Taxonomical and chorological remarks on the Mediterranean Poa maroccana (Poaceae) and the first record in Italy from the Sicilian flora

Introduction

Within the genus Poa L., a large cosmopolitan genus of the family Poaceae, the annual species hitherto known from the Mediterranean flora are examined. According to literature (Chrtek and Jiràsek, 1962,Hernandez Cardona 1978,Edmondson 1980,Nikolić 2000,Böhling and Scholz 2003,Valdés and Scholz 2009,Ibn Tattou and Fennane 2009,Banfi 2017,Cabi et al. 2017,Ortega-Olivencia and Devesa 2018,Brullo et al. 2019), they are currently represented by at least six taxa, such as Poa annua L., P. infirma Kunth, P. dimorphantha Mürbeck, P. cyrenaica E.A.Durand & Barratte, P. jubata A.Kern. and P. maroccana Nannf. All these species, except the last one, are usually considered in the literature as clearly distinct species, which differ from each other in several morphological characters, as well as in ecological requirements, chromosome complement, taxonomic and phylogenetic position (Nannfeldt 1938,Camus 1952,Tutin 1957,Gillespie and Soreng 2005, Gillespie et al. 2007,Cabi et al. 2017,Tkach et al. 2020). As concerns P. maroccana, it often has been treated as a doubtful taxon (cf.Edmondson 1980,Valdes et al. 2002,Strid 2016) or not quoted at all (cf.Ortega-Olivencia and Devesa 2018). In view of the large amount of literature data (Nannfeldt 1938,de Litardière 1938, 1939,Camus 1952,Tutin 1957,Chrtek and Jiràsek 1962,Scholz 1968,1993,1996,Böhling and Scholz 2003,Valdés and Scholz 2006,2009,Valdés 2013,Dimopoulos et al. 2013,Ibn Tattou 2014,Nosov et al. 2019), P. maroccana must be conversely considered a species morphologically clearly differentiated from all the other species belonging to the cycle of P. annua.

This species was described byNannfeldt (1938) based on herbarium materials collected by Samuelsson in Morocco during a trip of 1936 and also on cultivated plants using seeds taken from these specimens. Besides, this author emphasized the close relationships of P. maroccana with P. infirma, with which it shares loosely arranged and strongly compressed culms, lower inflorescence branches erect-patent after anthesis, spikelets with remote flowers not hiding the rachilla, apical flower not longer than a half of its pedicel and all lemma nerves densely villous. However, they clearly differ in some relevant features, since P. maroccana is characterized by a larger size, with culms up to 40 cm high, much longer leaf blades, larger spikelets (5–7.5 mm long), much longer bracts, anthers 0.7–1.2 mm long, while P.infirma shows a small size, with culms 5–20 cm high, usually shorter leaf blades, smaller spikelets (2–4 mm long), shorter bracts, anthers 0.2–0.5 mm long. The two species also differ in the chromosomic complement, which is tetraploid (2n = 28) in P. maroccana and diploid (2n = 14) in P. infirma, as shown byNannfeldt (1938) andde Litardière (1938, 1939). Another species quite similar to P. maroccana is P. annua, which is also tetraploid with 2n = 28, and yet shows a remarkable morphological variability (Tutin 1957,Mao and Huff 2012). Within the latter, in fact, numerous infraspecific taxa (subspecies or varieties) are known in the literature (Valdés and Scholz 2006,Ortega-Olivencia and Devesa 2018), of which P. annua subsp. pilantha (Ronniger) H.Scholz has greater similarities with P. maroccana, especially with respect to the lemma nerves being provided with long hairs (Scholz 1968). In particular, P. annua, which on a superficial observation could be confused with P. maroccana, differs very clearly from the latter because of its slightly compressed, often creeping, roots of the culms, the ovate-triangular and irregularly denticulated ligules, lower inflorescence branches spreading or deflexed after anthesis, spikelets with compact flowers hiding the rachilla, apical flower at least double as long as its pedicel and all lemma nerves usually subglabrous (rarely glabrous as in var. raniglumis Fröhner) or sparsely hairy, anthers lightly shorter (0.6 - 0.8 mm). Besides, recent molecular investigations carried out byNosov et al. (2019) have confirmed that P. maroccana is an autotetraploid of P. infirma, an origin previously hypothesized byChrtek and Jiràsek (1962) andScholz (1996). It should be noted that an eventual taxonomic affinity between P. maroccana and P. annua must be excluded in any case, since on the basis of experimental hybridizations carried out byNannfeldt (1938), where the hybrids obtained were characterized by chromosome count (2n = 28) and were completely sterile (Chrtek and Jiràsek 1962,Warwick 1979). Triploid hybrids (2n = 21) originating from a cross between P. maroccana and P. infirma, were also observed occasionally on the island of Crete byScholz (1996) and were described as P. x perinconspicua H. Scholz (cf.Scholz 1998); they are sterile or in any case have low fertility (seeNannfeldt 1938,Scholz 1993). Basing of these results, it can therefore be asserted that P. maroccana from the morphological, caryological and molecular viewpoint must be considered a species taxonomically distinct from other taxa belonging to the cycle of P. annua, having clear phylogenetic correlations only with P. infirma.

