Meeting Abstract

59.1  Tuesday, Jan. 6  Revisiting the niche: when is a mammalian herbivore a specialist? SHIPLEY, Lisa A.*; FORBEY, Jennifer; Washington State University; Boise State University shipley@wsu.edu

Although dietary specialization is considered rare in mammalian herbivores, examining the causes and consequences of the breadth of their feeding niche is critical for understanding selective pressures in diet and habitat selection, herbivory and coevolution. However, criteria for defining mammals as specialists has remained ambiguous and inconsistent. Unlike many phytophagous insects, no mammal is an absolute monophage. Therefore, placing mammals on a continuum from specialist to generalist, rather than assigning them to strict categories, allows ecologists to gain a comparative understanding about feeding strategies. Dietary specialization has been defined either by the fundamental niche (the range of nutritional tolerances in the absence of extrinsic pressures), or by the realized niche (the diet consumed in the natural habitat). The first approach may suffer from artificiality of lab conditions, and the second from known and stochastic variability in nature. As classically defined, specialists have a narrower realized niche than do generalists, but may have a larger fundamental niche because they may be able to tolerate a wider range of conditions along one niche axis (e.g., a specific plant toxin). Defining feeding specializations has also suffered from inconsistencies in the level of organization of both the diet and the herbivore (e.g., plant part, individual, population or species). In fact, many mammals are specialized to a functional aspect of plant food such as chemistry or architecture, rather than the plants taxonomy. A mammals feeding niche may also be defined and maintained by morphological and physiological adaptations or learned and inherited behavior. Current and longterm distribution of resources and strategies of competitors are key shapers of feeding strategies employed by mammals.