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Genetic diversity and species diversity are expected to covary according to area and isolation, but may not always covary with environmental heterogeneity. In this study, we examined how patterns of genetic and species diversity in stream fishes correspond to local and regional environmental conditions. To do so, we compared population size, genetic diversity and divergence in central stonerollers (Campostoma anomalum) to measures of species diversity and turnover in stream fish assemblages among similarly sized watersheds across an agriculture-forest land-use gradient in the Little Miami River basin (Ohio, USA). Significant correlations were found in many, but not all, pair-wise comparisons. Allelic richness and species richness were strongly correlated, for example, but diversity measures based on allele frequencies and assemblage structure were not. In-stream conditions related to agricultural land use were identified as significant predictors of genetic diversity and species diversity. Comparisons to population size indicate, however, that genetic diversity and species diversity are not necessarily independent and that variation also corresponds to watershed location and glaciation history in the drainage basin. Our findings demonstrate that genetic diversity and species diversity can covary in stream fish assemblages, and illustrate the potential importance of scaling observations to capture responses to hierarchical environmental variation. More comparisons according to life history variation could further improve understanding of conditions that give rise to parallel variation in genetic diversity and species diversity, which in turn could improve diagnosis of anthropogenic influences on aquatic ecosystems.

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The disposition of dichloroacetic acid (DCA) was investigated in Fischer 344 rats over the 48 h after oral gavage of 282 mg/kg of 1- or 2-[14C]-DCA (1-DCA or 2-DCA) and 28.2 mg/kg of 2-DCA. DCA was absorbed quickly, and the major route of disposition was through exhalation of carbon dioxide and elimination in the urine. The dispositions of 1- and 2-DCA at 282 mg/kg were similar. With 2-DCA, the disposition differed with dose in that the percentage of the dose expired as carbon dioxide decreased from 34.4% (28.2 mg/kg) to 25.0% (282 mg/kg), while the percentage of the radioactivity excreted in the urine increased from 12.7 to 35.2%. This percentage increase in the urinary excretion was mostly attributable to the presence of unmetabolized DCA, which comprised more than 20% at the higher dose and less than 1% at the lower dose. The major urinary metabolites were glycolic acid, glyoxylic acid, and oxalic acid. DCA and its metabolites accumulated in the tissues and were eliminated slowly. After 48 h, 36.4%, 26.2%, and 20.8% of the dose was retained in the tissues of rats administered 28.2 and 282 mg/kg of 2-DCA and 282 mg/kg of 1-DCA, respectively. Of the organs examined, the liver (4.9-7.9% of dose) and muscle (4.5-9.9%) contained the most radioactivity, followed by skin (3.3-4.5%), blood (1.4-2.6%), and intestines (1.0-1.7%). One metabolite, glyoxylic acid, which is mutagenic, might be responsible for or contribute to the carcinogenicity of DCA.