Infraspecific diversification of the star cloak fern (Notholaena standleyi) in the deserts of the United States and Mexico.
Abstract
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.
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https://hdl.handle.net/10161/21821Published Version (Please cite this version)
10.1002/ajb2.1461Publication Info
Kao, T; Rothfels, CJ; Melgoza‐Castillo, A; Pryer, KM; & Windham, MD (2020). Infraspecific diversification of the star cloak fern (Notholaena standleyi) in the
deserts of the United States and Mexico. American journal of botany, 107(4). pp. 658-675. 10.1002/ajb2.1461. Retrieved from https://hdl.handle.net/10161/21821.This is constructed from limited available data and may be imprecise. To cite this
article, please review & use the official citation provided by the journal.
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Kathleen M. Pryer
Professor of Biology

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