The Apennines are a southern European mountain range which can be considered a deep extension of the European continent within the central Mediterranean Sea. They can be divided into three large sub-units (Northern, Cen­tral and Southern Apennines). The Northern Apennines are the northernmost sub-unit and the lowest in altitude (the highest peak, M. Cimone is 2165 m a.s.l.). However, the Northern Apennines geographical contiguity with the Western Alps and the wide occurrence of siliceous flyschoid substrates makes this sub-unit much more similar to the Alps than to the rest of the Apennines, both in floristic and biogeographical terms (Foggi 1990; Tomaselli and Agostini 1994; Di Pietro et al. 2017). These similarities are evidenced by the fact that many species typical of the boreal forests and the heathlands of the Alps and northern Europe, such as Picea abies (L.) H.Karst., Pinus sylvestris L., Rhododendron ferrugineum L., Empetrum hermafroditum Hagerup, Vaccinium vitis-idaea L. establish their southernmost limit precisely in the Northern Apennines. On the other hand, the Southern Apennines, despite being a little bit higher in altitude than the Northern Apennines (M. Dolcedorme on the Pollino massif reaches 2235 m a.s.l.), are located very far to the South, so they are significantly more influenced by the Mediterranean climate. Due to their geographical position (centre of the Mediterranean Sea), the Southern Apennines were only marginally affected by the glaciations and this has led to a scarce occurrence of boreal and arctic-alpine species and communities in this area, whereas the biogeographical similarities with the western sector of the Balkans are much higher (Tomaselli et al. 2003; Di Pietro 2010). The Central Apennines represent by far the highest altitudinal sector of the whole Apennine range with numerous massifs exceeding 2400 m a.s.l., such as Gran Sasso, Majella, Sibillini, Laga and Velino-Sirente, with some peaks belonging to Gran Sasso and Majella ranges greatly exceeding this altitude (e.g. M. Corno Grande 2910 m a.s.l., M. Amaro 2786 m a.s.l.). The significant influence that the Quaternary climatic upheavals had on the vegetation history of the Italian Peninsula (Follieri et al. 1988; Magri 2008), together with the rise in temperatures that occurred since the end of the last glaciation, led numerous arctic-alpine or circumboreal communities (currently classified as Armerio-Salicetum herbaceae, Leontopodio-Elynetum myosuroidis, Caricetum kitaibelianae-rupestris, Galio-Silenetum acaulis, Achilleo-Saxifragetum aizoidis) to find refuge within the upper altitudinal belts of the highest mountains of the Central Apennines (Biondi et al. 1999: 2000; Blasi et al. 2003; Blasi et al. 2005; Chytrý et al. 2015).

The Laga Mountains represent the siliceous sub-unit of the Gran Sasso-Monti della Laga National Park (Fig. 1). Thanks to their pelithic-arenaceous substrates, capable of a high hydric retention, the Laga Mountains host a high number of microthermic meso-hygrophilous environments, such as mires, peat bogs or swamps that are absent or significantly much rarer in the adjacent Gran Sasso range, as well as in the other high altitude limestone massifs of the Central Apennines (e.g. Sibillini Mountains, M. Terminillo and M. Velino).

Over the last two decades there have been numerous floristic and vegetational studies which have expanded the floristic and phytosociological knowledge of the Laga Mountains, especially with regards to the boreal vascular plant species and communities (see Pedrotti and Cortini Pedrotti 1978; Lattanzi et al. 1999; Tondi 2000; Di Pietro et al. 2001; Blasi et al. 2003; Tondi et al. 2003; Di Pietro 2007; Di Pietro et al. 2007; Di Pietro et al. 2008; Conti and Tinti 2008; Conti and Bartolucci 2016; Di Pietro et al. 2016; Bartolucci et al. 2022). These studies contributed significantly to the updating of the National and European syntaxonomic frameworks and vascular plant checklists (see Biondi et al. 2014; Mucina et al. 2016; Bartolucci et al. 2018). Instead, the studies on the cryptogamic flora have undergone a sharp decrease since the end of the last millennium. For this reason, as part of a phytosociological survey campaign aimed at investigating the never previously unstudied Caricion davallianae grasslands of the Laga Mountains, the bryophyte component was also detected. In this paper, we will present the results concerning the bryophyte flora.

