No description available.

No description available.

No description available.

No description available.

No description available.

Assessing ecological risk to wildlife exposed to anthropogenic contamination in soil has traditionally been problematic. Attempts to standardize an approach to evaluate risk for various community types in North America have been challenging, given the variation in terrestrial communities and the values in which policy makers are bound to protect. This has resulted in vague, yet flexible guidance from the U.S. Environmental Protection Agency and other interested parties (e.g., the U.S. Army Corps of Engineers, and the Tri-Service Ecological Risk Assessment Working Group). Interpretation of these and other guidance has been variable, often resulting in conflicting opinions on how best to address the question of ecological risk to receptors that are exposed to xenobiotics in a soil matrix. This work reports the results of research designed to address the question of ecological risk to terrestrial vertebrates. Objective, ecologically-relevant criteria were used in the selection and development of models in this research. Several lines of logic were considered: 1) substance sensitivity, 2) ecological sensitivity (i.e., the species importance to the system; e.g., keystone species); and, 3) probability and extent of exposure. A primary soil contaminant at many U.S. Army installations is 2,4,6-trinitrotoluene (TNT). This was a result of the mass manufacturing, storing, and assembly of weapons from the early 1900's until the 1950s. The Army has reported soil concentrations of TNT ranging from 0.12 to 38,600 ug/g (Walsh and Jenkins 1992) and 0.08 to 64,000 ug/g (Hovatter et al. 1997). The chemical-physical properties of TNT result in a relatively unique compound, not easily amenable to current modeling techniques to estimate exposure to terrestrial wildlife. Moreover, there are few data describing the effects of exposure to TNT in other than mammals, fish, and specific invertebrates. In this research, the pathways of exposure and selected potential toxic effects from TNT exposure were investigated in a terrestrial salamander: Ambystoma tigrinum (tiger salamanders). A. tigrinum was chosen since they are exclusively carnivorous, relatively long-lived, have a thin integument, and are large enough to investigate individual effects. These investigations were designed to mimic natural conditions as closely as possible, though maintain a degree of homogeneity in a laboratory environment. All studies exposed salamanders to soil and food (earthworms) in identical preparations. As such, these exposures were considered complete, eliminating assumptions made regarding daily food consumption, systemic dermal dose, etc. The first study examined the relative contribution of dermal or oral exposures to the whole-body burdens of TNT and primary metabolites. A poly-chlorinated biphenyl (PCB) mixture (Aroclor7 1260) was used with TNT to simultaneously to assist in the evaluation of each pathway, since the fate and transport of PCBs are well characterized. Tiger salamanders were exposed 28 days in situ. The dermal route of exposure contributed the most to the final burdens of TNT in salamanders, with the primary reduction products, 2-amino-4,6-dinitrotoluene and 4-amino, 2,6-dinitrotoulene reaching higher concentrations than of parent compound. Other TNT metabolites were found in insignificant quantities. The concentrations of PCBs were higher in the oral treatment, as expected. These results were corroborated in a subsequent study using Ambystoma maculatum (spotted salamanders). The second series of investigations evaluated the potential toxic effects from TNT exposure. Two treatments consisting of TNT and a control were used to evaluate these effects to A. tigrinum. The salamanders were exposed in situ for 14 days to TNT in soil and food (earthworms of which were exposed to TNT in the soil in similar preparations). Non-specific immune effects were evaluated through the characterization of splenic phagocytes in their ability to: 1) phagocytize foreign particles, and 2) digest (through oxygen radicals) phagocytized material. This was conducted using fluorescent microspheres and a fluorescent chemical probe specific to hydrogen peroxide, measured per each cell using flow cytometry. Other data collected included histological examination (e.g., liver, kidney, and other miscellaneous organs), blood differentials, weight changes over time, organ/ body weight comparisons, and an analysis of organ-specific metabolism. No significant effects were noted in salamanders exposed to these conditions. Coordinated with the preceding study included a search for biomarkers of exposure and an investigation of the metabolites of TNT in situ. Biotransformation products of TNT were found including primary (e.g., 2-amino-4,6-dinitrotoluene) and secondary (e.g., 2,4-diamino-6-nitrotoluene) in relative concentrations in skin, liver, and kidney. Biomarkers of exposure included an analysis of cytochrome p450, b5, and the glutathione antioxidant enzymes in liver, kidney, skin, lung, and serum, respectively. Traces of parent compound were found in the skin and liver only. Levels of 2,4-diamino-6-nitrotoluene were found only in the liver and kidney, suggesting that TNT is reduced primarily in or on the skin. Levels of p450 were higher in TNT exposed salamanders than controls. Glutathione and related enzyme levels are reported. This work suggests that salamanders have levels of detoxification enzymes capable of the biotransformation of anthropogenic substances in soil rivaling that of mammals. Another investigation evaluated these same immunological parameters in white-footed mice (Peromyscus leucopus). This species was chosen based on the relative importance of small mammals to the community structure in many North American ecosystems. Mice were exposed to TNT in the feed at 0.264, 0.066, 0.033, and 0.017%, where actual daily dose estimates for males were 604, 275, 109, and 65; and for females was 544, 282, 143, and 70 mg/kg/d. An investigation to evaluate the specificity of commercially-available monoclonal antibodies specific to cell surface markers for thymocytes and splenocytes in inbred mice was unsuccessful. These results suggest the recognition epitopes of monoclonal antibodies prepared against Old-World mice are not conserved into Peromyscus, a New-World species. However, high dose males and females had larger spleens consistent with the hemolytic effects previously reported for mammals exposed to TNT. Further, males exposed at all levels had reduced phagocytic activity of splenocytes, and reduced hydrogen peroxide production associated with the two highest doses relative to controls. Females showed no response relative to treatment. This research has shown the feasibility for these types of investigations, and provides toxicity information valuable for modeling estimates of ecological risk. Further, the in situ exposures have provided media concentrations that are or are not toxic for species of concern. This type of information reduces the uncertainty associated with ingestion modeling estimates, dermal exposure estimates, and other factors not traditionally considered in toxicity studies. / Ph. D.

