PARENT SESSION
Oral Session #20: Invasions: Effects of invaders -- terrestrial systems. Presiding: R. Callaway.
Tuesday, August 7, 2001. 8:00 AM to 12:00 PM. Madison Ballroom C.
Invader-mediated changes in ground-dwelling arthropod assemblages.
Morgan, Darça1, Cushman, J1, 1
ABSTRACT- Non-native plant species are conspicuous features of terrestrial landscapes throughout the world. Although arthropods also dominate these systems, both in terms of biomass and species richness, few studies have considered the consequences of such plant invasions for the composition of arthropod assemblages. Giant reed (Arundo donax), periwinkle (Vinca major), and poison hemlock (Conium maculatum) are three non-native plant species that have invaded extensive portions of riparian habitat in California. Results from a two-year study indicate that overall arthropod abundance was significantly lower in Arundo patches compared to other vegetation. Predaceous arthropod abundance was also significantly reduced in Arundo, while detritivores increased in Vinca, suggesting that predators may be more vulnerable to exotic plant invasion than detritivores. We also examined arthropod response to experimental reductions in Arundo stem density. We did not detect an effect of Arundo reduction on arthropods after one year, despite the comparative findings discussed earlier. However, we suspect arthropod colonization of this heavily invaded area will eventually occur because 70% of arthropods collected are associated with early succession and disturbance. Findings from these studies will offer the first glimpse of the consequences of exotic plant invasion on arthropod biodiversity.
KEY WORDS: arthropods, invasive species, Arundo donax, Vinca major