TY - JOUR AU - Majure, Lucas C. PY - 2022/07/15 Y2 - 2024/03/28 TI - On the origin of the two putative allopolyploids, Opuntia curvispina and O. martiniana (Cactaceae): A case of cryptic speciation in prickly pear cacti JF - Journal of the Botanical Research Institute of Texas JA - J. Bot. Res. Inst. Texas VL - 16 IS - 1 SE - IN MEMORIAM DO - 10.17348/jbrit.v16.i1.1235 UR - https://journals.brit.org/jbrit/article/view/1235 SP - 317-333 AB - <p>The putative allopolyploid taxon, Opuntia curvispina, is distributed from northeastern Arizona and southern Nevada to southeastern California, where it often grows in close proximity to, or sympatric with, O. chlorotica, O. engelmannii and O. phaeacantha. Another putative allopolyploid, O. martiniana, grows sympatrically with O. curvispina in only one area north of the Hualapai Mts., northwestern Arizona. Both of these taxa have previously been treated as either nothospecies or mere spontaneous hybrids by previous researchers. My objectives were to determine the origins of both O. curvispina and O. martiniana to test previous hypotheses of hybrid origin, with O. curvispina putatively derived from O. chlorotica and O. phaeacantha and O. martiniana putatively derived from O. chlorotica and O. engelmannii. I also wanted to determine the overall extent of the ranges of the two taxa by expanding collections and verifying existing herbarium collections, as numerous specimens identified as O. martiniana and O. curvispina have been reported from outside of their expected ranges. My data indicate that O. curvispina indeed is partially derived from O. chlorotica, as well as another putative parent, likely O. phaeacantha, while O. martiniana appears to be most likely derived from O. curvispina and O. macrorhiza, two taxa not before implicated in the origin of O. martiniana. The hexaploid O. phaeacantha also appears to be non-monophyletic and may have been derived several times from different hybridization events. Careful morphological study of O. martiniana clearly separates that species from O. curvispina, although it may be considered cryptically different, a likely result of its partial putative origin from O. curvispina. Given the very broad distribution and dominance of O. curvispina in parts of its range, it is most appropriate to recognize this allopolyploid as a species, rather than as a nothotaxon, as previously designated. The unique feature of an obovate or urceolate style in Opuntia martiniana appears to be a transgressive trait rather than a synapomorphy, given that the taxon is derived from reticulation, and neither putative parent exhibits that character state. This work provides a framework for species recognition using DNA sequence data, morphological characters, geography and cytological information—a total evidence approach clearly needed for taxonomically difficult taxa, such as many within the genus Opuntia. A treatment of O. curvispina and O. martiniana is given with updated descriptions, and O. martiniana is neotypified.</p> ER -