DEFINING AND MEASURING ECOLOGICAL SPECIALIZATION.

Devictor V., Clavel J., Julliard R., Lavergne S., Mouillot D., Thuiller W., Venail P., Villeger S. and Mouquet N. (2010).

Journal of Applied Ecology, 47, 14-25, doi:10.1111/j.1365-2664.2009.01744.x

Key message : Ecological specialization is one of the main concepts in ecology and conservation. However, this concept has become highly context-dependent and is now obscured by the great variability of existing definitions and methods used to characterize ecological specialization. In this review, we clarify this concept by reviewing the strengths and limitations of different approaches commonly used to define and measure ecological specialization. We show that ecological specialization can either be considered as reflecting species’ requirements or species’ impacts. We explain how specialization depends on species-specific characteristics and on local and contingent environmental constraints. We show why and how ecological specialization should be scaled across spatial and temporal scales, and from individuals to communities. We illustrate how this review can be used as a practical toolbox to classify widely used metrics of ecological specialization in applied ecology, depending on the question being addressed, the method used, and the data available. Clarifying ecological specialization is useful to make explicit connections between several fields of ecology using the niche concept. Understanding the different facets of ecological specialization should facilitate to investigate the causes and consequences of biotic homogenization and to derive relevant indicators of biodiversity responses to land-use changes.

Most commonly used metrics of specialization can be positioned in this box according to the type of niche considered (Grinnellian vs. Eltonian) and whether the fundamental or the realized specialization is measured. Note that this typology is flexible. The figure represents a fish for which specialization is measured using different metrics: (a) the variation in species’ performance in a controlled experiment will reflect its fundamental Grinnellian specialization; (b) the variation in performance along different resource categories using field data will reflect the realized Grinnellian specialization; (c) the fundamental Eltonian specialization would be derived from metrics based on the species-specific functional traits. (d) Finally, the realized Eltonian specialization will be quantified using the diversity and strength of impact of the species on others (symbolized by geometrical items).

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OTHER TOPICS: Aesthetics of Biodiversity, Biogeography, Macroecology & Ecophylogenetics, Experimental Evolution, Functional Biogeography, Functional Rarity, Nature for Future, Metacommunities, Metaecosystems, Reviews and Synthesis, Trophic Biogeography & Metaweb