Porina leptalea
The typical material has small dull orange perithecia on a grey-green thallus and is found as an ephemeral early colonist on shaded bare bark and rarely on rock. Marked by the involucrellum only containing an orange pigment (Porina-yellow) and the three septate spores being less than 23 µm long. Porina lectissima has larger perithecia and ascospores, has an additional dark pigment in the involucrellum and is mainly found on rock. There are also two other distinct morphs currently included within Porina leptalea, which maybe separate species, these are described below as well.
Thallus superficial, very thin, smooth or finely granular, grey-green to dark olive-green. Perithecia 0.1–0.3 mm diam., one quarter to one half immersed, brownish orange; involucrellum orange (Porina-yellow), containing numerous photobiont cells; exciple colourless to yellow. Ascospores 3-septate, 14.5–23 × 3.5–5 µm. Pycnidia ca 100 µm diam., red-brown; conidia ellipsoidal to cylindrical, straight to slightly curved or dumb-bell-shaped, 1.7–2.5 × ca 1 µm.
Porina lectissima has larger perithecia and ascospores, and P. aenea, P. byssophila and P. chlorotica have blackish perithecia. Thelopsis rubella also has red perithecia, but these are larger and contain multispored asci.
Morphs with dark red-black perithecia, which are bright red when wet, and with narrow ascospores, occur in wound tracks on veteran Holly and Beech and are frequent in the New Forest and elsewhere in the south west, but are otherwise similar. Another morph has brighter red perithecia, longer and narrower ascospores and an orange finely sorediate thallus and has been recorded in the north of Ireland and in south west England. Their taxonomic status is unclear and is under investigation.
The red perithecia morph has a darker brown to black thallus, dark red-black perithecia, becoming rubby-red when wet, 0.08 – 0.15mm diameter, the involucrellum has an outer layer of dark purple-violet, K + bluish grey pigment (Sagedia-red), thickest at the apex, with orange pigment below (Porina-yellow) and has narrow 3-septate ascospores, 15 – 22 x 3 – 3.5 µm. The presence of Sagedia-red suggests this taxon is not referable to Porina leptalea, the apothecia are similar to those of Porina lectissima, but are too small and the spores are much too narrow, suggesting this is an undescribed species.
The sorediate morph has a pale brown thallus dominated by orange irregular soredia to 20µm diameter, rubby-red perithecia, the involucrellum has an outer layer of dark pigment (Sagedia-red?), but less thickened at the apex, over the orange pigment below (Porina-yellow) and has longer and narrower 3-septate ascospores, 20 – 28 x 3 – 3.5 µm.
On bark of broad-leaved trees (Alder, Beech, Elm, Hazel, Holly and others), but also frequent on the bases of conifers in plantations; also on damp rocks and stones, shade-tolerant. The typical orange perithecia morph is an early pioneer colonist of shaded bare bark. It usually only forms small thalli and is likely rather ephemeral in occurrence. In contrast, the red perithecia morph frequently forms large perennial colonies in rain tracks, especially on older Hollies. The sorediate morph appears to be a rare taxon of base rich bark on older trees.
Frequent. W. Britain, Ireland. The typical orange perithecia morph is widespread and probably found through out the range but is never abundant, the red perithecia morph appears to be more strongly south western in distribution and can be locally abundant in old woods.
Orange, A., Cannon, P., Malíček, J., Sanderson, N., Coppins, B. & Simkin, J. (2021). Ostropales: Porinaceae, including the genus Porina. Revisions of British and Irish Lichens 4: 1-12.
Text by N A Sanderson, based Orange et al (2021)