Chrysothrix chamaecyparicola

The lichen Chrysothrix chamaecyparicola is distinguished by its crustose, leprose thallus – a thin layer that often forms on the bark of conifer trees. It manifests as an array of dull yellow or greenish-yellow granules that, over time, may fade to a whitish-yellow, particularly in preserved herbarium specimens. These granules, which can vary between spherical and irregular shapes, have a size range of approximately 15 to 30 μm across.^[4]

Unlike some other lichen species, Chrysothrix chamaecyparicola does not have rhizohyphae (root-like hyphae that can penetrate the substrate). Its granules are loosely connected, meaning they lack the fungal hyphae that usually link granules together in many lichen species. Instead, the granules coalesce to form either small, discontinuous patches or more extensive regions that are typically one to a few granules thick. The lichen is supports to a chlorococcoid photobiont, which are green algae that can reach up to 8.5 μm in diameter. Chrysothrix chamaecyparicola does not develop apothecia or pycnidia, which are reproductive structures commonly found in many lichen species. Its chemistry is noteworthy as well: despite testing negative in typical lichen spot tests, it exhibits a dull to bright orange glow when exposed to ultraviolet (UV) light due to the presence of rhizocarpic acid.^[4] Chrysothrix chamaecyparicola closely resembles Chrysothrix flavovirentis, but the absence of diffractaic acid sets it apart.^[2]

Chrysothrix chamaecyparicola is a conspicuous member of the lichen biota in conifer swamps across temperate and subtropical eastern North America. It is often the most conspicuous lichen, coating the trunks of trees in these high-humidity, low-light environments. While particularly evident in cedar swamps near the coast, it is also found on a diverse range of other conifers in inland swamps, including cypress, hemlock, and pine.^[2]

The species is most prevalent in the mid-Atlantic region of the United States, namely in New Jersey, Maryland, and Pennsylvania. This is also the core distribution area of its preferred host plant, Chamaecyparis thyoides.^[2] Chrysothrix chamaecyparicola has also been recorded in North Carolina.^[5]