The Quantitative Assessment of Phylogenetic Constraints in Comparative Analyses: Sexual Dimorphism in Body Weight Among Primates

Abstract

We have presented a formal model for the quantitative analysis of phylogenetic and specific effects on the distribution of trait values among species. Total trait values are divided into phylogenetic values, inherited from an ancestral species, and specific values, the result of independent evolution. This allows a quantitative assessment of the strength of the phylogenetic inertia, or burden, displayed by a character in a lineage, so that questions concerning the relative importance of phylogenetic constraints in evolution can be answered. The separation of phylogenetic from specific effects proposed here also allows phylogenetic factors to be explicitly included in cross-species comparative analyses of adaptation. This solves a long-standing problem in evolutionary comparative studies. Only species' specific values can provide information concerning the independent evolution of characters in a set of related species. Therefore, only correlations among specific values for traits may be used as evidence for adaptation in cross-species comparative analyses. The phylogenetic autocorrelation model was applied to a comparative analysis of the determinants of sexual dimorphism in weight among 44 primate species. In addition to sexual dimorphism in weight, mating system, habitat, diet, and size (weight itself) were included in the analysis. All of the traits, except diet, were substantially influenced by phylogenetic inertia. The comparative analysis of the determinants of sexual dimorphism in weight indicates that 50% of the variation among primate species is due to phylogeny. Size, or scaling, could account for a total of 36% of the variance, making it almost as important as phylogeny in determining the level of dimorphism displayed by a species. Habitat, mating system, and diet follow, accounting for minor amounts of variation. Thus, in attempting to explain why a particular modern primate species is very dimorphic compared to other primates, we would say first because its ancestor was more dimorphic than average, second because it is a relatively large species, and third because it is terrestrial, polygynous, and folivorous.

A comparison of metrics for estimating phylogenetic signal under alternative evolutionary models

“…A detailed description of these metrics can be found elsewhere (Cheverud et al , 1985; Gittleman and Kot, 1990, Diniz-Filho et al 1998; Pagel, 1999; Freckleton et al , 2002; Blomberg et al , 2003). First, for statistical-based metrics, we used the Moran’s I autocorrelation coefficient, which is given by $I=\left(\frac{n}{S_0}\right)\left[\frac{\sum _{i=1}^n\sum _{j=1}^n(y_i-\overline{y})(y_j-\overline{y})w_{ij}}{\sum _{i=1}^n{(y_i-\overline{y})}^2}\right]$where n is the number of species, y i and y j are the trait values in a vector Y for species i and j ( i.e.…”

“…The earliest techniques were based on statistical methods ( e.g. , phylogenetic autocorrelation coefficients, phylogenetic correlograms and autoregressive models), that quantify the level of phylogenetic autocorrelation for a given trait of interest throughout the phylogeny (see Cheverud et al , 1985; Gittleman and Kot, 1990; Diniz-Filho et al , 1998), or under non-stationary processes (Diniz-Filho et al , 2010). When more detailed and accurate phylogenies are available, it is also possible to ascertain the expected divergence between species by assuming a theoretical model of trait evolution, and thus derive model-based metrics to compare expected and observed divergences ( e.g.…”

Sex Differences in Phenotypic Plasticity Affect Variation in Sexual Size Dimorphism in Insects: From Physiology to Evolution

“…The evolution of SSD is slowed by genetic (97), phylogenetic (26), developmental (8), and/or physiological (93) constraints. For example, empirical studies have shown that heritabilities are similar between the sexes and that the between-sex genetic correlations ( r G ) are near 1.0 (because males and females share the same genes that control growth and development) (79, 98, 102).…”

Does feeding zone influence egg size in slow-breeding seabirds?

“…In the same fashion, many life-history traits "scale" to body mass (Millar 1977;Western 1979;Western and Ssemakula 1982;Peters 1983;Calder 1984;Schmidt-Nielsen 1984;Charnov 1993), and we expected no exception when it comes to egg size. The second problem is that many organismal traits follow a phylogenetic pattern due to shared ancestry of groups of species (e.g., Cheverud et al 1985;Dobson 1985;Felsenstein 1985;Harvey and Pagel 1991;Miles and Dunham 1992). For albatrosses and petrels, these two issues are highly associated because body mass itself follows a strong phylogenetic pattern (network autocorrelation analysis, = 0.800, n = 44, P < 0.0001; Dobson and Jouventin 2010).…”