Bituminaria plumosa (Fabaceae), a critical species of the Croatian flora

1Department of Agricultural Botany, Faculty of Agriculture, University of Zagreb, Svetošimunska cesta 25, HR-10000 Zagreb, Croatia 2Centre of Excellence for Biodiversity and Molecular Plant Breeding, Svetošimunska cesta 25, HR-10000 Zagreb, Croatia 3Dipartimento di Scienze Biologiche, Geologiche e Ambientali, Università degli Studi di Catania, via A. Longo 19, IT-95125 Catania, Italy *Author for correspondence: sbogdanovic@agr.hr

In the framework of a research aiming at improving the knowledge on this poorly investigated genus of the Mediterranean flora, we studied a critical species, described by Reich enbach (1832) from Dalmatia (Croatia) and named Psoralea plumosa.Later, Reichenbach & Beck de Manna-Pl.Ecol. Evol. 149 (3), 2016getta (1903: Tav. 140 I) published a fine and colored illustration of this plant, but it was considered to represent a variety of Psoralea bituminosa, highlighting some of its most relevant diacritical features.This taxon was quoted by several authors (Grenier & Godron 1848, Nyman 1854-1855, 1878, Willkomm & Lange 1880, Cesati et al. 1884, Rouy 1899, Fiori & Paoletti 1900, Hayek 1927) who treated it at specific or infraspecific level, recording this legume from many other Mediterranean countries.Based on our study of herbarium specimens and field investigations, it is clear that the aforesaid authors used (as it is quite evident from the diagnostic descriptions reported in their floras) inappropriate morphological characters for the distinction of the taxon, thus leading to erroneous identifications.
In order to clarify the taxonomic, nomenclatural and phytogeographical aspects of this peculiar and still poorly known legume of the Mediterranean flora, in-depth investigations were carried out mainly in the area from which this plant was originally collected, as well as in the surrounding territories.Furthermore, such surveys allowed to shed a light on the ecology, distribution range, macro-and micro-morphology of this critical legume.This allowed to establish that P. plumosa is a taxon to be treated at specific level, distributed all over the Adriatic side of Croatia, and that it should be moved to the genus Bituminaria.

MATERIAL AND METHODS
The morphological analyses on Bituminaria plumosa were carried out on herbarium specimens (c.30) and several living plants coming from Istria and other localities of Croatia, while for the other species of Bituminaria the herbarium material recorded by Minissale et al. (2013) and Giusso del Galdo et al. (2015) was used.In addition, living plants included in this study are cultivated in the Botanical Garden of Catania, and are originated from seeds collected all over the Mediterranean (e.g.Spain, Baleares, Corsica, Sardinia, Sicily, Italy, Croatia, Greece, Cyprus, Turkey, Israel, Jordan, Tunisia, Morocco, Canary Islands, etc.).Finally, herbarium material preserved in the following herbaria was also studied: BEOU, BP, BR, CAT, CNHM, HEID, LJM, TUB, ZA, ZAGR, ZAHO, ZT, W and WU (abbreviations are according to Thiers 2015).Seed testa micro-morphology was studied on ten mature and dried seeds using a scanning electron microscope (SEM) Zeiss EVO LS10, according to the protocol reported by Stork et al. (1980), while terminology of the seed coat sculpturing follows Barthlott (1981) and Gontcharova et al. (2009).
Habitat and ecology -Based on field observations, B. plumosa grows at the margin of Quercus ilex woodlands (in Istria) and /or paths and roads within semi-natural phytocoenoses.
Taxonomic remarks -According to the literature and herbarium investigations, as well as morphological observations carried out on several living plants collected in many Mediterranean localities, B. plumosa is well differentiated from the other known species of this genus (see table 1).In particular, the main diagnostic features are represented by a dense villous indumentum covering the whole plant, leaflets ovate to ovate-lanceolate, provided with a long mucro, corolla purplish-pink with elliptical standard and longer pistil (fig. 3).Besides, there are relevant differences also in the seed coat sculptures, especially if compared with those of B. bituminosa, B. basaltica and B. kyreniae, already surveyed by Minissale et al. (2013) and Giusso del Galdo et al. (2015).
Table 1 provides an overview of these diagnostic features and their comparison with the other taxa belonging to Bituminaria subg.Bituminaria.
Main diagnostic characters of the species belonging to Bituminaria subgen.Bituminaria.