The role of ecological opportunity in shaping disparate diversification trajectories in a bicontinental primate radiation

Abstract

Exceptional species and phenotypic diversity commonly are attributed to ecological opportunity (EO). The conventional EO model predicts that rates of lineage diversification and phenotypic evolution are elevated early in a radiation only to decline later in response to niche availability. Foregut fermentation is hypothesized to be a key innovation that allowed colobine monkeys (subfamily Colobinae), the only primates with this trait, to successfully colonize folivore adaptive zones unavailable to other herbivorous species. Therefore, diversification rates also are expected to be strongly linked with the evolution of traits related to folivory in these monkeys. Using dated molecular phylogenies and a dataset of feeding morphology, I test predictions of the EO model to evaluate the role of EO conferred by foregut fermentation in shaping the African and Asian colobine radiations. Findings from diversification methods coupled with colobine biogeographic history provide compelling evidence that decreasing availability of new adaptive zones during colonization of Asia together with constraints presented by dietary specialization underlie temporal changes in diversification in the Asian but not African clade. Additionally, departures from the EO model likely reflect iterative diversification events in Asia.

The ecology of a continental evolutionary radiation: Is the radiation of sigmodontine rodents adaptive?

“…Derryberry et al. () found constrained morphological evolution in the radiation of Furnariidae, Tran () detected a possible lack of ecological opportunity in the radiation of African colobine monkeys, and Zelditch et al. () found that geography is a very important component in the speciation of diverse and rapidly diversifying continental squirrels.…”

“…Other studies on continental radiations have shown a more varied relationship between adaptive divergence and ecological opportunity. Derryberry et al (2011) found constrained morphological evolution in the radiation of Furnariidae, Tran (2014) detected a possible lack of ecological opportunity in the radiation of African colobine monkeys, and Zelditch et al (2015) found that geography is a very important component in the speciation of diverse and rapidly diversifying continental squirrels. At continental scales, patterns of species and morphological diversification are sometimes found to be decoupled, leading, for instance, to clades with high species diversity but limited ecological variability (Kozak et al 2006;Burbrink et al 2012).…”

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

“…Primates is one of the largest (>400 species), most ecologically diverse, socially complex, and broadly distributed orders of mammals (Lefebvre et al 2004;Dunbar and MacDonald 2013;Fahy et al 2013;Tran 2014). As a consequence, considerable interest has been placed in how Primates have diversified and the factors contributing to the uneven distribution of species diversity across its major clades (Fabre et al 2009;Stadler 2011;Springer et al 2012).…”

Relationships of diversity, disparity, and their evolutionary rates in squirrels (Sciuridae)

“…For example, ecological opportunity does not always lead to a classic early burst of both diversification and divergence (Burbrink et al ), even when clades share the same sources of ecological opportunity (Burbrink et al ). Also, key innovations that confer ecological opportunity need not increase diversification rates (Claramunt et al ), even when disparity is elevated (Alfaro et al ; Dornburg et al ), and may even depress diversification (Tran ). Fourth, a link between diversification and divergence is not expected for some kinds of radiations, especially those termed “nonadaptive,” in which diversification is not accompanied by niche divergence (Gittenberger ; Wilke et al ); consequently, nonadaptively radiating clades are diverse but not disparate (e.g., Kozak et al ; Rowe et al ; Smith et al ).…”