DISSERTATION RESEARCH: The evolution of major life-history transitions: a transcriptomic analysis of developmental shifts in echinoids

这个项目将调查交替类型幼虫发育的遗传基础。许多海洋动物物种都有自由生活的幼虫阶段，这通常是两种主要类型之一。它们要么是长寿命、取食的幼虫，在几个月到几年的过程中发育，要么是短寿命、不取食的幼虫，在几个小时到几天的时间里发育。幼虫类型(取食或不取食)具有许多重要的生态和进化分支，因为它影响物种范围的大小、种群之间的联系以及物种形成和灭绝的可能性。虽然从取食幼虫到非取食幼虫的进化转变频繁发生，但我们对这些转变背后的遗传变化知之甚少。该项目将检验幼虫发育类型取决于某些母体效应的假设：卵子中的信使RNA(信使RNA)。研究人员将收集沙子、金枪鱼和海饼干种类的蛋的mRNA测序数据，以确定不同的发育类型是否与不同的母体mRNA有关。此外，该项目还将支持少数民族本科生研究人员的培训和在自然中心创建公共展览。对两种关系密切的棘皮动物海饼干的初步研究表明，幼虫的发育模式强烈受母体因素的推动。虽然这种母性效应也在其他几个系统中驱动了幼虫的发育模式，但这种母性效应的根本原因尚不清楚。这个项目将检验这一新的假设，即母亲对发育的强烈影响是由于母亲储存的mRNA的差异。研究人员将对几个亲缘关系密切的物种的未受精卵中储存的mrna进行测序，这些物种包括沙鱼和海饼干，它们的幼虫类型互不相同。这些数据还将被用来创建时间校准的系统发育图，以校正系统发育信号。利用这些数据，该项目将确定喂食和不喂食棘皮动物幼虫的卵中母体沉积的mRNA有何不同，以及这些差异如何影响替代发育途径的进化。

This project will investigate the genetic basis of alternate types of larval development. Many ocean-dwelling animal species have a free-living larval stage, which is generally one of two major types. They are either long-lived, feeding larvae that develop over the course of months to years, or short-lived, non-feeding larvae that develop in a matter of hours to days. Larval type (feeding or non-feeding) has many important ecological and evolutionary ramifications, as it influences the size of species' ranges, connections between populations, and the potential for speciation and extinction. Although evolutionary transitions from feeding to non-feeding larvae occur frequently, we know little about the genetic changes that underlie these transitions. This project will test the hypothesis that larval development type depends upon certain maternal effects: messenger RNA (mRNA) in the eggs. The researchers will collect mRNA sequencing data from eggs of sand dollar and sea biscuit species to determine if differing developmental types are associated with different maternal mRNA. In addition, the project will support the training of minority undergraduate researchers and the creation of a public exhibit at a nature center.Preliminary research on two closely related species of echinoderm sea biscuits, which exhibit different larval developmental modes, demonstrated that larval developmental patterns are strongly driven by maternal factors. Although such maternal effects also drive the developmental patterns of larvae in several other systems, the underlying cause of this maternal effect remains unclear. This project will test the novel hypothesis that the strong maternal effect on development is due to differences in maternally deposited mRNA. The researchers will sequence the maternally deposited mRNA from unfertilized eggs of several closely related species pairs of sand dollars and sea biscuits that have alternate larval types. These data will also be used to create a time-calibrated phylogeny to correct for phylogenetic signal. Using these data, the project will determine how maternally deposited mRNA differs in eggs of feeding and non-feeding echinoderm larvae, and how those differences influence the evolution of alternate developmental pathways.