Phytosociology of Atractylis cancellata and Micromeria microphylla communities in southern Italy with insights on the xerothermic steno-Mediterranean grasslands high-rank syntaxa

In the present paper a phytosociological study on the dry grassland communities identified in the western sector of the Murgia Plateau (Murgia delle Gravine) and in the Lucanian badlands territory is presented. Forty vegetation releves were carried out using the Braun-Blanquet phytosociological approach. Two new associations characterized by a therophytic dominance, namely Lysimachio foeminae-Atractylidetum cancellatae and Campanulo erini-Micromerietum microphyllae, are described and discussed from a syntaxonomic and biogeographic viewpoint. In addition, new phytosociological data concerning the Petrosedum ochroleucum communities developed on limestone outcrops, the perennial Hyparrhenia hirta steppe-like grasslands of the low-altitude areas of the Murgia hills and the small-size Brachypodium distachyum therophytic communities are presented.


Introduction
Dry grasslands habitats are an extremely interesting and variegated element of the vegetation landscape of the hilly and montane areas of the central and southern Apennines. The bioclimatic position, intermediate between the Mediterranean and the Temperate Region, the very rich species pool available and the millennial multiform pattern of land-uses contributed to the high coenological diversification we are witnessing at present (Biondi and Blasi 1984;Biondi et al. 1995;Di Pietro 2011;Apostolova et al. 2015). The grasslands of the Murgia plateau and Gravinas gorges (an area majorly laying in the Apulia Region but comprising also territories in the administrative province of Matera in the Basilicata Region) can be distinguished from those occurring in the rest of the Apennines due to a more marked floristic and cenological similarities with the western Balkans vegetation. The situation is different as regards the grassland communities that develops on the clayey substrates subjected to accelerated erosion which appear in their typical form of Badlands (locally called "calanchi"). In that case, the vegetation shows greater similarities with what is known for the driest sectors of the Mediterranean basin characterized by the dominance of pre-desert steppe species, such as Lygeum spartum (Brullo et al. 1990). Over the past 20 years, the phytosociological knowledge of the study area (especially of the Murgia Plateau) was significantly improved (Forte et al 2005;Biondi and Guerra 2008;Terzi and D'Amico 2008;Terzi et al. 2010;Wagensommer 2008, 2014). Currently there is a good knowledge about the most common perennial grasslands (Acino suaveolen-tis-Stipetum austroitalicae and Irido pseudopumilae-Scorzoneretum columnae) and micro-garrigue associations (Helianthemo jonii-Corydothymetum capitati). Instead, the coenological knowledge on therophytic grasslands still shows many gaps. In fact, the syntaxonomy of perennial and therophytic grasslands remains uncertain for the higher ranks. In this paper, new phytosociological data for five community types are presented and discussed. In particular, we formalized the proposal of two new phytosociological associations of therophytic grasslands dominated by Atractylis cancellata and Micromeria microphylla, two species which exhibit a restricted distribution in the Italian peninsula. Atractylis cancellata (Fig. 1) is a therophyte having a Mediterranean-W-Asian distribution ranging from SW-Morocco and Canary islands (the native status of the species in these islands is still doubtful) to W-Pakistan throughout the southern sector of Iberian Peninsula, S-France, S-Italy, Sicily and Sardinia, N-E Greece and North Macedonia, Turkey, all the middle-East countries, the NE sector of the Arabian Peninsula and the coastal areas of Tunisia, Algeria, Libya and Egypt (Battandier and Trabut 1888;Pampanini 1931;Quezel and Santa 1962-63;Davis 1965Davis -1988Pottier-Alapetite 1979;Ozenda 1983;Benabib 2000;Boulos 2002;Fennane and Ibn Tattou 2009;López Martínez and Devesa 2014;Bammou et al. 2015;Hassler 2020;African Plant Database (version 3.4.0), Conservatoire et Jardin botaniques de la Ville de Genève and South African National Biodiversity Institute, Pretoria, "Retrieved [sept 2020]", from http://africanplantdatabase.ch). In southern Italy Atractylis cancellata occurs in the coastal and subcoastal areas of the Calabria Region and eastern Basilicata, in the Murgia plateau and Salento (Bartolucci et al. 2018). From an ecological point of view A. cancellata acts as a thermophilous species particularly resistant to drought (it occurs in the Negen and Dahna desert in Israel and Saudi-Arabia respectively) and exhibits a slight preference for neutral-alkaline soils with a significant clayey component (Pignatti et al. 2005).
Micromeria microphylla (Fig. 2) is a rare steno-Mediterranean micro-chamaephyte whose distribution range includes only Italy, Malta, Cyprus, Kriti and Lybia (Pampanini 1930;Euro+Med 2006-, Brullo et al. 2020. Additional records enlarge the distribution area of M. microphylla also to few localities of Spain (Balearic Islands) (Morales 1991;Castroviejo et al. 2010) and Croatia (Flora Croatica Database: https://hirc.botanic.hr/fcd/, accessed on August 2018). In Italy, Micromeria microphylla is known for various sites of Sicily, where it is located in the Drepano-Panormitano, Agrigentino, Camarinense and Ibleo phytogeographical districts, and for Egadi and Pelagie islands (Pignatti 1982;Brullo et al. 1995;Mazzola et al. 2001;Gueli and Lo Giudice 2004;Pasta et al. 2008). M. microphylla occurs also in the Apulia Region where it was recorded for the Adriatic coastal area between Andria and Otranto, and for few limestone rocky outcrops embedded in the dry grasslands of the Hippocrepido-Stipion near Grottaglie (Murgia Area). Further records for the Italian territory come from the archeological site of "Ostia antica" in the proximity of Rome where M. microphylla is considered an adventitious species (Lucchese 1988;Lucchese and Pignatti 2013).
Due to the very sporadic distribution of Micromeria microphylla in the Italian peninsula, this species was included in the Italian regional Red Lists and classified as "endangered" for the Apulia Region and as "low risk" for Sicily Region (Conti et al. 1997). However, the updated red list of plants of Apulia (Wagensommer et al. 2013) did not confirm the occurrence of M. microphylla for this Region.

