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

本项目将研究幼虫发育交替类型的遗传基础。许多海洋动物物种有一个自由生活的幼虫阶段，这通常是两个主要类型之一。它们要么是长寿的，在几个月到几年内发育的摄食幼虫，要么是短命的，在几小时到几天内发育的非摄食幼虫。幼虫类型（摄食或非摄食）具有许多重要的生态和进化影响，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。虽然从进食到不进食的幼虫的进化转变经常发生，但我们对这些转变背后的遗传变化知之甚少。该项目将测试幼虫发育类型取决于某些母体效应的假设：卵中的信使RNA（mRNA）。研究人员将从沙元和海饼干物种的卵中收集mRNA测序数据，以确定不同的发育类型是否与不同的母体mRNA相关。此外，该项目还将支持少数民族本科研究人员的培训，并在自然中心设立一个公共展览。对两种密切相关的棘皮动物海饼干的初步研究表明，幼虫的发育模式受到母体因素的强烈驱动。虽然这种母体效应也驱动了其他几个系统中幼虫的发育模式，但这种母体效应的根本原因仍不清楚。该项目将测试新的假设，即母亲对发育的强烈影响是由于母亲沉积mRNA的差异。研究人员将对几个密切相关的物种的未受精卵的母体沉积mRNA进行测序，这些物种包括成对的沙元和海饼干，它们具有交替的幼虫类型。这些数据还将用于创建时间校准的系统发育，以校正系统发育信号。利用这些数据，该项目将确定母体沉积的mRNA在摄食和非摄食棘皮动物幼虫的卵中有何不同，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.