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Of Asian forests and European fields: Eastern U.S. plant invasions in a global floristic context.

Fridley JD - PLoS ONE (2008)

Bottom Line: In contrast, EUS invasive species are most likely to come from East Asia (29%), a pattern that is magnified when the invasive pool is restricted to species that are native to a single floristic region (25% from East Asia, compared to only 11% from northern/central Europe and 2% from the Mediterranean).Moreover, East Asian invaders are mostly woody (56%, compared to just 23% of the total alien flora) and are significantly more likely to invade intact forests and riparian areas than European species, which dominate managed or disturbed ecosystems.This view must be superseded by a biogeographic invasion theory that is explicitly habitat-specific and can explain why particular world biotas tend to dominate particular environments.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, Syracuse University, Syracuse, New York, USA. fridley@syr.edu

ABSTRACT

Background: Biogeographic patterns of species invasions hold important clues to solving the recalcitrant 'who', 'where', and 'why' questions of invasion biology, but the few existing studies make no attempt to distinguish alien floras (all non-native occurrences) from invasive floras (rapidly spreading species of significant management concern), nor have invasion biologists asked whether particular habitats are consistently invaded by species from particular regions.

Methodology/principal findings: Here I describe the native floristic provenances of the 2629 alien plant taxa of the Eastern Deciduous Forest of the Eastern U.S. (EUS), and contrast these to the subset of 449 taxa that EUS management agencies have labeled 'invasive'. Although EUS alien plants come from all global floristic regions, nearly half (45%) have native ranges that include central and northern Europe or the Mediterranean (39%). In contrast, EUS invasive species are most likely to come from East Asia (29%), a pattern that is magnified when the invasive pool is restricted to species that are native to a single floristic region (25% from East Asia, compared to only 11% from northern/central Europe and 2% from the Mediterranean). Moreover, East Asian invaders are mostly woody (56%, compared to just 23% of the total alien flora) and are significantly more likely to invade intact forests and riparian areas than European species, which dominate managed or disturbed ecosystems.

Conclusions/significance: These patterns suggest that the often-invoked 'imperialist dogma' view of global invasions equating invasion events with the spread of European colonialism is at best a restricted framework for invasion in disturbed ecosystems. This view must be superseded by a biogeographic invasion theory that is explicitly habitat-specific and can explain why particular world biotas tend to dominate particular environments.

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Floristic signature of Eastern U.S. plant invasions by habitat type.Seven habitat types (Table 1) are illustrated with the total number of species described as “invasive” (out of 449 total in the Eastern U.S.) listed in bold parentheses. Floristic regions most positively and negatively associated with each habitat were determined by the most extreme positive and negative standardized residual values from a Pearson chi-square test of a contingency table of all floristic regions and habitat types (Table 3). Number of invaders contributed to each habitat by each listed region are noted in parentheses. Drawing by Eric Fridley.
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pone-0003630-g002: Floristic signature of Eastern U.S. plant invasions by habitat type.Seven habitat types (Table 1) are illustrated with the total number of species described as “invasive” (out of 449 total in the Eastern U.S.) listed in bold parentheses. Floristic regions most positively and negatively associated with each habitat were determined by the most extreme positive and negative standardized residual values from a Pearson chi-square test of a contingency table of all floristic regions and habitat types (Table 3). Number of invaders contributed to each habitat by each listed region are noted in parentheses. Drawing by Eric Fridley.

Mentions: The subset of 449 invasive EUS taxa is not a random sample of native floristic regions of the alien taxa (Table 2, Fig. 2). Twenty-nine percent of the alien taxa with native ranges that include the Eastern Asiatic region are reported invasive, compared to 22% and 20% of the alien taxa from Circumboreal and Mediterranean regions. Alien taxa present in the Saharo-Arabian and Irano-Turanian regions also include high proportions of invasive taxa (42% and 27%, respectively). However, when alien taxa were instead restricted to those that only occur in a single native region (region endemics), the amount of invasive taxa from Saharo-Arabian and Irano-Turanian regions essentially disappeared (0% and 3%, resp.), as did those from the Mediterranean (2%). This in part reflects the clear relationship between native range size, measured as the number of floristic regions inhabited, and invasion potential (Fig. 3). Despite the smaller overall invasive proportion of region-endemic alien taxa (13%; Table 2), endemics from East Asia have nearly as high an invasive percentage as non-endemics (25%), whereas the percentage of endemic invaders from the Circumboreal region is cut in half (11%, compared to 22% non-endemic invaders). The Neozeylandic region is the only region to lack any invasive contribution to the EUS flora.


