Wednesday, 4 September 2013

Taxon of the Day: Vandenboschia speciosa

Vandenboschia speciosa - a fertile frond

Today's Taxon of the Day has been produced by Michael Hassler the owner of the Catalogue of Life's new Global Species Database for Ferns. He writes:

Vandenboschia speciosa (Willd.) Kunkel (= Trichomanes speciosum Willd.) is a member of the Hymenophyllaceae, the Filmy Ferns. This is a family of ca. 500 species of small - often minute – ferns which resemble mosses more than typical ferns. They have thin, translucent tissue which requires wet habitats to live in, and reside mostly on bark, tree trunks or, more rarely, on wet earth or rocks, and can form large mats. Their mats can be intricately twined into “true” moss patches with whom they share not only the looks but also the habitat. Most species readily develop fertile fronds (sporophytes), but a few relict populations of northern and temperate climates have restricted themselves into existing as gametophytes only.




While the Filmy Ferns are usually easy to recognize as members of the Hymenophyllaceae family, the relationships and especially the genus circumscriptions within the family have changed frequently. Ebihara et al. (2006) have defined the most current and accepted classification, which led to the formerly large genus Trichomanes (sensu stricto) being restricted almost exclusively to the New World (with the exception of few African and Madagascar species). The well-known European species Trichomanes speciosum needed a change, too, and is now listed within Vandenboschia

Gametophytes can easily be mistaken for moss!

Vandenboschia speciosa is one of only three European members of the family. On this continent the family has probably been decimated by the harsh climate during the glacial age, and the remaining members cling to a meagre existence in ever-humid, sea-influenced habitats in Western Europe. These elusive species all are counted within the rarest plants of Europe, and new finds are always exciting. Most botanists have never seen a single specimen in Europe without going to great lengths to find it.

Vandenboschia speciosa exists in Germany and eastern France, at the eastern border of its range, only in a few cave entrances and under wet boulders as small patches of minute gametophytes. Then it resembles a moss and not a fern or a flowering plant at all (see picture above). In 2007 I managed to find a fertile frond (probably 2 cm across, top picture), which is extremely rare and almost never happens. This was – to my knowledge - the first fertile of this species frond to be documented in a photograph in Germany. On the British Isles, a few more places with fertile sporophytes are known.

CoL Dynamic Checklist: Trichomanes speciosum
CoL contributor: World Ferns
Image copyright: Michael Hassler

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