A major shift in diversification rate helps explain macroevolutionary patterns in primate species diversity

Abstract

Primates represent one of the most species rich, wide ranging, and ecologically diverse clades of mammals. What major macroevolutionary factors have driven their diversification and contributed to the modern distribution of primate species remains widely debated. We employed phylogenetic comparative methods to examine the role of clade age and evolutionary rate heterogeneity in the modern distribution of species diversity of Primates. Primate diversification has accelerated since its origin, with decreased extinction leading to a shift to even higher evolutionary rates in the most species rich family (Cercopithecidae). Older primate clades tended to be more diverse, however a shift in evolutionary rate was necessary to adequately explain the imbalance in species diversity. Species richness was also poorly explained by geographic distribution, especially once clade age and evolutionary rate shifts were accounted for, and may relate instead to other ecological factors. The global distribution of primate species diversity appears to have been strongly impacted by heterogeneity in evolutionary rates.

Primate diversification inferred from phylogenies and fossils

“…There is uncertainty in the true number of species in each clade, and recent taxonomic revisions have increased the number of recognized species substantially compared to past taxonomic reviews. The taxonomy used here follows the IUCN (accessed September 4, 2015), which recognized 425 species, in keeping with a recent study of primate diversification so that results are comparable (Arbour and Santana ), and similar to the species richness used by (Springer et al. ).…”

“…). Thus, in estimating nonzero extinction rates, the COMET model may capture signals of extinction better than other available models, which consistently find increasing net diversification through time and near zero extinction (e.g., using the Bayesian Analysis of Macroevolutionary Mixtures model of Rabosky , as in Arbour and Santana ). Even so, the rates inferred from phylogenies were never negative, as observed with the fossil record.…”

“…), while analyses of the phylogeny consistently report increasing speciation and diversification rates through time (Springer et al. ; Arbour and Santana ). I tested the hypothesis that extinction increased ∼34 Ma associated with declines in diversity and diversification rates.…”

Mammal extinctions and the increasing isolation of humans on the tree of life

“…A recent study suggests that extinction rates throughout primate history decline over time (Arbour & Santana, ). However, we suggest that the rhythm of primate extinctions is likely to change dramatically: by converting IUCN categories into probabilities that a species go extinct in the next 50, 100, or 200 years (Mooers et al., ), our study shows that extant primates have high risk of rapid extinctions, with our closest relatives being among the most likely to be lost first.…”

Platyrrhine color signals: New horizons to pursue

“…We coded for skin color using established categories: (a) depigmented (white skin [Figure a]); (b) hypervascularized (red skin [Figure b]); (c) mottled (depigmented skin with very small pigmented patches [Figure c]); and (d) hyperpigmented (dark skin [Figure d]). We then performed an ancestral state reconstruction by mapping the facial exposure (Figure ) and color traces (Figure ) on a current phylogenetic tree (auto‐correlated rates, soft‐bounded constraints) …”