The Laga Mountains are a 24 km long ridge with four peaks exceeding 2400 m a.s.l., which lies at the boundary between Lazio, Abruzzo and Marche regions, in the central Italy, and are the highest and largest siliceous massif of the whole Apennine range (Fig. 1). These mountains are characterized by a torbiditic succession of Messinian age known as “Laga Flysch” mainly composed of pelithic-arenaceous substrates (Fig. 2). The low permeability degree which characterizes the succession of sandstones and clays limits the percolation of rainfall waters and enables their superficial streaming out (Tondi and Plini 1995). Accordingly, the Laga Mountains are rich of springs and perennial streams even at high altitude where the accelerated erosion of the clayey-sandy substrates leads to the occurrence of deep and narrow valleys called “fossi” which characterize the whole subalpine and upper montane belts (Fig. 2d). In these areas, a high number of microthermic meso-hygrophilous environments, such as mires, peat bogs or swamps occurs. Within the stream banks of the deep N-facing valleys (Fosso della Pacina, Fosso Pelone, Cima della Laghetta), we identified high-altitude hygrophilous communities with abundant occurrence of bryophytes, characterized by the dominance of small sedges (e.g. Carex frigida All., C. flacca Schreber subsp. flacca, C. davalliana Sm.) and rushes (Juncus articulatus L. subsp. articulatus, J. alpinoarticulatus Chaix subsp. alpinoarticulatus, J. arcticus Willd.). At lower altitude (Fosso Cerruglia, Castellano river), more structured mires characterized by Menyanthes trifoliata L., Succisa pratensis Moench. and several medium-size sedges (Carex acuta L., C. panicea L., C. pallescens L.) and rushes (e.g. Juncus inflexus L., J. conglomeratus L.) were found.

From a bioclimatic point of view, the study area belongs to the Temperate region and to the cold axeric subregion. Mean annual temperature is 5.5°C and the mean temperature of the coldest month is –4°C. Rainfall exceeds 1600 mm/yr and in the period between November and May assume snowy features; frost occurs for more than one month yearly (Blasi 1994). These climatic features are significantly different from those observable in the ombrothermic diagrams of the only two climatic stations for which a series of precipitation and temperature data spanning several decades were available (i.e. Amatrice – Rieti and Campotosto – L'Aquila) and which are located (especially Amatrice) at altitudes much lower than that of the sampled areas (Fig. 3).

