Exploring the `Harperian' paradox: Leaving descendants in a crowded plant world

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Competition between near neighbours is conventionally*regarded as one of the most intense forces of natural selection that has shaped*the evolution and diversity of functional traits in plants. Most of the*traditional theory for evolved strategies of success in plants under resource*limitation (competitive ability) is based on a Size Advantage' hypothesis,*where superiority involves generally greater success in uptake/depletion of*contested resources, typically associated therefore with greater growth*accumulation and larger maximum potential body size (MAX). My recent research*however points to an alternative interpretation involving a Reproductive*Economy Advantage' hypothesis, where reproductive success within severely*crowded neighbourhoods is generally greater, not for species with larger MAX,*but for species with higher fecundity allocation', i.e. production of a larger*number of offspring (sexual or clonal) per*unit parent plant size per unit time. The research proposed here will use greenhouse*studies, field experiments in natural vegetation, and large scale census*surveys of the regional flora in eastern Ontario, Canada to identify the major*components of fecundity allocation and hence capacity for reproductive economy*in flowering plants. Emphasis will be placed on species at risk and vegetation*associated with ecosystem services of marginal lands for agriculture (e.g. old*fields). The main predictions are that high fecundity allocation is promoted by*four potential size metrics: (i) relatively small MIN (minimum threshold*parental body size for producing seed or clonal offspring); (ii) relatively*high above-ground body mass density (dry mass per unit of physical*space occupancy); (iii) relatively small seed size i.e. all*else being equal, a plant that makes smaller seeds, can make more of them per*unit plant body size; and (iv) relatively small leaf size i.e. a*plant that makes smaller leaves can make more leaves for a given body size of*supporting vegetative tissue (a higher leafing intensity'), which enables a*larger axillary bud bank' (per unit body size) available for deployment as*clonal and/or sexual reproductive meristems. Having a larger bud bank, we can predict, also means that more meristems*are available for strategic deployment in the expression of*architectural/growth-form plasticity (e.g. for branching intensity under variable light regimes), or as*a reserve' for survival and compensation following tissue loss to herbivores*or disturbance. These projects, over five years, will involve training for 2 PhD students, 4-5 MSc students, and 10 undergraduate thesis students with an average of 3-4 graduate students and 2 BSc (Hons) thesis students / summer student technicians working in my lab each year.**