Department of Plant Biology, Michigan State University, East Lansing, 48824, Michigan, USA.
Department of Biology, Indiana University, Bloomington, 47405, Indiana, USA.
Am J Bot. 2024 Sep;111(9):e16402. doi: 10.1002/ajb2.16402. Epub 2024 Sep 7.
A key goal of evolutionary biologists is to understand how and why genetic variation is partitioned within species. In the yellow monkeyflower, Mimulus guttatus (syn. Erythranthe guttata), coastal perennial populations constitute a single genetically and morphologically differentiated ecotype compared to inland M. guttatus populations. While the coastal ecotype's distinctiveness has now been well documented, there is also environmental variation across the ecotype's range that could drive more continuous differentiation among its component populations.
Based on previous observations of a potential cline within this ecotype, we quantified plant height, among other traits, across coastal perennial accessions from 74 populations in a greenhouse common garden experiment. To evaluate potential drivers of the relationship between trait variation and latitude, we regressed height against multiple climatic factors, including temperature, precipitation, and coastal wind speeds. We also accounted for exposure to the open ocean in all analyses.
Multiple traits were correlated with latitude of origin, but none more than plant height. Height was negatively correlated with latitude, and plants directly exposed to the open ocean were shorter than those protected from coastal winds. Further analyses revealed that height was correlated with climatic factors (precipitation, temperature, and wind speeds) that were autocorrelated with latitude. We hypothesize that one or more of these climatic factors drove the evolution of latitudinal clinal variation within the coastal ecotype.
Overall, our study illustrates the complexity of how the distribution of environmental variation can simultaneously drive the evolution of both distinct ecotypes and continuous clines within those ecotypes.
进化生物学家的一个主要目标是了解遗传变异在物种内是如何以及为何被分割的。在黄花蔓陀罗（Mimulus guttatus，也称 Erythranthe guttata）中，沿海多年生种群与内陆的 M. guttatus 种群相比，构成了一个单一的遗传和形态分化的生态型。虽然沿海生态型的独特性现在已经得到了很好的证明，但在其分布范围内也存在环境变化，这可能会导致其组成种群之间的连续分化。
基于之前对该生态型内潜在渐变的观察，我们在温室共同花园实验中，对来自 74 个沿海多年生种群的植物高度和其他特征进行了量化。为了评估性状变异与纬度之间的潜在驱动因素，我们将高度与包括温度、降水和沿海风速在内的多个气候因素进行了回归分析。我们还在所有分析中考虑了暴露在开阔海洋中的情况。
多个性状与起源纬度相关，但没有一个比植物高度更相关。高度与纬度呈负相关，直接暴露在开阔海洋中的植物比那些免受沿海风影响的植物更矮。进一步的分析表明，高度与纬度相关的气候因素（降水、温度和风速）呈正相关。我们假设这些气候因素中的一个或多个因素驱动了沿海生态型内纬度渐变的进化。
总的来说，我们的研究说明了环境变化的分布如何同时驱动独特生态型和这些生态型内连续渐变的进化的复杂性。
