''Xenolecia cataractarum'' is a species of

saxicolous A saxicolous lichen is a lichen that grows on rock. The prefix "sax" from the Latin means "rock" or "stone". Characteristics Saxicolous lichens exhibit very slow growth rates. They may develop on rock substrates for long periods of time, giv ...

and

crustose lichen Crustose lichens are lichens that form a crust which strongly adheres to the substrate (soil, rock, tree bark, etc.), making separation from the substrate impossible without destruction. The basic structure of crustose lichens consists of a cor ...

in the family

Lecideaceae The Lecideaceae are a family of lichens in the order Lecideales (Ascomycota, class Lecanoromycetes). Genera According to a recent (2022) estimate, the Lecideaceae comprise 29 genera and about 260 species. The following list indicates the genus ...

. It is only known to occur on

Campbell Island, New Zealand Campbell Island / Motu Ihupuku is an uninhabited subantarctic island of New Zealand, and the main island of the Campbell Island group. It covers of the group's , and is surrounded by numerous stacks, rocks and islets like Dent Island, Foll ...

Taxonomy

The lichen was formally described as a new species in 2017 by lichenologist Alan Fryday, based on

herbarium A herbarium (plural: herbaria) is a collection of preserved plant specimens and associated data used for scientific study. The specimens may be whole plants or plant parts; these will usually be in dried form mounted on a sheet of paper (calle ...

collections kept at

Michigan State University Michigan State University (Michigan State, MSU) is a public university, public Land-grant university, land-grant research university in East Lansing, Michigan. It was founded in 1855 as the Agricultural College of the State of Michigan, the fi ...

. The

type specimen In biology, a type is a particular specimen (or in some cases a group of specimens) of an organism to which the scientific name of that organism is formally attached. In other words, a type is an example that serves to anchor or centralizes the ...

was collected by

Henry Imshaug Henry Andrew Imshaug (1925–2010) was an American lichenologist notable for work on the genus '' Buellia'' and his "enormous and important collections from the Rocky Mountains, Great Lakes region, West Indies and subantarctic islands, together ...

in 1970, in ''

Dracophyllum ''Dracophyllum'' is a genus of plants belonging to the family Ericaceae, formerly Epacridaceae. There are 61 species in the genus, mostly shrubs, but also cushion plants and trees, found in New Zealand, Australia, Lord Howe Island and New Caled ...

'' scrubland on the south slope of

Mount Honey Mount Honey is the highest point on Campbell Island, the southernmost of New Zealand's subantarctic outlying islands. It is located to the south of Perseverance Harbour, a long lateral fissure which reaches the ocean in the island's southea ...

( Campbell Island). This area has several waterfalls; the lichen was found growing on

siliceous Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , most commonly found in nature as quartz and in various living organisms. In many parts of the world, silica is the major constituent of sand. Silica is ...

rock. The lichen is only known to occur at the

type locality Type locality may refer to: * Type locality (biology) * Type locality (geology) See also * Local (disambiguation) * Locality (disambiguation) {{disambiguation ...

, where Imshaug made several separate collections. The

specific epithet In taxonomy, binomial nomenclature ("two-term naming system"), also called nomenclature ("two-name naming system") or binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, bot ...

''cataractarum'', which is

Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power ...

for "waterfall", refers to that geographical feature of the type locality.

Description

The lichen has a creamy-white

thallus Thallus (plural: thalli), from Latinized Greek (), meaning "a green shoot" or " twig", is the vegetative tissue of some organisms in diverse groups such as algae, fungi, some liverworts, lichens, and the Myxogastria. Many of these organisms ...

with a margin outlined by an underlying bluish-black prothallus. It has numerous

apothecia An ascocarp, or ascoma (), is the fruiting body ( sporocarp) of an ascomycete phylum fungus. It consists of very tightly interwoven hyphae and millions of embedded asci, each of which typically contains four to eight ascospores. Ascocarps are mo ...

, which are sunk into the thallus surface like a black, concave disc (often surrounded by a blue-grey border) measuring 0.2–0.5 mm in diameter. The

photobiont A lichen ( , ) is a composite organism that arises from algae or cyanobacteria living among filaments of multiple fungi species in a mutualistic relationship.green alga The green algae (singular: green alga) are a group consisting of the Prasinodermophyta and its unnamed sister which contains the Chlorophyta and Charophyta/ Streptophyta. The land plants ( Embryophytes) have emerged deep in the Charophyte alg ...

with spherical to ovoid cells 5–7 μm across; these cells are loosely arranged in vertical bundles. ''Xenolecia cataractarum'' contains

norstictic acid Norstictic acid is a depsidone produced as a secondary metabolite Secondary metabolites, also called specialised metabolites, toxins, secondary products, or natural products, are organic compounds produced by any lifeform, e.g. bacteria, fu ...

, a secondary compound that can be detected using

thin-layer chromatography Thin-layer chromatography (TLC) is a chromatography technique used to separate non-volatile mixtures. Thin-layer chromatography is performed on a sheet of an inert substrate such as glass, plastic, or aluminium foil, which is coated with a t ...

. The expected results of standard chemical spot tests are K+ (red), C−, KC−, and PD+ (yellow).

References

{{Taxonbar, from=Q108479534 Lecideales Lichen species Lichens described in 2017 Lichens of New Zealand Taxa named by Alan Fryday