Tuesday, August 8, 8:00-11:30 am
COS 23 - Biogeography
Plantation Room, Cook Convention Center
Presiders: M Calef

Compositional similarity among urban floras within and across continents: the role of nonindigenous species.

La Sorte, Frank *,1, McKinney, Michael2, Pyek, Petr3, 1 University of Missouri - Columbia, Columbia, MO2 University of Tennessee, Knoxville, TN3 Academy of Sciences of the Czech Republic, Pr&udot;honice, Czech Republic

ABSTRACT- Anthropogenic activities have weakened biogeographic barriers to dispersal resulting in the global spread and establishment of an increasing number of nonindigenous species. We examine the broad-scale consequences of this phenomenon based on an analysis of compositional similarity across urban floras in the northeastern United States and Central Europe. We test the prediction that homogenization of specie composition is uniquely defined within vs. between continents based on the time and place of origin of nonindigenous species. In this case, for archaeophytes and neophytes in Europe (introduced before and after 1500 AD, respectively) and nonindigenous species originating from within or outside the US. Our results suggest that, in general, more species in urban floras are shared within than between continents. Within Europe, archaeophytes shared more species relative to neophytes; a strong association was not observed for nonindigenous species in the US. Between the two continents, nonindigenous species in the US that originated from outside the US shared species with European indigenous species and neophytes with the majority shared with archaeophytes. Our results suggest that archaeophytes, based on combination of biogeographic, evolutionary, and ecological factors in association with a long history of anthropogenic influence, have played a prominent role in intercontinental dispersal and intercontinental homogenization of species composition. This suggests that the uniform homogenization of the Earth's biota is not imminent and is presently directed by a combination of biogeographically defined anthropogenic and historical factors.

Key words: biotic homogenization, biogeography, urban floras

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