James M. Novak

FOOD QUALITY, HETEROZYGOSITY, AND FITNESS CORRELATES IN PEROMYSCUS POLIONOTUS

Oldfield mice (Peromyscus polionotus) that are more heterozygous utilize food and maintain body weight under varying degrees of dietary stress better than their less heterozygous counterparts. Mice were collected in southern Florida and fed diets of three qualities. During each dietary treatment, body weight, amount of food eaten, amount of food absorbed, and feeding efficiency were determined. Body weights for all mice decreased during the experiment. More heterozygous mice maintained their weight better during periods of dietary stress than those that were less heterozygous. Mice with different levels of genetic variability had essentially the same mean feeding efficiency with high quality diets. Mice with high heterozygosities maintained the same efficiency with low quality diets, but those with lower heterozygosities had decreased feeding efficiencies. A slight increase in available energy for mice of different heterozygosities can dramatically change fitness correlated characters, such as growth rates, body weights, energy stores, and reproductive rates.

Genetic Variation among Populations of River Otters in North America: Considerations for Reintroduction Projects

Horizontal starch gel electrophoresis was used to assess variability at 23 presumptive gene loci of 732 river otters obtained from fur-trappers in 18 states and three Canadian provinces. States and provinces providing otters were sorted into eight geographic regions for genetic comparisons. Multilocus heterozygosity and polymorphism ranged from 0.018 to 0.032 and 0.044 to 0.087, respectively. One locus, esterase-2, (EST-2) demonstrated a high level of polymorphism throughout all regions. Malate dehydrogenase-1 (MDH-1) was polymorphic throughout the Mississippi drainage but not elsewhere. Heterozygosity, occurrence of rare alleles, and mean number of alleles per locus were associated positively with estimated population sizes. Average heterozygosity and polymorphism values for otters within regions were lower than overall averages reported for mammals but similar to the range of those observed in other mammalian carnivores. Patterns of gene flow suggested by the distribution of polymorphism at the MDH-1 locus do not concur with the current taxonomic classification of river otters. Levels of genetic variation detected in this investigation present a positive outlook for the maintenance of genetic diversity in river otter populations, if sound management principles are applied for reintroductions.

Catch-effort estimation of white-tailed deer population size

Estimation of population size is important for most research in population biology and in the management of game species. Using a stochastic, catch-effort, competing risk model (Dupont 1983), we estimated the population size of the Savannah River Site white-tailed deer (Odocoileus virginianus) herd for 1985-86. Population size varied markedly in response to changes in both hunting method and pressure. Still hunters preferentially harvested older animals compared to dog hunters. Deer were 2.37 times more susceptible to harvest from dog hunting than from still hunting. Hunter-induced mortality was estimated as 1.73 and 4.10 times as large as nonhunting mortality for still and dog hunting, respectively. The temporal pattern of estimated prehunt population sizes was significantly correlated with the temporal pattern of car−deer accidents recorded on the site during the same time period, suggesting that the temporal pattern of the population, estimates is accurate. If the number of cohorts is large and an accurate estimate of hunter effort can be obtained, this technique may provide more reliable population estimates than previously available techniques because it imposes fewer and less stringent biological assumptions

Morphological asymmetry and interspecific hybridization: A case study using hylid frogs

The limited studies addressing developmental stability of interspecific hybrids suggest a positive association between the level of fluctuating asymmetry and 1) the degree of divergence between parental species, and 2) the recency of the contact zone. To evaluate these associations, we examined asymmetry in a recently‐established hybrid population of treefrogs (Hyla cinerea and H. gratiosa) that show marked structural gene divergence. Fluctuating asymmetry (FA), directional asymmetry, and antisymmetry were assessed for eight paired osteometric traits in allozymically‐defined parental and hybrid categories. FA levels varied considerably among traits. Nonetheless, for any given trait, the hybrid categories did not demonstrate elevated levels of FA compared to the parental categories, or compared to frogs from a non‐hybridizing parental population. The only trait that differed statistically among categories (pterygoid length) involved a significantly lower FA value for the F1 hybrids. Thus, observed FA values do not support expectations that the hybrid categories should experience decreased developmental stability.

Biochemical Systematics of notothenioid fishes from Antarctica

Abstract Genetic variation at 30 protein-coding loci was examined in seven forms of notothenioid fishes from Antarctica. Multilocus heterozygosity varied from 0.018 to 0.078 across taxa. An analysis of the allozyme data revealed the probable existence of an unrecognized cryptic species within Trematomus bernacchii. Pagothenia borchgrevinki is as closely related to some species of Trematomus as are some species of Trematomus to each other. Speciation among the species of Trematomus and Pagothenia appears to have taken place primarily after the separation of Antarctica from Australia.

Assessing Multiple Endpoints of Atrazine Ingestion on Gravid Northern Watersnakes (Nerodia sipedon) and Their Offspring

Ecotoxicological studies that focus on a single endpoint might not accurately and completely represent the true ecological effects of a contaminant. Exposure to atrazine, a widely used herbicide, disrupts endocrine function and sexual development in amphibians, but studies involving live‐bearing reptiles are lacking. This study tracks several effects of atrazine ingestion from female Northern Watersnakes (Nerodia sipedon) to their offspring exposed in utero. Twenty‐five gravid N. sipedon were fed fish dosed with one of the four levels of atrazine (0, 2, 20, or 200 ppb) twice weekly for the entirety of their gestation period. Endpoints for the mothers included blood estradiol levels measured weekly and survival more than 3 months. Endpoints for the offspring included morphometrics, clutch sex ratio, stillbirth, and asymmetry of dorsal scales and jaw length. Through these multiple endpoints, we show that atrazine ingestion can disrupt estradiol production in mothers, increase the likelihood of mortality from infection, alter clutch sex ratio, cause a higher proportion of stillborn offspring, and affect scale symmetry. We emphasize the need for additional research involving other reptile species using multiple endpoints to determine the full range of impacts of contaminant exposure.

