Collaborative Research: Replicated evolution of leaf form in a neo-tropical radiation of Viburnum (Adoxaceae)

关于生物多样性的起源，包括新物种的起源，仍有许多未知之处，但这些知识对于理解进化和预测对快速环境变化的反应至关重要。这项研究将调查一组树木和灌木（荚莲属植物）中的一个引人注目的案例，其中似乎反复发生快速分化，形成两种截然不同的植物形式。这些植物叶子的主要差异似乎是由于对环境变量略有不同的邻近森林类型的适应造成的。这一过程在整个新世界热带地区的几个不同山区得到了明显的复制，为批判性地测试快速生态物种形成模型提供了难得的机会。将在墨西哥不同山区对邻近植物种群进行详细研究，目的是确定有利于这些叶子性状快速进化的环境因素和种群内变异的性质。通过利用这些物种之间的自然杂交，还应该可以识别这些关键植物特征背后的基因。这些研究将对物种形成产生一般性的见解，同时也会对叶子性状的适应性意义产生影响，这些性状在整个开花植物中区分相关物种。这项研究将与墨西哥科学家合作进行，并将涉及多名本科生和研究生。外展活动旨在促进美国和墨西哥参与者之间的互动。 该项目特别侧重于了解墨西哥东部和南部山区三个物种对的物种形成驱动因素。每对中的两个物种在叶子大小和形状（大而圆形与小而椭圆形）、叶缘（有齿与光滑）以及叶子柔毛（浓密毛与缺乏毛）方面存在显着差异。该研究将侧重于量化单个植物内部、种群内部以及物种对之间的变异，并确定其森林栖息地之间不同的非生物和生物因素。将使用相邻栖息地之间的横断面和相互移植实验来测试关于叶子变量适应性值的假设。 在长期受到当地农业实践干扰的地区，广泛的杂交产生了各种各样的中间叶形式。 对这些杂种群的分子分析应该能够鉴定出导致叶子形状差异的主要基因。该项目由国际科学与工程办公室联合资助。

Much remains unknown about the genesis of biological diversity, including the origin of new species, yet such knowledge is critical to understand evolution and to make predictions about responses to rapid environmental change. This research will investigate a striking case in a group of trees and shrubs (Viburnum) in which rapid differentiation appears to have occurred repeatedly into two radically different plant forms. Major differences in the leaves of these plants appear to have resulted from adaptation to adjacent forest types that differ subtly in environmental variables. The evident replication of this process in several different mountain regions throughout the New World tropics, provides a rare opportunity to critically test a model of rapid ecological speciation. Detailed studies of adjacent plant populations will be carried out in different mountain regions in Mexico with the aim of identifying the environmental factors and the nature of the variation within populations that have favored the rapid evolution of these leaf traits. It should also be possible to identify genes that underlie these key plant characteristics by taking advantage of natural hybridization between these species. These studies will yield general insights into speciation but also into the adaptive significance of the leaf traits that differentiate related species throughout the flowering plants. This research will be carried out in collaboration with Mexican scientists and will involve multiple undergraduate and graduate students. Outreach activities have been designed to foster interactions between participants from the United States and Mexico. This project focuses specifically on understanding the drivers of speciation in three species pairs in the mountains of Eastern and Southern Mexico. The two species in each pair differ dramatically in leaf size and shape (large and round versus small and elliptical), in leaf margins (toothed versus smooth), and in leaf pubescence (densely hairy versus lacking hairs). The research will focus on quantifying variation within individual plants, within populations, and between the species pairs, and on determining the abiotic and biotic factors that differ between their forest habitats. Hypotheses on the adaptive value of the leaf variables will be tested using transects between adjacent habitats and a reciprocal transplant experiment. In areas that have long been disturbed by indigenous agricultural practices, extensive hybridization has resulted in a wide array of intermediate leaf forms. Molecular analyses of these hybrid swarms should allow the identification of the major genes that underlie differences in leaf form. This project is jointly funded with the Office of International Science and Engineering.