Distribution of the introduced Argentine ant (Iridomyrmex humilis) in natural habitats of the lower Sacramento Valley and its effects on the indigenous ant fauna

摘要: This study was designed to determine the extent which introduced Argentine ant (Iridomyrmex humilis), a pest in urban and agricultural environments, has invaded natural habitats in lower Sacramento Valley, its effects on native fauna. Of four natural surveyed (valley riparian woodland, foothill blue oak-digger pine chaparral), at 46 sites Yolo Solano counties, only valley woodland found have been colonized by I. humilis. Riparian occupied humilis permanent sources of water tend be environmentally degraded. Populations are common but patchily distributed along principal systems Yolo counties (Ulatis Creek, Putah Cache River). Observations indicate that patches semidisturbed provide refuges from populations may invade adjacent land, vice versa. The species richness native ants is markedly reduced Among ants, epigaeic (aboveground foraging) more susceptible displacement than hypogaeic species. three most adversely affected (Liometopum occidentale, Tapinoma sessile, Formica occidua [ = moki]), absent humilis, dominant ants; two least displaced (Stenamma diecki S. californicum) timid, cryptobiotic forage soil leaf litter.