian Bathysmatophorus and the western North American Ankosus, Carsonus, Errhomus, hylaius (new status), and Thatuna. The subtribe is here removed from Errhomenini (subfamily Aphrodinae) and elevated to tribal status. No longer included is the genus Lysteridea, which is here transferred from Errhomenini to Pagaroniini (subfamily Cicadellinae).