Once more unto the breach, dear friends: Resolving the origins and relationships of the Pellaea wrightiana hybrid complex

Abstract

Premise The taxonomic status of Wright's cliff brake fern, Pellaea wrightiana, has been in dispute ever since it was first described by Hooker in 1858. Previously published evidence suggested that this “taxon” may represent a polyploid complex rather than a single discrete species, a hypothesis tested here using a multifaceted analytical approach. Methods Data derived from cytogenetics, spore analyses, leaf morphometrics, enzyme electrophoresis, and phylogenetic analyses of plastid and nuclear DNA sequences are used to elucidate the origin, relationships, and taxonomic circumscription of P. wrightiana. Results Plants traditionally assigned to this taxon represent three distinct polyploids. The most widespread, P. wrightiana, is a fertile allotetraploid that arose through hybridization between two divergent diploid species, P. truncata and P. ternifolia. Sterile triploids commonly identified as P. wrightiana, were found to be backcross hybrids between this fertile tetraploid and diploid P. truncata. Relatively common across Arizona and New Mexico, they are here assigned to P. ×wagneri hyb. nov. In addition, occasional sterile tetraploid plants assigned to P. wrightiana are shown here to be hybrids between the fertile allotetraploid and the tetraploid P. ternifolia subsp. arizonica. These tetraploid hybrids originated independently in two regions of parental sympatry (southern Arizona and west Texas) and are here assigned to P. ×gooddingii hyb. nov. Conclusions Weaving together data from a diversity of taxonomic approaches, we show that plants identified as P. wrightiana represent three morphologically distinguishable polyploids that have arisen through repeated hybridization events involving the divergent sexual taxa P. ternifolia and P. truncata.

An in‐depth investigation of cryptic taxonomic diversity in the rare endemic mustard Draba maguirei

“…Despite being crucial in our quest to conserve biodiversity, cryptic taxa are a major challenge for taxonomists (Löve, 1964;Grant, 1981;Soltis et al, 2007) because their detection often requires more sophisticated tools than a hand lens or dissecting microscope. Deciphering a cryptic species complex is best achieved by integrating a broad set of systematic approaches (Scheen et al, 2002;Windham et al, 2022aWindham et al, , 2022b, and classifications based on a consensus of morphological, ecological, cytogenetic, and molecular characters are more likely to provide the higher levels of confidence required for protection under the Endangered Species Act (ESA) and other environmental laws (Haig et al, 2006). Here we apply this principle to resolving cryptic taxonomic diversity within the North American Draba maguirei complex (Brassicaceae).…”