A new species of perennial Bromus (Bromeae, Poaceae) from the Iberian Peninsula

Abstract During a survey of the genus Bromus for the ongoing Flora Iberica, B.picoeuropeanussp. nov., a new orophilous species of perennial Bromus from Picos de Europa National Park, was found, and it is described and illustrated here. This new species belongs to the Bromuserectus complex and differs from the other perennial species of this group occurring in the Iberian Peninsula in its well-developed rhizome, the small innovation leaves and all peduncles and branches shorter than the spikelets. B.picoeuropeanus grows on calcareous stony soils associated with dry places. We provide a description and illustrations of the new species and an identification key for the most related European perennial species belonging to the complex.


Introduction
The genus Bromus L. is the only representative of the tribe Bromeae in Southwest Europe. The genus comprises perennial and annual species, and both life forms are distributed throughout the genus. Bromus has a characteristic fleshy appendage above with broad distributions as well as narrow endemisms that are grouped within several complexes of cytologically and morphologically similar species (e.g. the Bromus erectus complex and the Bromus ramosus complex). The Bromus erectus complex includes perennial species, with old sheaths remaining intact or decaying into parallel fibres, inflorescences with some long branches and/or pedicels, and spikelets erect (Smith 1980, Acedo et al. 2009Pignatti et al. 2017). The taxonomy of some species or groups was studied in different regions e.g. "Bromus erectus Group" in Slovenia (Bačič and Jogan 2001) or the species B. erectus along the Cantabrian range and Pyrenean mountains in the Iberian Peninsula (Acedo et al. 2009). The Bromus erectus complex includes several endemics and probably some taxa remain undescribed, due to the lack of a global taxonomic revision.
The main objectives of this study are to describe a new species, to differentiate it from its relatives, and to characterize this new taxon.

Materials and methods
Several specimens of perennial Bromus were collected during a survey of the genus Bromus for the ongoing Flora Iberica project. This material was confirmed as a new species after a careful study and comparison with material deposited at JBAG, LEB, FCO, MA, MAF, JACA, SALA, SANT, VIT, representing the full distribution and variability of B. erectus Huds. from the Iberian Peninsula as well as specimens belonging to related species ( ). In addition, material from several important European Herbaria: C, K, FI, MSNM was studied. We also studied specimens and photographs of types and original material in B, P, and K, including the type specimen of B. erectus (Llamas and Acedo 2019, in press). Herbarium acronyms follow Thiers (2018+ continuously updated).
Specimen locality data were recorded in the field or via geo-referencing. We assessed the preliminary conservation status of the new species using our field knowledge, applying the IUCN (2017) criteria and performing a GeoCat analysis (Bachman et al. 2011). The extent of occurrence (EOO) and the area of occupancy (AOO) were estimated using GeoCat. For AOO calculation, a 2 km cell width was used. The information and measurements of the new and closely related species were taken from live and dried herbarium specimens, and from field data. The taxonomic treatment of the genus Bromus follows Acedo and Llamas (1999). Measurements and data for the diagnostic characters comparing the new species and B. erectus are presented in Table  1, and an identification key is provided to facilitate differentiation from the related European species. ) in having shorter habit; longer creeping rhizomes; non-cauline leaf blades short and never reaching the inflorescence, flat and similar to the cauline leaves; ligule truncated or round up to 1 mm; panicle 3-5(8) cm, contracted and smaller, with few spikelets, up to 11; all branches shorter than the spikelets; caryopsis thickened, inrolled or plicate, 8-9 mm, shorter than palea. B. picoeuropeanus also differs in its preference for stony soils.
Etymology. The specific epithet is a reference to the Spanish National Park Picos de Europa, where it was collected.

Discussion
Some thirty perennial species belonging to the genus Bromus occur in the Euro+Med area (Valdés and Scholz 2006;. Five perennials live in the Iberian Peninsula (Smith 1980;Acedo and Llamas 1999) including the cultivated and naturalized Bromus inermis Leyss. extensively cultivated all over the world, the weeds B. catharticus Vahl, and B. sitchensis Trin., and the native perennial species, B. benekenii (Lange) Trim., B. ramosus Huds., and B. erectus. This last species is the only one known in the Iberian Peninsula belonging to the B. erectus complex until now.
The Bromus erectus complex is differentiated by its persistent basal sheaths remaining intact or decaying into parallel fibers, and the non-cauline basal leaves typically longer and narrower than the cauline leaves. Its inflorescence is lax, spread or contracted, with erect branches and pedicels, more or less developed, but some of the pedicels longer than the spikelet. The multiflorous spikelet is supported by two subequal or unequal glumes with 1-5 nerves (Smith 1981;Acedo and Llamas 1999;Cope and Gray 2009;Pignatti et al. 2017). Other perennial species have old basal sheaths forming a reticulum as B. moesiacus Vell. or B. riparius. The complex lacks auricles as opposed to other perennial species having long lanceolate auricles (e.g. B. biebersteinii) or diminished auricles (e.g. B. stenostachyus Boiss.).
The morphological traits of Bromus picoeuropeanus suggest it must be classified within the Bromus erectus complex. Among the Iberian perennials, the specimens of B. picoeuropeanus are morphologically more similar to the widespread B. erectus. The presence of a developed rhizome 3-5(7) cm long (Fig. 1, 3) is a major difference with the remainder of the perennial Iberian taxa. This trait is relevant also in the differentiation of other perennial species such as the nemoral B. benekenii and B. ramosus (Cope and Gray 2009 (Fig. 1) than those of B. erectus, which has long and narrow leaves frequently reaching the inflorescence. Leaf hairs are very rare in B. picoeuropeanus, even more scarce than in B. erectus. In detailed descriptions of B. erectus, there is a large range of variability in other characters that are not useful for separating taxa: for instance, some floras (Pignatti et al. 2017) recognized Bromus longiflorus Willd. ex Spreng. as having long spikelets with 11-13 florets, which is a variation of B. erectus. We have observed that the number of florets is a variable character in several species (Acedo and Llamas

A B
1999; Acedo et al. 2009), and the floret number can be sometimes twice or more than its usual number.
While Bromus erectus has a wide distribution in most of Europe (except on the Scandinavian peninsula and the adjacent Northeastern countries), B. picoeuropeanus is known only in the National Park of the Picos de Europa, a small territory of the Cantabrian range. B. picoeuropeanus differs also in its ecological behavior from all the native Iberian perennial species. B. benekenii and B. ramosus occur in nemoral habitats and B. erectus mainly in mesophyllous meadows. B. picoeuropeanus, by contrast, occurs in stony and rocky places.