Intraspecific divergence and evolution of a life-history trade-off along a successional gradient in Hawaii's Metrosideros polymorpha.

The importance of environmental gradients in the diversification of long-lived tree species is poorly understood. Two morphologically distinct varieties of the endemic Hawaiian tree, 'ohi'a lehua (Metrosideros polymorpha), are the canopy dominants at alternate extremes of a successional gradient formed by the recurring disturbance of lava flows on east Hawai'i Island. The maintenance of these varieties despite hybridization may be due to disruptive selection at either end of the successional gradient. To test this hypothesis, seeds from three, replicate monotypic stands of each variety on east Hawai'i Island were germinated and the resulting seedlings grown under four combinations of light and nitrogen levels in a greenhouse, and at early- and late-successional field sites. Growth and survivorship measures revealed differential fitness of these varieties in high- and low-light environments in the greenhouse with corresponding differential fitness in early- and late-successional field sites. Unique light-by-nitrogen interaction effects on growth were observed in each variety, and only the late-successional variety appeared to be nitrogen limited. These two varieties exhibit the classic plant life-history trade-off between fast growth in high light and high survivorship in shade, but notably within a single tree species. These findings strongly implicate a role for Hawaii's striking environmental heterogeneity in the emergence of at least two endemic forms of this woody genus.

Understanding the context of healthcare utilization: assessing environmental and provider-related variables in the behavioral model of utilization.

OBJECTIVE: The behavioral model of utilization, developed by Andersen, Aday, and others, is one of the most frequently used frameworks for analyzing the factors that are associated with patient utilization of healthcare services. However, the use of the model for examining the context within which utilization occurs-the role of the environment and provider-related factors-has been largely neglected. OBJECTIVE: To conduct a systematic review and analysis to determine if studies of medical care utilization that have used the behavioral model during the last 20 years have included environmental and provider-related variables and the methods used to analyze these variables. We discuss barriers to the use of these contextual variables and potential solutions. DATA SOURCES: The Social Science Citation Index and Science Citation Index. We included all articles from 1975-1995 that cited any of three key articles on the behavioral model, that included all articles that were empirical analyses and studies of formal medical care utilization, and articles that specifically stated their use of the behavioral model (n = 139). STUDY DESIGN: Design was a systematic literature review. DATA ANALYSIS: We used a structured review process to code articles on whether they included contextual variables: (1) environmental variables (characteristics of the healthcare delivery system, external environment, and community-level enabling factors); and (2) provider-related variables (patient factors that may be influenced by providers and provider characteristics that interact with patient characteristics to influence utilization). We also examined the methods used in studies that included contextual variables. PRINCIPAL FINDINGS: Forty-five percent of the studies included environmental variables and 51 percent included provider-related variables. Few studies examined specific measures of the healthcare system or provider characteristics or used methods other than simple regression analysis with hierarchical entry of variables. Only 14 percent of studies analyzed the context of healthcare by including both environmental and provider-related variables as well as using relevant methods. CONCLUSIONS: By assessing whether and how contextual variables are used, we are able to highlight the contributions made by studies using these approaches, to identify variables and methods that have been relatively underused, and to suggest solutions to barriers in using contextual variables.

HIV counseling and testing of pregnant women and women of childbearing age by primary care providers: self-reported beliefs and practices.

This study describes primary care providers' beliefs and self-reported practices regarding HIV counseling and testing of pregnant women and women of childbearing age. The Centers for Disease Control and Prevention (CDC) recommends that providers counsel and encourage all pregnant women and women of childbearing age to be voluntarily tested, and California requires providers to offer voluntary testing to all pregnant women. We randomly sampled 180 primary care providers in 1995 from the nine-county San Francisco Bay area using a self-administered, mailed survey (response rate = 73%, N = 121). Eighty-six percent of primary care providers (obstetricians/gynecologists, internists, family practitioners, or general practitioners) support voluntary testing, 61% support routine testing without explicit consent, and 55% support mandatory testing. Although 90% of providers are very likely to encourage pregnant women with risk factors to be tested, only 34% are very likely to encourage pregnant women without risk factors to be tested and only 9% are very likely to encourage women of childbearing age without risk factors to be tested. Few providers state that they support policies targeting testing to women with risk factors, yet in practice, providers are much more likely to encourage testing for women with risk factors than those without risk factors. We conclude that providers may be missing opportunities to encourage women to be tested, and women may not be receiving adequate information to make an informed testing decision. Future research is needed to determine the viability of voluntary testing and how to remove barriers to its implementation.