Parasite abundance, body size, life histories, and the energetic equivalence rule

Per Arneberg, Arne Skorping, Andrew F. Read

Research output: Contribution to journalArticlepeer-review

75 Scopus citations


If common processes generate size-abundance relationships among all animals, then similar patterns should be observed across groups with different ecologies, such as parasites and free-living animals. We studied relationships among body size, life-history traits, and population intensity (density in infected hosts) among nematodes parasitizing mammals. Parasite size and intensity were negatively correlated independently of all other parasite and host factors considered and regardless of type of analyses (i.e., nonphylogenetic or phylogenetically based statistical analyses, and across or within communities). No other nematode life-history traits had independent effects on intensity. Slopes of size-intensity relationships were consistently shallow, around -0.20 on log-log scale, and thus inconsistent with the energetic equivalence rule. Within communities, slopes converged toward this global value as size range increased. A summary of published values suggests similar convergence toward a global value around -0.75 among free-living animals. Steeper slopes of size-abundance relationships among free-living animals could be related to fundamental differences in ecologies between parasites and free-living animals, although such generalizations require reexamination of size-abundance relationships among free-living animals with regard to confounding factors, in particular by use of phylogenetically based statistical methods. In any case, our analyses caution against simple generalizations about patterns of animal abundance.

Original languageEnglish (US)
Pages (from-to)497-513
Number of pages17
JournalAmerican Naturalist
Issue number6
StatePublished - 1998

All Science Journal Classification (ASJC) codes

  • Ecology, Evolution, Behavior and Systematics


Dive into the research topics of 'Parasite abundance, body size, life histories, and the energetic equivalence rule'. Together they form a unique fingerprint.

Cite this