Friday 14 August 2015

Adiantum shastense: A new species of Maidenhair Fern from California.

Maidenhair Ferns of the genus Adiantum are global in distribution, though most species are restricted to the tropics and subtropics.About 225 species (roughly 10% of the total number of described species in the genus) are found in temperate regions, though most of these are found only in Asia. Nine species of Adiantum are currently recognised from Canada and the United States, though four of these are essentially tropical species with the northernmost limit of their range in the southern US, one species is global in distribution and found on all continents except Antarctica, one is found in Asia as well as North America and one is thought to be introduced. However recent genetic studies of Maidenhair Fern populations suggest that many of these ‘species’ may in fact be clusters of cryptic morphospecies (plants which appear identical but which are genetically isolated from one-another), suggesting that the group may be larger and more complex than is currently understood.

In a paper published in the journal PhytoKeys on 21 July 2015, Layne Huiet of the Department of Biology at Duke University, Martin Lenz and Julie Nelson of the USDA Forest Service at Shasta-Trinity National Forest, Kathleen Pryer, also of the Department of Biology at Duke University and Alan Smith of the University Herbarium at the University of California, Berkeley, describe a new species of Maidenhair Fern from Shasta County in California.

The new species is named Adiantum shastense, where ‘shastense’ means ‘from Shasta’, the species having only been found to date around Lake Shasta in Shasta County, California, an area with a high number on endemic species (species not found elsewhere). It is essentially similar to Adiantum jordanii, a species wide-ranging in North America, being a rhizomatous Fern (Fern which can regrow each year from a creeping underground root) producing up to 10 fronds 30-60 cm in length. However it has a longer growing season than Adiantum jordanii, persisting later in the summer.

Fronds of Adiantum shastense growing in the wild. Huiet et al. (2015).

Adiantum shastense was first identified from herbarium specimens, some of which were collected over a hundred years ago, during a study into the globally distributed Adiantum capillus-veneris, in California; Adiantum shastense grows alongside Adiantum capillus-veneris in places, whereas Adiantum jordanii is generally intolerant of other Maidenhair species. DNA sequencing analysis of these herbarium specimens revealed that they were neither Adiantum capillus-veneris nor Adiantum jordanii, but a new and previously undescribed species apparently endemic to Shasta County. Subsequent investigations found it to be widespread within this area, growing on a variety of substrates, and in places forming the dominant understory plant. Since the species is currently known only from a limited area, Huiet et al. recommend that it be treated as having a California Rare Plant Rank of 4.3, though they note that unlike other endemic plants of the Shasta Lake area (but like other Maidenhair Ferns) Adiantum shastense is distributed via wind-blown spores, making it highly possible that it is also found at (as yet undiscovered) locations outside of this area.

See also…

Governor Laffan's Fern declared Extinct in the Wild.
The International Union for the Conservation of Nature published its annual update of its Red List of Threatened Species on Thursday 12 June 2014, marking the 50th year of the list's existence...

Three new species of Fern from the Middle Triassic of northern Italy.
Middle Triassic plant fossils have been collected from the Dolomites for at least a century and a half. These Triassic floras were dominated by Conifers, and were long thought to have lived in an arid...

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