Evolutionarily stable communities: a framework for understanding the role of trait evolution in the maintenance of diversity.

Biological diversity depends on the interplay between evolutionary diversification and ecological mechanisms allowing species to coexist. Current research increasingly integrates ecology and evolution over a range of timescales, but our common conceptual framework for understanding species coexistence requires better incorporation of evolutionary processes. Here, we focus on the idea of evolutionarily stable communities (ESCs), which are theoretical endpoints of evolution in a community context. We use ESCs as a unifying framework to highlight some important but under-appreciated theoretical results, and we review empirical research relevant to these theoretical predictions. We explain how, in addition to generating diversity, evolution can also limit diversity by reducing the effectiveness of coexistence mechanisms. The coevolving traits of competing species may either diverge or converge, depending on whether the number of species in the community is low (undersaturated) or high (oversaturated) relative to the ESC. Competition in oversaturated communities can lead to extinction or neutrally coexisting, ecologically equivalent species. It is critical to consider trait evolution when investigating fundamental ecological questions like the strength of different coexistence mechanisms, the feasibility of ecologically equivalent species, and the interpretation of different patterns of trait dispersion.

Test-retest reliability of alcohol measures: is there a difference between internet-based assessment and traditional methods?

This study compared Web-based assessment techniques with traditional paper-based methods of commonly used measures of alcohol use. Test-retest reliabilities were obtained, and tests of validity were conducted. A total of 255 participants were randomly assigned to 1 of 3 conditions: paper-based (P&P), Web-based (Web), or Web-based with interruption (Web-I). Follow-up assessments 1 week later indicated reliabilities ranging from .59 to .93 within all measures and across all assessment methods. Significantly high test-retest reliability coefficients support the use of these measures for research and clinical applications. Furthermore, no significant differences were found between assessment techniques, suggesting that Web-based methods are a suitable alternative to more traditional methods. This cost-efficient alternative has the advantage of minimizing data collection and entry errors while increasing survey accessibility.