COS 95-1 - Invasion and native species loss through local extinction

Thursday, August 11, 2011: 8:00 AM
10A, Austin Convention Center
Erin J. Questad1, Jarrod M. Thaxton2 and Susan Cordell1, (1)Institute of Pacific Islands Forestry, USDA Forest Service, Hilo, HI, (2)Department of Biological Sciences, Eastern Kentucky University, Richmond, KY

Despite concerns that invasive plant species may cause declines in native plant diversity, the ecological mechanisms potentially causing these declines are poorly understood. Invasive species may reduce native diversity by reducing colonization rates or accelerating extinction rates. We examined the relationships between invasion and declines in native plant diversity at local scales in a Hawaiian dry forest by experimentally removing non-native species, planting native species, and manipulating resources and environmental conditions.


We found higher invasion rates in habitats that supported the most native species, suggesting that underlying resource availability drives the distribution of both native and invasive species. Pennisetum setaceum, a dominant invasive perennial grass, was associated with accelerated local native extinction rates and declines in native diversity. Although invasion rates were greatest in more favorable habitats, the impact of invasion on native species loss was significant only in habitats with lower resource supply.

We found evidence supporting an “extinction debt” due to current levels of plant invasions, highlighting the importance of management programs for threatened and endangered plant species. Our study provides an important caveat to previous suggestions that invasion impacts on native diversity will be greatest in the most diverse plant communities. In some ecosystems it may be more effective to control invasive species in sensitive areas with low resource availability instead of in hotspots of biodiversity.

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