Predictable Patterns Of Disruptive Selection In Stickleback In Postglacial Lakes

Disruptive selection is often assumed to be relatively rare, because it is dynamically unstable and hence should be transient. However, frequency-dependent interactions such as intraspecific competition may stabilize fitness minima and make disruptive selection more common. Such selection helps explain the maintenance of genetic variation and may even contribute to sympatric speciation. There is thus great interest in determining when and where disruptive selection is most likely. Here, we show that there is a general trend toward weak disruptive selection on trophic morphology in three-spine stickleback (Gasterosteus aculeatus) in 14 lakes on Vancouver Island. Selection is inferred from the observation that, within a lake, fish with intermediate gill raker morphology exhibited slower growth than phenotypically extreme individuals. Such selection has previously been shown to arise from intraspecific competition for alternate resources. However, not all environments are equally conducive to disruptive selection, which was strongest in intermediate-sized lakes where both littoral and pelagic prey are roughly balanced. Also, consistent with theory, we find that sexual dimorphism in trophic traits tends to mitigate disruptive selection. These results suggest that it may be possible to anticipate the kinds of environments and populations most likely to experience disruptive selection.Integrative Biolog

Assortative Mating By Diet In A Phenotypically Unimodal But Ecologically Variable Population Of Stickleback

Speciation with gene flow may be driven by a combination of positive assortative mating and disruptive selection, particularly if selection and assortative mating act on the same trait, eliminating recombination between ecotype and mating type. Phenotypically unimodal populations of threespine stickleback (Gasterosteus aculeatus) are commonly subject to disruptive selection due to competition for alternate prey. Here we present evidence that stickleback also exhibit assortative mating by diet. Among-individual diet variation leads to variation in stable isotopes, which reflect prey use. We find a significant correlation between the isotopes of males and eggs within their nests. Because egg isotopes are derived from females, this correlation reflects assortative mating between males and females by diet. In concert with disruptive selection, this assortative mating should facilitate divergence. However, the stickleback population remains phenotypically unimodal, highlighting the fact that assortative mating and disruptive selection do not guarantee evolutionary divergence and speciation.Integrative Biolog

Sefela sa letsamayanaha - the wartime experiences of Potlako Kitchener Leballo

Paper presented at the Wits History Workshop: Structure and Experience in the Making of Apartheid, 6-10 February, 1990

Double-Cross: Potiako Leballo and the 1946 riots at Lovedale Missionary Institution

African Studies Seminar series. Paper presented 19 February, 199

Opsin expression predicts male nuptial color in threespine stickleback.

Theoretical models of sexual selection suggest that male courtship signals can evolve through the build-up of genetic correlations between the male signal and female preference. When preference is mediated via increased sensitivity of the signal characteristics, correlations between male signal and perception/sensitivity are expected. When signal expression is limited to males, we would expect to find signal-sensitivity correlations in males. Here, we document such a correlation within a breeding population of threespine stickleback mediated by differences in opsin expression. Males with redder nuptial coloration express more long-wavelength-sensitive (LWS) opsin, making them more sensitive to orange and red. This correlation is not an artifact of shared tuning to the optical microhabitat. Such correlations are an essential feature of many models of sexual selection, and our results highlight the potential importance of opsin expression variation as a substrate for signal-preference evolution. Finally, these results suggest a potential sensory mechanism that could drive negative frequency-dependent selection via male-male competition and thus maintain variation in male nuptial color

Comparative Harambee: history and theory of voluntary collective behaviour

This paper explores some case studies of Harambee activity in pre-Independence America (pre-1776) to illustrate some interesting parallels with Kenyan self-help. An attempt is then made to distill from the examples a socio-economic theory of the basis for voluntary provision of collective consumption goods, contrasting greatly with traditional theories of "free rider" motivation. Finally conclusions are drawn concerning the nature of Harambee in Kenya and possibilities for more rational channelling of Harambee energies. This paper was originally prepared for the East African Universities Social Science Council Conference, Dar es Salaam, December 1973

Combating Racial Health Disparities through Medical Education: The Need for Anthropological and Genetic Perspectives in Medical Training

Despite major public health initiatives, significant disparities persist among racially and ethnically defined groups in the prevalence of disease, access to medical care, quality of medical care, and health outcomes for common causes of morbidity and mortality in the United States. It is critical that we develop new and creative strategies to address such inequities; mitigate the social, environmental, institutional, and genetic determinants of poor health; and combat the persistence of racial profiling in clinical contexts that further exacerbates racial/ethnic health disparities. This article argues that medical education is a prime target for intervention and that anthropologists and human population geneticists should play a role in efforts to reform US medical curricula. Medical education would benefit greatly by incorporat- ing anthropological and genetic perspectives on the complexities of race, human genetic variation, epigenetics, and the causes of racial/ethnic disparities. Medical students and practicing physicians should also receive training on how to use this knowledge to improve clinical practice, diagnosis, and treatment for racially diverse populations

Non-random gene flow: An underappreciated force in evolution and ecology

Dispersal is an important life-history trait involved in species persistence, evolution, and diversification, yet is one of the least understood concepts in ecology and evolutionary biology. There is a growing realization that dispersal might not involve the random sample of genotypes as is typically assumed, but instead can be enriched for certain genotypes. Here, we review and compare various sources of such non-random gene flow, and summarize its effects on local adaptation and resource use, metapopulation dynamics, adaptation to climate change, biological invasion, and speciation. Given the possible ubiquity and impacts of non-random gene flow, there is an urgent need for the fields of evolution and ecology to test for non-random gene flow and to more fully incorporate its effects into theory. © 2012 Elsevier Ltd.Peer Reviewe