Study Area
The study area (Fig. 3) encompasses two different sites. The first site concerns the western side of the Murgia plateau, an area bordering the Taranto Gulf in the Ionian side of the Apulia Region which also extends for a minor part in the Basilicata administrative Region. Murgia is the local term for "stone" and, according to the geological literature, it identifies a wide geological unit composed of a large plateau originated by the fragmentation of the Mesozoic Apulian limestone platform. The highest culmination (Torre Disperata 686 m) places the Murgia in third place among the Apulian orographic system after the Daunian sub-Apennine (Mount Cornacchia 1190m) and the Gargano Promontory (Mount Calvo 1090m). The Ionian side of the Murge plateau is characterized by deep vertical gorges, locally called "Gravine". The study area extents in the colline belt of the Murgia of Gravine, with an altitude range between 200 and 450 m a.s.l. on substrates composed of Mesozoic limestones and Plio-Pleistocene calcareous sandstones. The second site is located in the south-eastern part of the Basilicata Region where a sequence of hills composed of Plio-Pleistocene marine clays (Bradanic foredeep) with interspersed sandy levels occur. These hills are in continuous rejuvenation by means of channel incisions resulting in the development of typical running water slope landforms known as "Calanchi" and "Biancane" (Patacca and Scandone 2007;Del Prete et al. 2008;Bentivenga et al. 2014).
From a bioclimatic standpoint (Fig. 4 and Fig. 5) the whole study areas ranges between the upper Meso-Mediterranean and lower Meso-Mediterranean thermotypes and between the upper dry and lower sub-humid umbrotypes (Blasi 2006). In terms of potential (zonal) vegetation the Murgia territory is characterized by different forest types ranging between Euphorbio apii-Quercetum trojanae of the flattish limestone plateaus, Teucrio siculi-Quercetum trojanae in the upper part of the Gravine gorges, Festuco exaltatae-Carpinetum orientalis within north-facing slopes and at the Gorges bottom and Fraxino orni-Quercetum ilicis within the rocky steep slopes (Bianco et al. 1988;Biondi and Guerra 2008;Di Pietro and Misano 2009). The potential vegetation of the whole Lucanian Badlands area can be broadly addressed to thermophilous Quercus pubescens woods (Lauro-Quercenion pubescentis) and Mediterranean maquis shrublands (Helictotricho-Pistacietum lentisci). However, if observations were made at a smaller scale, each single badland should be considered as as a single vegetation unit composed of a mosaic of permanent micro-communities. These communities are dominated, in turn, by Lygeum spartum, Atriplex halimus, Pharapholis incurva, Suaeda fruticosa, Sulla coronaria, Sulla capitata, Polygonum tenoreanum depending on micro-geomorphology and soil texture (Brullo et al. 1990;Corbetta et al. 1992;).

Data and Methods
During the period 2001-2018 40 relevés of grassland stands were carried out applying the phytosociological approach (Braun-Blanquet 1964;Westhoff and van der Maarel 1978). The plot size used in the sampling procedures was variable according to the sampled vegetation type (therophytic grasslands, micro-chamaephytic grasslands, hemycryptophytic grasslands). Taxonomic nomenclature follows the checklist of the Italian vascular flora by Bartolucci et al. (2018) while for identification and taxonomic classification reference were made to Pignatti et al. (2017Pignatti et al. ( -2019. Life form and chorological spectra were calculated only for the communities described as new in this paper and made reference to Pignatti (1982) and Pignatti et al. (2005). Three types of spectra were calculated according to: i) how many times a given corotype/ life form occurred in the communities in issue (presence spectrum), ii) summing the frequency of each corotype/ life form and multiplying this sum for the ratio between 100 and the number of relevés included in the phytosociological table (frequency spectrum) and iii) summing the average cover values (5 = 87.5; 4 = 62.5; 3 = 37.5; 2 = 17.5; 1 = 5; + = 1; r = 0.1) corresponding to each dominance-abundance Braun-Blanquet's cover index and multiplying this sum for the ratio between 100 and the number of relevés included in the phytosociological table (cover spectrum).  In the diagnosis of each plant community we have highlighted the "dominant taxa" (species showing cover-abundance higher than 3 according to the Braun-Blanquet scale in at least one of the relevés included in the phytosociological table) and the "highly frequent taxa" (species occurring in at least the 75% of the relevés of the phytosociological table). In naming the phytosociological syntaxa, we adhered to the rules of the fourth edition of the International Code of Phytosociological Nomenclature (ICPN, Theurillat et al. 2020). The syntaxonomic classification of each single species (at the rank of class) made reference to Mucina et al. (2016) and was used to build the syntaxonomic spectra of the two associations proposed as new in this paper.

Results
The field work led to the identification of five homogeneous plant communities all referring to open dry grassland and micro-garrigue habitats. Two of them, namely Lysymachio foeminae-Atractilidetum cancellatae and Campanulo erini-Micromerietum microphyllae, are here proposed as new associations. For these latter, a detailed floristic, ecological, chorological and syntaxonomic description was provided. Two communities, out of the other three communities identified, were referred to associations (Stipo austroitalicae-Hyparrhenietum hirtae, Medicago disciformis-Brachypodietum distachyi) which were already described for the study area by other authors (Biondi and Guerra 2008), while for the third community the preliminary rank of "community type" was used (i.e. Petrosedum ochroleucum subsp. mediterraneum community). Synecology -Therophytic communities colonizing the Pliocene clayey substrates of the Lucanian badlands and developed on extremely restricted areas (1-2 m2 or even less). The Lysymachio-Atractylideto typicum (Fig. 6) acts as a poor-in-species community (average number of species per relevé = 12) which characterizes the relatively stable parts of the badland's south-facing slopes. In particular this community is located above and below the steeper part of the badland characterized by accelerated erosion and occupied by the Camphorosmo-Lygeetum sparti Brullo et al. 1990. In this context the Lysymachio foeminae-Atractylidetum cancellatae gives rise to two separated therophytic transiction fringes between the Cam-  phorosmo-Lygeetum and the communities developed on its upper and lower sides. In most cases the communities developed at the upper side are those dominated by Sulla coronaria and Scorpiurus muricatus occurring at the top of each single badland unit. The communities developed at the Camphorosmo-Lygeetum lower side are generally dominated by Parapholis incurva and Sulla capitata these species finding their optimal conditions at the badland footslopes where the run-off waters tend to deposit the finest clays.

