Diagnosis: Thallus forming minute rosettes with ecorticate sorediate granules in the centre and pseudocorticate lobes along the margin; containing atranorin, chloroatranorin, diploicin and unidentified secalonic acid derivates.
Type: Ecuador, Galapagos, Floreana, ca. 500 m S of La Lobería, ca. 200 m inland from coast, 1˚17’12.7''S, 90˚29’36''W, 20 m alt., dry zone, open Bursera forest with Waltheria ovata, few shrubs of Scalesia affinis and some grasses, on rock below overhang, semi-shaded, wind- and rain-sheltered, 16 January 2011, Bungartz 9761 (CDS 47078−holotype).
Thallus saxicolous, leproid-placodioid, forming minute rosettes with sorediate granules in the centre and minute, squamulose lobes along the margin, adhering to the substrate by sparse, protruding hyphae forming an indistinct prothallus; upper surface white to greyish white; granules in the thallus centre compact, ecorticate with sparse, short protruding hyphae [(61–)76–91(–121) µm in diam.], but aggregating into coarse, compact, pseudocorticate lobes [(136–)152–212(–273) µm in diam.] towards the margin, photobiont layer and medulla not distinctly differentiated, unpigmented, IKI-, filled with minute crystals that dissolve in K and sparse, large crystals that are insoluble in K, no needles forming in H2SO4 (calcium oxalate absent). Apothecia not known. Pycnidia not known. Photobiont green, trebouxioid, 7–10 μm in diam.
Ecology and distribution: Known from a single locality along, ±sheltered rock along the coast of Floreana Island.
Etymology: Named for its rosettes composed of leproid granules.
Notes: The small rosettes of D. leproidica may be confused with those of D. squamulosa. The thalline rosettes and individual lobes of the two species are similar in size, but the pale white to greyish surface of marginal lobes of D. leproidica is rough and lacks a distinct cortex (pseudocorticate) and towards the centre the lobes irregularly disintegrate into coarse, ecorticate granules. The granules and lobes are not clearly differentiated internally. This contrasts with the ivory to pale beige, compact, dull upper surface of D. squamulosa. This species forms distinctly delimited, erumpent soralia, which may become confluent with age. Although it is sometimes difficult to discern, the squamules of D. squamulosa are anatomically clearly differentiated into phenocortex, photobiont layer, and medulla.
The two species are ecologically similar, growing in sheltered habitats typically protected below overhangs, unlike the much larger thalli of D. glebosa and D. neotropica, which are commonly found in exposed habitats. Nevertheless, habitat preferences of the two species are distinct. Diploicia leproidica grows in close proximity of the coast, whereas D. squamulosa occurs in the upper transition zone and the high altitude transition zone.