As concerns its taxonomic arrangement, P. maroccana falls within the P. sect. Ochlopoa described byAscherson and Graebner (1900), which groups species with annual or sometimes short-lived perennial habit, culms erect or shortly creeping, leaves flat, inflorescence branches smooth, lemma not lanate at base and more or less hairy in the nerves (Edmondson 1980). Later,Scholz (2003) andValdés and Scholz (2006) considered it more appropriate to arrange the species belonging to this section in a distinct genus, named Ochlopoa H.Scholz, including also P. maroccana. However, this treatment is not supported by the recent phylogenetic approaches that, using nuclear and plastidial sequences, have established that Poa is a large monophyletic genus, showing a cosmopolitan distribution, with about 550–575 species currently recognized (Gillespie and Soreng 2005,Gillespie et al. 2007,2018,Joshi et al. 2017,Soreng et al. 2015, 2017,Refulio-Rodriguez et al. 2012,Hoffmann et al. 2013,Cabi et al. 2017,Nosov et al. 2019,Tkach et al. 2020). Besides, these investigations emphasized that Poa must include many other species formerly attributed to other genera, formerly considered closely related to the latter. In particular as emphasized byGillespie et al. (2018) andTkach et al. (2020) it is necessary to place within Poa both Lindbergella sintenisii (H. Lindb.) Bor, described byLindberg (1942) as P. sintenisii and later included byBor (1968,1969) in the monospecific genus Lindbergella, accepted in the literature as an endemic from Cyprus (Meikle 1985,Watson et al. 1992,Soreng et al. 2015) and Libyella cyrenaica (Durand & Barratte) Pamp., also initially attributed byDurand and Barratte (1910) to the genus Poa, but recognized byPampanini (1925) as a taxonomically isolated species and referred to a new genus endemic from Cyrenaica, named Libyella, a treatment recognized by later authors (Maire 1953,Sherif and Siddiqi 1988,Watson et al. 1992,Soreng et al. 2015). Recently,Gillespie et al. (2018) andTkach et al. (2020) also arranged within Poa several annual species of Eremopoa Roshev., distributed in western and central Asia up to the Himalayas chain.

From the above-mentioned literature, six subgenera have been recognized within Poa, all of them usually well supported by phylogenetic studies. They are the following:

