Dr. Jim Cushing, University of Arizona
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Abstract: One of life history theory's oldest problems (pondered by the likes of Aristotle and Linneaus) is identifying the reasons why organisms are either semelparous or iteroparous. Semelparity is the life history strategy defined by a single bout of reproduction and is contrasted with iteroparity, defined by repeated bouts of reproduction throughout life. These reproductive strategies are exemplified by annuals and perennials in the plant world, but both parities are found throughout virtually all taxa. Seminal theoretical studies last century suggested semelparity should be favored by evolution, despite the ubiquity of iteroparous species throughout the world. However, subsequent contemporary studies have shown there is no simple answer to this question and that many factors can be in play, including density dependence, variable environmental conditions, and many others. Recent studies have further proposed that reproductive parity should not be binary, but instead should be a continuous variable. In that it involves continuous phenotypic traits subject to Darwinian evolution, the methodology of evolutionary game theoretic modeling is suitable for this approach. In this talk I will discuss Darwinian dynamic versions of some standard discrete time population models and their implications with regard to the evolution of semelparous and iteroparous life history strategies. A particular focus is on the role of density dependent reproduction and survival. The mathematical analysis revolves around equilibrium bifurcations and stability and involves multiple attractor scenarios.