Graduate Students | Cooperative Wildlife Research Laboratory | SIU

Wes Holland

w.holland@siu.edu

Advisor:  Dr. Justin Boyles

Testing Evolutionary Trade-Offs and Diversity in Soricidae (Mammalia: Soricomorpha)

Competition theory is a critical component of understanding speciation and adaptation in ecosystems. An important aspect of competition is the competitive exclusion principle, which states that complete competitors cannot coexist. Competitive exclusion and niche overlap determines how strongly two species might compete with one another. A primary example of niche differentiation occurs with character displacement and can depend on several facets including foraging behavior, morphology, and phenotypic responses to competition/interactions with other species. If competition and niche overlap exudes fixed pressure on members in an ecological community, the result may lead to niche differentiation.  I use shrews as appropriate models to test phenotypic plasticity among subspecific populations and species levels and to determine character displacement in areas where species overlap. Unlike previous studies, we look at Soricidae on a global scale, including morphometric data on a wide variety of genera/species from numerous habitats throughout the world to examine horizontal diversity by comparing the diversity of species within trophic levels or niches.   In particular, we are calculating bite forces of many different species of Soricidae and supplement with known phylogenetic, biogeographical, dietary, and life history literature (mating behavior, caching, territoriality) to infer patterns of competition.  We hypothesize that shrews will show more variation in bite force in areas of high species concentration and that bite force will vary across sub-specific groups, particularly among species with large ranges that encompass many different habitats.  We also predict bite force plays a role in prey selection and is reflected by competition with other shrews and insectivorous mammals. Lastly, we hypothesize that there is a trade-off in bite force strength and venom production and species that utilize venom will have a proportionally weaker bite force than species that do not rely on venom to subdue prey.  We are collaborating with the Field Museum of Natural History and Texas Tech University in the collection of morphological data.