Intervallides

Intervallides is a small genus of lichen-forming fungi in the family Parmeliaceae. The genus was first described in 1867 by Finnish lichenologist William Nylander, who distinguished it from the related genus Parmelia on the basis of distinctive interval spacing in the photobiont layer and the arrangement of isidia. The generic name is derived from the Latin *inter* ("between") and the suffix *-vallides*, referring to these characteristic intervals. Intervallides comprises four species, all of which are corticolous and commonly found on the bark of deciduous trees in temperate forest ecosystems.

Morphologically, species of Intervallides display a foliose thallus that is broadly lobed and slightly convex. The upper surface is typically pale green to yellowish, showing a granular texture, while the lower surface is black and is attached to the substrate by a dense network of rhizines. The reproductive structures are mainly apothecia with disc diameters ranging from 0.5 to 1.0 mm; some species also produce isidia that serve as a means of vegetative propagation. The medulla contains prismatic crystals that fluoresce weakly under UV light.

Ecologically, Intervallides species play a role in forest nutrient cycles by providing microhabitats for invertebrates and serving as bioindicators of air quality, given their sensitivity to atmospheric pollutants. In addition, their secondary metabolites, such as atranorin and usnic acid, have been studied for antimicrobial properties. Conservation status varies among the species; some are listed as Least Concern, while at least one species faces habitat fragmentation and is monitored by local conservation authorities.

The genus has been subject to molecular phylogenetic studies, which have confirmed its monophyly and clarified its relationships with closely related genera in the Parmeliaceae. Continued research into the chemical ecology and biogeography of Intervallides is expected to enhance understanding of lichen diversification in temperate forest ecosystems.