Summary: Nested diets: a novel pattern of individual-level resource use
Ma´rcio S. Arau´jo, Eduardo G. Martins, Leonardo D. Cruz, Fernanda R. Fernandes,
Ari´cio X. Linhares, Se´rgio F. dos Reis and Paulo R. Guimara~es Jr.
M. S. Arau´jo, E. G. Martins, L. D. Cruz, F. R. Fernandes, A. X. Linhares and S. F. dos Reis, Depto de Parasitologia, Inst. de Biologia, Univ.
Estadual de Campinas, Caixa Postal 6109, BR Á13083-970, Campinas, Sa~o Paulo, Brazil. * P. R. Guimara~es Jr. (firstname.lastname@example.org),
Dept of Ecology and Evolutionary Biology, Univ. of California, Santa Cruz, CA, 95064, USA, and Depto de Ecologia, Inst. de Biocie^ncias, CP
11294, Univ. de Sa~o Paulo, BR Á05422-970, Sa~o Paulo, SP, Brazil.
Many generalist populations may actually be composed of relatively specialist individuals. This `individual specialization'
may have important ecological and evolutionary implications. Although this phenomenon has been documented in more
than one hundred taxa, it is still unclear how individuals within a population actually partition resources. Here we applied
several methods based on network theory to investigate the intrapopulation patterns of resource use in the gracile mouse
opossum Gracilinanus microtarsus. We found evidence of significant individual specialization in this species and that the
diets of specialists are nested within the diets of generalists. This novel pattern is consistent with a recently proposed
model of optimal foraging and implies strong asymmetry in the interactions among individuals of a population.
Generalist populations using a wide range of resources
may actually be composed of individual specialists (Werner
and Sherry 1986, 1987, 1988, Svanba¨ck and Bolnick
2007). For example, the finch Pinaroloxias inornata in
Cocos island uses a diversity of resources, including seeds,
nectar and insects, but each individual consistently