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

近邻之间的竞争通常被认为是自然选择中最强烈的力量之一，它塑造了植物功能特征的进化和多样性。大多数关于资源有限（竞争能力）下植物进化成功策略的传统理论都是基于“尺寸优势”假设，其中优势通常涉及在竞争资源的摄取/消耗方面取得更大的成功，因此通常与更大的生长积累和更大的最大潜在体型（MAX）相关。然而，我最近的研究指出了另一种解释，涉及“生殖经济优势”假说，即在严重拥挤的社区中，繁殖成功率通常更高，而不是具有较大MAX的物种，而是具有较高繁殖力分配的物种，即每单位亲本植物大小在单位时间内产生更多数量的后代（有性或无性系）。本文提出的研究将利用温室研究、自然植被的野外实验和对加拿大安大略省东部地区植物区系的大规模普查来确定开花植物繁殖力分配的主要组成部分，从而确定繁殖经济的能力。重点将放在处于危险中的物种和与边际农业用地（如旧田）生态系统服务有关的植被上。主要的预测是，4个潜在的体型指标促进了高繁殖力分配：(i)相对较小的MIN（产生种子或无性系后代的最小阈值*亲本体型）；（ii）相对*高的地上质量密度（每单位物理空间占用的干质量）；（iii）种子大小相对较小，即在其他条件相同的情况下，一种植物产生较小的种子，每单位植物体大小可以产生更多的种子；（iv）相对较小的叶片大小，即，对于给定的身体大小的支持营养组织（更高的叶片强度），产生较小叶片的植物可以产生更多的叶片，这使得“更大的腋芽库”（单位身体大小）可用于作为无性繁殖和/或有性生殖分生组织展开。我们可以预测，拥有更大的芽库也意味着更多的分生组织可用于表达建筑/生长形式可塑性的战略部署（例如，在可变光照条件下的分支强度），或者作为生存和补偿组织因食草动物或干扰而损失的储备。这些项目为期5年，每年将培养2名博士生、4-5名硕士生、10名本科毕业论文学生，平均每年培养3-4名研究生和2名学士学位毕业论文学生/暑期实习技师

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.**