Poa L., Sp. Pl. 1: 67-70, 1753

Synonyms – Anthochloa Nees & Meyer, Reise Erde 2:14, 1834; Dissanthellium Trin., Linnaea 10:305, 1836; Aphanelytrum (Hack.) Hach, Oesterr. Bot. Z. 52:12, 1902; Libyella Pamp., Bull.Soc. Bot. Ital: 1925: 151, 1925; Lindbergia Bor, Svensk Bot. Tidskr 62: 467, 1968, nom illeg. non Kindb. 1897; Lindbergella Bor., Svensk Bot. Tidskr 63: 368, 1969; Eremopoa Roshev., Fl. URSS 2:429, 756, 1934; Austrofestuca (Tzvelev) E.B. Alexeev, Bjull. Moskovsk. Obàc, Isp. Prir. Biol. 81:35, 1976; Tovarochloa T.D. Macfarl. & But, Brittonia 34:478, 1982; Neuropoa Clayton, Kew Bull. 48:728, 1985; Tzvelia E.B. Alexeev, Bjull. Moskovsk. Obàc, Isp. Prir. Biol. 90: 103, 1985; Ochlopoa H. Scholz in Böhling & Scholz, Ber. Inst. Landschfts-Pflanzenökologie Univ.Hohenlm, Beih. 16: 58, 2003; Oreopoa H. Scholz & Parolly, Willdenowia 34: 146, 2004.

In particular, the annual species of Poa occurring in Euro-Mediterranean territories are distributed in various subgenera and sections. Among these, the taxa belonging to the P. annua cycle, such as P. annua s. str., P. infirma and P. maroccana, as well as P. dimorphonantha and P. cyrenaica, morphologically more isolated, are included within the subgen. Ochlopoa, described byHylander (1953), and in particular in sect. Micrantherae Stapf (= sect. Ochlopoa Asch. & Graeb.), while P. sintenisii is arranged in sect. Linbergella (Bor) Soreng, Cabi & L.J. Gillespie of the subgen. Pseudopoa. Finally, P. jubata was referred byCabi et al. (2017) to sect. Jubatae, a monotypic section whose attribution to a distinct subgenus is currently uncertain (cf.Brullo et al. 2019). AccordingNosov et al. (2019), all these taxa have been gathered to ‘basal Old World Poa s. str.’, diverging phylogenetically from other groups of annual Poa occurring in America, which belong to other subgenera and section, such as subgen. Poa (supersec. Homalopoa, sect. Homalopoa and Macropoda) or in the primitive sect. Paradiochloa. Much more complex are the positions of the numerous annual Poa species of East Asia, since some of them seem to have a hybridogenic origin among the taxa of sect. Homalopoa and those of Stenopoa, that do not allow them to be referred clearly to subgen. Poa or to subgen. Stenopoa (cf.Nosov et al. 2019).

In Italy, from the literature (Banfi 2017,Bartolucci et al. 2018,Brullo et al. 2019,Conti et al. 2020), 29 species of the genus Poa are currently recorded, to which P. maroccana must also now be added . As already pointed out, this species, showing a markedly thermophilous character, probably has an underestimated Mediterranean distribution. This is mainly due to the apparent similarity of P. maroccana with P. annua, with which, due to its habit, it can be easily confused. This also occurred in the casual discovery in Sicily of populations correctly attributable to P. maroccana, species that must be considered a new record for the vascular flora of the island, as for the whole of the Italian territory. This plant was first noticed along the edges of the urban roads of Catania (E Sicily), which attracted our attention for its vigorous and robust habit, very different from that of P. annua, which is much more slender, with which it was often mixed. Later, it was collected also along the urban roads of Giarre (N of Catania), but it is very probable that for the aforesaid reasons it may occur also in other Sicilian and Italian localities. Future careful investigations could certainly expand its current distribution.

Materials and methods

The morphological analysis of Poa maoccana was carried out on living specimens collected in urban stands of Catania and Giarre (Sicily), as well as on herbarium materials (viewed mainly online) kept in B, BC, BM, CAT, DAO, E, FR, GH, HSS, L, LD, LE, M, MA, MO, MPU, S, UPA and W (abbreviations are according toThiers 2020). For the identification of P. maroccana the morphological description, drawings and keys provided byNannfeldt (1938),Camus (1952),Chrtek and Jiràsek (1962),Scholz (1996) andBrullo et al. (2019) were used.

As concerns the processing of the morphological data listed inTable 1, it was based on the analysis of herbarium specimens, as well as on the literature treating the description of the mentioned species (Pampanini 1925,Nannfeldt 1938,Camus 1952,Maire 1953,1955,Edmondson 1980,1985,Meikle 1985,Watson et al. 1992,Zhu et al. 2006,Ibn Tattou 2014,Clayton et al. 2016,Banfi 2017,Brullo et al. 2019).