Vegetation description
Life forms and chorology -Therophytes dominates in all the life forms spectra followed by the hemicryptophytes. Geophytes are completely absent and chamaephytes are very scarce. In the chorological spectrum steno-Mediterraneans dominate followed by Euro -Mediterraneans. The other chorotypes exhibit percentages always lower than 4% (Fig. 7).
Syndynamic -The Lysimachio-Atractylidetum typicum can be considered as a fragment of the micro-permanent vegetation mosaic forming the "badland system" micro-geosygmetum. A reduction of the erosive action of the flooding waters leads to the rapid colonization of the space occupied by the Lysymachio foeminae-Atractylidetum cancellatae by the communities dominated by Sulla coronaria (upper part of badland) or Sulla capitata (lower part of badland) and subsequently by the final scrub stage of the Helictotricho convoluti-Pistacietum lentisci Di Pietro et Misano 2010. Synecology -On the limestone substrates of the Murgia delle Gravine (in this case in the Gravina of Matera), this community features small pockets of soil interposed between the steppe-like grasslands and the micro-garrigues and the Mediterranean maquis communities. The most natural and long-lasting aspect of this subassociation develops where a very thin layer of soil covers the flat and more or less crackless limestone rocky surfaces. However, there are also other aspects related to the more or less disturbed areas placed on the edge of the paths created by grazing cattle trampling. Compared to the Lysimachio-Atractylidetum typicum occurring within the clayey Badlands area, the subass. ononidetosum reclinatae shows a significantly higher floristic richness (average number of species per relevé = 24). This is due to the wider pool of available annual species coming from the surrounding habitats (dry grasslands and micro-garrigues on limestone) and to the fact that the calcareous lithosols of the Murgia area are less oligotrophic than the sub-halophytic clays of the badlands.
Life forms and chorology -Therophytes dominates in all the life forms spectra followed by chamaephytes and hemycryptophytic with similar percentages. In the chorological spectrum steno-Mediterraneans taxa dominate followed by Euro-Mediterraneans. The other chorotypes exhibit percentages always lower than 5% (Fig. 7).
Syndynamic -The progressive vegetation succession consists of a first step dominated by the Stipa austroitalica steppe-like grasslands and a second one character- Figure 7. Life forms, chorological and syntaxonomic spectra of the Lysimachio foeminae-Atractylidetum cancellatae (Lys-Atra). The 3-digits codes in syntaxonomic spectra represent the class codes provided in the Eurovegchecklist (Mucina et al. 2016). Abbreviations: n. species = spectra based on presence/absence data; frequency = spectra weighted by species frequency; cover = spectra weighted by species cover-abundance.        Biondi et al. 1999).

II
Syntaxonomy -The Lisymachio foemine-Atractylidetum cancellatae is an association provisionally described (sub Anagallido foeminae-Atractylidetum cancellatae) for the vegetation mosaic of the Lucanian badlands (Fascetti et al. 2001;Di Pietro et al. 2003) whose validation has never been formalized. The new samples from the Murgia territories of Apulian and Basilicata regions allowed to enlarge the distribution area and the ecological spectrum of this association that we consider as divided into two subassociations: typicum and ononidetosum reclinatae. In this paper we validate the Lisymachio foemine-Atractylidetum cancellatae taking into account the chronology of the studies that have concerned this community over time. Accordingly, we have here established as subassociation "typicum" the one comprising the relevés performed on the salty-clayey substrates of the Lucanian badlands, which is the place where the association was originally (invalidly) described. Instead, the subassociation Lisymachio foemine-Atractylidetum cancellatae ononidetosum reclinatae is restricted to the limestone substrates of the Murgia plateau of the Matera administrative territory.
The Lisymachio foemine-Atractylidetum cancellatae is strictly limited to southern Italy where A. cancellata range extends. At present, we have no knowledge about other associations in which A. cancellata acts as dominant species. The only reference for the Italian peninsula is the association Atractylido-Neatostometum apuli described for western Sicily (Brullo et al. 1994) which exhibit some similarities due to a shared Brachypodietalia distachyi floristic background. However, Atractylido-Neatostometum apuli exhibits a higher sub-halophytic and xerophilous character, probably related to the rocky coastal habitats in which this association was described, and a floristic composition quite different from that of Lysimachio-Atractylidetum cancellatae (see A-N synoptic column in Table 1). In addition to the lack of Neatostoma apulum, there are other high-frequency and characteristic species of Atractylido-Neatosometum apuli that are missing in Lysimachio foeminae-Atractylidetum cancellatae (e.g., Anthemis arvensis, Anisantha fasciculata, Catapodium marinum, Kundmannia sicula, Moraea sisyrinchium, Sulla spinosissima) which do not allow to classify our relevés under this community.