Thesis (Ph. D.)--Miami University, Dept. of Zoology, 2004. / Title from second page of PDF document. Document formatted into pages; contains [3], iii, 138 p. : ill. Includes bibliographical references (p.121-138).

The genetic structure of 49 natural populations of four species (P. attwateri, P. boylii, P. pectoralis, and P. polius) of the Peromyscus boylii species group was analyzed through application of chromosomal and electrophoretic techniques. Chromosomal variation within and among populations of the boylii species group was analyzed from 178 specimens. Electrophoretic techniques were utilized for the demonstration of variation in enzymes and other proteins encoded by structural loci and applied to the study of the evolution of the boylii species group by estimation of levels of genetic heterozygosity within populations, estimation of degree of genetic similarity between conspecific populations and between species, and determination of patterns of geographic variation in allelic frequencies and levels of heterozygosity. Six distinct chromosomal patterns were observed among the populations of the four species of the boylii species group. All specimens had a diploid number of 48 and the major difference in chromosomal morphology was in the number of pairs of large to medium biarmed autosomes. Little or no chromosomal variation was observed in three species (attwateri, pectoralis and polius), but considerable chromosomal variation occurred among populations of P. boylii. Generally, the chromosomal variation in P. bylii was between allopatric populations, with each chromosomal pattern limited to a recognized subspecies. Polymorphism was observed in two populations. The polymorphism observed in P. polius was the result of pericentric inversion involving the smallest pair of metacentric autosomes. The polymorphism observed in P. bolii cileus was interpreted at the result of gene flow between P. boylii rowleyi and P. boylii spicilegus. In addition to chromosomal evidence, analysis of electrophoretic data demonstrated and suggested effective gene flow between the chromosomal forms of P. boylii. Electrophoretically demonstrable variation was analyzed in 11 proteins encoded by 17 autosomal loci. Of the 17 structural loci, 11 were polymorphic in one or more populations . No more than five loci were observed to be polymorphic within a single population, with a mean number of polymorphic loci of 2.26. The levels of genetic variability, as measured by the proportion of loci in a heterozygous state in the average individual of a population, for populations of the boylii species group were within the range reported for other rodents. Populations of P. attwateri exhibited levels of heterozygosity considerably lower than those reported for other species of Peromyscus. The low level of genetic variability in P. attwateri was probably the result of founder effect of the original population which was isolated on the Edwards Plateau during the late Pleistocene and subsequent genetic drift which allowed fixation of genes within this isolated population. Geographic variation in levels of heterozygosity observed among populations of P. attwateri and P. boylii indicates a north to south cline of increasing heterozygosity with the most variable populations occurring in the southern portion of the range of each species. A wide range of the levels of heterozygosity and genetic similarity was observed among populations of P. pectoralis and is the result of genetic contribution from three Pleistocene refugia. Analysis of paired combinations of populations of P. boyli indicated that the various chromosomal forms of P. boylii. form a conspecific unit. Populations of P. attwateri were genetically distinct from other members of this group. Examination of specific loci for allelic homology suggested that P. attwateri arose from genetic divergence of a population of P. boylii isolated on the Edwards Plateau during the late Pleistocene.

