Mechanisms generating microgeographic clines in shell traits in intertidal snail populations

我的研究计划使用实验，基因组学和建模来检验这一假设，即直接发展的潮间带蜗牛种群内的遗传差异是由捕食者选择的空间变异和从波浪中驱逐的风险来维持的。我的长期领域捕食者入侵实验温哥华岛，加拿大测试的预测，移植掠食性海岸蟹到波浪暴露的地区，他们通常是罕见的，将导致演变的微地理渐变壳厚度在周围的人口的Littorina subrotundata。我模仿了入侵的非土著食肉动物建立一个本地的掠夺性紫色海岸蟹，允许访问猎物在两个波浪暴露的潮间带地区，那里很少有天然捕食者的蜗牛（Littorina）混凝土避难所。我们的拴系实验，以量化选择捕食海岸蟹厚壳甲在L。在我的实验捕食梯度附近的subrotundata允许我们参数化我的数量性状的空间模型。在这个资助周期中，我们将通过在一个共同的环境中培养我们实验种群中的蜗牛来验证我的模型，看看是否发生了厚度增加。然后，我们将参数化我的模型为两个生态型的L。saxatilis目前在西班牙西北部的波浪暴露的岩石海岸，显示出极端的遗传为基础的形态分歧的大小，壳厚度，脊和着色和部分生殖隔离通过大小-繁殖交配。我的博士一名学生开发了一种新的廉价方法，使用下一代测序（NGS）和共享的计算机网络，在个体蜗牛基因组的大小选择样本中同时发现和分型数千个DNA标记（单核苷酸多态性（SNP））。我的本科生已经在L.他们在圭尔夫大学的水族实验室里饲养着这对全同胞家庭。我的学生将寻找复杂性状（壳的大小，形状和质量）和SNP之间的关联。然后，我们将与特定性状相关的SNP映射到L草案上。岩藻基因组我们将使用这些相同的SNP标记，在基因组区域中找到离群位点，有助于两种生态型之间的遗传分化，并确定参与贝壳生物矿化的候选基因。一旦这个生态物种形成的模型系统得到更好的表征，我们将对我们的实验种群L。近圆形的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。我们的工作也有应用，以了解海洋酸化对钙化的无脊椎动物之间的捕食者-猎物相互作用的影响。**

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. **