Rhizocarpon vigilans


Rhizocarpon vigilans is a species of crustose lichen in the family Rhizocarpaceae. It is native to the southern Australian Capital Territory, particularly found in the Namadgi National Park on the summit of Sentry Box Mountain.

Taxonomy

Rhizocarpon vigilans was described as a new species by the lichenologists Patrick M. McCarthy and John Elix in 2014, expanding the known diversity within the Rhizocarpaceae. This species was distinguished from others in Rhizocarpon through a combination of morphological and chemical traits.
The type specimen of Rhizocarpon vigilans was collected by McCarthy on 12 December 2013. The collection took place at the summit of Sentry Box Mountain in the Namadgi National Park, Australian Capital Territory, at an elevation of, where it was found growing on sheltered granite surfaces. The holotype is preserved at the CANB.
The specific epithet vigilans is derived from Latin, meaning "watchful" or "vigilant". This name was chosen in reference to the type locality, Sentry Box Mountain, evoking the imagery of a lookout or guard post. The name reflects the exposed, high-elevation habitat where this lichen species was first identified.

Description

Rhizocarpon vigilans has a crustose, epilithic thallus that is pale to medium grey, sometimes greenish-grey, and forms colonies up to 2 cm wide. The thallus is with individual measuring 0.15 to 0.85 mm wide, which can be plane or slightly convex. The cortex is poorly defined, and the medulla is white and reacts positively to iodine staining, turning a deep blue, a key indicator of its chemical makeup. The apothecia of this species are numerous and dull black, initially plane but typically becoming convex as they mature, measuring between 0.30 and 0.77 mm in diameter.

Similar species

Rhizocarpon vigilans is similar to Rhizocarpon polycarpum, but is distinguished by its convex, immarginate apothecia and the mature that are dark greyish green to dark brown. The in R. vigilans is K–, contrasting with the K+ reaction found in R. polycarpum.

Habitat and distribution

Rhizocarpon vigilans grows on granite boulders and outcrops on mountain tops, within a lichen community that includes several other species. This habitat is characteristic of exposed alpine locations.