The first mention of bryophytes for the Laga Mountains dates back to the mid-1800s by Rabenhorst (1849–50) who reports the occurrence of Fontinalis antipyretica Hedw. along the course of the Castellano stream. Subsequently, Arcangeli (1887) mentions Bryum schleicheri Lam. et DC. [= Ptychostomum schleicheri (DC.) J.R.Spence ex D.Bell & Holyoak var. schleicheri] for Mount Pizzo di Sevo. Other sporadic reports were provided in the first half of the 1900s by Zodda (1910, 1947), Bottini (1913) and Barsali (1914) for various localities of the Laga Mountains. More recent are the contributions by Orsomando (1972), who cites 11 bryophyte (10 mosses and 1 liverwort) from the north-eastern sector of the Laga Mountains (site of “Valle della Corte” in the Marche administrative Region) and by Pedrotti (1982, 1985) who reports Polytrichum norvegicum Hedw. (= Polytrichastrum sexangulare (Brid.) G.L.Sm.) for the western side of Mount Pizzo di Sevo in the Lazio administrative Region. More substancial contributions regarding the bryophytes of the Laga Mountains are those carried out by Aleffi and Cortini Pedrotti (1991) and by Mastracci and Düll (1991) both based on the field excursion carried out in various localities of the Abruzzo administrative region during the Bryology International Congress held in L’Aquila in July 1991. In particular, Aleffi and Cortini Pedrotti added 3 liverworts and 24 mosses (from various sites of the Laga Mountains), while Mastracci and Düll listed a total of 24 liverworts and 85 mosses, all coming from the site of Bosco Martese, the widest Abies alba-Fagus sylvatica forest of the Central Apennines. A truly systematic study on the bryophyte flora of the Laga Mountains was carried out by Aleffi et al. (1997) where a total of 269 taxa of bryophytes were reported (75 liverworts and 194 mosses). Further sporadic contributions were those related to a general research on the vegetation of the upper montane and subalpine belts of the Laga Mountains, which led to the discovery of Plagiomnium ellipticum (Brid.) T.J.Kop., Palustriella commutata (Hedw.) Ochyra var. sulcata (Lindb.) Ochyra [= P. falcata (Brid.) Hedenäs] (Fig. 4) and Marchantia polymorpha L. subsp. montivagans (Privitera et al. 2006), and subsequently of Myurella sibirica (Müll.Hal.) Reimers, Dicranella cerviculata (Hedw.) Schimp., Dicranum flexicaule Brid., D. polysetum Sw. ex Anon. and Pseudoleskea patens (Lindb.) Kindb. (= Lescuraea patens Lindb.) (Puglisi et al. 2011). All these records confirmed the important role played by the Laga Mountains as a preferential refuge site for arctic-alpine taxa in the southern Europe. According to Aleffi et al. (1997), the bryophyte flora of the Laga mountains is characterized by a prevalence of the Temperate element, both among mosses (35.58%) and liverworts (29.34%). The contribution of the Boreal element is significant, especially among the liverworts (28%), while the Subarctic-Subalpine element is relevant among both liverworts (12%) and mosses (9.28%). The high incidence of the Subarctic-Subalpine and Boreal elements is largely related to the high average altitude of the Laga Mountains, but also to the dense network of runoff water (even at high altitudes) which allows the survival of many microthermic species by counteracting the drop in summer rainfall due to the influence of the Mediterranean climate.

Bryophyte specimens were collected during a phytosociological sampling campaign aimed to describe some types of wet meadows rich in boreal species occurring within the upper montane belt of the Laga Mountains and referable to Scheuchzerio palustris-Caricetea fuscae and presumably belonging to Habitat 7210 or 7220 of the Directive 92/43/ECC (see Discussion paragraph). The phytosociological sampling was carried out following the phytosociological approach (Braun-Blanquet 1964).

For the identification of the bryological component reference was made to Cortini Pedrotti (2001, 2005); nomenclature follows Hodgetts et al. (2020). Chorotypes were referred to Düll (1983, 1984, 1985). Species distribution in the Italian regions refers to Aleffi et al. (2023).

Regarding the conservation status of the species collected, reference was made to Puglisi et al. (2023) for liverworts and hornworts and to Puglisi et al. (2024) for mosses, on the basis of the criteria established by IUCN (2012a, 2012b, 2022). These assessments were compared with the ones proposed at European level by Hodgetts et al. (2019) and Hodgetts and Lockhart (2020) which were based on the IUCN Red Listing guidelines (IUCN 2014).

The bryophyte specimens were grouped according to the collection site. New records for the Apennines were marked with (§) while the new regional records were marked with an asterisk (*).

Voucher specimens are deposited in the Herbarium Flaminio (HFLA; Thiers, 2022 [continuously updated]).

For each site of collection of bryophytes, a phytosociological relevé describing the coenological features of the vascular plant communities was also carried out.

Vascular plants specimens were identified according to Pignatti et al. (2017–2019) whereas nomenclature follows Bartolucci et al. (2018). For the nomenclature of syntaxa and their classification at the class rank reference was made to Mucina et al. (2016). The complete names of the syntaxa are reported in Appendix 1.

