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David J. Hosken – One of the best experts on this subject based on the ideXlab platform.

  • Complex interactions between sperm Viability and female fertility
    Scientific Reports, 2019
    Co-Authors: Maximiliano Tourmente, C. Ruth Archer, David J. Hosken

    Sperm Viability is a major male fitness component, with higher sperm Viability associated with enhanced sperm competitiveness. While many studies have focussed on sperm Viability from the male fitness standpoint, its impact on female fitness is less clear. Here we used a panel of 32 isogenic Drosophila simulans lines to test for genetic variation in sperm Viability (percentage of viable cells). We then tested whether sperm Viability affected female fitness by mating females to males from low or high sperm Viability genotypes. We found significant variation in sperm Viability among genotypes, and consistent with this, sperm Viability was highly repeatable within genotypes. Additionally, females mated to high sperm Viability males laid more eggs in the first seven hours after mating, and produced more offspring in total. However, the early increase in oviposition did not result in more offspring in the 8 hours following mating, suggesting that mating with high sperm-Viability genotypes leads to egg wastage for females shortly after copulation. Although mating with high sperm-Viability males resulted in higher female fitness in the long term, high quality ejaculates would result in a short-term female fitness penalty, or at least lower realised fitness, potentially generating sexual conflict over optimal sperm Viability.

Mark L Shaffer – One of the best experts on this subject based on the ideXlab platform.

  • population Viability analysis
    Conservation Biology, 1990
    Co-Authors: Mark L Shaffer

    A central theme of conservation biology is understanding the extinction process and thereby elucidating the requirements for species persistence. Gilpin and Soule (1986) have outlined the conceptual framework of this central theme and christened it population Viability analysis (PVA). As they envision it, PVA is a structured, systematic, and comprehensive examination of the interacting factors that place a population or species at risk. Because we lack perfect knowledge of any species and of the myriad factors that can affect each of them, PVA is inherently speculative; it is predictive only in the probabilistic sense. Ginzburg et al. (1982) were the first to recognize that assessments of population Viability are really a form of risk analysis applied to issues of species conservation. Like the more usual forms of risk analysis applied to issues of public health and safety, PVA attempts to assess the likelihood of future events based on currently available data and theory, both of which contain some degree of uncertainty. In the case of PVA, the event of interest is the extinction of a particular wild plant or animal population by some specified time in the future under various scenarios of management. Employing a risk analysis approach to determining the likelihood of extinction of wild populations recognizes that management can never assure (i.e., probability = 1.0) the survival of any population. This approach also recognizes, and therefore can allow management to compensate for, those chance events that can determine the survival or extinction of wild populations. PVA is a new, emerging technique dealing with complex problems for which empirical, experimental, and theoretical knowledge is never complete. Consequently, PVA does not yet have a well-developed methodology or widely accepted standards. Nevertheless,

Mark S Boyce – One of the best experts on this subject based on the ideXlab platform.

  • population Viability analysis
    Annual Review of Ecology Evolution and Systematics, 1992
    Co-Authors: Mark S Boyce

    Population Viability analysis (PVA) is a process. It entails evaluation of data and models for a population to anticipate the likelihood that a population will persist for some arbitrarily chosen time into the future (125, 128). A closely related concept is minimum viable population (MVP) analysis. An MVP is an estimate of the minimum number of organisms of a particular species that constitutes a viable population. Reference is also made to population vulnerability analysis which is a negative appellation for PVA. PVA embraces MVP, but without seeking to estimate the absolute minimum population necessary to keep a species viable (136). In the United States, the US Forest Service has a mandate to preserve viable populations on its lands under the National Forest Management Act (158). Likewise, the US Fish and Wildlife Service and the National Marine Fisheries Service have been evaluating PVAs for many species or populations proposed for listing under the Endangered Species Act (152). Establishing criteria for what constitutes a viable population is no longer strictly an academic pursuit. PVAs have been attempted for at least 35 species; perhaps the most celebrated are those for the grizzly bear (Ursus arctos horribilis) (126, 129, 144), and the northern spotted owl (Strix occidentalis caurina) (18, 79, 95, 98a). Most PVAs are simulation studies that remain unpublished, or when published, they may only include outlines of model structure (95, 126, 131). Others invoke analytical methods or “rules of thumb,” always burdened with severe assumptions (31, 152). PVAs vary according to the ecology of the species, the expertise of the modelers, and the extent of available data.