Abstract
This study addresses reported discrepancies regarding the occurrence of Polypodium calirhiza in Mexico. The original paper describing this taxon cited collections from Mexico, but the species was omitted from the recent Pteridophytes of Mexico. Originally treated as a tetraploid cytotype of P. californicum, P. calirhiza now is hypothesized to have arisen through hybridization between P. glycyrrhiza and P. californicum. The tetraploid can be difficult to distinguish from either of its putative parents, but especially so from P. californicum. Our analyses show that a combination of spore length and abaxial rachis scale morphology consistently distinguishes P. calirhiza from P. californicum, and we confirm that both species occur in Mexico. Although occasionally found growing together in the United States, the two species are strongly allopatric in Mexico: P. californicum is restricted to coastal regions of the Baja California peninsula and neighboring Pacific islands, whereas P. calirhiza grows at high elevations in central and southern Mexico. The occurrence of P. calirhiza in Oaxaca, Mexico, marks the southernmost extent of the P. vulgare complex in the Western Hemisphere.
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Acknowledgments
The authors thank the curators and staff at the DUKE, JEPS, NY, and UC herbaria for loans and permission to sample spores and scales, without which this study would not have been possible. We are grateful to Amanda Grusz, Layne Huiet, Fay-Wei Li, Anne Johnson, Carl Rothfels, and manuscript reviewers for their helpful comments and edits. The National Science Foundation Doctoral Dissertation Improvement Grant 1110775 to K.M.P. and E.M.S. supported this research. This article is part of E.M.S.’s doctoral dissertation in Biology at Duke University.
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Sigel, E.M., Windham, M.D., Smith, A.R. et al. Rediscovery of Polypodium calirhiza (Polypodiaceae) in Mexico. Brittonia 66, 278–286 (2014). https://doi.org/10.1007/s12228-014-9332-6
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DOI: https://doi.org/10.1007/s12228-014-9332-6