Some bryophyte taxa, out of the 44 identified, are currently considered to be diagnostic for European habitats reported both in the EUNIS classification (Davies et al. 2004; Moss 2008), and in the Annex I of the 92/43/EEC Habitats Directive (European Commission 2013). As far as the EUNIS classification is concerned, we made reference to the Habitat factsheets deriving from the expert system EUNIS-ESy (Chytrý et al. 2020) where habitats description, distribution and combination of diagnostic and constant species was established according to the classification of vegetation plots taken from the European Vegetation Archive EVA (Chytrý et al. 2016).

Sixty phytosociological relevé were performed between 2021 and 2022 to describe and syntaxonomically classify the stream bank microthermic rush-sedge meadows of the N-facing slopes of the subalpine and upper montane belts of the Laga Mountains.

An analysis of the bryological component collected during the field sampling led to the identification of several taxa of biogeographical importance. Some of these taxa are considered diagnostic for EU. Habitats which are currently reported for the Central and Southern Apennines by the official documents of 92/43/EEC Directive but which knowledge (and geographical mapping) is essentially based on “virtual” information (no published data). Among the various taxa identified, we found several rare bryophytes exhibiting here their southernmost limit of distribution and acting as new records for the regional bryophyte flora of Italy. Four bryophyte taxa were never reported for the Central Apennines. These are Schljakovia kunzeana (Huebener) Konstant. & Vilnet and Ptychostomum cernuum (Hedw.) Hornsch. (new for the whole Apennines), Hamatocaulis vernicosus (Mitt.) Hedenäs, and Scorpidium cossonii (Schimp.) Hedenäs (new for the Central-Southern Apennines).

From a regional floristic point of view, nine species of bryophytes (i.e. Flexitrichum gracile (Mitt.) Ignatov & Fedosov, Hamatocaulis vernicosus (Mitt.) Hedenäs, Pellia neesiana (Gottsche) Limpr., Philonotis seriata Mitt., Ptychostomum cernuum (Hedw.) Hornsch., Riccardia multifida (L.) Gray subsp. multifida, Sarmentypnum exannulatum (Schimp.) Hedenäs, Schljakovia kunzeana (Huebener) Konstant. & Vilnet, Scorpidium cossonii (Schimp.) Hedenäs) were found to be new for the Lazio administrative Region and one species, Philonotis rigida Brid., for the Abruzzo Region. Two further species (Bryum canariense Brid. and Plagiomnium cuspidatum (Hedw.) T.J.Kop.) were confirmed after old records dating back to the early 1900s.

In the chorological spectrum (Fig. 5), the Boreal chorological element (which is divided into the four chorotypes, boreal, montane-boreal, dealp-boreal and sub-boreal) appears to be dominant, comprising about 50% of the species identified. Also relevant is the contribution of the Temperate element, which sums up approximately 36% of individuals, while the Mediterranean-Oceanic and Submediterranean-montane element exhibit very low percentages.

As far as the conservation status of the species is concerned, the assessments reported in Puglisi et al. (2023, 2024) for liverworts, hornworts and mosses, differ in part from what was previously reported in Hodgetts and Lockhart (2020) both at European and Country level. In fact, Ptychostomum cernuum (Hedw.) Hornsch. and Schljakovia kunzeana (Huebener) Konstant. & Vilnet are the only two species we collected which are classified as EN-endangered in Puglisi et al. (2023, 2024), whereas S. kunzeana was previously classified as CR-critically endangered in Hodgetts and Lockhart (2020). Dicranella rufescens (Dicks.) Schimp. and Philonotis rigida Brid. are both considered NT-near threatned in Puglisi et al. (2024), whereas they were respectively classified as LC-least concern and VU-vulnerable in Hodgetts and Lockhart (2020). Scorpidium cossonii was considered EN-endangered only in Hodgetts and Lockhart (2020). Ten species (i.e. Aneura pinguis (L.) Dumort., Conocephalum conicum (L.) Dumort. Marchantia polymorpha L. subsp. polymorpha, Marchantia quadrata Scop., Mesoptychia badensis (Gottsche ex Rabenh.) L.Söderstr. & Váňa, Mesoptychia bantriensis (Hook.) L.Söderstr. & Váňa, Pedinophyllum interruptum (Nees) Kaal., Pellia epiphylla (L.) Corda, Pellia neesiana (Gottsche) Limpr., Riccardia multifida (L.) Gray) were considered as NT in Hodgetts and Lockhart (2020), whereas they have been classified LC-Least Concern in Puglisi et al. (2023; 2024). Finally, Conocephalum salebrosum Szweyk., Buczk. & Odrzyk was considered as DD-Data deficient in Hodgetts and Lockhart (2020), and LC in Puglisi et al. (2023).

