Contribution to the Knowledge of Pontechium maculatum(Boraginaceae), a Species of High Conservation Concern in the Bulgarian Flora

Abstract

Pontechium maculatum (Boraginaceae) is a species of high conservation concern in the Bulgarian flora. It is assigned a national IUCN category ‘Vulnerable’, legally protected according to the national Biological Diversity Act, and listed in Annex II of the Habitats Directive (Council Directive 92/43/EEC). Recent studies in one of the largest populations in the country revealed some new data about the species which are reported here. The population studied is situated in Mt Lozenska, Mt Sredna Gora (Western) floristic region. Relevant taxonomic literature states that P. maculatum is a biennial plant, however, our observations revealed the plants in Mt Lozenska are perennial (possibly short-lived). A great variation in the corolla-colour was observed, most plants having bluish to violet corolla and only a few – reddish to dark red. This can be explained by either natural variation in the population, not reported in the taxonomic literature so far, or by hybridisation with Echium vulgare which cooccurs in the same locality. Large fluctuation in the number of flowering plants in two consecutive years was recorded, with some 180 blooming specimens in 2019 and only about 25 in 2020. Studies in the genome size of this population revealed the plants have significantly higher DNA-content (1C-value) than plants from the typical populations of the species in Northeast Bulgaria floristic region, e.g. Kabiyushka Mogila locality. Further biosystematics studies(chromosome number, genome size, genetic studies, etc.) are currently in progress to explain the observed phenomena within the Bulgarian populations of P. maculatum.