Taxonomy
- Kingdom: Fungi
- Division: Ascomycota
- Class: Lecanoromycetes
- Order: Lecanorales
- Family: Ramalinaceae
- Genus: Ramalina
- Species: R. celastri
Synonyms: Parmelia celastri Spreng. (original description, 1827); other historical synonyms reported in taxonomic literature.
Description
Ramalina celastri is a corticolous and lignicolous fruticose lichen, meaning it grows on the bark of trees and on wood substrates. The thallus is erect to somewhat pendulous, forming rigid, branched structures that may reach lengths of up to 15 cm. Branches are typically straw‑colored to pale green, solid, flattened, and lanceolate, with widths commonly ranging from 3–5 mm (occasionally 1–20 mm). Young branches are thin and smooth; mature thalli develop longitudinal or reticulate ridges due to cartilaginous tissue strands. Small pores called pseudocyphellae are frequently present on the surface, facilitating gas exchange, while soralia (asexual reproductive structures) are absent.
Reproductive structures consist of numerous apothecia that are usually lateral or laminal and supported by a short stalk (stipe). The apothecial disc is typically yellowish. No soredia are reported.
Habitat and Distribution
The species has a pantropical distribution, occurring throughout tropical regions worldwide. It is commonly found on the bark of various trees, including Celastrus pyracantha, which inspired its specific epithet “celastri.” In North America it is colloquially known as “palmetto lichen,” referencing its branching pattern reminiscent of palmetto leaves; in New Zealand it is called “cartilage lichen.”
Taxonomic History
The lichen was first formally described by Kurt Polycarp Joachim Sprengel in 1827 under the name Parmelia celastri, based on a type specimen collected by Christian Friedrich Ecklon in South Africa. In 1976, Hildur Krog and Thomas D. V. Swinscow transferred the species to the genus Ramalina. Molecular phylogenetic studies have confirmed its distinction from closely related taxa such as Ramalina ovalis, which was previously considered a synonym.
Ecological Significance
As a bark‑dwelling lichen, R. celastri contributes to nutrient cycling and provides microhabitats for various microorganisms. Its sensitivity to air pollutants makes it useful in biomonitoring studies of sulfur dioxide (SO₂) and nitrogen dioxide (NO₂), as well as investigations into atmospheric microplastic accumulation.
Conservation Status
According to NatureServe, the species holds a secure (G5) conservation status, indicating it is widespread and not currently at risk.
References: Wikipedia entry on Ramalina celastri; primary taxonomic literature cited therein.