PARENT SESSION
Oral Session #1: Conservation Ecology: Threatened and Endangered Species. Presiding: W. Bond.
Monday, August 6, 2001. 8:00 AM to 12:15 PM. Madison Ballroom C.
Effects of habitat loss and an invasive enemy on the persistence of a threatened beetle.
Talley*, Theresa1, Huxel, Gary1, Holyoak, Marcel1, Collinge, Sharon2, 1 2
ABSTRACT- Habitat loss and invasive species are two of the most important threats to the persistence of threatened and endangered species. We will discuss why and how these factors are threats to an endemic species of the Central Valley of California, the Valley elderberry longhorn beetle (VELB), Desmocerus californicus dimorphus. In the Central Valley, only 12,000 of an original 775,000 acres remain and are distributed in small, isolated fragments. These habitats are occupied by the VELB and its host plant, the Mexican elderberry Sambucus mexicana. Because the VELB is a specialist on elderberry, it is vulnerable loss or reduction in quality of riparian woodland. Our previous work has shown that isolated elderberry plants (and isolated drainages at a larger scale) have lower probabilities of use by the VELB. Additionally the invasion of the Argentine ant Linepithema humile poses an important threat to the VELB. Earlier work has shown a negative correlation between the VELB and the Argentine ant. We find that isolated riparian woodlands experience less habitat use by the Argentine ant. While isolated habitats have a lower probability occupancy by the VELB, they may be favorable VELB sites because of the absence of predatory Argentine ants. These problems require joint evaluation. We conclude that persistence of the VELB and other riparian specialists require a regional approach to selecting mitigation areas and for maintaining undisturbed sites that lack invasive species.
KEY WORDS: Desmocerus californicus dimorphus, Linepithema humile, habitat loss