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。关于植物在资源*限制(竞争能力)下的成功进化策略的大多数传统理论都建立在一个大小优势假说的基础上，*其中优势通常涉及在吸收/耗尽有争议的资源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*拥挤的社区内繁殖成功通常更大，不是具有较大MAX的物种*而是具有较高繁殖力分配的物种“，即在单位时间内产生*更多*数量的后代(有性或克隆)/单位亲本植株大小。这里提出的研究将利用温室研究、自然植被的田间试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，从而确定生殖经济能力。重点将放在濒危物种和与用于农业的边际土地(例如旧*田地)的生态系统服务有关的植被上。主要预测是：(I)相对较小的MIN(产生种子或克隆后代的最小阈值*亲本身体大小)；(Ii)相对*较高的地上身体质量密度(单位物理*空间占用的干质量)；(Iii)相对较小的种子大小，即在其他*条件相同的情况下，产生较小种子的植物可以在*单位植物身体大小中产生更多种子；以及(Iv)相对较小的叶片大小，即制造较小叶片的植物可以针对*支持营养组织(更高的叶片强度‘)的给定身体大小制造更多的叶片，这使得*更大的腋芽库’(单位身体大小)可以部署为*克隆和/或有性生殖分生组织。有一个更大的芽库，我们可以预测，也意味着有更多的分生组织*可用于表达*建筑/生长形式的可塑性(例如，在不同的光照条件下的分枝强度)，或者作为*组织丧失到食草动物*或干扰后的生存和补偿的储备。这些项目将在五年内培训2名博士生、4-5名硕士学生和10名本科生论文学生，平均每年有3-4名研究生和2名理科(荣誉)论文学生/暑期学生技术员在我的实验室工作。

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.**