Data from: Climatic niche differences between diploid and tetraploid cytotypes of Chamerion angustifolium (Onagraceae)

Premise of the study: Polyploidy—the possession of more than two copies of each chromosome in the nucleus—is common in flowering plants. Polyploid plants can occupy different geographic ranges than their diploid progenitors, but the factors responsible for maintaining these range differences are poorly understood. Polyploidy can have significant physiological consequences, and the present study aims to determine whether previously described physiological differences between cytotypes are correlated with climatic niches and geographic distributions. Methods: Prior research indicates that tetraploid Chamerion angustifolium (Onagraceae) are more tolerant of drought and less tolerant of freezing than diploids, which suggests that they should occupy a niche that is warmer and drier than that of diploids. We extracted climate data for 134 C. angustifolium populations classified as pure diploid, pure tetraploid, or mixed-ploidy. We compared climatic conditions between these population categories, and generated ecological niche models to compare their geographic distribution with prior qualitative estimates. Key results: Pure tetraploid populations occupy habitats that are warmer and drier than pure diploid populations. Mixed-ploidy populations occur in habitats that are not strictly intermediate between pure diploid and pure tetraploid populations, but are as cold as pure diploid populations and have intermediate soil moisture deficits. Our niche models were similar to previous qualitative estimates of cytotype geographic distribution. Conclusions: The correspondence between the physiological tolerances of cytotypes, their climatic niches, and their geographic distributions suggests that physiological traits are at least partially responsible for differences in the realized climatic niches of diploid and tetraploid C. angustifolium.

研究背景：多倍性（Polyploidy）指细胞核内每条染色体拥有两份以上拷贝的现象，在开花植物（flowering plants）中十分常见。多倍体植物的地理分布范围可与其二倍体祖先（diploid progenitors）存在差异，但维持这类分布差异的机制目前尚未被充分阐明。多倍性可对植物产生显著的生理效应，本研究旨在探明：此前已报道的不同细胞型（cytotypes）间的生理差异，是否与气候生态位（climatic niches）及地理分布相关联。
研究方法：已有研究表明，四倍体（tetraploid）柳兰（Chamerion angustifolium，柳叶菜科Onagraceae）较二倍体更耐旱，但耐寒性更弱，这提示四倍体的气候生态位应比二倍体更为温暖干燥。我们从134个被划分为纯二倍体、纯四倍体或混倍体（mixed-ploidy）的柳兰种群中提取气候数据，对比不同种群类群的气候条件，并构建生态位模型（ecological niche models）以将其地理分布与此前的定性估算结果进行比较。
主要结果：纯四倍体种群的生境相较于纯二倍体种群更为温暖干燥。混倍体种群的生境并非严格介于纯二倍体与纯四倍体之间，但其寒冷程度与纯二倍体种群相当，且土壤水分亏缺程度处于中间水平。本研究构建的生态位模型与此前关于细胞型地理分布的定性估算结果一致。
研究结论：不同细胞型的生理耐受特性、其气候生态位以及地理分布三者间的对应关系表明，生理性状至少部分决定了二倍体与四倍体柳兰的实际气候生态位（realized climatic niches）差异。