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The ecology and evolution of rare, soil specialist Astragalus plants in the arid western U.S.

机译：美国西部干旱地区稀有的土壤专业黄芪植物的生态学和进化

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摘要

Organisms that specialize in uncommon habitats are, by their very nature, inherently uncommon. Specialization has its advantages, namely reduced competition and predation, but it also incurs costs. Specialists often have small population sizes, narrow ranges, and fragmented habitat, all of which engender negative consequences on an evolutionary timescale. Herein, I examine benefits and costs of specialization in selenium-hyperaccumulating plants in the genus Astragalus (Fabaceae). These plants are disproportionately likely to be rare and of conservation concern. Thus, I optimized germination pretreatments for Astragalus species such that seed loss can be minimized during ex situ cultivation, and found that physical scarification is most effective in breaking hard-seed dormancy. Through analysis of soil in seleniferous habitats, I found that soil hydrology can rapidly deplete bioavailable selenium, potentially further reducing the habitat available for accumulators. To better understand the relationship between soil bioavailable selenium and plant performance, I subjected Astragalus species to a gradient of selenium concentrations in the greenhouse. Both non-accumulators and hyperaccumulators had less herbivory with increasing selenium concentrations, and also grew larger, despite the energetic cost of selenium uptake. One potential explanation for their larger growth is that selenium reduced inadvertent drought stress during the experiment, so I tested that hypothesis using a full factorial experiment of drought stress and selenium dosage. Although drought stress reduced lifespan and selenium extended it, there was no evidence that selenium ameliorated drought stress. As a case study of the potential population genetic consequences of specialization, I examined the genetic structure and diversity of two allopatric cryptic sister species of Astragalus. Despite known low pollen and seed dispersal and strong genetic isolation by distance, populations were relatively diverse and not substantially inbred. Additionally, the genetic data did not support a two-species arrangement, so I recommend the species be consolidated, although several populations are somewhat isolated and merit special conservation attention. In summary, hyperaccumulators derive ecological benefits from their specialization that outweigh its metabolic cost, but may suffer low connectivity between populations, if not necessarily inbreeding depression. Conservation efforts should thus focus primarily on minimizing threats to and preserving connectivity of specialist habitats.
机译：从本质上讲，专门针对不常见栖息地的生物本质上并不常见。专业化有其优势，即减少竞争和掠夺，但同时也会增加成本。专家通常人口少，范围窄，栖息地零散，所有这些都会在进化的时间尺度上造成负面影响。在本文中，我研究了黄芪（Fabaceae）属富硒硒植物的专业化的收益和成本。这些植物极少可能是稀有植物，并且具有保护意义。因此，我优化了黄芪物种的萌发预处理，以使异地栽培期间的种子损失最小，并发现物理划痕对打破硬种子休眠最有效。通过对硒化生境中土壤的分析，我发现土壤水文学可以迅速耗尽生物利用硒，有可能进一步减少可用于蓄积的生境。为了更好地了解土壤生物利用硒与植物生长性能之间的关系，我将黄芪物种置于温室中硒浓度梯度上。尽管硒的摄取成本高昂，但非蓄积性和高蓄积性的草食性都随着硒浓度的增加而降低，并且也变得更大。硒增长的一个可能原因是硒在实验过程中减少了无意的干旱胁迫，因此我使用干旱胁迫和硒剂量的全因子实验对这一假设进行了检验。尽管干旱胁迫缩短了寿命，硒延长了其寿命，但没有证据表明硒改善了干旱胁迫。作为对专业化的潜在种群遗传后果的案例研究，我研究了黄芪的两种异源隐性隐性姊妹物种的遗传结构和多样性。尽管已知花粉和种子的低散布性和远距离的遗传隔离性很强，但种群相对多样且基本不自交。此外，遗传数据不支持两个物种的安排，因此我建议对物种进行巩固，尽管几个种群有些孤立并且值得特别注意。总而言之，超级蓄积者从其专业化中获得的生态效益超过了其代谢成本，但种群之间的连通性可能较低，即使不一定是近亲抑郁症。因此，保护​​工作应主要集中于最大程度地减少对专业栖息地的威胁并保持其联系。

著录项

  • 作者

    Statwick, Joseph M.;

  • 作者单位

    University of Denver.;

  • 授予单位 University of Denver.;
  • 学科 Botany.;Conservation biology.;Evolution development.;Ecology.
  • 学位 Ph.D.
  • 年度 2016
  • 页码 140 p.
  • 总页数 140
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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