The bryophyte taxa currently considered diagnostic for the European habitats according both to the EUNIS classification system and the 92/43/EEC Directive Interpretation Manual are reported in Tables 1, 2.

It emerged that there is not an exclusive relationship between bryophyte species and Habitat type, but the same species can be classified as diagnostic in different habitats (e.g. Campylium stellatum is considered diagnostic for Habitats Q41, Q42, Q44, Q45, Q46 in the EUNIS classification as well as Scorpidium cossonii is considered diagnostic for Habitats 7220; 7230; 7240; 7310 in the Interpretation Manual of the Habitats Directive).

Twenty-three taxa were found to be classified as diagnostic species and/or constant species within 40 habitat factsheets reported by the EUNIS classification (Table 1) whereas 17 species distributed within 7 habitats were found to be diagnostic in the Habitats Directive Annex I (Table 2). The histograms displaying the distribution of the diagnostic species per Habitat type are reported in Figs 6, 7.

We report the list of bryophyte taxa gathered in each collection site. In order to provide information on the coenological features of the different sites of collections, eight phytosociological relevés (one for each site) of the related vascular plant communities are reported.

In this study, some montane and subalpine mires of the Laga Mountains were investigated. Despite a significant number of papers published concerning the vascular flora and boreal-type vegetation, the researches concerning the bryophyte flora of the Laga Mountains are very limited. Accordingly, in this study we provided new information useful not only for updating regional and national bryophyte lists, but also for investigating the ecological features of some rare boreal bryophyte species at the southernmost boundaries of their range. Moreover, we analysed the coenological and biogeographical correspondence between the bryophyte species identified and the Habitat types which are currently reported for the Apennines by the EUNIS classification and the 92/43/EEC Habitats Directive.

As expected, the chorological spectrum relating to all the 44 species identified is in accordance with the bioclimatic features of the sites of collection, which are located at the border between the upper-montane and the subalpine belts, and with the ecology of the communities investigated. The Boreal element is dominant and it exhibits higher percentages than the Temperate element, which is dominant when all the bryophytes of the whole Laga mountain territory are considered (Aleffi et al. 1997).

From a national (regional) floristic point of view, nine, out of the forty-four species of bryophytes collected, were found to be new for the Lazio administrative Region and one to be new for the Abruzzo Region. These regional records, which might seem of little interest from a large-scale perspective, become very important when dealing with procedures related to Habitats and biodiversity conservation and with the environmental policies involved in achieving this goal. The majority of the policies for biodiversity safeguarding in Italy, and the related evaluation of the conservation actions applied, are established and managed by the governance of the single administrative Regions, which normally is required to deal with matters of conservation concerning their own territory only. Accordingly, new regional floristic records represent the essential data set through which each administrative region is periodically called upon to implement new and more adequate conservation measures for safeguarding biodiversity or for modifying the existing measures (especially when these records concern rare or protected species or when SAC or other types of protected areas are involved).