Results

Poa maroccana Nannf., Svensk Bot. Tidskr. 32: 296, 1938 (Fig. 1)

Fig. 1 Drawing of Poa maroccana from living Sicilian specimens by S. Brullo: A – habit, B – spikelets, C – upper glume dorsal view, D – lower glume dorsal view, E – Lemma dorsal view, F – palea dorsal view, G – palea ventral view, H – stamens, pistil and lodicules, I – Anther, J – Pistil, K – caryopsis, L – ligules.

Lectotype – Iter Algeriense-Maroccanum, Flora Maroccana. Distr. boreali-centralis Taza in fossa ad viam, ca. 450 m. s. m., 1/5/1936, Gunnar Samuelsson 7256 (S-G-6765!), designated byScholz (1993); isotypes (MPU 010584!, LE 00009663!, GH 00024370!, LD 1217604!; S 13-31402!).

Synonyms – Poa annua L. var. maroccana (Nannf.) Litard., Rev. Cytol. et Cytophysiol. Végét., 4: 83, 1939; Ochlopoa maroccana H.Scholz in Böhling, & H. Scholz, Ber. Inst. Landschafts-Pflanzenökologie Univ. Hohenheim, Beih.16: 59, 2003.

Description (from Sicilian material) – Annual, glabrous, without rhizomes, tufted, many-stemmed, with intravaginal branching. Culms 10–40 cm tall, erect or weakly geniculate at base, glabrous, with 4–6 nodes. Leaves 4–6, with sheath 5–40 mm long, fused up to 1/3, stem covered one half or up to totally, throat and collar smooth and glabrous; ligule rounded, sometimes triangular-oblong, ca. 1 mm long, glabrous; blade flat, soft, 1.5–4 cm long, 1.5–4.5 mm wide, smooth to slightly scabrous at the margin. Panicle 4–9 cm long, triangular-ovate to oblong-rhombic, erect, lax, open, with 1–2 branches per node, erect to ascending, glabrous. Spikelets 5.5–6.5 mm long, narrowly ovate to oblong-linear, laterally compressed, green, with 4–5(6) spaced florets and well exposed rachilla. Glumes unequal, shorter than adjacent lemmas, glabrous, ovate-oblong to lanceolate, distinctively nerved, with surfaces smooth and hyaline at the margins; lower glume 2–3 mm long, 1-nerved, subacute; upper glumes 2.5–3(4) mm long, 3–nerved, obtuse to subacute. Lemmas 2.8–3.7 mm long, ovate to ovate-oblong, rounded to rounded-obtuse at the apex, with 5 clearly distinct nerves, all densely villous and not reaching the margin. Palea hyaline, 2.3–3 mm long, with keels villous throughout their length, shortly ciliolate along the upper 2/3, bifid at the apex, with flanges appressed. Flowers bisexual; lodicules 0.3–0.4 mm long, pyriform, glabrous; anthers 0.7–1.3 mm long, yellow, inserted on very short filaments; styles 0.7–0.8 mm long, plumose. Ovary 0.3 mm long. Caryopsis adherent to palea, 1–1.4 mm long, fusiform, subtrigonous in cross section, hilum inconspicuous. Flowering time is from January to April.

Karyology – According to the literature (Nannfeldt 1938,de Litardière 1938, 1939,Scholz 1993), the investigated material of P. maroccana is characterized by a tetraploid chromosome number 2n = 4x = 28. It is therefore well differentiated from the closely related P. infirma, which is always diploid with 2n = 2x = 14. Other tetraploid species of Poa sect. Micrantherae are P. dimorphantha, P. rivulorum and P. annua, while P. supina Schrad. is diploid (Nannfeldt 1935,1938). Unlike P. annua, which is an allotetraploid derived from natural hybridization processes between P. infirma and P. supina (Tutin 1957), P. maroccana is an autotetraploid originating from P. infirma as hypothesized byEdmondson (1980),Chrtek and Jiràsek (1962),Scholz (1996) and recently confirmed byNosov et al. (2019).

