Mechanisms of Community Assembly in a Guild of Tropical Anurans
I am interested in understanding how the mechanisms of competition, predation, and abiotic factors contribute to structuring the breeding ponds of frogs at the local level. In turn, I want to understand how these mechanisms scale up to the regional level and affect frog distribution and diversity. I am conducting my research in the Bolivian Gran Chaco, a mosaic of thorn forest and savannahs with seasonal rainfall, from November to April. The frogs inhabiting this ecosystem possess a variety adaptive traits to persist in the xeric habitat. Additionally, the frog fauna of the Chaco have as many as seven species of frog-eating frogs (with two of those species also having carnivorous tadpoles). However, the degree to which they structure the community is not known. I am just beginning my research in this area and I will have more details as time progresses.
Pictured above (left) is one species of frog-eating frog, a Cranwell's Horned Frog (Ceratophrys cranwelli) metamorph with its carnivorous tadpole. Pictured above (right) is an adult Cranwell's Horned Frog eating a Granulated Toad (Bufo granulosus).
of aquatic salamanders; implications for wetland
In summer 2007, I participated in a National Science Foundation REU program at the Savannah River Ecology Laboratory (SREL) under the tutelage of Dr. Whit Gibbons (pictured above left) and his gradate student, Tom Luhring. My project examined the movement ecology of two species of of poorly studied aquatic salamanders; the Greater Siren (Siren lacertina; pictured above right) and Two-toed Amphiuma (Amphiuma means). These species of large salamanders (they can grow to nearly a meter in length) occupy wetlands as far as 0.7 km from the next closest waterbody, which is suggestive of considerable dispersal ability. However, their dispersal ability and mode has yet to be conclusively determined. In a laboratory experiment, I assessed the vagility of these two species under three simulated environmental conditions: terrestrial, shallow standing water, and complete submergence. Both species demonstrated a trend toward exhaustion in all treatments, but were able to disperse the farthest in the submerged treatments. To disperse, these species likely rely on the formation of aquatic corridors during flooding events. Therefore, the human activities that disrupt the formation of these aquatic corridors may have important implications for wetland connectivity.
culvert design and placement to facilitate passage of
amphibians across roads.
During my senior year at SUNY-ESF, I assisted Drs. David Patrick and James Gibbs on a projectaimed to aid transporation departments when designing structures to alleviate road moratilty of amphibians. We assessed the crossing frequencies of Spotted Salamanders (Ambystoma maculatum) and American Toads (Bufo americanus) within a know crossing "hotspot" and examined that in relation to the habitat variables in the surrounding area. We also created an experiemental array of culverts to examine if the migrating Spotted Salamanders showed any preference in their use of these structures. Salamander crossing was closely associated with the presence of flowing water on the upslope, while toads tended to cross in areas where wetlands were absent on the downslope across the road. Additionally, the salamanders showed no preference in their use of the culverts. Our results suggest that their are areas within crossing "hotspots" that show species-specific patterns of occurrence and under natural conditions. Also, even though, Spotted Salamanders showed no preference for use, it may vary among species, thus a variety of structures may be most efficient in mitigating road mortality.
microhabitat use of the Greater Siren (Siren
an isolated wetland.
During the summer of 2008, I returned to SREL as an REU student to continue my research on the ecology of S. lacertina and A. means. The habitats of these species have been described on the coarse scale (e.g. ponds, swamps), but their microhabitat use within these bodies of water have not been examined. I set traps in three different microhabitats in a wetland; the water's surface and benthic zone (both in deep water), and a littoral zone. Siren lacertina were captured more frequently in the benthic zone, while A. means were captured more in the littoral zone. This difference in microhabitat use may reflect a difference in prey availability (aquatic insects were captured more frequently in the benthic zone with S. lacertina, while fish and crayfish were captured more in the littoral zone with A. means), or the salamanders may be minimizing competitive interactions.