DISSERTATION RESEARCH: Coevolution and co-divergence in a classical obligate mutualism between Joshua tree (Yucca brevifolia) and its pollinators (Tegeticula spp.)

协同进化是指捕食者与被捕食者、寄主与寄生虫、植物与传粉者等两个物种之间相互的自然选择和进化变化的关系。生物学家一直认为，共同进化帮助创造了地球上生命的多样性，但这种联系的证据只是间接的。这个项目将直接测试这样一个假设，即约书亚树和它的传粉蛾之间的共同进化导致了这些紧密相互作用的物种一起分化。 约书亚树由两种不同种类的丝兰蛾授粉，每种蛾都发生在宿主植物范围的一个单独部分;而由不同蛾类授粉的约书亚树本身在关键的花卉特征上也不同。为了确定这些平行的差异是否是由于共同进化，研究人员将利用唯一的约书亚树种群，其中两种树木类型和两种传粉者物种混合。研究人员将使用遗传标记来重建该地点约书亚树之间的家庭关系，这一方法与人类的亲子鉴定非常相似。然后，他们将使用这些重建的关系来估计约书亚树的性状在多大程度上是可遗传的，也就是说，一棵树与它的父母有多相似。如果约书亚树与丝兰蛾相互作用的特征在两种树之间表现出比与相互作用无关的特征更大的遗传差异，那么很可能是约书亚树和它的传粉者之间的共同进化造成了这些差异。该项目将涉及四名大学生志愿者助理，包括代表性不足的群体。数据将与莫哈韦国家保护区（MNP）和约书亚树国家公园（JTNP）的科学工作人员共享，这两个公园共同包含了大多数受保护的约书亚树种群。 信息有关约书亚树的相互作用，其传粉者和遗传多样性和结构的约书亚树种群是至关重要的保护这一旗舰物种，这是下越来越多的威胁，从人为的范围碎片化和全球气候变化。研究结果也将作为JTNP协会沙漠研究所系列讲座的一部分向公众展示。

Coevolution is a relationship of reciprocal natural selection and evolutionary change between two species, such as predator and prey, host and parasite, or plant and pollinator. Biologists have long believed that coevolution has helped create much of the diversity of life on Earth, but the evidence for such a connection is only indirect. This project will directly test the hypothesis that coevolution between Joshua tree and its pollinator moths has caused these tightly interacting species to diverge together. Joshua trees are pollinated by two different species of yucca moths, each occurring in a separate part of the host plant's range; and Joshua trees pollinated by different moth species themselves differ in key floral traits. To determine whether these parallel differences are due to coevolution, the investigators will make use of the only population of Joshua trees in which both tree types and both pollinator species are commingled. The investigators will use genetic markers to reconstruct family relationships between Joshua trees at this site, an approach very similar to paternity testing in humans. They will then use these reconstructed relationships to estimate the degree to which Joshua tree traits are heritable, that is, how much a tree resembles its parents. If Joshua tree traits involved in the interaction with yucca moths show greater heritable differences between the two tree types than traits unconnected to the interaction, then it is likely that coevolution between Joshua tree and its pollinators is responsible for those differences.The project will involve four undergraduate volunteer assistants, including underrepresented groups. Data will be shared with scientific staff at Mojave National Preserve (MNP) and Joshua Tree National Park (JTNP), which together contain the majority of protected Joshua tree populations. Information concerning Joshua tree's interactions with its pollinators and the genetic diversity and structure of Joshua tree populations are critical for conservation of this flagship species, which is under increasing threat from anthropogenic range fragmentation and global climate change. Results will also be presented to the public as part of the JTNP Association's Desert Research Institute lecture series.