The PhD thesis is devoted to the study of the taxonomic status and phylogenetic relationships of marine brown algae of the genus Cystoseira sensu lato (Cystoseira sensu stricto, Gongolaria Boehmer and Ericaria Stackhouse) in the Black Sea and the Levantine basin of the Mediterranean Sea to clarify information on their taxonomic diversity and distribution within the Mediterranean basin, as well as to improve protection measures for habitats formed by them.
According to the results, the genus Cystoseira s.l. in the Black Sea is represented by taxa that belong to genera Ericaria and Gongolaria. The morphological data support the transition of Gongolaria barbata (Stackhouse) Kuntze to the genus Gongolaria, which was previously proposed based solely on genetic data. The recognition of the separate intraspecific taxa in attached Gongolaria barbata is unreasonable. A new nomenclature combination, Gongolaria barbata f. repens (A.D. Zinova & Kalugina) S.S. Sadogurska comb. nov., has been proposed for the unattached form of Gongolaria barbata. The synonymy of this taxon and the species Cystoseira aurantia Kützing sensu Orellana et al., 2019 was rejected.
The molecular analysis of the Black Sea endemic Cystoseira bosphorica Sauvageau showed its affiliation to the genus Ericaria and conspecificity with the Mediterranean species Ericaria crinita (Duby) Molinari & Guiry and Ericaria barbatula (Kützing) Molinari & Guiry. Given the unique morphological features and geographical isolation, its endemicity was confirmed, and a new combination Ericaria crinita f. bosphorica (Sauvageau) S.S. Sadogurska, J. Neiva et A. Israel was proposed.
The nomenclature-taxonomic revision showed that taxa from the Levantine Basin belong to genera Cystoseira s.s. and Gongolaria. Three taxa belong to the genus Cystoseira s.s.: widespread species Cystoseira compressa (Esper) Gerloff & Nizamuddin, and two rare taxa – Cystoseira foeniculacea (Linnaeus) Greville (the first well-documented finding in the last 25 years) and Cystoseira compressa subsp. pustulata Ercegović. The latter taxon was mentioned for the Israeli seashore for the first time. Based on molecular phylogenetic analysis data, its affiliation to the species Cystoseira humilis Schousboe ex Kützing was shown, and a new combination Cystoseira humilis subsp. pustulata (Ercegović) S.S. Sadogurska et al. A.Israel comb. nov. was proposed.
Molecular phylogenetic and morphological analysis showed that the endemic Levantine species Cystoseira rayssiae Ramon belongs to the genus Gongolaria. Morphological variability of this taxon, which is most pronounced between specimens growing in the sublittoral and littoral zones, was described. The analysis of herbarium specimens proved that in the early XX century, Gongolaria barbata and Ericaria barbatula species also occurred in Israel, but currently they are most certainly extinct.
The understanding about the Cystoseira s.l. biogeography in the studied regions and the Mediterranean basin was reviewed. It was shown that the separation of Ericaria, Gongolaria, and Cystoseira s.s. probably took place in the Atlantic before the Messinian salinity crisis. Entering into the Mediterranean Sea and further resettlement of these three genera took place independently. According to biostratigraphy, the last penetration into the Black Sea probably occurred about 6-7 thousand years ago, and in the Sea of Azov – 3-4 thousand years ago.
Among the two studied endemic Cystoseira s.l. taxa, the species rank was confirmed only for Gongolaria rayssiae. It was shown that its endemism is probably due to the reduction of range rather than its emergence within the Levantine Basin. On the contrary, it was shown that the endemic taxon Ericaria crinita f. bosphorica is conspecific with Mediterranean taxa. It indicates a relatively recent emergence of the taxon.
A hydrobotanical study of a new locality of Gongolaria barbata in the Dzharylhach National Nature Park (NNP) was carried out. The polydominant community Gongolaria barbata - Codium vermilara + Laurencia coronopus (for the first time indicated on the Ukrainian coast) was registered; a total of 30 macroalgae species were identified, about half of which belong to the category of rare species. The results indicate the improvement of the ecological condition of the marine environment in of Dzharylhach Bay. However, these algal communities are subject to special protection, and therefore it is recommended to enlarge the area of the marine protected area of Dzharylhach NNP.
To ensure the protection of communities and habitats, formed by Cystoseira s.l. taxa, and other marine habitats at the national and international levels, the 16 new sites were proposed for the Emerald Network of Ukraine. It is recommended to include Ericaria crinita f. bosphorica in the regional and national red lists.
