ecological modelling 220 ( 2 0 0 9 ) 23–39 available at www.sciencedirect.com journal homepage: www.elsevier.com/locate/ecolmodel Exploring community assembly through an individual-based model for trophic interactions Henrique Corrêa Giacomini a,* , Paulo De Marco Jr. b , Miguel Petrere Jr. a a UNESP – Departamento de Ecologia, CP 199, CEP 13506-900 – Rio Claro (SP), Brazil b UFG – Laboratório de Ecologia Teórica e Síntese, Departamento de Biologia Geral, Rodovia Goiânia-Nerópolis km 5, Campus II, Setor Itatiaia, CP 131, CEP 74001-970 – Goiânia (GO), Brazil article info Article history: Received 26 April 2008 Received in revised form 27 August 2008 Accepted 5 September 2008 Published on line 18 October 2008 Keywords: Community assembly Individual-based modeling Predation Alometry Localized interactions Ecological tradeoffs abstract Traditionally, the dynamics of community assembly has been analyzed by means of deterministic models of differential equations. Despite the theoretical advances provided by such models, they are restricted to questions about community-wide features. The individual-based modeling offers an opportunity to link bionomic features to patterns at the community scale, allowing us to understand how trait-based assembly rules can arise by dynamical processes. The present paper introduces an individual-based model of commu- nity assembly, and discusses some of the major advantages and drawbacks of this approach. The model was framed to deal with predation among size-structured populations, incorpo- rating allometric constraints to energetic requirements, movement, life-history features and interaction relationships among individuals. A protocol of assembly procedure is proposed, in which a period of intense species introductions is followed by a period without intro- ductions. The resultant communities did not present any pattern of trait over-dispersion, meaning that the multivariate distances of bionomic features among co-occurring species were neither larger nor more regular than expected in a random collection of species. It suggests a weak influence of interspecific interactions in the model environment and indi- vidualistic rules of coexistence, driven mainly by the spatial structure. This highlights that trait over-dispersion and resource partitioning should not be considered a necessary con- dition for coexistence, even in communities entirely structured by internal processes like predation and competition. © 2008 Elsevier B.V. All rights reserved. 1. Introduction Ecological communities are not static structures, but present changes in the composition resulting from a historical bal- ance between colonizations and extinctions (MacArthur and Wilson, 1967; Drake, 1990a; McKinney and Drake, 1998). Nevertheless, most of the field studies interested in reveal- ing assembly rules rely on the present species composition (Weiher and Keddy, 1995). Within this framework, the anal- ∗ Corresponding author. Tel.: +55 19 35264237; fax: +55 19 35264226. E-mail addresses: hgiacomini@gmail.com (H.C. Giacomini), pdemarco@icb.ufg.br (P. De Marco Jr.). ysis of community patterns becomes more interesting when based on functional traits, assuming that they are useful as a signature of niche differentiation (McGill et al., 2006). Sev- eral studies have been successful in demonstrating patterns, providing evidences of regular spacing among co-occurrent species (Gotelli and Graves, 1996; Weiher and Keddy, 1999). The advantage of pure hypothesis-deductive mathemati- cal models over field studies is the possibility of following the whole process of community development, being the 0304-3800/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.ecolmodel.2008.09.005