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是至关重要的。一种常见的观察是，生物的特征不同，使它们独特地适合生活在特定的栖息地。这一过程被称为局部适应，通常被认为是适应性“权衡”的结果，即在一个环境中提高表现的特征会降低另一个环境中的表现。目前的研究考察了一年生野花Leptosiphon parviflorus的两个本地适应种群的适应性权衡。Leptosiphon parviflorus生活在加利福尼亚州草原上两种截然不同的土壤类型-砂岩和蛇纹石上。这项研究有几个广泛的影响。首先，了解适应性特征如何促进生物多样性，以及它们在交替环境中是否具有适应性后果，对于预测物种将如何应对环境变化非常重要。尽管人们认为植物的活动范围可能会因气候变化而改变，但重要的是要了解适应于特定土壤类型(如蛇纹岩)如何限制它们适合的栖息地。此外，了解特征如何影响不同环境中的健康状况，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特性都是重要的农业特性，例如在劣质土壤上生存的能力，或在干旱时期生存的能力。更多地了解这些特征对不同生境生长和生存的影响，可能会扩大适合耕作的区域。最后，该项目的合作PI通过NSF GK-12计划在一所农村中学工作，该计划旨在向K-12学生教授科学探究。这个项目的成果将通过教案和工作坊介绍给学生和老师。砂岩土壤具有足够的养分水平，而蛇纹岩土壤的重要植物养分含量较低，镁含量较高，这可能对植物有害。此外，蛇纹岩土壤比砂岩土壤更容易干燥。由于这些特性，许多独特的植物生活在蛇纹岩土壤中。尽管目前研究中的种群非常接近，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。这项研究调查了这些性状对每种土壤类型内的生长、生存和繁殖的影响，以及为什么在一种土壤类型上适应的性状会在另一种土壤类型上降低表现。将使用几种方法。首先，在温室里进行的一项实验进化研究，植物代表了双亲的基因组混合物，将在两种类型的土壤上生长出品系。经过5代后，为了确定温室试验品系的选择程度，将它们与对照非选育品系一起在田间两种生境中生长。如果植物在被选择的土壤上有更高的适合度，而在外来土壤上的适合度比未被选择的品系低，那么适应土壤类型就会导致适合度的权衡。这些取舍的大小可以用来确定本土土壤上的适合性优势是否与国外土壤上的适合性劣势相似。有趣的是，花的颜色似乎并不影响传粉者的来访，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。将利用一系列异花授粉产生的植物进一步研究花色，这些异花授粉从一个种群中分离出花色，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特征来衡量这一特征的影响。来自蛇纹岩种群的具有粉红色花色基因的植物将被导入到砂岩种群的遗传背景中。对于这些植物，可以测量两种生境中花朵颜色的适合度效应，以确定由于这一单一特征而产生的权衡程度。此外，我们将利用这些品系探索花色基因影响其他性状(如水分利用效率和养分吸收)的可能性，因为它们与土壤耐性有关，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.