Evol Ecol Res 9: 555-577 (2007)     Full PDF if your library subscribes.

Ecological generalization during adaptive radiation: evidence from Neogene mammals

Robert S. Feranec*

Department of Integrative Biology, University of California, Berkeley, CA 94720 and New York State Museum, CEC 3140, Albany, NY 12230, USA

e-mail: rferanec@mail.nysed.gov


Question: How does the evolution of a key adaptation affect niche breadth during an adaptive radiation?

Organisms: Cenozoic horse and camel species, as well as Pleistocene ungulates.

Predictions: Niche breadth theoretically could increase, decrease or remain the same as attainment of a key adaptation facilitates a niche shift. Simpson predicted a decrease in niche breadth (ecological specialization) when key adaptations lead to adaptive radiations. I test Simpson’s prediction by examining ecological response to attainment of high-crowned teeth (hypsodonty). The evolution of hyposdonty represents a key adaptation involved in many ungulate adaptive radiations.

Methods: To test whether hypsodont ungulates have potentially wider or narrower niche breadth in respect to their non-hypsodont, pre-adaptive radiation ancestors, I analysed δ13C values in the tooth enamel of Pleistocene ungulates as a proxy for dietary breadth. For Cenozoic horses and camels, I measured the total number of biogeographic provinces and the total number of fossil localities in which individual taxa were found to assess breadth of habitat use. I considered these two parameters (dietary breadth and habitat breadth) as two major niche axes from which I qualitatively estimated niche breadth. I also compared taxon survival between low-crowned and high-crowned taxa, reasoning that if high-crowned taxa had less broad niches, their probability of extinction should be higher and their temporal duration shorter.

Results: The δ13C values of herbivores from the Pleistocene of Florida revealed that high-crowned taxa fed on a diet of both C3 and C4 forage, while low-crowned taxa confined their feeding to C3 plants. In the Cenozoic horse and camel clades, there was no statistically significant difference between high-crowned and low-crowned taxa in the number of biogeographic provinces or localities occupied. Nor were there significant differences between high-crowned and low-crowned taxa in the duration of time a particular species survived.

Conclusions: Simpson’s prediction that key adaptations that lead to adaptive radiation also result in decreased niche breadth is not supported in the case of the evolution of hypsodonty by the ungulates. Instead, the attainment of hypsodonty in these taxa broadened niche space along one of the studied axes (dietary variety) and had no discernible effect on the other (habitat occupancy).

Keywords: adaptive radiation, diet, habitat, hypsodonty, key adaptation, mammal, niche breadth, Ungulata

IF you are connected using the IP of a subscribing institution (library, laboratory, etc.)
or through its VPN.


        © 2007 Robert S. Feranec. All EER articles are copyrighted by their authors. All authors endorse, permit and license Evolutionary Ecology Ltd. to grant its subscribing institutions/libraries the copying privileges specified below without additional consideration or payment to them or to Evolutionary Ecology, Ltd. These endorsements, in writing, are on file in the office of Evolutionary Ecology, Ltd. Consult authors for permission to use any portion of their work in derivative works, compilations or to distribute their work in any commercial manner.

       Subscribing institutions/libraries may grant individuals the privilege of making a single copy of an EER article for non-commercial educational or non-commercial research purposes. Subscribing institutions/libraries may also use articles for non-commercial educational purposes by making any number of copies for course packs or course reserve collections. Subscribing institutions/libraries may also loan single copies of articles to non-commercial libraries for educational purposes.

       All copies of abstracts and articles must preserve their copyright notice without modification.