DISSERTATION RESEARCH: Local adaptation and fitness trade-offs in the California annual, Leptosiphon parviflorus

适应研究对于理解自然生态系统的生物多样性和农业发展都至关重要。一个常见的观察是，生物的不同特征使它们独特地适合于特定的栖息地。这个过程被称为局部适应，通常被认为是适应性“权衡”的结果，在一种环境中提高表现的特征在另一种环境中会降低表现。目前的研究考察了一对本地适应种群的适应性权衡，一种一年生野花，Leptosiphon parviflorus，生活在两种截然不同的土壤类型，砂岩和蛇形，在加利福尼亚草原。这项研究有几个广泛的影响。首先，了解适应性性状如何促进生物多样性，以及它们是否在替代环境中具有适应性后果，对于预测物种如何应对环境变化非常重要。尽管人们认为植物可能会因气候变化而改变其活动范围，但了解对特定土壤类型（如蛇纹石）的适应如何限制它们的适宜栖息地是很重要的。此外，了解性状如何影响不同环境下的适应性对农业也有意义。育种者需要了解在一种环境中增加作物产量的性状是否会对另一种环境中的产量产生负面影响。通过这项研究将研究的许多生理性状都是重要的农业性状，例如在贫瘠土壤上生存的能力，或在干旱时期生存的能力。增加对这些性状在不同生境中对生长和生存的影响的认识，可能会扩大适合耕种的地区。最后，这个项目的共同负责人通过国家科学基金会的K-12项目在一所农村中学工作，该项目旨在向K-12学生教授科学探究。这个项目的成果将通过课程计划和研讨会介绍给学生和老师。砂岩土壤有足够的营养物质，而蛇纹石土壤中重要的植物营养物质含量低，镁含量高，镁对植物有毒。此外，蛇形土比砂岩土更容易干化。由于这些特点，许多独特的植物生活在蛇形土壤中。虽然目前研究的种群距离很近，但它们的花色和开花时间不同，这表明这些特征可能有助于适应性权衡。本研究调查了这些性状在每种土壤类型中对生长、生存和繁殖的影响，以及为什么在一种土壤类型中适应性的性状在另一种土壤类型中会降低性能。将使用几种方法。首先，在温室里进行一项试验性进化研究，用代表两种亲本基因组混合物的植物在两种土壤上生长。5代后，为了确定温室试验系的选择程度，将它们与一个对照非选择系一起在田间两个生境中生长。如果植物在被选择的土壤中具有较高的适合度，而在外来土壤中的适合度相对于非被选择的品系较低，那么对土壤类型的适应就会导致适合度的权衡。可以测量这些权衡的大小，以确定在本土的健身优势是否与在国外的健身劣势在大小上相似。有趣的是，花的颜色似乎不影响传粉者的访问，这表明它可能通过间接影响耐旱性或养分吸收来促进土壤适应。花的颜色将进一步研究，使用一系列异花授粉产生的植物，这些植物从一个种群中分离出花的颜色，并将其培育到另一个种群的遗传背景中。这使我们能够独立于其他因素来衡量这一特征的影响。蛇形群体中带有粉红色花座的植株将渗入砂岩群体的遗传背景中。在这些植物中，可以测量两种栖息地中颜色的适应性效应，以确定由于这一单一性状而产生的权衡的大小。此外，我们将利用这些品系探讨花色基因影响其他性状的可能性，如水分利用效率和养分吸收，因为它们与土壤耐受性有关，并可能与花色素共享生化途径。

The study of adaptation is central both to understanding the biological diversity of natural ecosystems and to the development of agriculture. A common observation is that organisms differ in traits that make them uniquely suited to live in a particular habitat. This process, called local adaptation, is often thought to result from adaptive "trade-offs", where traits that improve performance in one environment reduce it in another. The current study examines adaptive trade-offs in a pair of locally adapted populations of an annual wildflower, Leptosiphon parviflorus, which lives on two contrasting soil types, sandstone and serpentine, in a California grassland. There are several broad impacts to this research. First, understanding how adaptive traits contribute to biological diversity and whether they have fitness consequences in alternate environments is important for predicting how species will respond to environmental change. Although it is believed that plants may shift their ranges as a result of climate change, it is important to understand how adaptation to a particular soil type, such as serpentine, can limit their suitable habitat. In addition, understanding how traits affect fitness in different environments has implications for agriculture. Breeders need to understand whether traits that increase crop yields in one environment can negatively impact yields in another environment. Many physiological traits that will be studied through this research are important agricultural traits, such as the ability to live on poor quality soils, or to survive periods of drought. Increased knowledge of the consequences of these traits on growth and survival in different habitats may expand suitable areas for farming. Finally, the co-PI for this project works in a rural middle school through the NSF GK-12 program, a program that aims to teach scientific inquiry to K-12 students. Results from this project will be introduced to students and teachers through lesson plans and workshops.Sandstone soils have adequate levels of nutrients, while serpentine soils are low in vital plant nutrients and have high levels of magnesium, which can be toxic to plants. In addition, serpentine soils dry out more easily than sandstone soils. Due to these characteristics, many unique plants live in serpentine soils. Although the populations in the current study are in close proximity, they differ in their flower color and flowering times, indicating that these traits may contribute to adaptive trade-offs. This research investigates the effects that these traits have on growth, survival and reproduction within each soil type, and why traits that are adaptive in one soil type decrease performance in the other. Several methods will be used. First, an experimental evolution study in the greenhouse with plants that represent a genomic mixture of the two parents, will grow lines on both types of soil. After 5 generations, to determine the extent of selection in the greenhouse experimental lines, they will be grown in both habitats in the field along with a control non-selected line. If plants have higher fitness on the soil from which they were selected and reduced fitness on the foreign soil relative to the non-selected line, then adaptation to soil type results in fitness trade-offs. The magnitude of these trade-offs can be measured to determine if fitness advantages on the home soil are similar in magnitude to fitness disadvantages on foreign soil.Interestingly, flower color does not appear to affect pollinator visitation, suggesting that it may contribute to soil adaptation through indirect effects on drought tolerance or nutrient uptake. Flower color will be studied further using plants produced from a series of cross-pollinations that have isolated the flower color from one population and bred it into the genetic background of the other. This allows us to measure effects of this trait independently of others. The plants with the pink flower color locus from the serpentine population will be introgressed into the genetic background of the sandstone population. With these plants, the fitness effects of flower color in both habitats can be measured to determine the magnitude of trade-offs due to this single trait. Furthermore, we will explore the possibility that the flower color gene affects other traits such as water use efficiency and nutrient uptake using these lines, as they are implicated in soil tolerance and potentially share biochemical pathways with floral pigments.