Genetic diversity and species diversity of stream fishes covary across a land-use gradient.

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.

Genetic diversity and structure of an estuarine fish (Fundulus heteroclitus) indigenous to sites associated with a highly contaminated urban harbor.

Intense selection on isolated populations can cause loss of genetic diversity, which if persistent, reduces adaptive potential and increases extinction probability. Phenotypic evidence of inherited tolerance suggests that polychlorinated biphenyls (PCBs), have acted as strong selective agents on populations of a non-migratory fish, Fundulus heteroclitus, indigenous to heavily contaminated sites. To evaluate population genetic structure and test for effects of intense, multi-generational PCB contamination on genetic diversity, we used AFLP analysis on fish collected from six sites along the east coast of North America that varied widely in PCB contamination. The sites included a heavily contaminated urban harbor (New Bedford, MA), an adjacent moderately contaminated sub-estuary (Buzzards Bay, MA), and an uncontaminated estuary 60 km away (Narragansett, RI). AFLP markers distinguished populations at moderate and small scales, suggesting genetic differentiation at distances of 2 km or less. Genetic diversity did not differ across the study sites. Genome-wide diversity may have been preserved because of large effective population sizes and/or because the mechanism for genetic adaptation to these contaminants affected only a small number of loci. Alternatively, loss in diversity may have been restored with moderate levels of migration and relatively short generation time for this species.

Prospective assessment of outcomes improvement following fusion for low back pain.

BACKGROUND: This prospective study was performed to improve the quality of outcomes data in patients undergoing spinal fusion for low back pain. There is an accepted deficiency of this form of outcomes assessment in the literature. The aim was to determine the effectiveness of the surgical procedure in terms of patient satisfaction, outcome scores, and third-party measures. METHODS: The measures of outcomes assessment included patient satisfaction, pain scores, low back outcome and Prolo scores, medication use, and employment status. Data collection was prospective prior to and at final follow-up. Eighty percent of 35 patients were followed for a mean of 31 months. RESULTS: Patient satisfaction was 71%; however, only 28.6% of patients followed achieved good or excellent low back outcome scores. Yet significant improvement occurred: 46.4% achieved a good or excellent outcome using the Prolo score. There was a 75% reduction in medication usage, and 75% of nonworking compensation patients returned to gainful employment. Patient satisfaction was markedly higher than improvement measured by the outcome scores. Dramatic improvements in medication usage and return to work were achieved, despite less than spectacular outcome scores. CONCLUSIONS: These findings support cautious use of posterior spinal fusion. Patients must appreciate improvement rather than normality as a realistic aim.