American Alligator (Alligator Mississippiensis) Ecology Within Human-Dominated Landscapes

Urbanization is an ever-increasing threat to wildlife and their habitats, yet research has been limited to a small number of taxa. The American alligator (Alligator mississippiensis) is an apex predator that has surprisingly received minimal attention within urban areas. To investigate the potential effects of urban land use on spatial ecology, we conducted surveys of relative alligator abundance in nine tributaries surrounding the St. Johns River. We used these data to explore the potential effects of urban development on alligator spatial distribution and habitat selection. At the coarse scale, we found no correlation between percent developed land and relative alligator abundance. Instead, salinity is the primary driver of relative abundance. At the fine scale, we found that alligators prefer habitats characterized by more open water and highly vegetated shorelines and avoid anthropogenic structure. Only one out of 93 sighted individuals was an adult, and recent data suggests that adults are relatively rare in our study area. Thus, juveniles still occupy urban habitats because they are not being targeted and they face virtually no competition from adults. To investigate the potential effects of land development on trophic ecology, we performed gut content analysis on golf course alligators found on Jekyll Island, Georgia. We made comparisons with alligators found in more natural areas on Sapelo Island, Georgia. Percent index of relative importance values reveal that there may be functional differences in prey choice or availability, but analysis of similarity, non-metric multidimensional scaling, and simplified Morisita index analyses show no significant difference. Further land development and increasing human activity may therefore degrade available habitat and limit the distribution of breeding adult alligators in once suitable areas and possibly shift diets toward reliance on prey items usually of lesser importance. These potentially interacting spatial and trophic effects could lead to local population declines

What do alligators eat on golf courses?

Urbanization is an ever-increasing threat to wildlife and their natural habitats, yet research has been limited to a small number of taxa and very few large predator species. The American alligator (Alligator mississippiensis) is an apex predator across the southeast U.S. and has surprisingly received minimal attention within urban areas. To investigate the potential effects of land development on alligator trophic ecology, we performed gut content analysis on golf course alligators found on Jekyll Island, Georgia. We then made comparisons with alligators found in more natural areas on Sapelo Island, Georgia. In total, we collected stomach content samples from 25 alligators on Jekyll Island golf courses, of which only one had an empty stomach. Data provided from Sapelo Island consisted of 93 alligators within our alligator size range, of which only one had an empty stomach. While analysis of similarity, non-metric multidimensional scaling, and simplified Morisita index analyses show no significant difference in diets between the two areas (possibly because of a low sample size from Jekyll Island), %IRI values for prey items reveal that there may be functional differences in prey choice or availability. Further land development and increasing human activity may therefore shift diets toward reliance on prey items usually of lesser importance. These trophic effects could possibly lead to local population declines, if paired with habitat degradation or other stressors

Ecological Energetics of an Abundant Aerial Insectivore, the Purple Martin

We thank T. Fagin for help with estimating the seasonal range area occupied by Purple Martins. We thank an anonymous reviewer, Mark Brigham, and J Boyles for their comments on this manuscript.Conceived and designed the experiments: JFK ESB WFF PBC. Performed the experiments: JFK PBC. Analyzed the data: JFK PBC. Wrote the manuscript: JFK ESB WFF PBC. Developed the model in Matlab: JFK PBC.The atmospheric boundary layer and lower free atmosphere, or aerosphere, is increasingly important for human transportation, communication, environmental monitoring, and energy production. The impacts of anthropogenic encroachment into aerial habitats are not well understood. Insectivorous birds and bats are inherently valuable components of biodiversity and play an integral role in aerial trophic dynamics. Many of these insectivores are experiencing range-wide population declines. As a first step toward gaging the potential impacts of these declines on the aerosphere’s trophic system, estimates of the biomass and energy consumed by aerial insectivores are needed. We developed a suite of energetics models for one of the largest and most common avian aerial insectivores in North America, the Purple Martin (Progne subis). The base model estimated that Purple Martins consumed 412 (± 104) billion insects*y-1 with a biomass of 115,860 (± 29,192) metric tonnes*y-1. During the breeding season Purple Martins consume 10.3 (+ 3.0) kg of prey biomass per km3 of aerial habitat, equal to about 36,000 individual insects*km-3. Based on these calculations, the cumulative seasonal consumption of insects*km-3 is greater in North America during the breeding season than during other phases of the annual cycle, however the maximum daily insect consumption*km-3 occurs during fall migration. This analysis provides the first range-wide quantitative estimate of the magnitude of the trophic impact of this large and common aerial insectivore. Future studies could use a similar modeling approach to estimate impacts of the entire guild of aerial insectivores at a variety of temporal and spatial scales. These analyses would inform our understanding of the impact of population declines among aerial insectivores on the aerosphere’s trophic dynamics.Yeshttp://www.plosone.org/static/editorial#pee

Robust estimation of bacterial cell count from optical density

Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data

Detection of dopaminergic cell loss and neural transplantation using pharmacological MRI, PET and behavioral assessment

We demonstrate the use of magnetic resonance imaging (MRI) for detection of neurotransmitter stimulation using the dopamine transporter ligands amphetamine and CFT (2beta-carbomethoxy-3beta-(4-fluorophenyl)tropane) as pharmacological challenges. We demonstrate that the unilateral loss of a hemodynamic response to either amphetamine or CFT challenge by unilateral 6-hydroxydopamine lesioning is restored by transplantation of fetal dopamine neurons in the striatum. The time course for the hemodynamic changes parallels the time courses for dopamine release, measured by prior microdialysis studies, and also for the rotational behavior in the unilaterally lesioned animals. Transplantation of the fetal cells results in hemodynamic time courses after CFT or amphetamine challenges at the graft site that are identical to those induced both before transplantation and on the intact contralateral side. The transplantation also results in complete behavioral recovery. The spatial extent of the dopaminergic recovery in the lesioned striatum is the same when measured using either PET of tracer levels of [11C]CFT binding or MRI. These results show great promise for the application of pharmacological MRI for application to studies of dopamine cell loss and potential recovery in Parkinson\u27s disease