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Publication year : 0
Thematic : Invasive Alien Species
Language : English
Note
In this chapter, we examine how the ecology of invasions helps clarify the relationships
among community saturation, diversity, and ecosystem functioning.
We begin with a theoretical approach that suggests a common underlying
mechanism for the negative effect of diversity on community invasibility and
other ecosystem functions, such as productivity. This stochastic model of community
assembly predicts that, within a given habitat, increasing species richness
should reduce resource availability and decrease invasion success. A brief
review of evidence from the fossil record of biotic interchanges reveals that the
less diverse region is typically more invaded by species than the more speciesrich
region. The reason for this could be either that species-poor regions have
greater resource availability (there are empty niches), or that species from
more diverse regions are competitively superior. Experimental studies with recent
invaders suggest that, all else being equal, increasing diversity decreases
invasion success by decreasing resource availability. More complete or efficient
utilization of resources at higher diversity extends beyond invasion resistance
in its contribution to other ecosystem processes, such as productivity,
nutrient recycling, and stability/consistency. In accord with theory, data from
both grassland plants and marine invertebrates suggest that successful invaders
are those with niche requirements most different from those of species
in the existing community, providing a degree of determinism to an otherwise
Species Invasions
and the Relationships
between Species Diversity,
Community Saturation,
and Ecosystem Functioning
2
John J. Stachowicz and David Tilman
stochastic community assembly process. We also suggest some other ways in
which the study of introduced species could increase our understanding of diversity
and its impacts on ecosystem processes.
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Keywords : Gujarat
Encoded by : Pauline Carmel Joy Eje
