Collaborative Research: Hidden Dimensions of Diversity in Woodland Salamanders: Investigating Ecophysiological Evolution in a Classic Non-Adaptive Radiation

生物学中最持久的模式之一是物种丰富度在生命之树上的分布是不均匀的：尽管有些谱系在产生新物种方面异常多产，但其他谱系却物种贫乏，即使在漫长的进化时间跨度中也是如此。人们普遍认为，为了物种丰富，一个谱系也必须具有生态多样性。然而，情况并非总是如此。这一建议的重点是林地蝾螈（Plethodon属），一个高度多样化的两栖动物谱系在北美东部的阿巴拉契亚地区。这个谱系以物种丰富度高而闻名，尽管生态多样性很小。尽管如此，对多齿兽辐射的研究主要是从单一的生态位轴——结构栖息地的使用和相应的形态轴——开始的。同样重要，但在很大程度上被忽视的是，热和水文栖息地的利用，以及与气候因素的相互作用如何产生生物多样性。作为没有肺的蝾螈，这些生物与它们的热环境和水环境进行着微妙的舞蹈，以确保皮肤呼吸。这个奖项的中心是发现生理多样性是如何在整个谱系中构建的，以及生理进化是如何促进平齿兽的高度物种多样性的。这个奖项很重要，因为它将促进我们对生物多样性起源的理解。具体来说，研究人员将沿着几个生态轴揭示多样性（或缺乏多样性）如何塑造物种丰富度的大范围模式。该奖项也很重要，因为它将提供有关蝾螈对持续环境变化脆弱性的详细和最新信息。该项目将为本科生和高中生提供培训机会。理论认为，生物多样性的差异反映了世系之间的生态差异。在一个极端，适应性辐射的特点是迅速和丰富的多样化到众多的生态位，在另一端，低生态多样性的谱系也往往只有很少的物种。所谓的“非适应性”辐射占据了一个神秘的中间地带，其特征是物种丰富度高，但生态多样性低。也许这些辐射中最著名的是多齿螈（无肺）。这个谱系以长期形态停滞而闻名，这表明多样化是由中性过程驱动的。利用一系列的系统发育因果模型，研究人员将探索生理多样性的进化模式，并确定其因果机制。然后，使用进化速率矩阵，研究人员将比较形态和生理进化的速率和模式。然后，研究人员将探索物种分布的生理相关性，以探索为什么阿巴拉契亚地区的无肺两栖动物物种如此丰富。最后，利用一系列新的机制模型，研究人员将探索下个世纪蝾螈的分布将如何改变。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

One of the most persistent patterns in biology is that species richness is unequally distributed across the tree of life: whereas some lineages are exceptionally prolific in generating new species, others are species-poor, even over long evolutionary timespans. It is generally thought that, in order to be species-rich, a lineage must also be ecologically diverse. Yet, this is not always the case. This proposal focuses on woodland salamanders (genus Plethodon), a highly diverse amphibian lineage in the Appalachian region of eastern North America. This lineage is renowned for high species richness despite little ecological diversity. Nonetheless, the story of the Plethodon radiation has largely been studied from a single niche axis – that of structural habitat use and corresponding morphology. Just as important, but largely ignored, is thermal and hydric habitat use, and how interactions with climatic factors may generate biodiversity. As lungless salamanders, these organisms perform a delicate dance with their thermal and hydric environments to ensure cutaneous respiration. This award centers around discovering how physiological diversity is structured across the lineage, and how physiological evolution contributes to the high species diversity of Plethodon. This award is important because it will advance our understanding of how biodiversity originates. Specifically, the researchers will unpack how diversification (or lack thereof) along several ecological axes sculpts broad-scale patterns of species richness. The award is also important because it will provide detailed and updated information about salamander vulnerability to ongoing environmental change. This project will provide training opportunities for undergraduates and high school students.Theory suggests that disparity in biodiversity reflects ecological differences among lineages. At one extreme, adaptive radiation is characterized by rapid and prolific diversification into numerous ecological niches and, at the other end, lineages with low ecological diversity also tend to have few species. So-called ‘non-adaptive’ radiations occupy an enigmatic middle ground characterized by high species richness despite low ecological diversity. Perhaps most famous among these radiations are the plethodontid (lungless) salamanders. This lineage is renowned for long-term morphological stasis, suggesting that diversification has been driven by neutral processes. Using a series of phylogenetic causal models, the researchers will explore evolutionary patterns of physiological diversity, and determine their causal mechanism(s). Then, using evolutionary rate matrices, the researchers will compare rates and patterns of morphological and physiological evolution. Then, the researchers will explore the physiological correlates of species’ distributions to explore why the Appalachian region is so species rich in lungless amphibians. Lastly, using a series of new mechanistic models, the researchers will explore how salamander distributions will be altered over the next century.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.