Seed size variation and coexistence: testing a novel hypothesis

种子大小的变化和共存：检验一个新的假设

• 批准号: 1553518
• 负责人: John Maron
• 金额: $ 53.97万
• 依托单位: University of Montana
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-06-01 至 2021-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1553518&HistoricalAwards=false
• 关键词: Seed; size; variation; coexistence; testing

Plant species compete for nutrients, water and light, yet differ in competitive ability. Ecological theory predicts that the superior competitor should drive inferior competitors to local extinction (i.e. the best fighter wins!) Yet, plant communities contain many species with varying competitive abilities, so a central question in ecology is: How do competing species coexist in nature? For example, co-occurring plant species differ dramatically in seed size, and larger seeded species are often better competitors and also sometimes better at tolerating stressful conditions than smaller seeded species. Given these inequalities, how is seed size variation maintained? A leading theory is that small-seeded species have better dispersal abilities than large-seeded species, enabling them to reach local sites where large-seeded species are absent. This theory, however, ignores the fact that large-seeded species often have substantially more of their seeds eaten by rodents than do small-seeded species. Thus, this research will experimentally test the novel idea that large and small-seeded species coexist because rodent seed predators preferentially feed on large seeded species, thereby countering the imbalance in competitive ability among these species based on their seed size. This research will generate a deeper understanding of the mechanisms that promote coexistence and a fuller appreciation for the ecological forces that determine the relative abundance and diversity of species in communities. This work will also be used to increase public understanding of grassland ecology and enhance knowledge of how plant communities are organized, which is essential for effectively managing these habitats. Seed size and number have long been considered central to coexistence strategies, yet empirical evidence showing how these traits are shaped by specific coexistence mechanisms remains scarce. Within sites, seeds of 18 co-occurring forb species (9 small-seeded, 9 large-seeded) will be added to plots with and without resident bunchgrass competitors to test how species vary in competitive tolerance. Across 12 sites that vary in productivity and other abiotic factors, seeds of the same focal species will be added to plots at different densities where competition from resident dominant bunchgrasses and rodent seed predation are manipulated. This will allow an evaluation of how competition, seed predation, and ability to handle stressful abiotic conditions influences recruitment functions of species with different seed sizes. It will also enable an exploration of whether seed size is part of a suite of correlated traits that form "syndromes" that predict demographic performance under distinct biotic and/or abiotic conditions.

植物物种竞争养分、水分和光照，但竞争能力不同。生态学理论预测，上级竞争者应该把低级竞争者赶到局部灭绝（即最好的战士获胜！） 然而，植物群落包含许多具有不同竞争能力的物种，因此生态学的一个中心问题是：竞争物种如何在自然界中共存？ 例如，共生的植物物种在种子大小上差异很大，种子较大的物种往往是更好的竞争者，有时也比种子较小的物种更能耐受压力条件。 鉴于这些不平等，如何保持种子大小的变化？一个主要的理论是，小种子物种比大种子物种有更好的传播能力，使它们能够到达缺乏大种子物种的地方。 然而，这一理论忽略了一个事实，即大种子物种的种子通常比小种子物种被啮齿动物吃掉的种子要多得多。 因此，这项研究将通过实验测试大种子和小种子物种共存的新想法，因为啮齿动物种子捕食者优先喂养大种子物种，从而对抗这些物种之间基于种子大小的竞争能力的不平衡。 这项研究将使人们更深入地了解促进共存的机制，并更充分地了解决定社区物种相对丰富和多样性的生态力量。 这项工作还将用于增加公众对草原生态的了解，并提高对植物群落如何组织的知识，这对有效管理这些生境至关重要。种子的大小和数量一直被认为是共存策略的核心，但经验证据表明，这些特征是如何形成的特定共存机制仍然很少。在网站内，种子的18个共同发生的杂类草物种（9个小种子，9个大种子）将被添加到地块与居民束草竞争对手，以测试如何在竞争耐受性的物种变化。 在12个不同的生产力和其他非生物因素的网站，相同的焦点物种的种子将被添加到不同密度的地块，从居民占主导地位的bunchgrasses和啮齿动物种子捕食的竞争被操纵。这将允许竞争，种子捕食，并处理压力的非生物条件下的能力如何影响招聘功能的不同种子大小的物种进行评估。 它还将使探索种子大小是否是一套相关性状的一部分，这些性状形成“综合征”，预测在不同的生物和/或非生物条件下的人口表现。