Habitat and ecology – As concerns its ecological requirements, P. maroccana is usually linked to synanthropic stands, represented mainly by roadsides, uncultivated areas, gardens, ditches, depressions temporarily submerged and in any case habitats normally affected by anthropic disturbance, characterized by more or less damp and nitrified soils. In these places, it behaves like a ruderal plant, often growing with other annual species of Poa, such as P. annua and P. infirma, as emphasized also byNannfeldt (1938) andScholz (1993,1996).

Geographical distribution – Based on herbarium investigation and literature data (Nannfeldt 1938,Maire and Samuelsson 1939,Camus 1952,Maire 1955,Edmondson 1980;Scholz 1968,1993,1996,1998,2003,Turland et al. 2004,Valdés and Scholz 2009,Valdés 2013,Dimopoulos et al. 2013,Ibn Tattou 2014,Strid 2016,Zarco 2016,Nosov et al. 2019), P. maroccana shows a scattered distribution in many countries of the Mediterranean area (Fig. 2). In particular, it occurs in Morocco, Algeria, Tunisia, Libya, Portugal, Spain, Greece, Crete, Turkey, Syria, Crimea and also in Sicily, the latter also representing the first record for the Italian flora as a whole. As previously highlighted byScholz (1993), P. maroccana is most likely more widespread than it might seem based on current information due mainly to former misidentifications, as it has already been ascertained by examination of herbarium specimens.

Fig. 2 General distribution map of Poa maroccana from herbarium and literature data.

Conservation status – Being a strictly synanthropic species, although native to the Mediterranean and with a real distribution still underestimated, P. maroccana does not seem currently to be under threat or at risk of disappearance due to anthropic pressure. Therefore, P. maroccana can undoubtedly be regarded as an unthreatened species (LC) according to the IUCN protocol (IUCN 2017).

Specimina visa – Algeria: Tenit et Haad en une mare, May 1883, Trabut 3 (W-Hackel 1916-0007962); Dép. Oran. Mostaganem, 1848, B. Balansa s.n. (L 1319919); Dép. Oran: Monts de Tlemcen, lieux humides à Terni, L. Trabut s.n. (MPU), seeNannfeldt (1938); Ténira, near Sidi-Bel-Abbès, “lieux humides, 650 m s. m., 11 April 1931, A. Faure s.n. (S), seeNannfeldt (1938); ibid. “pelouses vers l’Oued”, 650 m s. m., 11 April 1931, A. Faure s.n. (MPU), seeNannfeldt (1938); Tiaret, L. Trabut s.n. (MPU), seeNannfeldt (1938); ibid. May 1905, J. A. Battandier s.n. (MPU), seeNannfeldt (1938); Dèp. Alger: Teniet-el-Had, 25 April 1889, Mac-Cartthy (?) s.n. (MPU), seeNannfeldt (1938); mare, May 1883, L. Trabut 3 (MPU), seeNannfeldt (1938); Rouiba, “lieux humides”, L. Trabut (MPU), seeNannfeldt (1938); Dép. Constantine: Aïn-Elmelouk, Joly s.n. (MPU); seeNannfeldt (1938); Pl. Saharae algerienses Territories du Sud: les oasis: Ouargla, ad margines rivulorum, 3 March 1904, L. Chevallier 646 (MPU), seeNannfeldt (1938).

Crimea: Crimea, near the settlement Frunzenskoe, Tzvelev s. n. (LE), seeNosov et al. (2019).