The classification of Lysimachio foeminae-Atractylidetum cancellatae at syntaxonomic ranks higher than association is rather complex. The ephemeral communities that develop on limestone substrates or more generally on the neutral-alkaline ones that do not have an extremely limiting factor in the mineral component of the soil tend to be dominated by a group of wide-distribution steno-Mediterranean species occurring throughout the whole Mediterranean coastal and subcoastal areas. These communities are often distinguished each-other by differences in the abundance-dominance values of the species more than by the occurrence of unshared diagnostic characteristic species. As regards the classification of the Lysimachio-Atractylydetum cancellatae in the higher-rank syntaxa, two different options are available: i) to adopt a conservative choice considering few largescale syntaxa well-distinguishable from a floristic and chorological point of view, ii) to opt for a more divisive choice considering a syntaxonomic framework based on a higher number of alliances having a more or less similar floristic composition. De Foucault (1999) followed this second option distributing the European therophytic dry grasslands into many alliances and orders. In our specific case, we included Lysimachio-Atractylidetum into the Stipo-Trachynietea distachyae class, whose verbal diagnosis ("Mediterranean calciphilous annual and ephemeroid swards and grasslands", Mucina et al. 2016) is well suited for the community in issue. As regards the rank of order, Rivas-Martínez (1978) classified Atractylis cancellata among the characteristic species of the order Trachynietalia distachyae. In contrast, Brullo et al. (2001) classified A. cancellata as characteristic species of the order Stipo-Bupleuretalia semicompositi which they considered as xerothermic variant of the Trachynietalia distachyae. Biondi et al. (2014) confirmed the syntaxonomic framework of Brullo et al. (2001) vas-Mart. 1963). On the other hand, Mucina et al. (2016), who considered the Trachynietalia distachyae (synonym of Brachypodietalia distachyi) as a strictly W-Mediterranean order, advanced the hypothesis of classifying the Stipo-Bupleuretalia semicompositi in the Saginetea maritimae this order being typified by the Plantagini-Catapodion marini, an alliance comprising the sub-halophilous therophitic communities of the coastal areas. Accordingly, Mucina et al. (2016) proposed the new order Ptilostemono stellati-Vulpietalia ciliatae for "the Central and Eastern Mediterranean therophytic swards on shallow sandy and loamy soils over limestone and gypsum substrates". In this new provisional order the authors included the following alliances: Onobrychido-Ptilostemonion stellati, Vulpio ciliatae-Crepidion neglectae, Xeranthemion annui, Vulpion ligusticae. It is interesting to note that, basing on different reasons, the Prodrome of Italian Vegetation (Bi-ondi et al. 2014) and the Eurovegchecklist (Mucina et al. 2016) considered the xerothermic therophytic communities of the central Mediterranean as belonging to an order other than Trachynietalia distachyae (Brachypodietalia distachyi). Mucina et al. (2016) based their hypothesis on biogeographical reasons (Brachypodietalia distachyi was classified as a strictly W-Mediterranean order) whereas Biondi et al. (2014) based their hypothesis on bioclimatic reasons (Trachynietalia distachyae would not be occurring in dry Thermo and Infra-Mediterranean bioclimates where it would be substituted by Stipo-Bupleuretalia semicompositi). In our opinion, the main problem is that Stipo-Bupleuretalia and Brachypodietalia distachyi exhibit a clear floristic-ecological-biogeographical overlapping. It is not by chance that De Foucault (1999) considered the alliance Trachynion distachyae (proposed under the new name Sideritido-Brachypodion distachyi) as partly belonging to the Stipo-Bupleuretalia semicompositi and partly to the Trachynietalia distachyae. The syn-chorological question is therefore to establish whether Brachypodietalia distachyi (= Trachynietalia distachyae syntax. syn.) could be a proper reference for the therophytic communities of southern Italy, considering that it was already and abundantly used for similar communities in central Italy (Filesi et al. 1996;Biondi et al. 1997;Di Pietro et al. 2002;Fanelli et al. 2010). Instead, the ecological question is to establish whether Brachypodietalia distachyi is sufficiently "xerophilous" to include the highly xerothermic communities of southern Italy. To answer these questions, we can do nothing but base ourselves on the original diagnosis of the syntaxa in question and on their groups of characteristic species. The order Trachynietalia distachyae was originally defined as including all the therophytic communities occurring throughout the Mediterranean basin on neutral-basic substrates (Rivas-Martínez 1978). Among the characteristic species of this order are included the majority of the annual species we found in the Lysimachio-Atractylidetum cancellatae, such as Atractylis cancellata, Brachypodium distachyon, Catapodium rigidum, Crupina crupinastrum, Euphorbia exigua, Linum strictum, Stachys romana (etc.). The original diagnosis of the alliance Trachynion distachyae (sensu Rivas -Martínez 1978) perfectly overlapped the diagnosis of the order, as regards the chorological aspects, where instead it differed from it in ecological terms. In fact, the ecological range of Thero-Brachypodion was originally defined as including only the therophytic communities distributed within the potential vegetation areas for the Quercetalia ilicis and the thermophilous fringe of Quercetalia pubescenti-petraeae. Instead, the therophytic communities developed within the potential vegetation areas for the Pistacio-Rhamnetalia alaterni were referred to the Stipion retortae. Among the characteristic species of the Thero-Brachypodion there are taxa (Bupleurum baldense, Campanula erinus, Ononis reclinata) which occur in our samples, together with taxa (Euphorbia sulcata, Dianthus nudiflorus, Hornungia petraea and Neatostema apulum) which occur in Italy but not in our samples, and other taxa (the majority) which exhibited a W-Mediterranean distribution non including Italy (e.g., Arabis parvula, Astragalus stella, Brachyapium dichotum, etc.). On the other hand, Stipo-Bupleuretalia semicompositi is typified by a sub-halophilous coastal alliance (Sedo-Ctenopsion gypsophilae), but includes also many "non halophilous" associations belonging to the thermo-Mediterranean bioclimate. In the Aspromonte massif (Brullo et al. 2001), Atractylis cancellata was reported as a high-frequency species in the communities of the alliance Onobrychido-Ptilostemonion stellati. This alliance, which included the neutral and basiphilous therophytic communities of the Infra-and Thermo-Mediterranean bioclimates was proposed as a geographical vicariant of the Stipion retortae in the central Mediterranean. However only Ptilostemon stellatus, out of the seven characteristic species designated in the diagnosis (Brullo et al. 2001), exhibits a distribution restricted to C-Mediterranean (southern Italy and W-Balkans) whereas the others (Onobrychis caput-galli, Crucianella angustifolia, Hippocrepis ciliata, Filago eriocephala, etc.) exhibited a wide Mediterranean distribution.
