06/12/06

Research Focus

     My research focuses on understanding how organisms interact and persist in aquatic communities.  Biotic (predation, competition) and abiotic (drought, temperature) processes operate to limit local abundances of species through direct and indirect interactions.  These interactions affect the density as well as the traits of species.  I am interested in quantifying the relative importance of both biotic and abiotic interactions in structuring communities through the use of field, lab, and mesocosm experiments.  Such an approach provides the opportunity to tease apart density- and trait-mediated direct and indirect interactions.  Mesocosm and lab experiments give insight into the importance of different interactions while field experiments confirm these potentially artificial observations.

     My dissertation work investigates the limits on the abundance of two species of pulmonate snails, the seminole ramshorm (Planorbella duryi) and the mesa ramshorn (Planorbella scalaris) in the Florida Everglades.  The Everglades has large amounts of primary production (periphyton) but low standing crops of animals.  This is particularly strange for herbivourous snails, given the amount primary production.  I am approaching the mechanisms limiting snails in the Everglades from both top-down and bottom-up perspectives by examining threats of predation (crayfish, fish, Belistoma) and the potential for the primary producers to be defended from grazers.

     I am also interested in comparing snail abundances in the Florida Everglades to other aquatic systems like ponds, lakes, and other wetlands.  Such comparisons will enable me to establish if the Everglades has relatively low abundances of snails or if this is only perceived when compared to other systems.  Additionally, I want to collect data from other wetlands in the sub-tropics and tropics that are similar to the Everglades to determine if they too have low abundances of aquatic snails.  There are wetlands similar to the Everglades in Belize, Cuba, and the Yucatan peninsula of Mexico.

Research Projects:

Food web manipulations

Joel Trexler, Nate Dorn, and I are working together to examine the extent of behavioral responses to the threat of predation over space and time by using predator exclosure devices along gradients of nutrient enrichment in both the dry and rainy seasons.

Evolution of Phenotypic Plasticity

This work was done in collaboration with Thom DeWitt at Texas A&M University during my Master's degree.  We are examined how food type and orientation affect the external morphology of mosquitofish (Gambusia affinis).  We also considered how mosquitofish respond morphologically to fine-grain (daily) resource variation.  Additionally, we explored the indirect effects predators have on the trophic morphology of prey through habitat alteration and thus changes in resource use.  To see animations of the food type and orientation shape change click here.  This work has been published in Evolutionary Ecology Research.

Red drum (Sciaenops ocellatus) supplementation & phenotypic plasticity

I conducted this work with Thom DeWitt and Texas Parks and Wildlife.  Texas supplements natural populations of red drum with large numbers of post larval (~32mm) hatchery reared red drum.  In an initial study examining the extent of external, internal, muscular, and behavioral plasticity of hatchery red drum we found feeding red drum hard food (crayfish limbs) items induced significant differences in external morphology, muscle mass, and initially behavior.  Interestingly, fish reared on soft food items (crayfish meat) learned how to consume hard food items over the course of two days.  Future work will include aspects of predator driven morphological and behavioral plasticity.  The goal of this work is to discover ways to enhance survival of released fish.

Scale of morphological variation in estuarine fishes

This work is in collaboration with Virginia Shervette and Thom DeWitt at Texas A&M.  We seek to understand the consequences of different substrates (oyster shell, seagrass, and sand) on the morphology of pinfish (Lagodon rhomboides), spot (Leiostomus xanthurus), and silver perch (Bairdiella chrysoura).  We are also interested in how spatial scale affects the morphological differences within and among bay systems.