Orthotrichum bistratosum (Schiffn.) J.Guerra

Osman, Imen Ben, Hugonnot, Vincent, Muller, Serge D. & Daoud-Bouattour, Amina, 2021, Four bryophytes collected in Tunisia, new for mainland Africa, Cryptogamie, Bryologie 20 (16), pp. 213-219 : 214-215

Orthotrichum bistratosum (Schiffn.) J.Guerra

SPECIMENS EXAMINED. — Tunisia, High Tell, Beja Governorate, Delegation of Thibar: Djebba (36°28’15.20”N, 09°05’57.03”E;

620 m a.s.l.; site 2019-104), 13.IV.2019, leg. Imen Ben Osman, Vincent Hugonnot, TUN2019-280; Tunisia, Northern Tell, Beja Governorate, Delegation of Beja North: Jbel Zebla (36°49’23.60”N, 09°15’36.91”E, 552 m a.s.l; site 2019- 106), 13.IV.2019, leg. Imen Ben Osman, Vincent Hugonnot, TUN2019-281.

DISTRIBUTION. — S Europe ( France, Spain, Greece; Ros et al. 2013; Lara & Garilleti 2014; Ellis et al. 2016); SW Asia ( Iraq, Israel, Syria and Turkey; Kürschner & Frey 2020).

FLORISTIC ELEMENT. — Mediterranean.

HABITAT

Cultivated slope (fig tree, pomegranate…) and xerophytic scrubland on dry, exposed limestone rocks. The vascular plant communities are mainly composed of grazing-resistant species. In Tunisia, Orthotrichum bistratosum was accompanied by mundane xerophytic taxa: Encalypta vulgaris Hedw. , Grimmia orbicularis Bruch ex Wilson , G. pulvinata (Hedw.) Sm. , Orthotrichum anomalum Hedw. , Syntrichia montana Nees , Tortella nitida (Lindb.) Broth. , Tortula muralis Hedw. , Trichostomum brachydontium Bruch and Weissia condensa (Voit) Lindb.

At the Djebba site, tourism is particularly high and worrying since walkers may pull out moss cushions and ascend along rock outcrops, severely damaging lithophytic communities, as can be observed on site. Organising and limited public access through fencing and accompaniment by guides would be desirable.

This species had abundant sporophytes at each locality.

COMMENTS

Orthotrichum cupulatum Brid. var. bistratosum Schiffn. was raised to species rank by Guerra (1985) and this status has been confirmed by Lara & Garilleti (2014). Orthotrichum bistratosum is characterised by immersed sporophytes with cryptopore stomata, spreading exostome, uniformly bistratose lamina in the apical half of leaves, partially bistratose to unistratose to base. The leaf margins occasionally appear swollen with 3-4-stratose patches. The typical jet-black colour may be much less pronounced in Tunisian material than in material from other parts of its range. We have verified that this characteristic is not associated with the more unistratose patches of lamina and therefore consider it to be linked to phenotypic variation.