RUI: Ecology and Evolution of Range Limits in Intertidal Organisms

随着全球气候变化，海洋和陆地分类群的范围界限正在发生巨大变化，但预测范围变化需要对限制分布的因素有机械性的理解。尽管许多无脊椎动物的活动范围迅速变化，但对于潮间带动物来说，活动范围的因果决定因素在很大程度上仍然未知。提高对范围界限的理解对海洋生态学和进化生物学至关重要，对于预测持续气候变化的生态影响也是必要的。智力优势：首席研究员将确定Alderia spp.的范围限制因素，这是理解气候变化影响的极好模型。PI和他的同事们的分子遗传学研究表明，莫德斯塔病毒出现在旧金山(SF)的北部，但一种发育可变的神秘姐妹物种(被描述为A.willowi)出现在旧金山南部。该系统的优点包括：(1)Alderia spp(2)它们的线性范围很容易在空间和时间上刻画，并且在过去50年中发生了变化；(3)姐妹种在SF湾一年中的不同时间持续出现，表明在温度和盐度耐受性方面的权衡决定了它们的生态位；(4)寄主依赖可能影响这些专门的草食动物的范围，正如模型预测的那样；(5)可以使用识别幼虫的遗传方法来量化每个物种对边缘种群的幼虫供应；(6)柳杉在实验室培养中的世代时间为3周，是人工选择实验的理想选择对象。这项研究将集中于三个问题：(A)物理或生物环境的哪些特征将一个物种限制在目前的范围内？现场调查将使成虫和幼虫的丰度与环境参数相关，实验室实验将测试成虫和幼虫的盐度和温度阈值。还将测试依赖寄主的幼虫定居和成虫适合度，以确定Alderia spp.适应了它们寄主藻类的区域菌株。(B)是什么因素驱动了牧场边缘的集合种群动态？边缘栖息地的幼虫供应将使用物种特异性引物和多重PCR来量化，以区分Alderia spp.的幼虫。来自每月的浮游生物拖网。实验室研究将测试Alderia的交配系统是否允许任何一个物种在数量丰富时通过Allee效应抑制其同类物种的定居。(C)是什么阻止适应设定范围限制的环境门槛？人工选择实验将估计(1)柳树边缘种群和中心种群关键性状的现有遗传变异，以及(2)经过36代选择后热盐耐受性、繁殖和生长之间的权衡，这两个问题都是基本的进化重要问题。广泛的影响：本项目将阐明两种常见腹足类活动范围限制的生态学和遗传学基础，为可能在其他潮间带分类群中设定边界的一般机制提供洞察。这些数据对于预测生物对气候变化的反应至关重要。资金将允许年轻的PI建立在先前支持的基础上，将分子和幼虫生态学与生物生物学相结合。学生培训是这项提案的主要内容，它将为CSULA提供新的研究机会，CSULA是一家服务于拉美裔美国人的机构。每年将资助一名本科生和两名硕士学生，可能是少数民族；PI从代表性不足的群体招募，目前5名学生中有3名是拉丁裔。PI出版了本科生和研究生，在过去的两年里，有三个以前的学生进入了博士课程。通过与地区高中教师建立伙伴关系，国际和平协会和所有学生将在生物课上进行研究讲座，带领实地考察，每年1-2名高中高年级学生将在该协会的实验室进行研究项目；这些活动加强了对少数群体的接触，同时教育当地学生人类对沿海环境的影响。

Range limits of marine and terrestrial taxa are shifting dramatically in response to global climate change, but predicting range shifts requires a mechanistic understanding of factors that limit distributions. Causal determinants of range limits remain largely unknown for intertidal animals, despite the fact that many invertebrates have rapidly changing ranges. An improved understanding of range limits is fundamentally important to marine ecology and evolutionary biology, and is necessary to predict the ecological impacts of ongoing climate change.Intellectual merits: The principal investigator will identify range-limiting factors for Alderia spp., intertidal sea slugs that are excellent models for understanding the effects of climate change. A molecular genetic study by the PI and colleagues showed A. modesta occurs north of San Francisco (SF), but a cryptic sister species with variable development (described as A. willowi) occurs south of SF. Advantages to this system include: (1) Alderia spp. are strictly intertidal, with no subtidal refuge from high temperature; (2) their linear ranges are easy to characterize spatially and temporally, and have shifted in the past 50 years; (3) the sister species consistently occur at different times of the year in SF Bay, suggesting that trade-offs in temperature and salinity tolerance define their niches; (4) host-dependency may affect ranges of these specialized herbivores, as predicted by modeling; (5) larval supply to edge populations can be quantified for each species using a genetic method for identifying larvae; and (6) A. willowi has a 3-week generation time in lab culture, making it ideal for artificial selection experiments. The research will focus on 3 questions: (A) What features of the physical or biological environment limit a species to its current range? Field surveys will correlate adult and larval abundance with environmental parameters, and lab experiments will test salinity and temperature thresholds for both adults and larvae. Host-dependent larval settlement and adult fitness will also be tested to determine if Alderia spp. are adapted to regional strains of their host alga. (B) What factors drive metapopulation dynamics at range edges? Larval supply to edge habitats will be quantified using species-specific primers and multiplex PCR to differentiate larvae of Alderia spp. from monthly plankton tows. Lab studies will test whether the mating system of Alderia allows either species, when abundant, to inhibit colonization by its congener via Allee effects. (C) What inhibits adaptation to environmental thresholds that set range limits? Artificial selection experiments will estimate (1) extant genetic variation in edge vs. center populations of A. willowi for key traits, and (2) trade-offs between heat and salinity tolerance, reproduction and growth after 36 generations of selection, both issues of fundamental evolutionary importance.Broader impacts: This project will elucidate the ecological and genetic basis for range limits in two common gastropods, providing insight into general mechanisms that may set borders in other intertidal taxa. Such data are critical for predicting biological response to climate change. Funding will allow a young PI to build on prior support, integrating molecular and larval ecology with organismal biology. Student training is a major thrust of this proposal, which will provide new research opportunities at CSULA, a Hispanic-serving institution. One undergraduate and two masters students will be supported each year, likely ethnic minorities; the PI recruits from under-represented groups, and 3 of 5 current students are Latino. The PI has published with both undergraduate and graduate students, and three former students entered Ph.D. programs in the last 2 years. Through established partnerships with area high school teachers, the PI and all students will give research talks to biology classes, lead field trips, and 1-2 high school seniors per year will perform research projects in the PI's lab; these activities enhance outreach to minority groups while educating local students about human impacts on the coastal environment.