J. Fox

Search for other papers by J. Fox in
Current site
Google Scholar
C. BarretoImperial College NERC Centre for Population Biology Silwood Park Ascot, Berkshire SL5 7PY United Kingdom

Search for other papers by C. Barreto in
Current site
Google Scholar
View More View Less
Restricted access

Competing species often coexist, but the mechanisms allowing long-term coexistence are rarely tested via direct experimental manipulation. We experimentally tested the mechanisms of coexistence in a classic model system, laboratory microcosms in which two species of ciliate protists competed for bacteria. Previous work shows that the species used here compete for bacteria, but can coexist despite large differences in grazing ability. We tested three hypotheses that might explain this surprising coexistence: resource partitioning, chemically-mediated interference competition, and differential use of space. To test for resource partitioning, we conducted an experiment testing the effects of bacterial species richness and composition on the long-term outcome of competition. Manipulating bacterial diversity and composition alters the scope for resource partitioning. Despite strong evidence for differential resource use (e.g., the two ciliates shifted bacterial species composition in different ways), initial bacterial richness and composition did not affect the long-term outcome of competition. Remarkably, the competitive outcome was unchanged even when ciliates competed for a single bacterial species, indicating that the observed resource partitioning is irrelevant to the competitive outcome. In further experiments, we ruled out differential space use and chemically-mediated interference competition as explanations for this surprising coexistence. Coexistence of ciliates on a single bacterial species might reflect partitioning of intraspecific bacterial diversity, and/or osmotrophy or consumption of particulate detritus by the weaker competitor. The results show that this classic model system is not as well-understood as had been previously thought. More broadly, the results dramatically illustrate that merely observing “niche differences” between coexisting species is no evidence that those differences are either necessary or sufficient for long-term coexistence.

  • Collapse
  • Expand

To see the editorial board, please visit the website of Springer Nature.

Manuscript Submission: HERE

For subscription options, please visit the website of Springer Nature.

Community Ecology
Language English
Size A4
Year of
per Year
per Year
Founder Akadémiai Kiadó
H-1117 Budapest, Hungary 1516 Budapest, PO Box 245
Publisher Akadémiai Kiadó
Springer Nature Switzerland AG
H-1117 Budapest, Hungary 1516 Budapest, PO Box 245.
CH-6330 Cham, Switzerland Gewerbestrasse 11.
Chief Executive Officer, Akadémiai Kiadó
ISSN 1585-8553 (Print)
ISSN 1588-2756 (Online)