Specialization: A Multidimensional and Integrative Perspective.

Abstract

Specialization remains as a controversial and ambiguous term in ecology. Although it has been usually measured using a dichotomic and simplified classification of specialists and generalists, its nature is by far more complex. In the context of biotic interactions, assigning these two labels is usually based on the number of interacting partners (one or few vs. many). Here, we provide a more precise, quantitative, and objective interpretation of the specialization phenomenon combining three different dimensions (specificity, preference, and selectivity) that offer complementary information to quantify specialization. Hence, partner richness is a metric associated with the specificity, Simpson's evenness is related to the preference and d′ index to the selectivity of the biotic interactions. Consequently, we propose a 3D specialization space combining these three metrics which allows to identify the degree of biotic specialization fleeing from its simplified historical interpretation. The proposed space was subsequently evaluated in five natural interacting systems (host–parasite, plant–ant, plant–pollinator, plant–seed disperser, and mycobiont–cyanobacteria) using available data comprising 116 networks with quantitative observations. The results indicate the prevalence of a lax specialization, where most organisms tended to show low values in at least one of the metrics. Predominantly, observations showed high values of specificity and low values of preference and selectivity. This relaxed specialization provides advantages of being specialized, without sentencing it when being too tight. The implementation of this framework provides a useful tool that allows to identify specialization in a more objective, integrative, and universal way for future specialization studies.