Species spotlight: Utricularia dichotoma subsp. monanthos
monanthos

Species spotlight: Utricularia dichotoma subsp. monanthos

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.

A bloom of Utricularia dichotoma subsp. monanthos with a size card.

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.

Posterior view of Utricularia dichotoma subsp. monanthos bloom, with a clear display of the bracts and bracteoles. The basifixed (attached at the bottom) and slightly gibbous (rounded protuberant) base of the bracts/bracteoles distinguishes it from alpine forms of Utricularia dichotoma subsp. dichotoma.

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.

Lateral view of Utricularia dichotoma subsp. monanthos bloom in the Baw Baw Plateau. Note that the bottom spur (sharp pointy bit at the bottom) is significantly shorter than the lower lip of the corolla. When fully open, the lower lip of the corolla reflexes downwards.

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.

Utricularia dichotoma subsp. monanthos growing alongside Drosera arcturi in Falls Creek, Victoria.

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.

Bladder trap of Utricularia dichotoma subsp. monanthos.

Utricularia dichotoma subsp. monanthos growing underwater.

The habitat of Utricularia dichotoma subsp. monanthos on the Baw Baw Plateau. The plants grow in a peaty seep at this location.

Utricularia dichotoma subsp. monanthos growing alongside Drosera arcturi in Falls Creek, Victoria.

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.

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