myth of plant species saturation

Plant species assemblages, communities or regional floras might be termed 'saturated' when additional immigrant species are unsuccessful at establishing due to competitive exclusion or other inter-specific interactions, or when the immigration of species is off-set by extirpation of specie...

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Bibliographic Details
Published in:Ecology letters 2008-04, Vol.11 (4), p.313-322
Main Authors: Stohlgren, Thomas J, Barnett, David T, Jarnevich, Catherine S, Flather, Curtis, Kartesz, John
Format: Article
Language:English
Subjects:
Animal and plant ecology
Animal, plant and microbial ecology
Biodiversity
Biological and medical sciences
Biotic resistance
Botany
colonizing ability
competitive exclusion
Demecology
Ecology
Flowers & plants
Fundamental and applied biological sciences. Psychology
General aspects
Geography
habitat heterogeneity
indigenous species
introduced plants
invasion
invasive species
Nonnative species
Northwestern United States
plant communities
plant competition
plant diversity
Plants
saturation
Southwestern United States
spatial variation
species richness
temporal variation
Time Factors
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Summary:Plant species assemblages, communities or regional floras might be termed 'saturated' when additional immigrant species are unsuccessful at establishing due to competitive exclusion or other inter-specific interactions, or when the immigration of species is off-set by extirpation of species. This is clearly not the case for state, regional or national floras in the USA where colonization (i.e. invasion by exotic species) exceeds extirpation by roughly a 24 to 1 margin. We report an alarming temporal trend in plant invasions in the Pacific Northwest over the past 100 years whereby counties highest in native species richness appear increasingly invaded over time. Despite the possibility of some increased awareness and reporting of native and exotic plant species in recent decades, historical records show a significant, consistent long-term increase in exotic species (number and frequency) at county, state and regional scales in the Pacific Northwest. Here, as in other regions of the country, colonization rates by exotic species are high and extirpation rates are negligible. The rates of species accumulation in space in multi-scale vegetation plots may provide some clues to the mechanisms of the invasion process from local to national scales.
ISSN:1461-023X
1461-0248
DOI:10.1111/j.1461-0248.2008.01153.x