T. inconspicua partially buried under sediment. Photo by Jeremy Rolfe
Vegetative characteristics
Trithuria inconspicua is a small, 15–55 mm tall, aquatic,[1] perennial,[1][5] rhizomatous[1][6] herb with adventitious roots and glabrous,[1] linear-filiform,[7] 15–55 mm long, and 0.25–0.4 mm wide leaves.[1] The rhizome is up to 2 cm long, and up to 3 mm wide.[6]
Generative characteristics
It can be seen as either a monoicous, or in part as an exclusively female species. It can possess either bisexual, or unisexual reproductive units ("flowers").[5] Female plants are more frequent, although male and bisexual individuals also occur.[7][6] The male flowers consist of bright red 10 mm long filaments, whilst the female flowers are yellow-brown and contain 5-10 styles bunched at the apex.[1]
The specific epithet inconspicua means inconspicous, not easily visible.[1][10]
The first flowering plant?
Based on molecular data from a single plastid gene (rbcL)T. inconspicua was originally believed to a monocot.[11] However, a more recent study using multiple genetic loci, supported by a subsequent re-evaluation of morphological characteristics, now places T. inconspicua as a sister group with the water lilies (Nymphaeales).[12] This new placement of T. inconspicua means only a single lineage of flowering plant is thought to be older, that being the woody New Caledonian shrub Amborella trichopoda.[13]
The predominant view that Amborella represents the oldest flowering plant was recently challenged in a study by Goremykini et al (2013),[14] who showed that when highly variable sites were removed from the dataset, T. inconspicua was consistently identified as the oldest angiosperm lineage. This proposal has attracted criticism from Drew et al (2014), who argued that the basal placement of T. inconspicua is an artifact of the variable site filtering method used by Goremykini et al (2013).[15] One of the main reasons why people are interested in this question is that placing T. inconspicua at the base of the angiosperm lineage would suggest the first angiosperms were soft bodied aquatic plants, rather than a woody terrestrial plants like Amborella. These competing theories have been given the light hearted monikers "wet and wild" and "dark and disturbed".[15][16][17]
Conservation status
Trithuria inconspicua is seriously threatened[1] due to the competition by the introduced bladder wort (Utricularia gibba) as well as other fresh water weeds.
Ecology
It occurs in coastal dune lakes and glacial lakes[7] in shallow to 5–7 m deep waters. It grows in mud, sand, and gravel substrates.[1] The plants are often partly buried within the substrate.[7][1]
Cultural significance
It has been chosen to be the New Zealand's Favourite Plant 2024.[18][19]
^Michelangeli, Fabian A., Jerrold I. Davis, and Dennis Wm Stevenson. 2003. "Phylogenetic Relationships among Poaceae and Related Families as Inferred from Morphology, Inversions in the Plastid Genome, and Sequence Data from the Mitochondrial and Plastid Genomes." American Journal of Botany 90 (1): 93–106.
^Saarela, Jeffery M., Hardeep S. Rai, James A. Doyle, Peter K. Endress, Sarah Mathews, Adam D. Marchant, Barbara G. Briggs, and Sean W. Graham. 2007. "Hydatellaceae Identified as a New Branch near the Base of the Angiosperm Phylogenetic Tree." Nature 446 (7133): 312–15.
^Friis, Else Marie, and Peter Crane. 2007. "Botany: New Home for Tiny Aquatics." Nature 446 (7133): 269–70.
^Goremykini, V.V.; Nikiforova, S.V.; Biggs, P.J.; Zhong, B. de Lange, P.; Martin, W.; Woetzel, S.; Atherton, R.A., McLenachan, T.; Lockhart, P.J. 2013: The evolutionary root of flowering plants. Systematic Biology61 (1) 50–61.
^ abDrew, Bryan T., Brad R. Ruhfel, Stephen A. Smith, Michael J. Moore, Barbara G. Briggs, Matthew A. Gitzendanner, Pamela S. Soltis, and Douglas E. Soltis. 2014. "Another Look at the Root of the Angiosperms Reveals a Familiar Tale." Systematic Biology 63 (3): 368–82.
^Feild, Taylor S., Nan Crystal Arens, James A. Doyle, Todd E. Dawson, and Michael J. Donoghue. 2004. "Dark and Disturbed: A New Image of Early Angiosperm Ecology." Paleobiology 30 (1): 82–107.
^Coiffard, C., B. Gomez, and F. Thevenard. 2007. "Early Cretaceous Angiosperm Invasion of Western Europe and Major Environmental Changes." Annals of Botany 100 (3): 545–53.
