Ecological Opportunity and Adaptive Radiation

Abstract

The process of adaptive radiation—the proliferation of species from a single ancestor and diversification into many ecologically different forms—has been of great interest to evolutionary biologists since Darwin. Since the middle of the last century, ecological opportunity has been invoked as a potential key to understanding when and how adaptive radiation occurs. Interest in the topic of ecological opportunity has accelerated as research on adaptive radiation has experienced a resurgence, fueled in part by advances in phylogenetic approaches to studying evolutionary diversification. Nonetheless, what the term actually means, much less how it mechanistically leads to adaptive diversification, is currently debated; whether the term has any predictive value or is a heuristic useful only for post hoc explanation also remains unclear. Recent recognition that evolutionary change can occur rapidly and on a timescale commensurate with ecological processes suggests that it is time to synthesize ecological and evolutionary approaches to the study of community assembly and evolutionary diversification.

Neotropical frogs and mating songs: The evolution of advertisement calls in glassfrogs

“…Following the idea of “ecological opportunity” (Stroud & Losos, ), the strong and temporarily coincidental significant increase in disparity observed in call duration, number of notes, bandwidth frequency and TL/SVL could have been triggered by past environmental changes or dispersals into new areas. When considering the historical biogeography of Centrolenidae (Castroviejo‐Fisher et al., ), the time estimates for the onset of increasing disparity coincide with (a) major changes within biogeographic areas already inhabited by ancestral glassfrogs, such as the main orogeny of the Andes and the formation of the modern Amazon basin (Hoorn & Wesselingh, ) and (b) the dispersal into new biogeographic areas such the large radiation of Cochranellini and the colonization of the MRCA of Teratohyla of the Amazonian lowlands and of Celsiella of the highlands.…”

Allopatric and sympatric diversification within roach (Rutilus rutilus) of large pre‐alpine lakes

“…Much of the existing species diversity of freshwater fish in northern climate zones is of recent origin, having evolved since the end of the last glaciation period ~12 kyrs ago (Hewitt, ; Seehausen & Wagner, ). During the invasion of newly available freshwater bodies and associated range expansion, many fish species colonized a variety of different environments and as a result may have experienced competitive release that may have triggered adaptive diversification (Bolnick, Svanbäck, Araujo, & Persson, ; Stroud & Losos, ). Divergent selection between habitats frequently led to the emergence of ecologically distinct populations, ecotypes and species.…”

Dispersal is associated with morphological innovation, but not increased diversification, in Cyphostemma (Vitaceae)

“…Although many factors, such as ecological opportunity, that are expected to foster adaptive radiation may be present, clades may fail to undergo radiation making the prediction of when and how adaptive radiations occur difficult (Losos, ; Stroud & Losos, ). Stroud & Losos () offer two conditions for ecological opportunity to foster diversification: (i) diversification of resource use by taxa within the lineage of interest, and (ii) lability in trait evolution.…”

“…Although many factors, such as ecological opportunity, that are expected to foster adaptive radiation may be present, clades may fail to undergo radiation making the prediction of when and how adaptive radiations occur difficult (Losos, ; Stroud & Losos, ). Stroud & Losos () offer two conditions for ecological opportunity to foster diversification: (i) diversification of resource use by taxa within the lineage of interest, and (ii) lability in trait evolution. The conditions seem ripe for adaptive radiation to have occurred within Cyphostemma : (i) dispersal and speciation within a diversity of habitats in Madagascar, (ii) labile evolution of ecologically important traits such as stem succulence, and (iii) dispersal into complex landscapes and multiple habitats.…”

“…Diversification of traits (disparification) is often closely associated with adaptive radiations as lineages adapt to open niche space (Ackerly, ; Nürk et al, ; Simões et al, ). Recent discussions of the concept of key innovation suggest that shifts in rates of lineage diversification provide a poor basis for key innovation tests (Rabosky, ), highlighting, instead, how key innovations facilitate new interactions with the environment (Stroud & Losos, ; Rabosky, ).…”