In light of the recent review of the Utricularia dichotoma complex (Jobson 2020), I decided to take a trip up to the Baw Baw Plateau to take some reference photos of Utricularia monanthos for my personal study. I was successful in locating the plant in bloom on a seep at approximately 1500 m elevation.
U. monanthos describes a small affixed aquatic and emergent species with tiny purple blooms roughly half a centimeter in width. The lower lip of the corolla has 2-3 yellow ridges and is slightly longer than petal spur. The upper lip of the corolla is notched and features vertical veins. The bracts and bracteoles are basifixed (attached at their base) and slightly gibbous at the base. The plants are usually found in alpine habitats across Tasmania, Victoria and New South Wales in boggy meadows, creeks and seeps.
The Utricularia dichotoma complex, consisting of several taxa which have purple flowers and yellow flowers with somewhat similar morphology, has long been the subject of review. Taxa within this complex, including Utricularia monanthos, are constantly being shifted from species to subspecies status as new data and new interpretations of data are applied.
Jobson (2020) performs DNA analysis on plant samples to determine the genetic relationships between taxa in the complex. These data show that ‘monanthos‘ specimens cluster strongly together as a distinct taxon. However, the monanthos cluster is ultimately nested alongside other similar taxa, which together comprise the Utricularia dichotoma species complex. Based on this, Jobson places ‘monanthos‘ as a subspecies of Utricularia dichotoma.
Interestingly, all specimens from New Zealand that were sampled clustered as a separate group (Utricularia dichotoma subsp. novae-zelandiae) and Utricularia dichtoma subsp. monanthos is not found in New Zealand. I have observed plants that superficially resemble monanthos in New Zealand, but in light of this publication, I believe that it is a case of convergent evolution in alpine environments.
Ref: Jobson Richard W., Baleeiro Paulo C. (2020) Radiations of fairy-aprons (Utricularia dichotoma, Lentibulariaceae) in Australia and New Zealand: molecular evidence and proposal of new subspecies. Australian Systematic Botany33, 278-310.