Coexistence of competitive species with a stage‐structured life cycle

Abstract

Ecological theory provides explanations for exclusion or coexistence of competing species. Most theoretical works on competition dynamics that have shaped current perspectives on coexistence assume a simple life cycle. This simplification, however, may omit important realities. We present a simple two-stage structured competition model to investigate the effects of life-history characteristics on coexistence. The achievement and the stability of coexistence depend not only on competition coefficients but also on a set of life-history parameters that reflect the viability of an individual, namely, adult death rate, maturation rate, and birth rate. High individual viability is necessary for a species to persist, but it does not necessarily facilitate coexistence. Intense competition at the juvenile or adult stage may require higher or lower viability, respectively, for stable coexistence to be possible. The stability mechanism can be explained by the refuge effect of the less competitive stage, and the birth performance, which preserves the less competitive stage as a refuge. Coexistence might readily collapse if the life-history characteristics, which together constitute individual viability, change, even though two species have an inherent competitive relation conducive to stable coexistence.

Ontogenetic Diet Shifts Result in Niche Partitioning between Two Consumer Species Irrespective of Competitive Abilities

“…In contrast to his claim, however, it was assumed that the resource for juvenile competitors was completely distinct from that of adults, excluding competition between the life stages. This resource segregation between life-history stages is conceptually identical to the habitat segregation between stages assumed in other studies (Haefner and Edson 1984;Loreau and Ebenhoh 1994;Mougi and Nishimura 2005;Moll and Brown 2008). Consequently, the type of coexistence that McCann (1998) referred to as "density-dependent coexistence" occurs under the same conditions as coexistence in studies with explicit habitat segregation, namely, that a competitive advantage at one life stage has to be balanced by a disadvantage at another life stage.…”

“…In regard to interspecific competition, however, theory has focused on the interactions with populations exhibiting ontogenetic habitat shifts (Haefner and Edson 1984;Loreau and Ebenhoh 1994;Mougi and Nishimura 2005;Moll and Brown 2008). Some studies even represented competitive interactions as negative density dependence affecting reproduction and maturation instead of explicitly representing competition for resources (e.g., Haefner and Edson 1984;Mougi and Nishimura 2005;Moll and Brown 2008).…”

“…Some studies even represented competitive interactions as negative density dependence affecting reproduction and maturation instead of explicitly representing competition for resources (e.g., Haefner and Edson 1984;Mougi and Nishimura 2005;Moll and Brown 2008). This emphasizes the focus of these studies on the effect of habitat segregation on competition instead of the effect of differences in resource use.…”

Feeding strategies, resource utilisation and potential mechanisms for competitive coexistence of Atlantic salmon and alpine bullhead in a sub-Arctic river

“…A number of theoretical studies have furthermore developed models that allow coexistence of competitive species without significant resource partitioning (e.g. Abrams and Wilson 2004;Amarasekare et al 2004;Loladze et al 2004;Mougi and Nishimura 2005), and recent literature has also requested empirical investigations to elaborate alternative mechanisms for competitive coexistence (e.g. Amarasekare 2003).…”

Competitive interactions between walleye (Sander vitreus) and smallmouth bass (Micropterus dolomieu) under various controlled conditions

“…Competition may vary by life stage whereby competitive interactions are negligible or differ at the larval, juvenile, or adult stage as a result of ontogenetic niche shifts in morphology, physiology, or behavior (Werner and Gilliam 1984;Mougi and Nishimura 2005). Lifetime fitness may be established early in life as dominant individuals are able to garner territories and resources before subordinates; thus, younger fish may be more aggressive against competitors than during the adult stage after dominance hierarchies have been established among populations and communities (Berejikian et al 2001).…”