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Abstract BIOGEOGRAPHY OF MARINE INVASIONS: CURRENT STATUS AND FUTURE PREDICTIONS Gregory M. Ruiz, Paul Fofonoff, Brian Steves,
Kristen Larson, Linda McCann, A. Whitman Miller and Anson H. Hines. Biological invasions are a significant force of change in coastal
ecosystems. Invasions have occurred throughout Earth’s history,
but the scale and tempo has increased strongly in recent time due
to global trade. Available data suggest there is a strong latitudinal
pattern in recent marine invasions, with more non-native species
documented in temperate marine communities than polar or tropical
systems. This geographic pattern of invasion may reflect historical
biases in search effort and taxonomic knowledge. Contemporary surveys
suggest these patterns are robust across mid- and high-latitudes,
when controlling for search effort. For example, a standardized
survey of sessile invertebrate assemblages in estuaries of western
North America found a significant decrease in non-native species
richness with increasing latitude (32 to 61oN). Several mechanisms
may explain the observed invasion pattern across latitudes, operating
alone or in combination, such as differences in (a) propagule supply,
(b) biotic resistance to invasion, (c) environmental resistance
to invasion, and (d) disturbance regime. To date, the relative importance
of these mechanisms across geographic regions has not been evaluated,
but each may be expected to change over time. Of particular interest
and concern are the interactive effects of climate change and human
activities on marine invasions, especially at high latitudes. Current
climate change models predict not only an increase in sea surface
temperatures but also a rapid reduction in sea ice in the Artic.
Combined with human responses, climate change is predicted to cause
directional shifts in invasion biogeography, including increased
invasion opportunity at high northern latitudes.
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