DISSERTATION RESEARCH: Evolution of hyperaccumulation in wild Helianthus: a phylogenetically explicit assessment of evolutionary history and adaptive hypotheses

超过500种开花植物是金属超氧化物，这意味着它们能够将极高浓度的通常有毒的金属吸收到它们的茎组织中。这种自然能力可以用于有用的技术应用，包括植物修复（使用植物清理污染地区的环境）以及生物强化（富含铁等关键营养素的作物）。拟议研究的广泛目标是了解金属超积累能力的发展如何依赖于金属耐受性，以及超积累能力如何使野生植物受益。超积累对植物的好处包括减少植食性和疾病，提高耐旱性，减少竞争。这项研究将使用向日葵属（向日葵）来测试这些拟议的好处，向日葵是一组在北美栖息地发现的不同物种。向日葵是许多人熟知的农业和园艺上重要的作物物种向日葵，其本身是已知的至少五种不同重金属的超积累植物。除了提高我们对植物生态学的理解外，这项研究还将为向日葵的改良育种和技术应用提供对超积累植物生理学的直接见解。金属耐受性和金属超积累的进化相互作用将使用35种野生向日葵物种进行评估，通过操纵温室研究产生由10个单独处理水平组成的土壤镍梯度，其中耐受性和超积累的进化被分解为单独和不同的特征。假定的成本和效益的超积累将在温室实验中进行检查，将量化健身相关的成本，同时评估五个领先的适应性假设。金属超积累演化的遗传学明确的方法可以显着提高金属超积累的生态和进化背景的理解。更广泛地说，这项研究将促进进化毒理学这一新兴领域的进一步发展，并将实施新的系统发育比较方法来评估环境响应性状，从而改进一系列工具来解决现有和新出现的环境问题。

Over 500 species of flowering plants are metal hyperaccumulators, meaning they possess the ability to take up extremely high concentrations of normally toxic metals into their shoot tissues. This natural ability may be harnessed for useful technological applications, including phytoremediation (the use of plants for environmental cleanup of polluted areas) as well as biofortification (the enrichment of crops with key nutrients like iron). The broad objective of the proposed research is to understand how the development of metal hyperaccumulation ability depends on metal tolerance, and how hyperaccumulation ability may benefit wild plants. Proposed benefits of hyperaccumulation to plants have included reduced herbivory and disease, improved drought tolerance, and reduced competition. This research will test these proposed benefits using the genus Helianthus (the sunflowers), a group of diverse species found in habitats across North America. Sunflowers are known to many for the agriculturally and horticulturally important crop species Helianthus annuus, which is itself a known hyperaccumulator of at least five different heavy metals. In addition to improving our understanding of plant ecology, this research will provide direct insights into hyperaccumulator physiology for the improved breeding and use of sunflower in technological applications.The evolutionary interactions of metal tolerance and metal hyperaccumulation will be assessed using 35 wild Helianthus species, through a manipulative greenhouse study generating a soil nickel gradient consisting of ten separate treatment levels, in which the evolution of tolerance and hyperaccumulation are parsed apart as separate and distinct traits. The putative costs and benefits of hyperaccumulation will be examined in greenhouse experiments which will quantify fitness-related costs while simultaneously evaluating five leading adaptive hypotheses. A phylogenetically explicit approach to the study of metal hyperaccumulation evolution can dramatically improve the understanding of the ecological and evolutionary context of metal hyperaccumulation. More broadly, this research will promote further development of the newly emerging field of evolutionary toxicology and will implement novel phylogenetic comparative methods for assessing environmentally responsive traits, allowing for an improved range of tools to address existing and emerging environmental concerns.