PARENT SESSION
Poster Session #37: Invertebrate Ecology.
Thursday, August 9, 2001. Presentation from 10:30 AM to 12:00 PM. Exhibition Hall

Wings and mucus in space and time: Patterns of invertebrate biogeography in Grand Canyon.

STEVENS, LAWRENCE¹, NORTH, ERIC¹, MERETSKY, VICKY², ^{1 2}

ABSTRACT- Taxa with vastly differing vagility may encounter similar dispersal challenges in complex terrain over evolutionary time. Diverse topography and Pleistocene-Holocene climate changes have affected invertebrate biogeography in the Grand Canyon region. Museum collections and published data allowed us to examine the biogeographic role of Grand Canyon as a barrier/filter, corridor, refuge, or null effect. We studied the distribution of landsnails, Odonata, Orthoptera, semi-aquatic Heteroptera, butterflies, and bees. Grand Canyon is a barrier/filter that limits the northward expansion of desert species, and a southern boundary for some Rocky Mountain taxa. The neorefugial inner Grand Canyon desert is depauperate and has low levels of endemism, a conclusion supported by the distribution of 31 semi-aquatic Heteroptera, >110 butterflies and skippers, 38 Colorado River chironomid midge species. Butterfly diversity in the desert (42 taxa) is lower than that on either rim (58 and 77 species on the South and North rims, respectively), and that in southern Arizona. The positive relationship between butterfly diversity and elevation is likely an artifact of the small, isolated area of low desert habitat, the evolutionarily brief time (10,000 yr) it has supported desert vegetation, and the long-linear habitat shape. Similar patterns exist among 20 landsnail taxa, with only one endemic snail at one inner canyon spring. However, more than 60 percent of invertebrate taxa are affected by the Grand Canyon as a biogeographic feature.

KEY WORDS: invertebrates, Grand Canyon, biogeography