Citation: Liber, Z.; Radosavljevi´ c, I.; Šatovi´ c, Z.; Hodja, M.; Židovec, V.; Boguni´ c, F.; Ballian, D.; Steševi´ c, D.; Jelaska, S.D.; Kremer, D. Morphological and Molecular Characterization of Micromeria croatica (Lamiaceae), an Endemic and Potentially Valuable Horticultural Species of the Dinaric Alps. Horticulturae 2023, 9, 418. https://doi.org/10.3390/ horticulturae9040418 Academic Editor: Carlo Nicoletto Received: 28 February 2023 Revised: 8 March 2023 Accepted: 21 March 2023 Published: 23 March 2023 Copyright: © 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). horticulturae Article Morphological and Molecular Characterization of Micromeria croatica (Lamiaceae), an Endemic and Potentially Valuable Horticultural Species of the Dinaric Alps Zlatko Liber 1,2 , Ivan Radosavljevi´ c 1 , Zlatko Šatovi´ c 1,3 , Marija Hodja 4 , Vesna Židovec 3 , Faruk Boguni´ c 5 , Dalibor Ballian 5,6,7 , Danijela Steševi´ c 8 , Sven D. Jelaska 1 and Dario Kremer 9, * 1 Faculty of Science, University of Zagreb, Maruli´ cev trg 9A, 10000 Zagreb, Croatia; zlatko.liber@biol.pmf.hr (Z.L.); ivan.radosavljevic@biol.pmf.hr (I.R.); zsatovic@agr.hr (Z.Š.); sven.jelaska@biol.pmf.hr (S.D.J.) 2 Centre of Excellence for Biodiversity and Molecular Plant Breeding, Svetošimunska Cesta 25, 10000 Zagreb, Croatia 3 Faculty of Agriculture, University of Zagreb, Svetošimunska Cesta 25, 10000 Zagreb, Croatia; vzidovec@agr.hr 4 Croatian Paying Agency for Agriculture, Fisheries and Rural Development, Ulica Grada Vukovara 269d, 10000 Zagreb, Croatia 5 Faculty of Forestry, University of Sarajevo, Zagrebaˇ cka 20, 71000 Sarajevo, Bosnia and Herzegovina; f.bogunic@sfsa.unsa.ba (F.B.); balliandalibor9@gmail.com (D.B.) 6 Slovenian Forestry Institute, Veˇ cna Pot 2, 1000 Ljubljana, Slovenia 7 Academy of sciences and arts of Bosnia and Herzegovina, Bistrik 7, 71000 Sarajevo, Bosnia and Herzegovina 8 Faculty of Natural Sciences and Mathematics, University of Montenegro, Džordža Vašingtona bb, 81 000 Podgorica, Montenegro; danijela.stesevic@ucg.ac.me 9 Faculty of Pharmacy and Biochemistry, University of Zagreb, A. Kovaˇ ci´ ca 1, 10000 Zagreb, Croatia * Correspondence: dkremer@pharma.hr; Tel.: +38-51-4619-492 Abstract: Due to climate extremes and limited natural resources, especially water, we can expect increased demand in the future for species that can better tolerate climate extremes such as drought. One potentially valuable horticultural species is the endemic species of the Dinaride Mountains Micromeria croatica (Pers.) Schott (family Lamiaceae). It grows in the crevices of carbonate rocks, extending from an altitude of 150 m to more than 2000 m. This study aims to provide additional insight into the genetic and morphological diversity of this endemic species, focusing on valuable horticultural traits. To achieve this goal, morphological and molecular analyses were performed on ten natural populations. Through STRUCTURE and PCoA analyses, ten M. croatica populations were placed into western and eastern genetic groups, with several individuals from western populations assigned to the eastern group and vice versa. These atypical individuals assigned to the new genetic group by BAPS analysis indicate gene flow between western and eastern populations. Similarly, an analysis of molecular variance revealed fewer genetic differences than within studied populations. Both PCA and CANDISC analysis based on eleven morphological traits largely confirmed the existence of two slightly different genetic groups. Two populations containing plants with the most flowers per shoot, one with white-flowered individuals, one with the roundest leaves, and one with the narrowest leaves proved to be the most horticulturally valuable. The genetic and morphological variability found should be a sufficient basis for the potential selection of M. croatica populations and individuals for horticultural purposes. Keywords: AFLP; Balkan Peninsula; BAPS; DA; PCA; PCoA; STRUCTURE 1. Introduction Bearing in mind climate changes and the limitation of natural resources, the need for more rational management of natural resources arises. Among such limited natural resources, we can include water, whose availability for horticultural needs will probably Horticulturae 2023, 9, 418. https://doi.org/10.3390/horticulturae9040418 https://www.mdpi.com/journal/horticulturae