Hydropunctaria amphibia

Hydropunctaria amphibia is a species of saxicolous (rock-dwelling), crustose lichen in the family Verrucariaceae. One of several marine lichens in the genus Hydropunctaria, is widely distributed across Europe, extending from Norway to the Mediterranean and the Iberian coasts, and has a nearly ubiquitous presence along the Catalan coast of Spain. In North America, it is found along the Atlantic Coast from Nova Scotia to the Boston Harbor islands, where its presence in low-pollution areas indicates its potential as a bioindicator for marine lichen community health, and on the west coast in British Columbia, particularly in the Gwaii Haanas's upper littoral fringe. The black, crust-like thallus grows on seashore rocks – both siliceous rocks and limestone – in the lower supralittoral zone, an area also known as the splash zone. Originally described more than two centuries ago as a species of Verrucaria, Hydropunctaria amphibia sets itself apart from other species in Hydropunctaria through the distinct shape of the perithecium (fruiting body) apex, which is either flat-topped or scalloped, in contrast to the typically rounded or immersed apex seen in its relatives.

Taxonomy

The lichen was originally described in 1807 by the Spanish botanist Simón de Roxas Clemente y Rubio, who classified it as a species of Verrucaria. His Latin description of the species was Crusta subtartarea suborbiculari uniformi contigua aequabili picea nitida, tuberculis subcylindricis tandem subpatellulaeformibus ('The crust is almost tartarean, suborbicular, uniform, contiguous, even, pitch-black, shiny, with tubercles initially subcylindrical then eventually somewhat in the form of a small patella (kneecap)'). In 2011, Claude Roux reclassified the taxon to Hydropunctaria, a genus previously branched out from Verrucaria in 2009 to form its own distinct group. Alan Orange, apparently unaware of this transfer, proposed a similar transfer himself the following year.

Description

The crustose lichen Hydropunctaria amphibia is characterised by a prothallus that is typically inconspicuous, but in some specific, small areas, it can become visible as a whitish layer.