Most empirical and theoretical studies of resource use and population dynamics treat conspecific individuals as ecologically equivalent. This simplification is only justified if interindividual niche variation is rare, weak, or has a trivial effect on ecological processes. This article reviews the incidence, degree, causes, and implications of individual-level niche variation to challenge these simplifications. Evidence for individual specialization is available for 93 species distributed across a broad range of taxonomic groups. Although few studies have quantified the degree to which individuals are specialized relative to their population, between-individual variation can sometimes comprise the majority of the population's niche width. The degree of individual specialization varies widely among species and among populations, reflecting a diverse array of physiological, behavioral, and ecological mechanisms that can generate intrapopulation variation. Finally, individual specialization has potentially important ecological, evolutionary, and conservation implications. Theory suggests that niche variation facilitates frequency-dependent interactions that can profoundly affect the population's stability, the amount of intraspecific competition, fitness-function shapes, and the population's capacity to diversify and speciate rapidly. Our collection of case studies suggests that individual specialization is a widespread but underappreciated phenomenon that poses many important but unanswered questions.

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Since early 1985, blood donations in the United States have been screened for antibody to human immunodeficiency virus (HIV). To identify instances of HIV transmission by antibody-negative donations, we investigated 13 persons seropositive for HIV who had received blood from 7 donors who were screened as negative for HIV antibody at the time of donation. Twelve of the 13 recipients had no identifiable risk factors for HIV infection other than the transfusions they had received. On evaluation 8 to 20 months after transfusion, HIV-related illnesses had developed in three recipients, and the acquired immunodeficiency syndrome had developed in one. All seven donors were found to be infected with HIV. On interview, six reported a risk factor for HIV infection, and five had engaged in high-risk activities or had had an illness suggestive of acute retroviral syndrome within the four months preceding their HIV-seronegative donation. Thus, these donors had apparently been infected only recently, and so were negative at the time of blood donation according to available antibody tests. We conclude that there is a small but identifiable risk of HIV infection for recipients of screened blood. To minimize this risk, the reasons for deferral of donation need to be communicated more effectively to blood donors who are at high risk of HIV infection, and new assays that detect HIV infection earlier should be evaluated for their effectiveness in screening donated blood.

An important question in sea turtle biology is the number of males that contribute to the fertilization of a clutch of eggs. Previous studies on other sea turtle species have indicated little to no multiple paternity. We conclude here that female Kemp's ridleys, Lepidochelys kempi, are polyandrous. DNA from 26 mother and offspring groups was analysed at three microsatellite loci to identify paternal alleles. Three paternal alleles were observed among 14 of the clutches; four paternal alleles were observed among the offspring of an additional female. A maximum likelihood analysis not only rejects the model of single paternity, but also rejects the model of equal paternal contribution to the clutch. By explicitly addressing the high mutation rate of microsatellite markers, our analysis rejected mutation as the sole cause of multiple paternal alleles.

Popular music is pervasive in our culture and in the lives of our students. Its inclusion in music education curricula requires authentic approaches through collaborative informal learning processes. It has been our experience that college students may be notation dependent and while they may recognize and utilize informal processes outside the classroom, they have not pedagogically considered its use in their future classrooms. This article revolves around the experiences of American University students in one secondary general music methods classroom and their engagement of informal learning processes in order to foster a vision and formulate a pedagogical plan for the incorporation of popular music in the classroom. From the instructors' perspective a three-fold process occurred that enabled meaningful engagement in this experience, that of: (1) disequilibrium; (2) breaking down existing barriers; and (3) student transformation. Corporately we discovered the inclusion of popular music unleashed a thriving discourse concerning connection and relevancy to students' lives. Downloaded from Davis and Blair 125 music classrooms and have discovered that when given the opportunity to engage with popular music in school settings, our K-12 (kindergarten to 12th grade) students have demonstrated sophisticated musical understanding that was previously unknown to us.We have found that in spite of their youth and affinity for popular music, pre-service teachers in our classrooms initially seemed skeptical about the appropriateness of its use in school contexts. With the prevalence of popular music in the lives of our students and their students, it seems important for pre-service teachers to have opportunities for meaningful engagement with popular music in order to foster a vision for its authentic use in their future classrooms.In this article, we discuss the evolving experiences of students in one secondary general music methods classroom engaged in informal learning processes in order to better understand the notion of popular music and popular music-making. Narratives shared here were drawn from class discussions, performance experiences, online forum discussions and students' journals. The co-author, as the class instructor, and her pre-service teachers worked together to 'cover' (copy) a popular song, perform it in class, and then dialogue about their experience and the potential for using informal learning processes in a music classroom. Through the process of engaging in performance, listening, analysis of popular music (selected examples) and reading current literature, students verbalized their increasing awareness of using aural processes in a new and rich way and its value in overall musicianship. Central to their experience was the realization of (1) the importance of using music that is 'rooted in students' cultural lives' (excerpt from student journal) as a means of meaningful musical engagement; and (2) that popular music and the authenticity of aural and informal musical processes enables students to exper...