Comparative and Experimental Studies of Morphology and Development

动物形态的巨大多样性是如何产生的，这仍然是一个持久的挑战。两个主要问题仍然困扰着进化生物学家：1)基因和环境的影响在多大程度上促进了自然选择产生新形式生物的新变异？2)这些新形式是以什么顺序在不同动物群体的早期谱系中进化起来的？我们过去的工作已经为“基因作为跟随者”的进化模式提供了强有力的证据，在这种模式中，可观察到的变异首先通过发育中的可塑性形式变化而出现，而影响发育的遗传变异(突变)随后出现。这项工作极大地促进了人们越来越多地认识到，就进化而言，发展可能与遗传学一样是新形式的重要来源。通过实验室和野外实验，以及比较研究，我们将继续探索发育和进化之间的这一关键相互作用。1)使用我们易于研究的藤壶系统--其中腿部形状的巨大差异是可以预测的--我们将：a)测试它们对哪些线索(食物供应或水流的机械作用)做出反应，以及b)梳理导致腿长度和腿节段数量如此大差异的细胞和分子机制。通常，节肢动物的腿节数是固定的，所以藤壶腿的这种巨大变化为研究节肢动物的腿节数如何增加或减少提供了一个极好的工具，节肢动物是地球上最多样化的动物群体。2)我们将测试滤食性瓷蟹的摄食腿形状是否像藤壶腿一样不同。滤食性瓷蟹生活在海浪肆虐的海岸上。这项研究测试了两个共同出现但进化上相距遥远的群体--藤壶和螃蟹--发育可塑性的趋同进化。它还将帮助我们理解筛状进料结构的形式是如何受到流经广泛水速范围的限制的。3)研究蜗牛如何控制贝壳的形成。几个世纪以来，蜗牛壳的巨大美感和多样性一直吸引着生物学家和非生物学家。但令人惊讶的是，人们对蜗牛如何形成特殊的贝壳特征知之甚少。我们将研究两种类型的贝壳雕塑：褶边叶片和螺旋肋骨。通过控制食物供应和过去刀片的位置，我们将测试这些因素如何影响新刀片的放置(内部时钟或外部提示？)。我们还将使用现代显微镜技术来研究产生新壳的地衣组织在同一物种中两种遗传不同的形式(光滑或螺旋肋骨)之间的差异。4)利用化石的新数据，以及对“原始”活动物的仔细解剖学研究，我们将重温生命树的两个令人费解的区域：真正的螃蟹(短尾蟹)和脊椎动物的基枝。在螃蟹中，我们将重点研究眼睛、四肢和腹部的形状。在无颌鱼中，我们将研究头部解剖特征(软骨、肌肉、神经、摄食结构)。5)我们将测试一个关于明显的左右不对称的进化起源的耐人寻味的假说：手的行为是否通过发育可塑性导致肢体形状的不对称？我们将a)在硬壳饲料中培育破壳癌症幼蟹，以研究手的行为和爪子不对称随时间的发展，以及b)测试差异使用是否是导致雄性招潮蟹壮观的大信号爪只在一侧生长的触发因素，以及c)对显示随机和固定不对称的分类群之间的进化关系进行调查。大部分工作将在加拿大顶尖的海洋实地研究设施完成：温哥华岛的班菲尔德海洋科学中心。

How the great diversity of animal forms arose remains an enduring challenge. Two major questions still puzzle evolutionary biologists: 1) To what degree do the effects of genes and environment contribute to the new variation upon which natural selection acts to yield novel forms of organisms? 2) In what order did these novel forms arise evolutionary among early lineages of diverse animal groups? Our past work has yielded strong evidence for a ‘genes as followers’ mode of evolution, where observable variation arises first by developmentally plastic changes in form and where genetic variants (mutations) that influence development arise later. This work has contributed significantly to a growing appreciation that, in terms of evolution, development may be as important a source of novel forms as genetics. Using lab and field experiments, and comparative studies, we will continue to explore this crucial interplay between development and evolution. 1) Using our easily studied barnacle system — where large differences in leg form can be induced predictably — we will: a) test which cues they are responding to (food supply or mechanical action of moving water), and b) tease apart the cellular and molecular mechanisms that give rise to such big differences in leg length and leg segment number. Usually, leg segment number is fixed in arthropods, so this great variation in barnacle legs offers a superb tool for studying how leg segment number may increase — or decrease — in arthropods, the most diverse animal group on Earth. 2) We will test whether feeding leg form in filter-feeding porcelain crabs, which live in huge numbers on wave-swept shores, varies as in barnacle legs. This study tests for convergent evolution of developmental plasticity in two co-occurring yet evolutionarily distant groups — barnacles and crabs. It will also help us understand how the form of sieve-like feeding structures is constrained by flow across a wide range of water velocities. 3) We will study how snails control shell form. The great beauty and diversity of snail shells has intrigued biologists and non-biologists alike for centuries. But surprisingly little is known about how snails grow particular shell features. We will study two types of shell sculpture: frilly blades and spiral ribs. By manipulating food supply and position of past blades we will test how these affect placement of new blades (internal ‘clock’ or external cues?). We will also use modern microscopy techniques to study how mantle tissue, which produces the new shell, differs between two genetically different forms (smooth or spiral ribs) in a polymorphic species. 4) Using new data from fossils, and careful anatomical studies of ‘primitive’ living animals, we will revisit two puzzling regions of the Tree of Life: the basal branches of the true crabs (Brachyura) and the vertebrates. In crabs we will focus on eye, limb and abdomen form. In jawless fishes we will study features of head anatomy (cartilages, muscles, nerves, feeding structures). 5) We will test an intriguing hypothesis about the evolutionary origin of conspicuous right-left asymmetries: does handed behavior induce asymmetries in limb form via developmental plasticity? We will a) grow juvenile shell-breaking Cancer crabs on hard-shelled diets to study the development of handed behavior and claw asymmetry over time, and b) test whether differential use is the trigger that induces the spectacular large signaling claw to grow on only one side in male fiddler crabs, and c) do surveys of evolutionary relations among taxa that show random and fixed asymmetry. Most work will be done at Canada’s top marine field-research facility: Bamfield Marine Sciences Centre, Vancouver Island.