Thinking Outside the Niche

Ecologist and evolutionary biologist Dr. Mark McPeek (Professor at Dartmouth College, and Editor-in-Chief of The American Naturalist) spoke at Florida State Thursday and Friday of last week. Unfortunately, fieldwork prevented my attendance at the first lecture, but luckily I did manage to make Friday’s session.

McPeek’s recent work has centered on community assembly in freshwater ponds, with a specific focus on the evolution and ecology of damselflies. His work as a whole (See his publications HERE) demonstrates an exceptional cross-discipline framework with representation from both the applied and theoretical aspects of population ecology, genetics, molecular systematics, comparative biology, geology and paleontology.

During Friday’s talk, McPeek discussed the biogeography, reproduction, speciation and coexistence/co-occurrence of several Enallagma species. After first describing the spatial and temporal similarities that exist between periods of past glaciation and the range expansion/speciation events recorded in the DNA of damselflies, he moved on to the neutral theory of community ecology.

The neutral theory of ecology basically maintains that a portion of the biodiversity displayed within an ecosystem is attributable to species that occupy identical, or nearly identical, niches (i. e. these species occupy comparable positions in the foodweb and utilize the same biotic and non-biotic resources). In addition, the neutral perspective states that although some phenotypic disparities may occur between different species, these disparities have no affect on the critters’ fitness or demography.

Using Enallagma as a case study, McPeek described a recent experiment in which the neutral theory was put to the test. Through directly manipulating the relative abundance (the number of one species) and absolute abundance (the total number of both species) of two like-species, McPeek placed two varieties of Enallagma in identical cages with tightly controlled environmental parameters; included as part of the tightly controlled parameters was the presence of a fish – a predator of Enallagma.

What McPeek discovered was that manipulation of one species’ relative abundance affected fitness little, whereas manipulation of the total abundance of both species showed direct effects for both.

His conclusion…

Although the two varieties of damselflies are sexually isolated, for the purposes of ecological functionality the two species are essentially one in the same.


For more on McPeek’s ideas regarding the neutral theory and niche differentiation, check out his publications list (linked above), specifically the article:

Leibold, M., & McPeek, M. (2006). COEXISTENCE OF THE NICHE AND NEUTRAL PERSPECTIVES IN COMMUNITY ECOLOGY Ecology, 87 (6), 1399-1410 DOI: 10.1890/0012-9658(2006)87[1399:COTNAN]2.0.CO;2