The prickly pear cacti, Opuntia, are renowned for their ability to hybridize, as well as to form polyploid taxa, where roughly 60% of species in the clade have undergone genome duplication. Species complexes, composed of diploids and their polyploid derivatives are common in this group, although very few of those complexes have been studied in any detail. I take a molecular phylogenetic approach to determine parentage of two tetraploid taxa from Arizona, California and Nevada and use existing locality data from herbaria, as well as newly acquired locality data to infer the ecological niche breadth of those two putative allopolyploids, as compared to their progenitors.
Although both allopolyploids bare a striking resemblance to their putative progenitors and one another, suites of morphological characters can be used to recognize them both, and DNA sequence data support their origin from those putative progenitors, one of which is shared by both tetraploids. Both polyploid taxa demonstrated a much-reduced distribution, as compared to their progenitors. However, one allopolyploid appears to be better suited to harsher environmental conditions than either of its putative progenitors (i.e., lower elevation Mojave desert), which may have allowed it to expand into and persist in different ecological niches. Our results demonstrate the flexibility of polyploid taxa to expand into novel ecological niches unsuitable for progenitor taxa, as well as the use of existing herbarium data to determine phenological and ecological differences among taxa.