Data from: The Parmotrema acid test: a look at species delineation in the P. perforatum group 40 y later

Parmotrema perforatum and its relatives form a morphologically distinctive group of species, most of which are common and endemic to eastern North America. Species delimitation in this ecologically important group was the subject of extensive inquiry before the advent of molecular systematics and computationally intensive niche modeling. As part of a large-scale lichen biodiversity inventory of the Mid-Atlantic Coastal Plain, we used ITS sequence data to examine the utility of characters (morphological, chemical, reproductive, ecological) in circumscribing four species in this group (P. hypoleucinum, P. hypotropum, P. perforatum, P. subrigidum). We found that P. hypoleucinum and P. subrigidum as currently circumscribed are monophyletic and the latter comprises two chemotypes differing in the presence or absence of norstictic acid in addition to alectoronic acid. The sequences of P. hypotropum and P. perforatum, which are chemically identical species and differ only in reproductive mode, were intermixed in a single, well-supported clade. The two chemotypes of P. subrigidum are partially allopatric and their sequences are > 99% identical. Nonetheless, niche modeling suggests they occupy significantly different ecological niches. These results provide a new perspective on much-debated questions on species circumscription in lichens and suggest new avenues for genetic, ecological and systematic research.穿孔叶梅（Parmotrema perforatum）及其近缘类群构成一个形态特征鲜明的物种类群，其中多数物种常见且为北美东部特有分布。在分子系统学与计算密集型生态位建模兴起之前，这一具有重要生态价值的类群的物种界定问题曾是广泛研究的核心议题。作为中大西洋沿海平原（Mid-Atlantic Coastal Plain）大规模地衣生物多样性普查的一部分，本研究利用ITS序列（内部转录间隔区序列，ITS）数据，分析了形态、化学、繁殖与生态特征在界定该类群4个物种（P. hypoleucinum、P. hypotropum、P. perforatum、P. subrigidum）时的有效性。研究结果显示，当前界定的P. hypoleucinum与P. subrigidum均为单系类群；其中P. subrigidum包含两个化学型，二者除均含有阿勒托罗酸（alectoronic acid）外，是否含有诺尔斯蒂克酸（norstictic acid）存在差异。P. hypotropum与P. perforatum为化学特征完全一致、仅繁殖方式不同的物种，其序列聚类于同一个支持度良好的演化支中，且彼此相互混杂。P. subrigidum的两个化学型呈部分异域分布，其序列相似度超过99%；但生态位建模结果表明二者占据的生态位存在显著差异。本研究为地衣分类学中长期存在的物种界定争议问题提供了全新视角，并为遗传学、生态学与系统学研究开辟了新的方向。