The Quotient Method (QM), a laboratory-based risk assessment methodology used by the Environmental Protection Agency to evaluate pesticides for registration and use, has not been thoroughly field-tested and its performance has not always been reliable. My objective was to determine if variation in vegetation structure or diet of exposed animals could result in adverse ecological effects that were not predicted by the QM. In April and early May 1993, I established populations of herbivorous gray-tailed voles (Microtus canicaudus) and omnivorous deer mice (Peromyscus maniculatus) in 24 0.2-ha enclosures planted with alfalfa (Medicago sativa). Alfalfa in 12 enclosures was mowed on 22 June to reduce vegetation height. Small mammal populations were monitored by live trapping from May through August 1993. On 14 July, an organophosphorus insecticide, azinphos-methyl, was applied at 0, 0.88, and 3.61 kg/ha. Insecticide residues were measured on canopy-level spray cards, soil samples, and alfalfa. I compared the observed residue concentrations with predictions based on the nomogram used to estimate exposure for QM risk assessments. I also compared QM predictions of risk with observed effects on population size and growth, survival, reproductive activity, recruitment, body growth, movements, and diet of the small mammals. Much of the insecticide reached ground level in mowed enclosures, but dense alfalfa intercepted most of the spray in unmowed enclosures. The mean half-life of azinphos-methyl on alfalfa was 3.4 days and was not affected by mowing. Mean residue concentrations on mowed alfalfa and the top 15 cm of unmowed alfalfa were underestimated by the QM exposure nomogram. Therefore, pesticides may pose greater risk to organisms inhabiting sparse vegetation or the tops of plants than predicted by the QM. Treatment with azinphos-methyl at 3.61 kg/ha caused severe effects in both mowed and unmowed enclosures on population size and growth, survival, recruitment, and body growth of voles. Effects of azinphos-methyl on vole recruitment and body growth and on survival of female voles were greater in mowed than in unmowed enclosures. However, I did not find that population-level responses of voles to the chemical differed between mowing treatments. Most effects on voles were of short duration (<27 days) but vole densities in 3.61 kg/ha enclosures remained depressed >6 weeks after spraying. The 3.61 kg/ha application rate resulted in a 42% decrease in deer mouse densities in mowed enclosures during the week of spraying, but the insecticide had no adverse effects on deer mice in unmowed enclosures. In addition, the insecticide may have reduced recruitment of deer mice in mowed enclosures. Analysis of deer mouse feces indicated that consumption of arthropods increased in insecticide-treated enclosures just after spraying occurred. Survival, reproductive activity, body growth, and movements of deer mice were highly variable and not significantly affected by azinphos-methyl. Mowing resulted in greater residue concentrations than predicted and, consequently, the insecticide adversely affected voles and deer mice in mowed enclosures at application rates characterized as low risk by the QM. However, food aversion or selective feeding on alfalfa tops may have resulted in similar exposure of voles to the 3.61 kg/ha treatment in mowed and unmowed enclosures. I did not find that insectivorous feeding behavior of deer mice made them more susceptible than predicted. Although residue concentrations on alfalfa did not follow predictions, the gross pattern of effects on small mammals was consistent with QM risk characterization. However, the QM may underestimate exposure and risk when pesticides are sprayed on sparse vegetation. / Graduation date: 1995

Sexual imprinting, the process of learning mate preferences at a young age, could promote speciation by reducing attraction to individuals from divergent populations or species, consequently creating or maintaining reproductive isolation. Yet, despite the documentation of sexual imprinting in many taxa, its connection to speciation has been understudied. I chose to explore the potential link between sexual imprinting and reproductive isolation and in two North American rodents--the white-footed mouse (Peromyscus leucopus) and its sister species, the cotton mouse (Peromyscus gossypinus). These species have overlapping distributions in nature, possibly allowing interbreeding and admixture. In Chapter 1, I used double-digest restriction-associated DNA sequencing to test for hybridization in sympatric natural populations and found that 1.5% of sampled individuals showed evidence of admixture yet the species have maintained genetic distinctness in sympatry. In the lab, the species hybridize when given no choice of mates but mate more readily with conspecifics, suggesting that mating preferences may prevent hybridization in the wild. In Chapter 2, I tested whether mating preferences create significant reproductive isolation. I measured mating preferences in controlled laboratory conditions and found that both species and sexes preferred conspecific to heterospecific mates in 85% of trials. I then raised offspring with foster parents of the opposite species and found that P. leucopus has a genetically-determined preference while P. gossypinus learns its preference. In Chapter 3, I tested whether sexual imprinting on parental diet could generate assortative mating within a species. I tested this hypothesis by feeding P. gossypinus parents either orange- or garlic-flavored water, thereby exposing their offspring to these flavors through their parents until weaning. I tested the preferences of these offspring as adults and found that P. gossypinus, especially females, had strong assortative mating preferences. This implies that at least females learn parental dietary information and that assortative mating could evolve within a single generation. Together, my results confirm that sexual imprinting on parental traits--possibly mediated through dietary differences--can create assortative mating capable of generating sexual isolation and reducing gene flow between species. My research supports the importance of mating preferences and learning in speciation.