Carex × ligniciensis Figert, Allg. Bot. Z. Syst.

Koopman, Jacob, Dajdok, Zygmunt, Więcław, Helena, Martinetto, Edoardo, Grulich, Vít, Řepka, Radomír & Jiménez-Mejías, Pedro, 2018, Global distribution of Carex buekii (Cyperaceae) reappraised, Phytotaxa 358 (2), pp. 139-161 : 150

Carex × ligniciensis Figert, Allg. Bot. Z. Syst. 6: 38 (1900)

[ C. buekii × C. nigra ]

This hybrid, described from Poland ( Figert 1900), is also mentioned for the Czech Republic ( Grulich & Řepka 2002), Hungary ( Soó 1973) and Italy ( Koopman 2011). Kiffe (2004) gave a record for Germany: “Regenauen im Lkr. Regensburg.” Carex ×ligniciensis is relatively easy to recognise from the intermediate size, reddish-brown not reticulate basal sheaths and especially from the amphistomatic leaves. This last character makes this hybrid impossible to confuse with the other C. buekii hybrids, as C. nigra is the only species within the section Phacocystis with stomata on the adaxial side of the leaves (epistomatic) that co-exists with the hypostomatic C. buekii ( Wallnöfer 2006) . This hybrid has rarely been found in the Czech Republic, only at six localities, where both parent species grow together. Besides, in the Šumava Mountains, a hybrid population was identified and confirmed by flow cytometry and molecular markers, and shown to originate from hybridisation of C. buekii and C. nigra subsp. juncea Fr. It creates conspicuous tussocks and is clearly morphologically different from C. × ligniciensis (Řepka & Lustyk in prep.).

The occurrence of the four hybrids in Italy ( Koopman, 2011) is doubtful, as C. buekii is extremely rare in Italy. The presence of C. × viadrina is especially improbable given the doubtful presence of C. cespitosa in Italy ( Jiménez-Mejías et al. 2014b). Such a record could have been misled by the ambiguous usage of the name C. cespitosa to refer to other Phacocystis species in Italy ( Pignatti 1982; Jiménez-Mejías et al. 2014b).

During fieldwork in the surroundings of Wrocław (PL) in May 2015 the first three authors were able to find and tentatively identify material of three hybrids, C. × alluvialis [ C. buekii × C. elata ], C. × viadrina [ C. buekii × C. cespitosa ] and C. × vratislaviensis [ C. acuta × C. buekii ]. In all three cases both parents were present in the close surroundings. Peculiarly, during these four days fieldwork, we could not find any C. nigra nor its hybrid with C. buekii , C. × ligniciensis . This may have been caused by the low viability of this hybrid, which lives for a limited time and then disappears from the locality. Also there have been dramatic human impacts on the landscape during the past 50–60 years, so where this rare hybrid once occurred it might easily have been eliminated by changes in the water regime of a site, by direct destruction of marshes and wet meadows, or by their eutrophication.