Greece: Fthiótis, Fthiotidhos, S Lamia, 1 April 1999, Willing R., Willing E. 73436 (B-JACQ-ID 825003); Évvoia, W Asmini, 11 May 2011, Willing R., Willing E. 217599 (B 10 0403169); Évvoia, W Edipsos, 10 May 2011, Willing R., Willing E. 217455 (B 10 0403170); Évvoia, SO Prokopi, 06 May 2011, Willing R., Willing E. 216044 (B 10 0403171); Évvoia, NNO Orion, 30 April 2011, Willing R., Willing E. 214031 (B 10 0403172); Évvoia, NO Avlonari, 30 April 2011, Willing R., Willing E. 213778 (B 100403173); Évvoia, S Aliveri, 26 April 2011, Willing R., Willing E.. 212512 (B 10 0403174); Évvoia, S Zarakes, 19 April 2011, Willing R., Willing E. 210250 (B 10 0403175); Voiotía, Mavrojia, 10 April 2011, Willing R., Willing E. 207192 (B 10 0403176); Voiotía, SW Orchomenos, 08 April 2011 Willing R., Willing E. 206425 (B 10 0403177); Fokídos, O Itea, 05 April 2011, Willing R., Willing E. 205661 (B 10 0403178); Fokídos, NW Itea, 05 April 2011, Willing R., Willing E. 205411 (B 10 0403179); Voiotía, Thivon, N Vagia, 13 April 1999, Willing E., Eisenblätter R. 76590 (B 10 0733741); Crete, distr. Heraklion: Malia, edge of lawn in a hotel recreation area, with Poa infirma and P. annua, 10 April, 1994, H. Scholz s. n. (B), seeScholz (1996); Crete., olive-tree plantation near K. Karouzana N of Kasteli, 17 April 1994, H. Scholz s. n. (B), seeScholz (1996); Crete., potato field and irrigation ditches in the hinterland of the beach near Malia, 22 April 1994, H. Scholz s. n. (B), seeScholz (1996); Crete distr. Lasithi: Lasithi Plateau, near Pinakiano, fallow land, with P. infirma, 15 April 1994, H. Scholz s. n. (B), seeScholz (1996); Crete, Nom. Lasithiou, Ep. Lasithiou: Lasithi plain, SE of Kristallenia monastery, 840 m, large level ploughed field, 4500 m², many similar fields and orchards in the area, 7 April 2003, Bareka, Turland s.n. (B, BM, MO, UPA), seeTurland et al. (2004); Crete, Chanion., Ep. Apokoronou, near Georgiopolis, fallow land, 15 April 1996, Scholz s.n. (B), seeScholz (2003); Crete, Lasithiou, Ep. Ierapetras, Thripti, weedy vineyard, 700 m alt., 24 March 1998, Bohling, Raus 7218 (B), seeScholz (2003); Crete, Ep. Lasithiou, Ag. Kroustalenias, open weed vegetation on seasonally wet field, 820 m a.s.l., 1 May 1997, Bohling 5436 (B), seeScholz (2003).

Italy: Catania, 15 January 2020, S. Brullo s.n. (CAT); Sicily, Catania, 18 February 2020, S. Bogdanović, S. Brullo, G. Tavilla s.n. (CAT); Catania, 3 March 2020, S. Brullo s.n. (CAT); Giarre, 8 March 2020, S. Bogdanović s.n. (CAT).

Libya: Tripoli, garden weed, 2 April 1970, H. Scholz s. n. (B, sub P. annua), seeScholz (1996).

Morocco: Seeds from herbarium specimen: Morocco, reg.bor.-centralis, Taza, in fossa ad viam, c. 450 m s.m., 1 May 1936, G. Samuelsson 7256., 6 July 1938, J. AX. Nannfeldt, 1938: 1 (B 10 0574487; E00381970; E00381971; E00381972; L.1319920); Plantae in horto Botanico Upsaliensi Cultae; Grow from seeds of the type collection: Morocco: reg. bor.-centr.: Taza, “in fossa ad viam”, ca. 450 m s.m., 1. May 1936, G. Samuelsson no. 7256., May.1938, J. AX. Nannfeldt s.n. (M-0103340; DAO000464910; FR0038639); Reg. bor.-occid.: “prope Salè (5 km ad orient.), in ripa stagni exsiccantis”, 2 April 1936, G. Samuelsson 6266 (S); seeds of this gathering were cultivated by me as 1936:8), seeNannfeldt (1938); ad ripas lacunarum ad orientem urbis Salè, solo arenoso, 2 April 1936, R. Maire (MPU), seeNannfeldt (1938); Casablanca, endroits frais incultes ou cultivés, 13 January 1918, L. Ducellier (MPU), seeNannfeldt (1938); Reg. austro-centr.: Aïn-Gernounch, Zaër, “ruisseaux sur le granit”, 11 March 1926, L. Emberger (MPU), seeNannfeldt (1938).

