Modeling body size evolution in Felidae under alternative phylogenetic hypotheses

Abstract

The use of phylogenetic comparative methods in ecological research has advanced during the last twenty years, mainly due to accurate phylogenetic reconstructions based on molecular data and computational and statistical advances. We used phylogenetic correlograms and phylogenetic eigenvector regression (PVR) to model body size evolution in 35 worldwide Felidae (Mammalia, Carnivora) species using two alternative phylogenies and published body size data. The purpose was not to contrast the phylogenetic hypotheses but to evaluate how analyses of body size evolution patterns can be affected by the phylogeny used for comparative analyses (CA). Both phylogenies produced a strong phylogenetic pattern, with closely related species having similar body sizes and the similarity decreasing with increasing distances in time. The PVR explained 65% to 67% of body size variation and all Moran's I values for the PVR residuals were non-significant, indicating that both these models explained phylogenetic structures in trait variation. Even though our results did not suggest that any phylogeny can be used for CA with the same power, or that “good” phylogenies are unnecessary for the correct interpretation of the evolutionary dynamics of ecological, biogeographical, physiological or behavioral patterns, it does suggest that developments in CA can, and indeed should, proceed without waiting for perfect and fully resolved phylogenies.

Phylogenetically structured variance in felid bite force: the role of phylogeny in the evolution of biting performance

“…The dominance of phylogenetically structured phenotypic variance in absolute bite force indicates a strong phylogenetic signal and thus inertia in phenotypic changes associated with this biomechanical variable. However, because our morphometric variables still incorporate size information (PC1 is greatly associated with size and explains most of the morphological variance), and as Diniz‐Filho & Nabout (2009) report that 65% to 67% of the variance in felid body mass is explained by phylogeny, the inertia or constraint put upon the evolution of absolute bite force is perhaps mostly because of whatever evolutionary constraint that works on body size evolution. Indeed, skeletal muscle mass has been observed to represent a constant proportion of total body mass (Calder, 1984; Schmidt‐Nielsen, 1984), and muscle force has been also argued to be constrained by size increase at a theoretical scaling factor of 2/3 [or M 0.67 where M is body mass (Calder, 1984; Schmidt‐Nielsen, 1984; Swartz & Biewener, 1992)].…”

On the selection of phylogenetic eigenvectors for ecological analyses

“…First, we used the coefficients of determination (R 2 ) of the models as measures of goodness of fit. As a second criterion, we used the Akaike information criterion (AIC) to select the best model in terms of minimum adequate model (Diniz‐Filho and Nabout 2009), which can be viewed as representing a compromise between the magnitude of phylogenetic signal captured by the regression and the number of eigenvectors used. To measure the amount of phylogenic structure of D retained by the eigenvectors, we also computed, for each set of eigenvectors, an Euclidean distance among species based on the selected eigenvectors, and correlated this matrix with the original matrix of phylogenetic distances (this is called cophenetic correlation in multivariate analyses –Sokal and Rohlf 1962, Legendre and Legendre 1998).…”

“…We use a global Carnivora database with log-transformed body size data for 209 species (see Diniz-Filho et al 2009 for details) to illustrate the application of PVR and to evaluate the approaches used to select eigenvectors (see below). We used diff erent sets of eigenvectors in an OLS multiple regression model of the form…”

“…According to recent applications of PVR in studying Bergmann ' s rule (Diniz-Filho et al 2007), we also ana-lyzed geographic patterns in the mean S-component by mapping them using assemblages from a total of 4031 cells (1 Њ latitude ϫ 1 Њ longitude) covering the New World (see Diniz-Filho et al 2009 for details). Th e idea is that Bergmann ' s rule can be interpreted as a recent non-phylogenetic (referred to here as ' adaptive ' ) response in the mean S-component within cells, indicating independent responses in the species found in a region, that correlates positively with climate (see also Diniz-Filho et al 2007, Ramirez et al 2008, Terribile et al 2009, Olalla-T á rraga et al 2010).…”

“…Partitioning trait variation using PVR allows not only studying the spatial variation in mean body size across species assemblages (as in a classical assemblage-based approach), but also the mean S-component (PVR residuals). For instance, Diniz-Filho et al (2009) showed that total mean body size in Carnivora decreases towards higher latitudes (see also Rodriguez et al 2008), probably related to macroevolutionary events such as higher species turnover in these regions. On the other hand, the mean S-component, expressing deviations from expected body size due to phylogenetic eff ects, shows a clearer Bergmannian gradient, with large bodied species (or deviations from phylogenetic expectation) in colder parts of the world, reinforcing adaptive explanations linked with climatic variation.…”