From a strictly chorological point of view, our findings are to be considered of a large-scale interest, given that the aforementioned new records also involve a southward extension of the overall range of some of the rare species identified (e.g. Hamatocaulis vernicosus, Ptychostomum cernuum, Schljakovia kunzeana, Scorpidium cossonii). The modifications of the known distribution area of species with high biogeographical importance always receive much attention in the field of conservation biology, especially when these modifications concern populations that are more or less isolated or restricted to the very edge of their range. It is not by chance that such species are often attributed an importance similar to that normally given to narrow endemics or rare taxa (Lesica and Allendorf 1995; Rossi and Gentili 2006; Abeli et al. 2018). In fact, edge-range populations are more sensitive to environmental stresses compared to the populations occupying the core of the range, and face a higher risk of extinction when some critical environmental factors undergo significant variations (Abeli et al. 2012; Carbognani et al. 2019). This is precisely what is happening at present in many montane areas of southern Europe (e.g. the Central Apennines) due to the negative effects of global warming. A typical example are the micro-thermic boreal or arctic-alpine communities developed within the subalpine or alpine belt, whose survival is put at risk by the rise in altitude of the more thermophilious grassland and shrubland communities of the underlying bioclimatic belts (Evangelista et al. 2016).

In this perspective, one of the most important findings of our study is the new record for Hamatocaulis vernicosus, a species currently included in the Annex II of the Habitats Directive and distributed in North and South America, Asia and throughout Europe, except for the Mediterranean region (Hedenäs et al. 2022). In Italy, H. vernicosus is known for the Alps and the northern slope of the Northern Apennines. This new record from the Laga Mountains moves the current distribution limit of H. vernicosus in the Italian Peninsula significantly southwards. According to Hedenäs and Eldenäs (2007) and Hedenäs et al. (2022), H. vernicosus is known to give rise to two cryptic species (i.e. species indistinguishable from a morphological point of view but well-differentiated molecularly), which exhibit a partly different distribution in Europe. These two cryptic species were found to overlap significantly in central Europe and the Alps, but only one of them (CRS1) occurs in southwestern Europe, while only the other one (CRS2) was found to occur in northern Scandinavia. According to the distribution maps published in Hedenäs et al. (2022), it is not possible to hypothesize to which cryptic species the new H. vernicosus population we recorded in the Laga Mountains belong. Indeed, both CRS1 and CRS2 are currently considered to occur along the southern slope of the Alps and in the Western Balkans, which are the portions of the H. vernicosus range closest (in terms of geographical distance) to the Laga Mountains. However, the authors hypothesised that CRS1 only survived the glaciations in refuge areas located in south Europe, whereas CRS2 in refuge areas located in northern and/or eastern Europe. Accordingly, new genetic analysis to be carried out on the southernmost edge-range populations of H. vernicosus from the Laga Mountains could provide important information to confirm: i) which of the two aforementioned cryptospecies is actually present in the Central Apennines, ii) whether CRS1 has also survived in glacial refuges occurring in the Italian Peninsula in addition to those already known for the Iberian Peninsula and the Balkans.

According to Hedenäs et al. (2022), H. vernicosus is experiencing an expansion phase in central Europe thanks to the new opportunities created by the implementation of extensive agriculture that gives an advantage to less competitive plants, such as bryophytes, over the vascular plants (Singh et al. 2021). Obviously, this cannot happen in the Apennines given that H. vernicosus is found exclusively in primary (almost unexplored) sites of the upper montane and subalpine belts which are not, or only marginally, affected by the presence of human activity or grazing livestock (and there is very little chance that an implementation of grazing will happen in the near future considering the socio-economic changes that have affected the montane areas over the last fifty years). Indeed, H. vernicosus is seriously at risk of extinction in the Apennines due to the constant increase in temperatures and the simultaneous decrease in snowfall. For the foregoing reasons constant monitoring of the existing populations of this species is urgently required. It is quite surprising, therefore, that, as a boreal relict species included in Annex II of the Habitats Directive, H. vernicosus falls into a low threat category in Italy (LC in Puglisi et al. 2024), despite having already been classified as VU-Vulnerable at pan-European level (see Hodgetts and Lockhart 2020). Probably the fact that this species is currently reported for five, out of the seven northern Italy administrative regions facing the southern slope of the Alps, meant that it has been considered as a non-risk species. In contrast, other countries crossed by the Alps, such as Germany or Switzerland, consider it at EN and NT conservation status, respectively. This new record of H. vernicosus for the Laga Mountains, could lend support to a proposal for a change in its conservation status at least at regional level, especially considering the somewhat scattered occurrence in the Apennines of its preferential hosting habitat type (Caricion davallianae grasslands). On the other hand, in other Mediterranean countries, such as Spain and Bulgaria, this species is considered EN-Endangered and VU-Vulnerable, respectively, and in Bulgaria, H. vernicosus is also included in annex II of the Bulgarian Biodiversity Protection law (Ganeva and Natcheva 2004; Natcheva et al. 2006).

