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Intracoastal shipping drives patterns of regional population expansion by an invasive marine invertebrate
Citation:
DARLING, J., L. Herborg, AND I. C. Davidson. Intracoastal shipping drives patterns of regional population expansion by an invasive marine invertebrate. Ecology and Evolution. Wiley-Blackwell Publishing, Hoboken, NJ, 2(10):2557-2566, (2012).
Impact/Purpose:
Non-indigenous aquatic species (NIAS) are widely recognized as a major environmental threat to ecosystems and economies across the United States (US). Continued introduction and spread of NIAS ranks second only to habitat loss in terms of effects on native biodiversity, effects on existing food webs and resulting economic costs. NIAS introductions have been increasing at unprecedented rates over past decades, largely due to modernization and growth of global transport infrastructure and economic trade. Understanding the role played by principle vectors and conditions favoring NIAS spread must become a critical element of any comprehensive plan for environmental protection that ensures the sustainability of endemic ecosystems and the beneficial resources they provide. EERD has initiated a research effort to develop tools to detect morphologically cryptic NIAS, understand transport pathways and secondary spread of invasive species, and assess patterns and environmental influences on hybridization between native and invading taxa. A primary objective of this research is to evaluate the relative contributions of coastal versus long-distance ballast mediated introductions, and to differentiate secondary introductions via ballast transport from post-introduction range expansion.The study includes targeted screening of ballast (from international and coastal traffic) and population genetic surveys for species of concern to determine whether San Francisco Bay is acting as a local source pool for secondary spread (via ship and/or current transport) to other west coast estuaries. Target organisms include Spartina alterniflora,which has disrupted Pacific Coast ecosystem processes and threatens endemic cordgrass species due to competition and hybridization, as well as globally significant invaders such as European green crab (Carcinus maenas) and the Chinese mitten crab (Eriocheir sinensis). In a related study, EERD researchers are assessing the use of DNA identification tools for early detection and monitoring of invasive species in high risk ports across the Great Lakes.
Description:
Understanding the factors contributing to expansion of non-native populations is a critical step toward accurate risk assessment and effective management of biological invasions. Numerous studies have attempted to predict spread of invasive populations by assessing habitat suitability or modeling movement of anthropogenic dispersal vectors. At the same time, genetic data is commonly employed to reconstruct invasion histories and draw inferences regarding most likely pathways and vectors contributing to contemporary distributions of introduced species. However, few studies have attempted to explicitly test hypotheses regarding factors driving invasive spread by seeking correlations between patterns of vector movement and patterns of genetic connectivity. Here we describe such an attempt to for the invasive tunicate Styela clava in the northheastern Pacific. We utilize microsatellite data to estimate gene flow between samples collected throughout the known range of S. clava in the region, and attempt to correlate these estimates with patterns of intra-coastal commercial vessel traffic.
