From Plant Press, Vol. 20, No. 1, January 2017.
Stunningly underwhelming, species of the genus Isoetes, commonly known as quillworts, bear amazing similarity to grass plants with which they are often confused. The U.S. state of Mississippi has now given its name to a new species of the enigmatic quillwort group. The study was published in the open access journal PhytoKeys.
The new species, Isoetes mississippiensis, is an unusually large representative of the genus, first discovered in 1996 by Steve Leonard. For years it was known by the informal name “Big Dog,” a reference to its size.
Further microscopic and cytological study by Rebecca Bray, Lytton Musselman, and Peter Schafran (Old Dominion University), and W. Carl Taylor (National Museum of Natural History) revealed that this is in fact a new species, rather than a strange form of the wide-ranging Midwestern I. melanopoda. The megaspores of I. mississippiensis appear smooth under a hand lens (~30X magnification), only revealing their echinate micro-ornamentation with magnification >200X. Megaspores of I. melanopoda generally display bumps and ridges visible with a hand lens. The coverage of vela over the sporangia also separates these species, where I. mississippiensis has 15-33 percent coverage and I. melanopoda has 5-15 percent coverage. Isoetes mississippiensis is a basic diploid, and is a parent of a tetraploid taxon also occurring in southern Mississippi (Zimmer et al. in prep).
Interestingly, despite considerable field work, only two populations of I. mississippiensis are known from a tributary stream of the Pearl River suggesting the extreme rarity of this Mississippi endemic, which already puts the new species at risk of extinction from human development.
Despite their understated looks, quillworts can have an important role in biodiversity and conservation science, helping us interpret the environment—water quality, phytogeography, and evolution.
The unexpected and unexplored diversity of quillworts in the American South, for example, could be due to the machinations of glaciers, according to scientists. The last glacial epoch pushed northern quillworts south where they could cross with previously isolated species.
“Understanding the diversity of quillworts and their genetic makeup allows making hypotheses as to the movement of these plants and, by extension, to other plants in the same flora,” comments Musselman. “We do not know how old this species is but we do know that it has been able to survive in its present habitat despite extensive perturbation of hydrology and natural vegetation.”
“When one southern Senator was told about an endangered quillwort in his state, he made a public statement questioning why anyone would be interested in this “grass,” shares Musselman. “Despite their ecological importance, quillworts are largely ignored due to their understated appearance. No one knows how many quillworts have been extirpated without being described, and what those could tell us about the past and future of their environment.”