Author: Berumen Michael
Publisher: Springer Publishing Company
ISSN: 0340-5443
Source: Behavioral Ecology and Sociobiology, Vol.62, Iss.6, 2008-04, pp. : 989-994
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Abstract
Increasing dietary specialization is an inherently risky strategy because it increases a species’ vulnerability to resource depletion. However, risks associated with dietary specialization may be offset by increased performance when feeding on preferred prey. Although rarely demonstrated, highly specialized species are expected to outperform generalists when feeding on their preferred prey, whereas generalists are predicted to have more similar performance across a range of different prey. To test this theory, we compared the growth rates of two obligate coral-feeding butterflyfishes (Chaetodon trifascialis</i> and Chaetodon plebeius</i>) maintained on exclusive diets of preferred vs nonpreferred prey. In the field, C. trifascialis</i> was the most specialized species, feeding almost exclusively on just one coral species, Acropora hyacinthus</i>. C. plebeius</i> meanwhile, was much less specialized, but fed predominantly on Pocillopora damicornis</i>. During growth experiments, C. trifascialis</i> grew fastest when feeding on A. hyacinthus</i> and did not grow at all when feeding on less preferred prey (P. damicornis</i> and Porites cylindrica</i>). C. plebeius</i> performed equally well on both A. hyacinthus</i> and P. damicornis</i> (its preferred prey), but performed poorly when feeding on P. cylindrica</i>. Both butterflyfishes select coral species that maximize juvenile growth, but contrary to expectations, the more specialized species (C. trifascialis</i>) did not outperform the generalist species (C. plebeius</i>) when both consumed their preferred prey. Increased dietary specialization, therefore, appears to be a questionable strategy, as there was no evidence of any increased benefits to offset increases in susceptibility to disturbance.
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