PREMISE Not all ferns grow in moist and shaded habitats. One well-known example is Notholaena standleyi, a species that thrives in deserts of the southwestern United States and Mexico. This species exhibits several "chemotypes" that differ in farina (flavonoid exudates) color and chemistry. By integrating data from molecular phylogenetics, cytology, biochemistry, and biogeography, we circumscribed the major evolutionary lineages within N. standleyi and reconstructed their diversification histories. METHODS Forty-eight samples were selected from across the geographic distribution of N. standleyi. Phylogenetic relationships were inferred using four plastid and five nuclear markers. Ploidy levels were inferred using spore sizes calibrated by chromosome counts, and farina chemistry was compared using thin-layer chromatography. RESULTS Four clades are recognized, three of which roughly correspond to previously recognized chemotypes. The diploid clades G and Y are found in the Sonoran and Chihuahuan deserts, respectively; they are estimated to have diverged in the Pleistocene, congruent with the postulated timing of climatological events separating these two deserts. Clade P/YG is tetraploid and partially overlaps the distribution of clade Y in the eastern Chihuahuan Desert. It is apparently confined to limestone, a geologic substrate rarely occupied by members of the other clades. The cryptic (C) clade, a diploid group known only from southern Mexico and highly disjunct from the other three clades, is newly recognized here. CONCLUSIONS Our results reveal a complex intraspecific diversification history of N. standleyi, traceable to a variety of evolutionary drivers including classic allopatry, parapatry with or without changes in geologic substrate, and sympatric divergence through polyploidization.

中文翻译：

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美国和墨西哥沙漠中星斗篷蕨（Notholaena standleyi）的种下多样化

前提并非所有蕨类植物都生长在潮湿和阴凉的栖息地。一个著名的例子是 Notholaena standleyi，一种在美国西南部和墨西哥的沙漠中繁衍生息的物种。该物种表现出几种不同的“化学型”，它们在粉尘（类黄酮渗出物）的颜色和化学上有所不同。通过整合来自分子系统发育学、细胞学、生物化学和生物地理学的数据，我们确定了 N. standleyi 内的主要进化谱系，并重建了它们的多样化历史。方法 从 N. standleyi 的地理分布中选择了 48 个样本。使用四个质体和五个核标记推断系统发育关系。使用通过染色体计数校准的孢子大小推断倍性水平，并使用薄层色谱法比较粉状化学。结果 识别出四个进化枝，其中三个大致对应于先前识别的化学型。二倍体进化枝G和Y分别在Sonoran和Chihuahuan沙漠中发现；据估计，它们在更新世出现分歧，与分隔这两个沙漠的气候事件的假设时间一致。进化枝 P/YG 是四倍体，与奇瓦环沙漠东部进化枝 Y 的分布部分重叠。它显然仅限于石灰岩，这是一种很少被其他进化枝成员占据的地质基质。神秘的 (C) 进化枝，一个仅在墨西哥南部已知的二倍体群，与其他三个进化枝高度分离，在这里新发现。结论 我们的结果揭示了 N. standleyi 复杂的种内多样化历史，