DNA Double-Strand Breakage as an Endpoint to Examine Metal and Radionuclide Exposure Effects to Water Snakes on a Nuclear Industrial Site

ABSTRACT This study examined metal levels (especially U and Ni) in the tail tissues of water snakes from contaminated (Tims Branch) and reference areas on the Department of Energys Savannah River Site (SRS). Home ranges of snakes were quantified to determine the ratio of the habitat that they use in relation to the contaminated areas to better estimate exposure Compared to conventional methods that do not. The exposure assessment indicated that water snakes in the contaminated areas could expect U exposure at 3–4 orders of magnitude greater than the Agency for Toxic Substances and Disease Registrys Minimum Risk Level (MRL) from ingestion of amphibians and fish. Ni and U, in addition to Se, Mn, and Cu, were related to increased DNA double-strand breakage (DDSB) in water snakes. We report burdens for each metal individually, but the results of the DDSB indicated that these metals did not behave independently, but as a suite. If we did not have a secondary endpoint (DDSB), we might have assumed from the exposure predictions and tissue burden analyses that U was the sole metal of concern to water snakes in Tims Branch. These data also imply that these toxicants do not biomagnify at the spatial and temporal scale of this study.

Atrazine and glyphosate dynamics in a lotic ecosystem: the common snapping turtle as a sentinel species

Atrazine and glyphosate are two of the most common pesticides used in the US Midwest that impact water quality via runoff, and the common snapping turtle (Chelydra serpentina) is an excellent indicator species to monitor these pesticides especially in lotic systems. The goals of this study were to (1) quantify atrazine, the atrazine metabolite diaminochlorotriazine (DACT), and glyphosate burdens in common snapping turtle tissue from individuals collected within the Embarras River in Illinois; (2) quantify atrazine, DACT, and glyphosate loads in water from the aquatic habitats in which common snapping turtles reside; and (3) investigate tissue loads based on turtle morphology and habitat choice. Concentrations of atrazine, DACT, and glyphosate in tissue did not show any relationship with lake habitat, carapace length, width, or mass. Both atrazine and glyphosate tissue samples varied as a function of site (river vs. lake), but DACT did not. Atrazine and glyphosate concentrations in water samples showed a linear effect on distance from the reservoir spillway and a deviation from linearity. Water column concentrations of all three contaminants varied across capture sites, but atrazine water concentration did not influence DACT water concentration nor did it exhibit a site interaction. Water atrazine and glyphosate concentrations were greater than tissue concentrations, whereas DACT water and tissue concentrations did not differ. This study showed that turtles are useful in long-term pesticide monitoring, and because DACT as a metabolite is less sensitive to variation, it should be considered as a preferred biomarker for pesticide runoff.

Are U, Ni, and Hg an Environmental Risk within a RCRA/CERCLA Unit on the U.S. Department of Energy's Savannah River Site?

ABSTRACT The U.S. Department of Energys Savannah River Site (SRS) is a former nuclear weapon production facility. From 1954–1985, releases of Al, Cu, Cr, Hg, Ni, Pb, U, and Zn were discharged into the Tims Branch-Steed Pond water system. This study investigates whether metal concentrations in Tims Branchs sediment, biofilm, and other biota exceed screening level risk calculations to determine if remedial actions should be pursued for the Contaminants of Potential Concern (U, Ni, Hg). Transfer factors (TFs) were calculated to determine metal concentration changes throughout lower trophic levels and results were compared with sediment benchmarks to create hazard quotients (HQs) to assess risk and a scientific-management decision point. Most TFs for Ni and U from lower to higher trophic level biota were <1, suggesting no biomagnifications; however HQs > 1 and cumulative distributions showed the majority of the samples exceeded action levels. Elevated TFs and HQs > 1 in the upper trophic levels for Hg indicated a high degree of bioavailability and biomagnification. Monte Carlo resampling analyses supported these empirical results. This system should continue to be closely monitored to ensure that contamination does not move off the SRS.

A Spatially Explicit Model to Predict Radiocesium Body Burdens of White- Tailed Deer on the U.S. Department of Energy's Savannah River Site

ABSTRACT We developed a spatially explicit exposure model to interpolate and predict radiocesium (137Cs) body burdens found in white-tailed deer (Odocoileus virginianus) on the U.S. Department of Energys (USDOE) Savannah River Site (SRS) to gain insight into and differentiate between the main contributing sources of this radionuclide for use in harvest management strategies that focus on minimizing human risk. Hunting has been allowed from permanent stands as a mechanism to manage the deer herd since 1965. All animals are monitored in the field for gross beta and gamma activity levels, providing a spatially explicit dataset. The models described here use the relative locations of the hunt-stands to predict 137Cs exposure distributions. We used kriging to create an interpolation surface using average white-tailed deer body burdens. Cross-validations of the kriged surfaces differentiated between sources of 137Cs and where deer reside on the SRS. The kriged surfaces, coupled with additional regression analyses, provide a comprehensive assessment of deers 137Cs body burdens with predictive capability that quantifies the scale at which such investigations can be conducted. Although the models are local in scale, the methods presented here can be used as a template for other large areas that are being monitored for radioactive fallout.