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Combination of seven surveys of blood parasites in North American passerines reveals weak, highly significant association over species between incidence of chronic blood infections (five genera of protozoa and one nematode) and striking display (three characters: male "brightness," female "brightness," and male song). This result conforms to a model of(More)
Sex differences in parasite infection rates, intensities, or population patterns are common in a wide range of taxa. These differences are usually attributed to 1 of 2 causes: (1) ecological (sociological in humans); and (2) physiological, usually hormonal in origin. Examples of the first cause include differential exposure to pathogens because of(More)
Recent interest has focused on immune response in an evolutionary context, with particular attention to disease resistance as a life-history trait, subject to trade-offs against other traits such as reproductive effort. Immune defense has several characteristics that complicate this approach, however; for example, because of the risk of autoimmunity,(More)
Arguments about which constitutes the 'weaker sex' notwithstanding, sex differences in mortality and disease susceptibility have been noted in many species of animals, including humans. In this article, Marlene Zuk examines the possible reasons for these differences, relating them to reproductive strategies, and suggests how they may have resulted from(More)
Same-sex sexual behavior has been extensively documented in non-human animals. Here we review the contexts in which it has been studied, focusing on case studies that have tested both adaptive and non-adaptive explanations for the persistence of same-sex sexual behavior. Researchers have begun to make headway unraveling possible evolutionary origins of(More)
Sexual signals are often critical for mate attraction and reproduction, although their conspicuousness exposes them to parasites and predators. We document the near-disappearance of song, the sexual signal of crickets, and its replacement with a novel silent morph, in a population subject to strong natural selection by a deadly acoustically orienting(More)
We examined barriers to gene flow in a hybrid zone of two subspecies of the song sparrow (Melospiza melodia). We focused on how mating signals and mate choice changed along an environmental gradient and gathered data on the morphology, genetics, ecology, and behavior across the zone. Melospiza m. heermanni of the Pacific slope of California and M. m. fallax(More)
Some populations of the field cricket Teleogryllus oceanicus are parasitized by the phonotactic fly Ormia ochracea. Flies locate crickets by their song and deposit larvae onto them. The larvae develop inside the cricket for 1 week before killing the host upon emergence. The reproductive compensation hypothesis predicts that parasitized crickets should(More)
Arguments about the weaker sex notwithstanding, there is no contest about the identity of the sicker sex—it is males, almost every time. Everyone knows that old age homes have more widows than widowers, but the disparity extends far beyond the elderly. Fewer women than men died in the 1917–1918 influenza epidemic; the differential mortality was not related(More)