In addition to H. vernicosus, there are further two species, Scorpidium cossonii (Schimp.) Hedenäs and Schljakovia kunzeana (Huebener) Konstant. & Vilnet, whose Italian distribution was known for northern Italy only (Aleffi et al. 2023). The considerations made for Hamatocaulis vernicosus are largely valid also for Scorpidium cossonii, a species of pre-Quaternary Arctic origin that survived the glaciations in some cold areas of the central and southern Europe (Hedenäs and Eldenäs 2008; Hedenäs 2009). S. cossonii is described as a taxon typical of the species-rich calcareous fens, a habitat type which is described as currently endangered by many factors, such as land-use changes, nutrient enrichment, and fragmentation (Kophimai et al. 2014). The new record for the Laga Mountains acts as the new southernmost distribution limit for this species in the Italian Peninsula.

As far as Schljakovia kunzeana is concerned, the new finding of the species in the Laga Mountains is located along the current southernmost limit of its range, more or less at the same latitude of its south-western limit (Iberian Peninsula) and its south-eastern limit (Southern Balkans) (see GBIF at https://www.gbif.org/species/4891040). Indeed, the already established southernmost records of S. kunzeana for the Iberian Peninsula are located in the mountains of Navarra and Asturias in northwestern Spain and in the Central Pyrenees (Casas Sicart 1986; Fernández Ordoñez and Collado Prieto 2003; Dort 2021), whereas those for the Balkan Peninsula are reported for the Pirin massif and the Rila Mountains in Bulgaria (Ganeva and Natcheva 2003).

The chorological identity of Ptychostomum cernuum is a little different. This species is currently reported for three administrative regions of northern Italy (Lombardy, Piedmont, and Trentino-Alto Adige) only based on old data deriving from collections published before 1968 (Aleffi et al. 2023). As a consequence, this finding on the Laga Mountains represents the first record of P. cernuum in the last fifty years for the entire Italian Peninsula, as well as being the first record of this species for the entire Apennines. Curiously, although this boreal species is currently absent throughout the rest of central and southern Italy (where there are several montainous massifs characterized by subalpine and alpine belts rich in circumboreal species), it reappears in Sicily where populations of this species have recently been reported (Puglisi and Privitera 2018) for the Etna Volcano, at relatively low altitude (about 1000 m a.s.l.). For this reason, the new record of P. cernuum for the Laga Mountains area, although it is the first for the Apennines, does not imply any further southern extension of the range currently known for this species, either on a global or Italian country level.

Many of the bryophyte species found in the study area represent diagnostic species of different Habitats listed in the European conservation Directives. On the basis of the EUNIS European Habitats classification (Chytrý et al. 2020), we found that Habitat Q42 – Extremely rich moss-sedge fen, and Habitat Q41 – Alkaline, calcareous, carbonate-rich small-sedge spring fen, are those including the majority of the aforementioned bryophyte diagnostic species (Q42: Aneura pinguis, Aulacomnium palustre, Campylium stellatum, Hamatocaulis vernicosus, Ptychostomum pseudotriquetrum; Q41 Campylium stellatum, Palustriella commutata, Philonotis calcarea, Ptychostomum pseudotriquetrum). The diagnosis of Habitat Q42 refers to base-rich fens classified in alliances, such as Saxifrago-Tomentypnion and Sphagno warnstorfii-Tomentypnion nitentis, which includes associations always dominated by bryophytes, with calcium-tolerant Sphagnum mosses playing the leading role. Habitat Q42 is not reported for the Central Apennines at present, its southernmost limit being located in the Northern Apennines. Instead, Habitat Q41 would certainly be among the most suitable to encompass some of the communities we investigated (especially those we sampled in sites 1, 2, 3, 8). Indeed, Habitat Q41 is known to include small-sedge communities, and, among these, those belonging to Caricion davallianae and Caricion viridulo-trinervis. Moreover, Q41 has already been reported for the Central Apennines (see Q41 map in Chytrý et al. 2020). In addition to the aforementioned Q41 diagnostic bryophytes, the communities we sampled exhibited many vascular plant species (most of them playing a dominant role in the communities investigated), which are also considered to be diagnostic for this habitat, such as Carex davalliana, C. viridula, C. lepidocarpa, Eleocharis quinqueflora, Eriophorum latifolium, Juncus alpinoarticulatus, Parnassia palustris, Pinguicula vulgaris, Tofieldia calyculata.

