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Genetic perspectives on marine biological invasions
Citation:
Geller, J. B., J. A. DARLING, AND J. T. Carlton. Genetic perspectives on marine biological invasions. Annual Review of Marine Science. Annual Reviews Inc., Palo Alto, CA, 2:367-393, (2010).
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. Freshwater fish invasions of rivers in the Southeastern U.S. also provide unique opportunities for understanding ecological and genetic consequences of NIAS introductions. EERD has begun a collaborative and interdisciplinary study to evaluate the spread of red shiner (Cyprinella lutrensis) across Southeastern drainages relative to competition and hybridization with endemic blacktail shiners (C. venusta), land use patterns, and stream remediation scenarios. The research is aimed at determining whether spread and introgresive hybridization by C. lutrensisis facilitated by land use impacts on water quality (ie. urbanization and turbidity). Corresponding genetic studies on the longitudinal distribution of C. lutrensis x C. venusta hybridization will further indicate whether land use impacts on water quality correspond to genetic pathways of invasion. Additional laboratory studies on C. lutrensis and C. venusta mate recognition and hybrid fitness are being conducted to experimentally test whether increased turbidity eliminates or weakens interspecific reproductive barriers and increase rates of hybridization. The information gained from these studies will ultimately feed into spatially explicit population models to evaluate how remediation strategies might limit ecological competition and hybridization to maintain drainage specific evolutionary lineages of C. venusta and other native congeners. This research also represents an application of an integrative approach EERD is developing for assessing the condition of aquatic habitats based on landscape, community, and genetic analyses.
Description:
The last few decades have seen increasing concern for the state of the ocean's biota. A growing list of stressors has led to extensive changes in the distribution and composition of species on the world's coastlines, in the ocean's water column, and even on the deep sea floor. This review deals with one of those stressors, human-assisted marine biological invasions, defined as the establishment of species in geographic regions outside the reach of their natural dispersal mechanisms.