January 31 2013

5:00 pm BSRB 154

EcoEvoPub Series

Graduate Student Presentations


Sarah Joy Bittick
Department of Ecology and Evolutionary Biology

"Effects of nutrients and herbivores on the abundance of the tropical brown macroalga Turbinaria ornata"

For reasons that remain unclear, the range and abundance of Turbinaria ornata, a brown macroalga native to the South Pacific, has increased dramatically since the 1980s. The increased prevalence of other types of macroalgae has been linked to either increased nutrient input (bottom-up effect) or decreased herbivory pressure by fishes (top-down effect). However, these explanations alone may not explain the unprecedented increase in T. ornata as there is little evidence that nutrients limit its growth rate and it is chemically and structurally defended from many herbivores. Through a series of field manipulations, I investigate the dual roles of nutrient availability and herbivory on the biomass of T. ornata. The results suggest that nutrient enrichment causes T. ornata to become less palatable to fishes by bolstering its structural defenses. As a result, T. ornata may be released from herbivore control and, hence, able to increase dramatically in abundance. Thus, it may be the interplay between bottom-up (nutrients) and top-down (herbivory) processes that is promoting the unprecedented increase in T. ornata on reefs in the South Pacific.

Caitlin Brown
Department of Ecology and Evolutionary Biology

"Looking Moose in the Mouth: Few Sweet Teeth on Isle Royale"

Teeth are critical to mammalian lifestyles and receive considerable developmental priority. However, stressful events in the life histories of wild and domestic animals, most notably food shortage, can still slow or stop their formation. High incidents of interrupted tooth development and decreased rates of weekly growth are expected to accompany food shortage and high population densities, though no studies have yet assessed these features in a population outside the laboratory. I look to use evidence of food shortage recorded in the teeth of modern moose (Alces alces) and elk (Cervus canadensis) over several decades to conclusively link dental anomalies with high population density. I will discuss the challenges of scaling up tooth tissue analyses to assess the health of entire populations and the preliminary results of this work. The findings of this research will provide a method for estimating relative population sizes, a tool particularly valuable to paleontologists studying taphonomically unusual sites such as the Rancho La Brea tar seeps.
















































































































































































































































































































































































































































































































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