Mechanisms generating microgeographic clines in shell traits in intertidal snail populations

潮间带蜗牛群体壳性状微地理特征的产生机制

• 批准号: RGPIN-2015-05468
• 负责人: Boulding, Elizabeth
• 金额: $ 1.53万
• 依托单位: University of Guelph
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2019
• 资助国家: 加拿大
• 起止时间: 2019-01-01 至 2020-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=678473
• 关键词: Mechanisms; generating; microgeographic; clines; shell

My research program uses experiments, genomics, and modelling to test the hypothesis that genetic divergence within populations of direct-developing intertidal snails is maintained by spatial variation in selection by predators and by the risk of dislodgement from waves. My long-term field predator invasion experiments on Vancouver Island, Canada test the prediction that transplanting predatory shore crabs into wave-exposed areas where they are normally rare will cause evolution of a microgeographic cline in shell thickness in the surrounding populations of Littorina subrotundata. I mimicked an invasion of non-indigenous predators by building concrete refuges for a native predatory purple shore crab that allows access to prey in two wave-exposed intertidal areas where there are few natural predators on snails (Littorina). Our tethering experiments to quantify selection by predatory shore crabs for thicker shell armour in L. subrotundata near my experimental predation gradient allow us to parameterize my spatial model of a quantitative trait. During this grant cycle we will validate my model by culturing snails from our experimental populations in a common environment to see if increases in thickness have occurred. We will then parameterize my model for two ecotypes of L. saxatilis present on wave-exposed rocky shores in NW Spain that show extreme genetically-based morphological divergence for size, shell thickness, ridging and colouration and partial reproductive isolation through size-assortative mating. My Ph.D. student has developed a new inexpensive method using Next Generation Sequencing (NGS) and a shared computer network to simultaneously find and genotype thousands of DNA markers (Single Nucleotide Polymorphisms (SNPs)) in a size-selected sample of individual snail genomes. My undergraduate students have created backcrosses between the upper- and lower-shore ecotypes of L. saxatilis and are rearing the full-sibling families in the University of Guelph's AquaLab. My students will look for associations between complex traits (shell size, shape, and mass) and SNPs. We will then map the SNPs associated with a particular trait onto the draft L. saxatilis genome. We will use these same SNP markers to find outlier loci in genomic regions contributing to genetic differentiation between the two ecotypes and identify candidate genes involved in biomineralization of shell armour. Once this model system for ecological speciation is better characterized, we will use the same NGS methodology on our experimental populations of L. subrotundata. Our work contributes to predicting the effects of increased rates of predator invasions attributable to climate change. Our work also has applications to understanding the effects of ocean acidification on predator-prey interactions between calcified invertebrates. **

我的研究项目使用实验、基因组学和建模来检验这样的假设：直接发育的潮间带蜗牛种群内的遗传分化是通过捕食者选择的空间变化和从波浪中移出的风险来维持的。我在加拿大温哥华岛进行的长期野外捕食者入侵实验验证了这样的预测：将捕食性岸蟹移植到通常很少见的暴露于波浪的区域将导致周围的 Littorina subrotundata 种群的壳厚度发生微地理梯度的演化。我模仿了非本地捕食者的入侵，为本地捕食性紫色岸蟹建造了混凝土避难所，让它们能够在两个暴露在波浪中的潮间带区域捕食，那里的蜗牛（Littorina）几乎没有天敌。我们的系绳实验量化了捕食性岸蟹对靠近我的实验捕食梯度的 L. subrotundata 中较厚壳甲的选择，使我们能够参数化我的数量性状的空间模型。在这个资助周期中，我们将通过在公共环境中培养我们的实验群体中的蜗牛来验证我的模型，看看厚度是否发生增加。然后，我们将对西班牙西北部暴露在波浪中的岩石海岸上的两种 L. saxatilis 生态型的模型进行参数化，这些生态型在大小、壳厚度、起皱和颜色以及通过大小选配交配的部分生殖隔离方面表现出基于遗传的极端形态差异。我的博士学位学生开发了一种新的廉价方法，使用下一代测序 (NGS) 和共享计算机网络，在单个蜗牛基因组的大小选择样本中同时查找和基因分型数千个 DNA 标记（单核苷酸多态性 (SNP)）。我的本科生已经在上岸和下游生态型的 L. saxatilis 之间进行回交，并在圭尔夫大学的 AquaLab 中培育全兄弟家族。我的学生将寻找复杂性状（壳大小、形状和质量）与 SNP 之间的关联。然后，我们将与特定性状相关的 SNP 映射到 L. saxatilis 基因组草案上。我们将使用这些相同的 SNP 标记来查找基因组区域中导致两种生态型之间遗传分化的异常位点，并识别参与甲壳生物矿化的候选基因。一旦这个生态物种形成模型系统得到更好的表征，我们将在 L. subrotundata 实验种群上使用相同的 NGS 方法。我们的工作有助于预测气候变化导致的捕食者入侵率增加的影响。我们的工作还适用于了解海洋酸化对钙化无脊椎动物之间捕食者-猎物相互作用的影响。 **