Evol Ecol Res 20: 471-485 (2019)     Full PDF if your library subscribes.

An experimental test of Hamiltonian habitat selection

Kerman Bajina1,2, Douglas W. Morris1 & Per Lundberg3

1Department of Biology, Lakehead University, Thunder Bay, Ontario, Canada
2EDI Environmental Dynamics, Inc., Whitehorse, Yukon, Canada
3Theoretical Population Ecology and Evolution Group (ThePEG), Department of Biology, Lund University, Lund, Sweden

Correspondence: D.W. Morris, Department of Biology, Lakehead University, 955 Oliver Road, Thunder Bay, Ontario, P7B 5E1, Canada.
email: dmorris@lakeheadu.ca


Question: Does a population of clones choose habitat according to inclusive or to individual fitness?

Theory: Gompertz equation, evolutionarily stable strategies, isodars, ideal free distribution.

Study species: Folsomia candida (Collembola).

Methods: We manipulated habitat quality by modifying moisture concentrations of substrate in petri dishes occupied by a single clone. We varied the abundance of animals, allowed them to lay a single clutch, and used the number of emergent adult offspring to estimate the effect of density on fitness. We used the fitness functions to predict the evolutionarily stable strategies of habitat selection for selfish versus cooperating individuals. We divided dishes into two discrete habitats and released variable numbers of animals at the boundary to evaluate whether they chose habitats consistent with selfish versus cooperative strategies. We transferred animals choosing each habitat into new dishes composed only of that habitat, allowed the animals to lay a single clutch, and used the number of emergent adults to estimate fitness accrued by habitat selection. We used habitat isodars to test the theory by regressing the density in moist versus drier habitats.

Results: The relationship between fitness and population density was highly convex-upward in all habitats. Maximum fitness was similar in habitats with 100%, 37.5%, and 25% moisture, but was much less in the driest (12.5%) habitat. Fitness declined more rapidly with density after habitat selection than in controls. Differences in convexity enabled habitat-selecting Folsomia clones to produce isodars that achieved higher mean fitness than predicted for selfish individuals.

Conclusions: Related individuals choose habitat consistent with expectations of their inclusive fitness. Habitat isodars, predicted from theory and built by experiment, reliably revealed the emergent adaptive patterns of distribution and abundance.

Keywords: density-dependence, ESS, Folsomia candida, ideal free distribution, inclusive fitness, spatial dynamics

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