Posteruption arthropod succession on the Mount St. Helens volcano: the ground-dwelling beetle fauna (Coleoptera).

The 1980 eruptions of Mount St. Helens created a complex mosaic of disturbance types over a 600 km2 area. From 1980 through 2000 we monitored beetle species relative abundance and faunal composition of assemblages at undisturbed reference sites and in areas subjected to tephra-fall, blowdown, and pyroclastic flow volcanic disturbance. We collected 27,074 beetles representing 39 families and 279 species. Five families made up 64 percent of all species collected. Patterns of beetle recolonization and succession were consistent with predicted patterns from relay succession theory, with individual species being sequentially replaced through time as each site's environmental characteristics changed. The beetle assemblages exhibited predictable patterns of similarity, with the least similar assemblages being at opposite ends of the disturbance gradient.