The associations belonging to the Onobrychido-Ptilostemonion stellati exhibit a clear prevalence of xerophytic therophytes (e.g., Stipellula capensis, Trifolium scabrum, Evax pygmaea, Ononis reclinata, Plantago lagopus) which are also common in the most of the Brachypodietalia distachyi communities. It is therefore confirmed that Brachypodietalia distachyi and Stipo-Bupleruetalia semicompositi are widely overlapping and the presumed vicariant distribution areas of these two syntaxa (i.e., Brachypodietalia distachyi in the western Mediterranean and Stipo-Bupleuretalia semicompositi in the central-eastern Mediterranean) are not consistent in floristic terms. Atractylis cancellata being originally considered a characteristic species of the Brachypodietalia distachyi and the latter order having nomenclatural priority over Stipo-Bupleuretalia semicompositi we have opted to use Brachypodietalia distachyi as a reference for Lysimachio-Atractylidetum cancellatae and to consider Stipo-Bupleuretalia semicompositi as a pro-parte syntaxonomic synonym. As regards the choice of the alliance we have decided to assign a surplus of diagnostic value (both in ecological and biogeographic terms) to the guide-species of the association. This procedure is not a novelty in terms of syntaxonomic classification. For example, the order Pinetalia halepensis is essentially based on the dominance of Pinus halepensis in communities almost completely composed of Pistacio-Rhamnetalia and Quercetalia ilicis characteristic species (see Pesaresi et al. 2017). As regards grasslands the most emblematic case is probably the decisive role played by the circumboreal Carex myosuroides (= Kobresia myosuroides) in the decision of using the class Carici-Kobresietea instead of Elyno-Seslerietea for the classification of the rush-sward grasslands of the central Apennines although the latter were almost completely composed of SE-European orophytes (Biondi et al. 2000;Blasi et al. 2003;Chytry et al. 2015). For this reason, the large dominance of Atractylis cancellata in the Lysimachio-Atractylidetum does not allow, in our opinion, to classify this association neither in the Trachynion distachyae nor in other alliances considered by Mucina et al. (2016) as possibly occurring in Italy, such as Vulpio ciliatae-Crepidion neglectae and Vulpion ligusticae. In fact, A. cancellata is a South-Mediterranean/Irano-Turanian species typical of habitats which are too dry and warm to be related to the original diagnosis of the Trachynion distachyae (Izco 1974;Rivas-Martinez 1976;Lapraz 1982;Izco et al. 1986). It is not by chance that Guinochet (1978) proposed the alliance Atractylido cancellatae-Stipion retortae Guinochet 1978 for the dry sub-steppic territories of north-Africa. For this reason, we classified the Lysimachio-Atractylidetum in the Onobrychido-Ptilostemonion stellati and proposed the displacement of this alliance from Stipo-Bupleretalia semicompositi to the Brachypodietalia distachyi. The Onobrychido-Ptilostemonion stellati was originally described as an alliance not specifically linked to a particular type of substrate. For this reason, it appears as well suited to host the Lysimachio-Atractylidetum cancellatae, this association being found on different bedrock types, such as Pliocene clays, Quaternary sands, and limestones. In chorological terms the Onobrychido-Ptilostemonion stellati acts as a central Mediterranean vicariant of the W-Mediterranean Stipion retortae and the north-eastern-African Atractylido-Stipion retortae Guinochet 1978. However, adopting a less divisive syntaxonomic interpretation, these three alliances could be brought together within a single central and western Mediterranean alliance whose nomenclatural priority would go to the Stipion retortae. In fact, precisely to the Stipion retortae made reference Guarino and Pasta (2017) in their classification of the therophytic ephemeral swards of the alkaline loamy and clayey substrates of western Sicily.
CAMPANULO ERINI-MICROMERIETUM MICRO-PHYLLI ass nov. (Table 2 Synecology -Small-size communities (1 m2 or less) developed on the extremely superficial substrates of the limestone outcrops of the Murgia hills where they are found on flattish sites characterized by extremely shallow soils (1-2 cm deep) (Fig. 8). The community exhibits the co-dominance of Micromeria microphylla and various annual species. Micromeria microphylla in addition of being the syntaxon name-giving species is the only high-frequency chamaephyte occurring in the community (the other one, Ajuga iva, occurs in two relevés only). Where soils are slightly deeper, the Campanulo-Micromerietum microphyllae tends to be colonized by taller annual grasses, such in particular Stipellula capensis (sub-nitrophilous variant with Stipellula capensis, Table 2). The preferential location of the community in environments not completely free from anthropic disturbance (especially human and animal trampling) justifies the occurrence of some sub-nitrophilous annual species, such as Erodium cicutarium, Plantago lagopus, Rostraria cristata, Sonchus tenerrimus.
Life forms and chorology -Therophytes dominate in all the life forms spectra. These are followed by the chamaephytes, whose high values in the cover spectrum are almost exclusively due to the contribution of Micromeria microphylla. In the chorological spectrum Euro-Mediterranean species dominates followed by the steno-Mediterranean ones. Surprisingly high are the percentages of the Eurasiatic component (Fig. 9).
Syndynamic -The evolution of the soils leads the Campanulo erini-Micromerietum microphylli to be substituted by therophytic communities of greater size, as those dominated by Stipellula capensis, and subsequently by Mediterranean garrigues with Corydothymus capitatus and Helianthemum jonium. The final stage of the dynamic succession is a Mediterranean maquis community dominated by Pistacia lentiscus and Phillyrea latifolia.
