A unified framework for diversity gradients: The adaptive trait continuum

[Aim] Adaptive trait continua are axes of covariation observed in multivariate trait data for a given taxonomic group. These continua quantify and summarize life-history variation at the inter-specific level in multi-specific assemblages. Here we examine whether trait continua can provide a useful framework to link life-history variation with demographic and evolutionary processes in species richness gradients. Taking an altitudinal species richness gradient for Mediterranean butterflies as a study case, we examined a suite of traits (larval diet breadth, adult phenology, dispersal capacity and wing length) and species-specific habitat measures (temperature and aridity breadth). We tested whether traits and species-specific habitat measures tend to co-vary, whether they are phylogenetically conserved, and whether they are able to explain species distributions and spatial genetic variation in a large number of butterfly assemblages.[Location] Catalonia, Spain.[Methods] We formulated predictions associated with species richness gradients and adaptive trait continua. We applied principal components analyses (PCAs), structural equation modelling and phylogenetic generalized least squares models. [Results] We found that traits and species-specific habitat measures covaried along a main PCA axis, ranging from multivoltine trophic generalists with high dispersal capacity to univoltine (i.e. one generation per year), trophic specialist species with low dispersal capacity. This trait continuum was closely associated with the observed distributions along the altitudinal gradient and predicted inter-specific differences in patterns of spatial genetic variability (FST and genetic distances), population responses to the impacts of global change and local turnover dynamics.[Main conclusions] The adaptive trait continuum of Mediterranean butterflies provides an integrative and mechanistic framework to: (1) analyse geographical gradients in species richness, (2) explain inter-specific differences in population abundances, spatial distributions and demographic trends, (3) explain inter-specific differences in patterns of genetic variation (FST and genetic distances), and (4) study specialist-generalist life-history transitions frequently involved in butterfly diversification processes. © 2012 Blackwell Publishing Ltd.This research was supported by grants from the Spanish Government (CGL2006-04025/BOS, CGL2007-60516/BOS, CGL2010-21226/BOS, CGL2010-17172 and Consolider-Ingenio Montes CSD2008-00040) and the Catalan Government (SGR 2009-458 and SGR 2009-88). J.C. was funded by 2008-0200 MEC/Fulbright and VENI-NWO 863.11.021 post-doctoral research grants and V.D. by a doctoral fellowship from the Wenner-Gren Foundation Sweden. The Butterfly Monitoring Scheme in Catalonia (CBMS) and the Biodiversity Data Bank of Catalonia are funded by the Departament de Territori i Sostenibilitat de la Generalitat de Catalunya. The BMSAnd project is supported by the Centre d'Estudis de la Neu i la Muntanya d'Andorra (CENMA). The Diputació de Barcelona, Patronat Metropolità Parc de Collserola and Fundació Caixa de Catalunya also provide financial support for the CBMS project.Peer Reviewe

A unified framework for diversity gradients:The adaptive trait continuum

Aim Adaptive trait continua are axes of covariation observed in multivariate trait data for a given taxonomic group. These continua quantify and summarize life-history variation at the inter-specific level in multi-specific assemblages. Here we examine whether trait continua can provide a useful framework to link life-history variation with demographic and evolutionary processes in species richness gradients. Taking an altitudinal species richness gradient for Mediterranean butterflies as a study case, we examined a suite of traits (larval diet breadth, adult phenology, dispersal capacity and wing length) and species-specific habitat measures (temperature and aridity breadth). We tested whether traits and species-specific habitat measures tend to co-vary, whether they are phylogenetically conserved, and whether they are able to explain species distributions and spatial genetic variation in a large number of butterfly assemblages. Location Catalonia, Spain. Methods We formulated predictions associated with species richness gradients and adaptive trait continua. We applied principal components analyses (PCAs), structural equation modelling and phylogenetic generalized least squares models. Results We found that traits and species-specific habitat measures covaried along a main PCA axis, ranging from multivoltine trophic generalists with high dispersal capacity to univoltine (i.e. one generation per year), trophic specialist species with low dispersal capacity. This trait continuum was closely associated with the observed distributions along the altitudinal gradient and predicted inter-specific differences in patterns of spatial genetic variability (FST and genetic distances), population responses to the impacts of global change and local turnover dynamics. Main conclusions The adaptive trait continuum of Mediterranean butterflies provides an integrative and mechanistic framework to: (1) analyse geographical gradients in species richness, (2) explain inter-specific differences in population abundances, spatial distributions and demographic trends, (3) explain inter-specific differences in patterns of genetic variation (FST and genetic distances), and (4) study specialistgeneralist life-history transitions frequently involved in butterfly diversification processes