Of Asian forests and European fields: Eastern U.S. plant invasions in a global floristic context.

Fridley JD - PLoS ONE (2008)

Floristic signature of Eastern U.S. plant invasions by habitat type.Seven habitat types (Table 1) are illustrated with the total number of species described as “invasive” (out of 449 total in the Eastern U.S.) listed in bold parentheses. Floristic regions most positively and negatively associated with each habitat were determined by the most extreme positive and negative standardized residual values from a Pearson chi-square test of a contingency table of all floristic regions and habitat types (Table 3). Number of invaders contributed to each habitat by each listed region are noted in parentheses. Drawing by Eric Fridley.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2572842&req=5

pone-0003630-g002: Floristic signature of Eastern U.S. plant invasions by habitat type.Seven habitat types (Table 1) are illustrated with the total number of species described as “invasive” (out of 449 total in the Eastern U.S.) listed in bold parentheses. Floristic regions most positively and negatively associated with each habitat were determined by the most extreme positive and negative standardized residual values from a Pearson chi-square test of a contingency table of all floristic regions and habitat types (Table 3). Number of invaders contributed to each habitat by each listed region are noted in parentheses. Drawing by Eric Fridley.
Mentions: The subset of 449 invasive EUS taxa is not a random sample of native floristic regions of the alien taxa (Table 2, Fig. 2). Twenty-nine percent of the alien taxa with native ranges that include the Eastern Asiatic region are reported invasive, compared to 22% and 20% of the alien taxa from Circumboreal and Mediterranean regions. Alien taxa present in the Saharo-Arabian and Irano-Turanian regions also include high proportions of invasive taxa (42% and 27%, respectively). However, when alien taxa were instead restricted to those that only occur in a single native region (region endemics), the amount of invasive taxa from Saharo-Arabian and Irano-Turanian regions essentially disappeared (0% and 3%, resp.), as did those from the Mediterranean (2%). This in part reflects the clear relationship between native range size, measured as the number of floristic regions inhabited, and invasion potential (Fig. 3). Despite the smaller overall invasive proportion of region-endemic alien taxa (13%; Table 2), endemics from East Asia have nearly as high an invasive percentage as non-endemics (25%), whereas the percentage of endemic invaders from the Circumboreal region is cut in half (11%, compared to 22% non-endemic invaders). The Neozeylandic region is the only region to lack any invasive contribution to the EUS flora.

Bottom Line: In contrast, EUS invasive species are most likely to come from East Asia (29%), a pattern that is magnified when the invasive pool is restricted to species that are native to a single floristic region (25% from East Asia, compared to only 11% from northern/central Europe and 2% from the Mediterranean).Moreover, East Asian invaders are mostly woody (56%, compared to just 23% of the total alien flora) and are significantly more likely to invade intact forests and riparian areas than European species, which dominate managed or disturbed ecosystems.This view must be superseded by a biogeographic invasion theory that is explicitly habitat-specific and can explain why particular world biotas tend to dominate particular environments.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, Syracuse University, Syracuse, New York, USA. fridley@syr.edu

ABSTRACT

Background: Biogeographic patterns of species invasions hold important clues to solving the recalcitrant 'who', 'where', and 'why' questions of invasion biology, but the few existing studies make no attempt to distinguish alien floras (all non-native occurrences) from invasive floras (rapidly spreading species of significant management concern), nor have invasion biologists asked whether particular habitats are consistently invaded by species from particular regions.

Methodology/principal findings: Here I describe the native floristic provenances of the 2629 alien plant taxa of the Eastern Deciduous Forest of the Eastern U.S. (EUS), and contrast these to the subset of 449 taxa that EUS management agencies have labeled 'invasive'. Although EUS alien plants come from all global floristic regions, nearly half (45%) have native ranges that include central and northern Europe or the Mediterranean (39%). In contrast, EUS invasive species are most likely to come from East Asia (29%), a pattern that is magnified when the invasive pool is restricted to species that are native to a single floristic region (25% from East Asia, compared to only 11% from northern/central Europe and 2% from the Mediterranean). Moreover, East Asian invaders are mostly woody (56%, compared to just 23% of the total alien flora) and are significantly more likely to invade intact forests and riparian areas than European species, which dominate managed or disturbed ecosystems.

Conclusions/significance: These patterns suggest that the often-invoked 'imperialist dogma' view of global invasions equating invasion events with the spread of European colonialism is at best a restricted framework for invasion in disturbed ecosystems. This view must be superseded by a biogeographic invasion theory that is explicitly habitat-specific and can explain why particular world biotas tend to dominate particular environments.

Show MeSH