Portugal: Alto Alentejo (AAl): Alandroal, 31 March 2009, F.M. Vázquez & al. s.n. (HSS 41564), seeVazquez Pardo and Garcia Alonso (2016).

Spain: Prov. Murcia: Cartagena, entre los sambrados de la Huerta de San Antón, 15 February 1902, F. A. Ibáňez s.n. (MA 156755, sub Poa annua), seeScholz (1968); Prov. Cádiz: in cultis prope Jarez, 6 March 1875, Perez-Lara s.n. (MA 11141, sub Poa annua), seeScholz (1968); Badajoz (Ba): Calera de León, sierra de Tentudía, zonas altimontanas, 700 msm, 20 February 1997, F.M. Vázquez s.n. (HSS 2625), seeVazquez Pardo and Garcia Alonso (2016); Barcellona, L'Hospitalet del Llobregat, Gran Via Sur, 10 April 2014, Pyke SBP 6902 (BC 940161).

Syria: since loc., 1986?, D. J. Samuel 191 (B), seeScholz (1996).

Tunisia: Djebel Goraa, in irrigation ditches, 12 April 1968, H. Scholz 772 (B, sub P. annua), seeScholz (1996).

Turkey: Muĝla (C1): Bafa-Gölü/Besparmak Daĝi (Latmos-Gebirge), Kaprikiri, Ruinenstätte Herakleia am Latmos, alt. c. 150 m, 17 March 1998, Kürschner & Parolly 98-26 (B), seeScholz (1998).

Identification key to the annual species of Poa in the Euro-Mediterranean territory

Discussion

According to the literature data (Watson et al. 1992), the genus Poa is represented in the Mediterranean territories mainly by perennial species, with caespitose habit and often provided with rhizomes, stolons or bulbs, while the annual species are not very frequent. Among these latter the following must be mentioned: P. annua (cosmopolitan), P. infirma (Mediterranean-Irano-Turanian) and P. maroccana (Mediterranean), which are closely related among them, while taxonomically more isolated are P. dimorphantha (Morocco), P. sintenisii (Cyprus). P. cyrenaica (Libya) and Poa jubata (South-East European), species widely investigated by several authors (seeNannfeldt 1938,Camus 1952,Chrtek and Jiràsek 1962,Scholz 1968,1993,1996,2003,Hernandez Cardona 1978,Edmondson 1975,Ibn Tattou 2014,Clayton et al. 2016,Gillespie et al. 2018,Nosov et al. 2019,Tkach et al. 2020). As already highlighted, these species are taxonomically well differentiated and their systematic arrangement is widely supported by phylogenetic investigations.

In order to highlight the morphological features that allow us to distinguish the aforesaid species from each other and especially P. maroccana, a table is provided where all the diacritical characters for their easy identification are listed (Table 1). Besides, an analytical key was processed for their identification.

Based on our results, P. maroccana can be considered an autonomous species, morphologically and karyologically clearly differentiated from the other species belonging to the P. annua cycle, which were included in the sect. Micrantherae of a subgen. Ochlopoa, arrangement well supported by recent molecular phylogenetic analyses too. With respect to its ecology, this species, usually linked to wet habitats with soils rich in nitrates, allows its wild populations to spread also in typically synanthropic stands, as for instance the roadsides. Besides, because its habit is very similar to that of P. annua, it has often been confused with the latter, this at the expense of knowledge on its real distribution in the Mediterranean territories. It should also be considered that P. maroccana often occurs together with P. annua and P. infima, growing mixed in the same habitats; nevertheless, although closely related to these last two species, it never gives rise to fertile hybrids, was and it has been experimentally verified that they are genetically incompatible. However, it is to be believed that P. maroccana is almost certainly much more widespread than is currently known and that more accurate and extensive investigations, to be carried out both in the field and also in the herbaria, will provide more information on its true distribution.