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Abstract LATITUDINAL GRADIENTS AND POLE WARD SPREAD OF BIOLOGICAL INVASIONS IN MARINE ECOSYSTEMS Chad L. Hewitt1
and Gregory M. Ruiz2 Marine biological invasions are a significant force of change in marine ecosystems throughout the world, impacting many dimensions of biodiversity, community function, and human society. Although invasions have occurred throughout Earth’s history, the rate of documented invasions has increased dramatically in recent time, resulting from the human-mediated transfer of organisms across historical dispersal barriers such as oceans and continents. Although no region of the world’s coastal ecosystems is free of human-mediated invasions, strong latitudinal gradients exist in the number of known non-indigenous species, declining from temperate regions (where most invasions are documented) to polar regions. This pattern may result from a combination of multiple factors, including: a) limited knowledge of polar biodiversity, in part due to limited or restricted surveys; b) relatively low exposure to transport (reduced inoculation pressures) of non-indigenous species; and c) differences in susceptibility to invasion of high latitude systems, due to constraints in either physiological compatibility for arriving organisms or opportunity (invasibility) of the recipient community. Expanding our knowledge of polar biodiversity, through survey and sampling activities, can help address the limited understanding of past invasion histories across latitudes. However, it is also important to recognize the dynamic nature of invasions, with many of the key drivers (especially inoculation rates and climate) changing through time, such that past history may not adequately describe future invasion risk(s). We review the current state knowledge for high latitude invasions, examining patterns of non-indigenous species delivery and establishment, to explore underlying mechanisms and future changes for Arctic and Antarctic ecosystems.
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