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AN EMPIRICAL MODEL OF SPECIES COEXISTENCE IN A SPATIALLY STRUCTURED ENVIRONMENT

AN EMPIRICAL MODEL OF SPECIES COEXISTENCE IN A SPATIALLY STRUCTURED ENVIRONMENT Ecological theory has long supported the idea that species coexistence in a homogeneous habitat is promoted by spatial structure, but empirical evidence for this hypothesis has lagged behind theory. Here we describe a Neotropical ant––plant symbiosis that is ideally suited for testing spatial models of coexistence. Two genera of ants, Allomerus cf. demerarae and three species of Azteca are specialized to live on a single species of ant-plant, Cordia nodosa, in a Western Amazonian tropical rain forest. Empirically, using census data from widely separated localities, we show that the relative colonization abilities of the two ant genera are a function of plant density. A parameterized model shows that this pattern alone is sufficiently robust to explain coexistence in the system. Census and experimental data suggest that Azteca queens are better long-distance flyers, but that Allomerus colonies are more fecund. Thus, Azteca can dominate in areas where host-plant densities are low (and parent colony––sapling distances are long), and Allomerus can dominate in areas where host-plant densities are high. Existing spatial heterogeneity in host-plant densities therefore can allow regional coexistence, and intersite dispersal can produce local mixing. In conclusion, a dispersal––fecundity trade-off appears to allow the two genera to treat spatial heterogeneity in patch density as a niche axis. This study further suggests that a spatially structured approach is essential in understanding the persistence of some mutualisms in the presence of parasites. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Ecology Ecological Society of America

AN EMPIRICAL MODEL OF SPECIES COEXISTENCE IN A SPATIALLY STRUCTURED ENVIRONMENT

Yu, Douglas W.; Wilson, Howard B.; Pierce, Naomi E.
Ecology , Volume 82 (6) – Jun 1, 2001
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Publisher
Ecological Society of America
Copyright
Copyright © 2001 by the Ecological Society of America
Subject
Regular Article
ISSN
0012-9658
DOI
10.1890/0012-9658%282001%29082%5B1761:AEMOSC%5D2.0.CO%3B2
Publisher site
See Article on Publisher Site

Abstract

Ecological theory has long supported the idea that species coexistence in a homogeneous habitat is promoted by spatial structure, but empirical evidence for this hypothesis has lagged behind theory. Here we describe a Neotropical ant––plant symbiosis that is ideally suited for testing spatial models of coexistence. Two genera of ants, Allomerus cf. demerarae and three species of Azteca are specialized to live on a single species of ant-plant, Cordia nodosa, in a Western Amazonian tropical rain forest. Empirically, using census data from widely separated localities, we show that the relative colonization abilities of the two ant genera are a function of plant density. A parameterized model shows that this pattern alone is sufficiently robust to explain coexistence in the system. Census and experimental data suggest that Azteca queens are better long-distance flyers, but that Allomerus colonies are more fecund. Thus, Azteca can dominate in areas where host-plant densities are low (and parent colony––sapling distances are long), and Allomerus can dominate in areas where host-plant densities are high. Existing spatial heterogeneity in host-plant densities therefore can allow regional coexistence, and intersite dispersal can produce local mixing. In conclusion, a dispersal––fecundity trade-off appears to allow the two genera to treat spatial heterogeneity in patch density as a niche axis. This study further suggests that a spatially structured approach is essential in understanding the persistence of some mutualisms in the presence of parasites.

Journal

Ecology – Ecological Society of America

Published: Jun 1, 2001

Keywords: Allomerus; ; ant––plant symbiosis ; Azteca; ; competition––colonization trade-off ; Cordia nodosa ; dispersal––fecundity trade-off ; habitat destruction and selection hypotheses ; lottery model ; metapopulation ; parasite ; source––sink dynamics ; storage effect

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