Relationship Between Variation and Evolution in Fossil Stickleback Fish

早就知道，相关种群或物种内部和之间的表型变异模式是相似的。这一观察有时被解释为意味着进化变化偏向于最大变异的方向。另一种解释是，有利于某一方向进化的相同因素也塑造了种群内的变异模式。关于群体内最大加性遗传方差的多变量方向Gmax和它们之间的多变量进化方向Z如何走向同一方向的问题，一直没有令人满意的答案。这个问题一直困扰着从数量遗传学到古生物学的各个领域的工作者。这项拟议的研究将利用化石记录中的时间元素来帮助解决这个棘手的问题。这项研究的基础是一种特殊的三刺鱼化石沉积，它来自中新世晚期，Truckee组的中段位于内华达州中西部。大量保存完好的标本在采石场的大小、盔甲和鳍射线数上显示出惊人的地层变化模式，该采石场已被首席调查员在之前的几项研究中使用。这种沉积物本身具有特殊的性质，为数千年来以固定的时间间隔制作大容量刺鱼样本提供了理想的条件。这些特性中最不重要的是存在不间断的年度层片(Varie)。此外，古生态证据和与现存三刺鱼的类比表明，化石序列中的样本代表了具有祖先-后代关系(即谱系)的种群。这正是检验种群内变异和进化方向之间的联系所需要的。从这一化石谱系获得的形态测量数据将被用来检验化石样本内最大表型变异的多变量方向P和连续样本之间的多变量进化方向Z之间的关系。P和Z的方向将使用间隔1000年的11到24个大样本的形态测量数据来估计。将比较P和Z之间的洛杉矶，看一个样本中的P是否倾向于偏离它和下一个样本之间的进化方向(Z)，或者P是否倾向于在它和前一个样本之间摆动以匹配Z的方向。这两种影响都可能发生。化石谱系的使用将允许对经常观察到的种群内和种群间变异方向相似的原因进行批判性分析。这项拟议的研究将是利用化石记录提供的关键时间元素进行的第一次此类分析。这项拟议的研究不仅将是第一次这样的分析，而且还将有助于形态计量学的方法学发展和关于刺鱼进化的越来越多的文献。

9870337BellIt has long been known that patterns of phenotypic variation within and among related populations or species are similar. This observation has sometimes been interpreted to mean that evolutionary change is biased toward the direction of greatest variation. An alternative explanation is that the same factors that favor evolution in a certain direction also shape patterns of variation within populations. There has never been a satisfactory answer to the question of how Gmax, the multivariate direction of greatest additive genetic variance within populations, and Z, the direction of multivariate evolution between them, become oriented in the same direction.This problem has puzzled workers in fields ranging from quantitative genetics to paleontology since. The proposed research will exploit the element of time in the fossil record to help resolve this stubborn problem. The basis for this study is an extraordinary deposit of fossil threespine stickleback fish, Gasterosteus doryssus, from the late middle Miocene, middle member of the Truckee Formation is west-central Nevada. Abundant, beautifully-preserved specimens exhibit striking patterns of stratigraphic variation for size, armor, and fin ray number in a quarry that has been used in several previous studies by the Principal Investigator. The deposit itself has special properties that offer ideal conditions to make large stickleback samples at regular time intervals over thousands of years. Not the least important of these properties is the presence of uninterrupted annual laminations (varves). Furthermore, paleoecological evidence and analogy with extant threespine stickleback show that samples from the fossil sequence represent populations with ancestor-descendant relationships (i.e., a lineage). This is exactly what is needed to examine the link between variation within populations and the direction of evolution.Morphometric data obtained from this fossil lineage will be used to examine the relationship between the multivariate direction of greatest phenotypic variance within fossil samples, P, and the direction of multivariate evolution, Z, between successive samples. The directions of P and Z will be estimated using the morphometric data from 11 to 24 large samples spaced at 1000-year intervals. Angeles between P and Z will be compared to see if P within a sample tends to bias the direction of evolution (Z) between it and the next sample, or whether P tends to swing around to match the direction of Z between it and the previous sample. Both effects may occur.Use of a fossil lineage will allow a critical analysis of the cause for the often-observed similarity between the direction of variation within and among populations. The proposed research will be the first such analysis that utilizes the crucial element of time provided by the fossil record. Not only will the proposed research be the first such analysis, but it will also contribute to methodological developments in morphometrics and the growing literature on stickleback evolution.