Syntaxonomy -Despite the apparent floristic simplicity, the Campanulo erini-Micromerietum microphylli is never-theless problematic as regards its classification at the highest ranks of syntaxonomy. The physiognomic dominance of Micromeria microphylla, although not overwhelming, would suggest a possible classification in the Cisto incani-Ericion multiflorae, in particular in the micro-garrigue sub-alliance Thymo capitati-Helianthemenion jonii Di Pietro and Misano 2010 which was described precisely in the western Murgia Plateau (Di Pietro and Misano 2010). On the other hand, the preferential location on natural calcareous pavement, and the occurrence in the community of Petrorhagia saxifraga, accompanied by therophytes such as Arenaria leptoclados, Campanula erinus, Herniaria glabra, Silene conica, Sabulina tenuifolia and Valerianella muricata suggest to classify the Campanulo erini-Micromerietum microphylli in the Sedo-Scleranthetea. A third hypothesis, would be that of classifying this community in the Trachynietea distachyae taking into account the absolute dominance of the steno-Mediterranean therophytic component (both as number of species and cover percentage). A fourth and last option (unlikely in truth) would be to consider this community in the less synanthropic fringe of Chenopodietea, considering the partial anthropogenic character of the environments in which this community was found. The phytosociological literature is rather scarce as regards communities similar to the Campanulo-Micromerietum. In Sicily Micromeria microphylla is reported as a guide species of the association Putorio calabricae-Micromerietum microphyllae nom. inval. (Brullo and Marcenò 1979; Brullo et al.  (Terzi et al. 2017). This is a chasmophytic association composed of two subassociations (typicum and chiliadenetosum bocconei) which was classified in the Dianthion rupicolae, an alliance endemic to southern Italy in the class Asplenietea trichomanis (Terzi et al. 2017(Terzi et al. , 2018. The chasmophytic behavior of Micromeria microphylla was also reported by Lucchese and Pignatti (2013) who recorded the sporadic occurrence of this species within the ancient Roman walls of Ostia Antica (Rome, Italy) and hypothesized its arrival to be related with the transport of marble blocks from distant locations. The authors named the community with dominant Micromeria microphylla occurring on the walls of Ostia Antica simply as "Micromeria microphylla community" and classified it in the Parietarietea judaicae. However, none connection with Asplenietea trichomanis or Parietarietea judaicae, either ecological or floristic, was identifiable for the Campanulo erini-Micromerietum microphylli of the Murgia hills. A classification in the Ononido-Rosmarinetea does not seem feasible too. Although the Ononido-Rosmarinetea communities are abundant in the study area, especially on rocky or pebbly substrates, these are normally characterized by a clear physiognomic dominance of nano-phanerophytes and chamaephyes (Di Pietro and Misano 2010). Looking exclusively at the lithological and geomorphological characteristics of the sampled sites (fissured and flat limestone pavements), the reference to the Sedo-Scleranthetea would seem the most appropriate. However, observing the specific composition of the community, the most typical species of Sedo-Scleranthetea were absent, in particular those belonging to the genus Sedum and therophytes, such as Alyssum alyssoides, Erophyla verna, Hornungia petraea, Saxifraga trydactylites, Thlaspi perfoliatum (etc.). The dominance of steno-Mediterranean therophytes suggested us to classify the Campanulo erini-Micromerietum microphylli in the Stipo-Trachynietea distachyae (Brachypodietalia distachyae, Trachynion distachyae). In fact, although, Micromeria microphylla is the species displaying the highest specific cover index considering the entire phytosociological table, its cover values in several samples are comparable to those of some therophytes, such as Campanula erinus, Medicago minima or Stipellula capensis. Moreover, the extremely small size of Micromeria microphylla make this species physiognomically and functionally comparable to a small therophyte. However, the doubt in the choice between Trachynietea distachyae and Sedo-Sclerantherea is legitimate and recurrent. In particular, coenological overlaps and classification difficulties between Sedo-Scleranthetea and Trachynietea distachyae are well-known especially as regards those communities in which the dominant guide-species are therophytes (i.e., Chaenorhino-Saxifragetum trydactylites, Acino-Trifolietum scabri etc.). In our case, the situation is even more complex and would seems to be unbalanced towards the Sedo-Scleranthetea since the community has a micro-chamaephyte as guide-species. . The 3-digits codes in syntaxonomic spectra represent the class codes provided in the Eurovegchecklist (Mucina et al. 2016). Abbreviations: n. species = spectra based on presence/ absence data; frequency = spectra weighted by species frequency; cover = spectra weighted by species cover-abundance.  1  2  3  4  5  6  7  8  9 10 11 12 13 14  Altitude  115 115 115 115 115 115 115 115 115 115 115 115 115 115  Aspect  0  0  0  0  0  0  0  0  0  0  0  0  0  0  Slope°0  0  0  0  0  0  0  0  0  0  0  0  0  0  Area m2  1  1  1  1  1  1  1  1  1  1  1  1  1  1  Cover%  40 30 50 35 50 35 40 35 60 40 40 50 60  However, the aforementioned reasons seem consistent with our choice to opt for the Stipo-Trachynietea. Fanelli (2007), in order to discriminate between the two classes emphasized on the important diagnostic role played by the bryophytic component in the Sedo-Scleranthetea communities, whereas it would be significantly lower in the Stipo-Trachynietea ones. In the case of Campanulo-Micromerietum microphylli the role of the bryophytic component was found to be very low (substancially limited to a low cover percentage of Grimmia pulvinata) and this would further support our choice to classify the community in the Stipo-Trachynietea.
