Developmental Modules & Evolvability: The Gastropod Foregut as a Model

发展模块

• 批准号: RGPIN-2015-06484
• 负责人: Page, Louise
• 金额: $ 2.19万
• 依托单位: University of Victoria
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2019
• 资助国家: 加拿大
• 起止时间: 2019-01-01 至 2020-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=683428
• 关键词: Developmental; Modules; Evolvability; Gastropod; Foregut

Why have some groups of organisms diversified explosively since their first appearance, while others have puttered along for millions of years without much change at all? This mystery is a core issue for the emerging field of Evolutionary Developmental Biology, which is dissatisfied with the traditional view that natural selection acting on random, genetically-specified variation among offspring provides the complete story about how species evolve. Although selection is clearly important, evolutionary developmental biologists emphasize that transfer of information from genotype to phenotype occurs via the process of development and developmental organization can influence the amount and kind of variation produced as raw material for selection. The prevailing hypothesis suggests that the greatest amount of `evolvability' will be found among developmental systems organized into semi-autonomous modules that can spin off variant phenotypes without disrupting the developmental integrity of whole complex structures. This hypothesis is conceptually appealing but its validity depends on finding systems in which a link between high rates of evolution and a modular organization of development can be demonstrated.***My students and I have identified a promising model system for investigating the relationship between evolvability and developmental modules. We study the developing foregut in gastropods (snails), which are diverse and abundant within Canada's rich resources in marine biodiversity, although tropical species will also be included in our research. The research will test the following hypotheses: 1) differences in time of development for two foregut modules helped facilitate the evolution of feeding from non-feeding larvae early in the evolutionary history of gastropods, which in turn had a profound effect on extinction and speciation rates, 2) a physical dissociation between two foregut developmental modules has facilitated high capacity for evolvability in a large group of predatory snails, which will be tested by characterizing development in a second group of snails that may have independently evolved this key developmental innovation, and 3) one of the foregut modules may have been co-opted and re-purposed to allow encapsulated embryos to feed on nurse eggs, which may have ultimately allowed encapsulated embryos that have lost free-swimming larvae from their life history to subsequently re-evolve into swimming larvae that feed on microalgae within the water column. This research will provide valuable training opportunities for students in contemporary methods of morphological analysis, while encouraging them to extend the conceptual boundaries of an exciting new view of evolution.**

为什么有些生物体自首次出现以来就发生了爆炸性的多样化，而另一些生物体却缓慢地发展了数百万年而没有发生太大变化？这个谜团是进化发育生物学新兴领域的一个核心问题，该领域对传统观点不满意，即自然选择作用于后代中随机的、基因特定的变异，提供了物种如何进化的完整故事。尽管选择显然很重要，但进化发育生物学家强调，信息从基因型到表型的转移是通过发育过程发生的，发育组织可以影响作为选择原材料产生的变异的数量和种类。普遍的假设表明，最大程度的“进化性”将出现在组织成半自主模块的发育系统中，这些模块可以在不破坏整个复杂结构的发育完整性的情况下产生变异表型。这个假设在概念上很有吸引力，但其有效性取决于找到可以证明高进化率和模块化发展组织之间联系的系统。***我和我的学生已经确定了一个有前途的模型系统，用于研究可进化性之间的关系和发展模块。我们研究腹足动物（蜗牛）发育中的前肠，尽管热带物种也将包括在我们的研究中，但腹足动物在加拿大丰富的海洋生物多样性资源中种类繁多且丰富。该研究将检验以下假设：1）两个前肠模块发育时间的差异有助于促进腹足动物进化史早期非进食幼虫的进食进化，这反过来对灭绝和物种形成率产生深远影响，2）两个前肠发育模块之间的物理分离促进了一大群掠食性蜗牛的高进化能力，这将通过表征发育特征来测试第二组蜗牛可能独立进化出了这一关键的发育创新，并且3）其中一个前肠模块可能已被增选和重新设计，以允许封装的胚胎以保育卵为食，这可能最终允许封装的胚胎生活史中失去了自由游动的幼虫，随后重新进化成以水柱内的微藻为食的游动幼虫。这项研究将为学生提供当代形态分析方法的宝贵培训机会，同时鼓励他们扩展令人兴奋的新进化观的概念界限。 **