Candelariaceae

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Candelariaceae is a family of mostly small, yellow to yellow-green lichens, recognized by their bright coloration, thin thalli, and frequent occurrence on tree bark and wood. Members of this family are especially noticeable in the field due to their vivid color, even though individual thalli are often small and delicate.

Growth Form and Thallus

The thallus ranges from crustose to foliose, sometimes appearing leprose or squamulose. Lobes, when present, are typically narrow, thin, and fragile, often forming small rosettes or irregular patches. The surface is usually smooth to finely granular.

Color is one of the most distinctive features of the family: thalli are typically bright yellow, lemon-yellow, or yellow-green, a result of characteristic secondary compounds.

Substrate and Habitat

Candelariaceae species occur mainly on tree bark and wood, occasionally on rock. They are common in open woodlands, forest edges, and urban or suburban environments, often favoring nutrient-enriched or slightly disturbed substrates.

Photobiont

The photobiont is a green alga, most commonly Trebouxia.

Reproductive Structures

Reproductive structures vary among genera and species.

• Apothecia: When present, apothecia are usually lecanorine, with a yellow to pale margin and a slightly darker yellow or orange disc. Apothecia are often small and may be sparse or absent.
• Asci: Typically contain eight spores per ascus.
• Ascospores: Simple, colorless, ellipsoid to oblong.

Many species reproduce primarily by asexual means, producing abundant soredia or granular propagules, which can give the thallus a powdery or leprose appearance.

Chemistry

Members of Candelariaceae contain pulvinic acid derivatives, responsible for their bright yellow coloration. Spot tests are often K− or weak, but the intense color is usually sufficient for family-level recognition in the field.

Ecology and Role

Candelariaceae species are generally fast-growing and short-lived, thriving in well-lit environments with moderate nutrient availability. They are often among the first lichens to colonize young bark or exposed wood and can serve as indicators of increased light or mild nutrient enrichment.

Representative Genera

• Candelaria – small foliose to squamulose species with narrow lobes
• Candelariella – primarily crustose species, often forming bright yellow patches on bark or rock

Similar Lichen Families

Candelariaceae may be confused with other yellow lichen families. Teloschistaceae also includes bright yellow to orange species but is distinguished by anthraquinone pigments, strong spot test reactions (often K+ purple), and frequently more robust thalli. Lecanoraceae includes some yellowish crusts but typically lacks the intense lemon-yellow coloration and pulvinic acid chemistry. Acarosporaceae may overlap in color on rock but differs in growth form, ecology, and polysporous asci.

Family overview intended for field study and photographic reference; microscopic examination may be required for species-level identification.