STIPO AUSTROITALICAE-HYPARRHENIETUM HIR-TAE Biondi et Guerra 2008 (Table 3) The communities dominated by Hyparrhenia hirta characterize the lower parts of the Murgia of Gravina and replace the grasslands dominated by Stipa austroitalica and Scorzonera villosa subsp. columnae of the summit areas of the Murgia plateau. These communities exhibits intermediate floristic features between three classes (Festuco-Brometea, Lygeo-Stipetea and Festuco hystricis-Ononidetea striatae) and testify the coenological transition between the Apennine-Balkan biogeographical province (Euro-Siberian Region) and the Adriatic province (Mediterranean Region). This transition is clearly observable moving from the summit areas of the Murgia plateau, still affected by cold winds from north-eastern Europe, to the lowlands facing the Taranto Gulf where the influence of the warm winds of south-western origin occurs. Hyparrhenia hirta is absolutely the dominant species of these xerothermic steppe-like communities especially when developed on partially leached soils rich in fine debris. Stipa austroitalica is constantly occurring in the dominant tall grasses layer, whereas Scorzonera villosa subsp. columnae do the same in the undergrowth. In addition, the Hyparrhenia hirta communities host some species typical of the Hippocrepido-Stipion austroitalicae dry-grasslands (Festuco-Brometea) such as Hippocrepis glauca, Anthyllis vulneraria subsp. rubriflora, Convolvulus elegantissimus. The steno-Mediterranean and Euro-Mediterranean component however remains dominant and would justify the classification of this community in the Lygeo-Stipetea, Hyparrhenietalia hirtae and Hyparrhenion hirtae as already proposed in Biondi and Guerra (2008). As regards the rank of order we object to a purely nomenclatural question, namely we have followed Mucina et al. (2016) which consider Cymbopogono-Brachypodietalia ramosi to be a prior syntaxonomic synonym of Hyparrhenietalia hirtae Rivas-Mart. 1978 (nom. inval.). Instead, the choice of the alliance is a more complex question. Hyparrhenion hirtae and Cymbopogono-Brachypodion ramosi are both accepted in the Eurovegchecklist as geographically vicariant alliances, the first occurring in the western Mediterranean and the southern Regions of the central Mediterranean whereas the second being restricted to the eastern Mediterranean. In our opinion, the classification of the Stipo austroitalicae-Hyparrhenietum should be based on comparing the floristic-coenological characteristics of the sampled communities with the original diagnoses of the two aforementioned alliances. Accordingly, we noticed that our Hyparrhenia hirta grasslands are characterized by the simultaneous occurrence of two taxa (Stipa austroitalica and Scorzonera villosa subsp. columnae) belonging to the Stipa pennata s.l. and Scorzonera villosa s.l. collective taxa respectively. This is a typical feature of the eastern Adriatic Mediterranean steppe-like grasslands too, where the two taxa in issue are Scorzonera villosa subsp. villosa and Stipa eriocaulis. Moreover, in the Stipo austroitalicae-Hyparrhenietum hirtae occur East-European or amphi-Adriatic species (Dasypyrum villosum, Charybdis pancration, Hippocrepis glauca, Melica transsylvanica, Thapsia garganica, Asyneuma limonifolium, Centaurea deusta, Ornitoghalum gussonei) which are species not included in the Hyparrhenion hirtae range. For this reason, we classified the Stipo austroitalicae-Hyparrhenietum in the Cymbopogono-Brachypodion ramosi. However, considering that the above-mentioned differential species of Stipo-Hyparrhenietum are all belonging to classes other than Lygeo-Stipetea, a different framework could be hypothesized. In practice it would be a question of considering a single Mediterranean alliance for both "eastern" and "western" Hyparrhenia hirta communities and delegating possible biogeographic differentiation to the lower syntaxonomic ranks, such as suballiances or associations. This consideration would be also supported by the fact that the species which were originally considered as characteristic species of both Cymbopogono-Brachypodion ramosi and Cymbopogono-Brachypodietalia ramosi (Allium sphaerocephalon, Briza maxima, Crucianella latifolia, Heteropogon contortus, Hyparrhenia hirta, Medicago minima, Lagurus ovatus, Linum strictum and Lotus edulis), display a wide Mediterranean distribution and do not suggest Cymbopogono-Brachypodion ramosi as an alliance restricted solely to the central-eastern Mediterranean. The situation does not change even adding the species considered by Horvatić (1973;1975) as transgressive or ingressive in Cymbopogono-Brachypodietalia ramosi (e.g., Allium subhirsutum, Bituminaria bituminosa, Carex divulsa, Clinopodium nepeta, Filago germanica, Hedypnois rhagadioloides, Hymenocarpos circinnatus, Lotus ornithopodioides, Oloptum miliaceum, Scorpiurus subvillosus, Trifolium angustifolium, Trifolium scabrum). In fact, more than the list of characteristic species of Cymbopogono-Brachypodion, it was the great biogeographic selectivity of the characteristic species of the Hyparrhenion hirtae (see Diaz-Garretas and Asensi 1999) that discouraged Hyparrhenion hirtae to be used as syntaxonomic reference for our relevés. In addition to species occurring throughout the whole Mediterranean basin (e.g. Andropogon distachyos, Hyparrhenia hirta, Heteropogon contortus, Bothriochloa ischaemum, Convolvulus althaeoides), the Hyparrhenion hirtae exhibits characteristic species which are strictly western Mediterranean (Daucus crinitus and D. setifolius) or species not occurring in the Adriatic area (Aristida adscensionis, Carex depressa, Tricholaena teneriffae), or not occurring in It-  (Hoda and Mersinllari 2000). However, it is possible that the Thymo-Hyparrhenietum hirtae described in Di Pietro et al. (2002) for the coastal sectors of southern Lazio, originally classified in the Hyparrhenion hirtae, could be moved in the Cymbopogono-Brachypodion by virtue of its successional and/or spatial link with eastern European potential forest vegetation types (Blasi and Di Pietro 1998).
MEDICAGO DISCIFORMIS-BRACHYPODIETUM DIS-TACHYI Biondi et Guerra 2008 (Table 4, rels 1-4) This community shows a clear dominance of Brachypodium distachyum and characterizes small calcareous outcrops or preferential walking sites for animals within the perennial communities dominated by Scorzonera villosa subsp. columnae, Stipa austroitalica and Hyparrhenia hirta. Due to the few relevès carried out in this paper, it does not seem appropriate to promote a too deep syntaxonomic discussion. However, as already highlighted in the previous paragraph, the syntaxonomic classification of the Mediterranean therophytic communities in Italy still remains a heated point of debate (see Biondi et al. 1997;Di Pietro et al. 2002;Fanelli et al. 2010;Di Pietro et al. 2017). In this case we have decided to make reference to the Medicago disciformis-Brachypodietum distachyi, which was already described for the study area (Biondi and Guerra 2008). This association is probably the only therophytic association of the Trachynietea distachyae described in Italy displaying a clear dominance of Brachypodium distachyum. Precisely the dominance of Brachypodium distachyon suggested us to include this association in the Trachynion distachyae. Instead, Biondi and Guerra (2008) proposed to classify this association in the new alliance Hypochaeridion achyrophori Biondi & Guerra 2008, (eastern geo-vicariant    Coronilla scorpioides. In particular, the therophitic communities of the Murgia hills were included in the suballiance Ononidenion ornithopodioidis Biondi & Guerra 2008 whose differential species were selected in Ononis ornithopodioides, Trifolium lucanicum, Bromus fasciculatus, Odontites lutea, Ammoides pusilla, Romulea bulbocodium and Convolvulus elegantissimus. In our opinion, the whole characteristic component of the Hypochaeridion achyrophori does not identify any geographical peculiarity since all the characteristic species display a wide Mediterranean distribution. Accordingly, we don't think there is any reason to distinguish floristically and biogeographically Hypochaeridion achyrophori from the Trachynion distachyae. According to Mucina et al. (2016) the Hypochaeridion achyrophori, as well as being invalid, is to be considered a syntaxonomic synonym of Vulpio ciliatae-Crepidion neglectae Poldini 1989. Where small depressions are formed on the limestone crust with greater soil coverage, especially in areas where the passage of grazing animals is more frequent, annual species with slightly more anthropogenic character, such as Anisantha madritensis and Lagurus ovatus take over as dominant (Table 4, rels 5-6). In syntaxonomic terms, these communities can be interpreted as the transition between Brachypodietalia distachyi and Brometalia rubenti-tectorum (Chenopodietea).
