Individual differences in microhabitat use in a Caribbean cleaning goby: a buffer effect in a marine species?
I.M. Côté, Centre for Ecology, Evolution and Conservation, School of Biological Sciences, University of East Anglia, Norwich NR4 7TJ, UK. E-mail: firstname.lastname@example.org
- 1Buffer effects occur when changes in population size result in the disproportionate use of poor-quality habitats. Thus, at low population sizes high-quality habitats are used preferentially. As population size increases an increasing proportion of the population uses poorer-quality habitats. Assessment of the temporal and spatial variation in patterns of habitat occupancy can therefore shed light on the differences in quality between habitats and the individual fitness consequences of habitat choice.
- 2We provide the first evidence of the potential operation of a buffer effect for a site-attached marine species. Caribbean cleaning gobies Elacatinus prochilos (Böhlke & Robins) occupy coral and sponge on fringing reefs in Barbados. For adult gobies, resource selection indices suggested a preference for sponge. However, as cleaning goby population size increased, the number of adult cleaning gobies occupying sponge increased more rapidly than the number occupying coral. In contrast, adults preferentially re-colonized coral following experimental removals and at these low population densities the rate of population increase was greater on coral. Our results suggest that coral may be the preferred habitat, but in Barbados this habitat becomes saturated at very low population densities as a consequence of low client densities and ectoparasite loads. Thus, a larger proportion of the population occupies sponge at most observed population densities.
- 3Patterns of habitat occupancy with population size for recruits and juveniles suggest only a small difference in habitat quality between sponge and coral. Indeed, recruits and juveniles do not discriminate between sponge and coral. The population shift towards sponge rather than coral occupancy between recruitment and maturity may arise as a combination of differing survival of recruits and juveniles on coral and sponge and active movement of individuals towards sponge.
- 4Our results demonstrate that interactions among individuals are an integral part of population distribution and dynamics and are therefore important in future studies of habitat choice and its associated fitness consequences.