Browsing by Author "Afkhami, Michelle E."

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    Cheaters must prosper: reconciling theoretical and empirical perspectives on cheating in mutualism
    (John Wiley & Sons, Inc., 2015) Jones, Emily I.; Afkhami, Michelle E.; Akçay, Erol; Bronstein, Judith L.; Bshary, Redouan; Frederickson, Megan E.; Heath, Katy D.; Hoeksema, Jason D.; Ness, Joshua H.; Pankey, M.Sabrina; Porter, Stephanie S.; Sachs, Joel L.; Scharnagl, Klara; Friesen, Ma
    Cheating is a focal concept in the study of mutualism, with the majority of researchers considering cheating to be both prevalent and highly damaging. However, current definitions of cheating do not reliably capture the evolutionary threat that has been a central motivation for the study of cheating. We describe the development of the cheating concept and distill a relative-fitness-based definition of cheating that encapsulates the evolutionary threat posed by cheating, i.e. that cheaters will spread and erode the benefits of mutualism. We then describe experiments required to conclude that cheating is occurring and to quantify fitness conflict more generally. Next, we discuss how our definition and methods can generate comparability and integration of theory and experiments, which are currently divided by their respective prioritisations of fitness consequences and traits. To evaluate the current empirical evidence for cheating, we review the literature on several of the best-studied mutualisms. We find that although there are numerous observations of low-quality partners, there is currently very little support from fitness data that any of these meet our criteria to be considered cheaters. Finally, we highlight future directions for research on conflict in mutualisms, including novel research avenues opened by a relative-fitness-based definition of cheating.
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    Fungal Symbionts as Manipulators of Plant Reproductive Biology
    (The University of Chicago, 2013-04) Gorischek, Alexander M.; Afkhami, Michelle E.; Seifert, Elizabeth K.; Rudgers, Jennifer A.
    Symbioses have shaped the evolution of life, most notably through the fixation of heritable symbionts into organelles. The inheritance of symbionts promotes mutualism and fixation by coupling partner fitness. However, conflicts arise if symbionts are transmitted through only one sex and can shift host resources toward the sex through which they propagate. Such reproductive manipulators have been documented in animals with separate sexes but not in other phyla or sexual systems. Here we investigated whether the investment in male relative to female reproduction differed between hermaphroditic host plants with versus without a maternally inherited fungal symbiont. Plants with the fungus produced more seeds and less pollen than plants lacking the fungus, resulting in an ∼40% shift in functional gender and a switch from male-biased to female-biased sex allocation. Given the ubiquity of endophytes in plants, reproductive manipulators of hermaphrodites may be widespread in nature.