PETROSEDUM OCHROLEUCUM SUBSP. MEDITER-RANEUM community (Table 5) In environmental situations of undulating rocky outcrops characterized by micro-depressions in the calcareous plateau profile, communities with a clear dominance of Petrosedum ochroleucum subsp. mediterraneum accompanied by a few other chamaephytes and a rich therophytic component are found. The degree of vegetation cover is quite high as there are very few parts of the sampling plots not covered by a thin layer of soil at least. From a syntaxonomic point of view, the coenological role of Petrosedum ochroleucum was already known in the study area, this taxon being one of the guide species of the association Sedo ochroleuci-Saturejetum cuneifoliae already described for the small-size terraces bordering the Gravina gorges (Di Pietro and Misano 2010). However, this reference cannot be used for our relevés the habitat type of the Sedo-Saturejetum cuneifoliae being quite different and Satureja cuneifolia being completely absent in our relevés. In the Italian peninsula, other communities dominated by species belonging to the genus Petrosedum have already been described, such as the Sedetum rupestris-sexangularis Di Pietro et al. 2006 of the Prenestini mountains in the Lazio region pre-Apennines (Di Pietro et al. 2006) and the Linario purpureae-Petrosedetum rupestris Ciaschetti et al. 2020 of the hilly and lower-montane belts of the Abruzzo Apennines (Ciaschetti et al. 2020). However, both these communities have different guide species (e.g., Petrosedum rupestris) and exhibit quite different floristic compositions compared with those of the Apulian communities. A suitable syntaxonomic reference already published not being available and our relevés being too few to propose a new association, we preferred to preliminary name this community simply as Petrosedum ochroleucum subsp. mediterraneum comm. In terms of higher synatxonomical ranks, the most plausible references are Alysso-Sedion, Alysso-Sedetalia and Sedo-Scleranthetea.

Conclusions
In this paper, two new associations were identified and described for the south-eastern sector of Peninsular Italy, namely the xerophytic annual grasslands and micro-garrigues dominated by Atractylis cancellata and Micromeria microphylla. These taxa are two S-Mediterranean species whose Italian distribution is restricted to southern Italy and for which very scarce phytosociological references were available. Moreover, new phytosociological data and syntaxonomical insights were provided on other types of Mediterranean dry grasslands and micro-garrigues, identified in the study area. The new association Campanulo erini-Micromerietum microphyllae was classified in the class Stipo-Trachynietea this choice representing a novelty for the communities dominated by Micromeria microphylla, for which the only references available at present were the classes Parietarietea judaicae and Asplenietea trichomanis. The new association Lysymachio foeminae-Atractylidetum cancellatae was here classified in the alliance Onobrychido-Ptilostemonion stellati (that we moved from Stipo-Bupleretalia semicompositi to Brachypodietalia distachyi). This alliance susbstitutes the W-Mediterranean Stipion retortae and the S-Mediterranean Atractylido-Stipion retortae in encompassing the most xerothermic fringe of the order Brachypodietalia distachyi in southern Italy. At the same time, we have still considered the occurrence of Trachynion distachyae in our study area classifying in this alliance the association Medicago disciformis-Brachypodietum distachyi. In our opinion, in southern Italy there is an overlap between the ephemeral communities of the Meso-Mediterranean belt coming from the coastal sectors of central-northern Italy and those of the dry-Thermo-Mediterranean belt coming from the pre-desert areas of the south-eastern Mediterranean. For this reason the identification and separation of two different alliances (Trachynion distachyae and Onobrychido-Ptilostemonion stellati) in the study area was not easy as these two alliances shared a large part of their therophytic component. As a useful tool for classification we reiterated the diagnostic importance expressed by the guide species (dominant species) of a community. In our opinion, the physiognomical dominance of a given species should not exclusively to be interpreted as the response to the current environmental conditions but also as the result of previous epiontho-logical processes. For this reason, the dominant species should express a syntaxonomical diagnostic power (especially when the syntaxonomic debate is about the choice of order or class) greater than what would be assigned to it based on its mere presence in the community. In our specific case of the Lysimachio-Atractylidetum cancellatae, the dominance of Atractylis cancellata was considered as the sign of previous occurrences of a xerothermic Irano-Turanian pre-desertic vegetation that migrated in southern Europe from the Messinian Age on. This interpretation is in accordance with the spatial contact of Lysimachio-Atractylidetum cancellatae with the perennial Lygeum spartum or Hyparrhenia hirta communities and with successional stages tending to potential vegetation types belonging to Pistacio-Rhamnetalia alaterni. Our syntaxonomical choices, however, cannot solve the problem the floristic similarities between the Onobrychido-Ptilostemonion stellati and the Trachynion distachyae. In fact, despite being alliances belonging to two different orders, they share a large part of their characteristic species. Accordingly, we will address the resolution of this syntaxonomic question for future researches to be carried out using a much larger amount of phytosociological data from the entire Mediterranean basin. Basing on biogeographic and nomenclatural reasons, the association Stipo austroitalicae-Hyparrhenietum hirtae was classified in the Cymbopogono-Brachypodietalia ramosi and Cymbopogono-Brachypodion ramosi although the floristic and ecological boundaries between the latter alliance and the W-Mediterranean alliance Hyparrhenion hirtae still remain undefined.
Some points of discussion raised in this paper turned out to be only partially in agreement with the frameworks provided by both the Vegetation Prodrome of Italy (Biondi et al. 2014) and the Eurovegchecklist (Mucina et al. 2016) leaving open the way to possible proposals for syntaxonomic changes in the future.