EUNIS Habitat Q43 (Tall-sedge base-rich fen), which is described as including “tall-sedge fens and medium to tall graminoids over a ground carpet of rich-fen bryophytes”, acts as a possible alternative reference, especially for the communities developed over larger dimension flat landforms. This environmental type could be applied to the communities we found at Fosso Cerruglia and along the banks of the Castellano river (sites 4 and 7, respectively). In these sites, the physiognomic dominance is given by tall sedges (e.g. Carex acuta, C. panicea, C. pallescens) and other medium-size species (Juncus effusus, J. inflexus, Deschampsia cespitosa), together with species considered to be diagnostic and frequently occurring in Q43 habitat (e.g. Carex echinata, C. rostrata, Menyanthes trifoliata, Potentilla erecta, Succisa pratensis). Regarding bryophytes considered as diagnostic in Habitat Q43, we found Aneura pinguis and Campylium stellatum. In addition, we found Calliergonella cuspidata, Ctenidium molluscum, Palustriella commutata, Ptychostomum pseudotri­quetrum as constant species. It is worth highlighting that Habitat Q43 is one of the two habitats, out of those identified in this study, exhibiting the highest number of bryophyte constant species. The other one is Habitat Q23 - Relict mire of Mediterranean mountains. Habitat Q23 characterizes the oligo-mesotrophic mires occurring in the montane and subalpine belts over siliceous bedrocks and exhibits a peculiar geographical distribution that comprises the Balkans, the mountains of Corsica and the Sierra Nevada massif in southern Spain. The diagnostic bryophyte species we collected in our samples are Philonotis seriata, Ptychostomum pseudo triquetrum and Sarmentypnum exannulatum. The finding of this habitat in the middle of the Italian Peninsula could be considered evidence for a natural geographical connection bridging an anomalous biogeographical gap along the W-E (or E-W) alignment of the Mediterranean mountain ranges. Moreover, the Laga Mountains, being a siliceous Mediterranean massif characterized by acidic soil, correspond significantly to the diagnosis of Habitat Q23, especially considering that the communities we sampled are developed at the edge of melting snow streams in the upper montane and subalpine belts. Last, but not least, the Central Apennines are biogeographically strictly related to the Balkans (core area of Q23 Habitat) and form the Apennine-Balkan biogeographical Province (see Rivas-Martínez et al. 2004). Despite all this, Habitat Q23 cannot serve as useful reference for the communities described in this paper. In fact, the vascular plant species reported in the EUNIS Habitat factsheet as those bearing the highest diagnostic coefficient for habitat Q23 are all species displaying a restricted Balkan distribution (e,g. Pinguicula balcanica Casper, Gymnadenia frivaldii Hampe ex Griseb., Plantago gentianoides Sibth. & Sm., Primula frondosa Janka, Dactylorhiza cordigera (Fr.) Soó, Carex bulgarica (Domin) Lazare). Moreover, the syntaxonomic references reported (Narthecion scardici, Festucion frigidae and Caricion intricatae) are strictly related to the Balkans, Sierra Nevada and Corsica, respectively. Obviously, if, as a result of our study, it should be established that the Central Apennines too are a suitable site for hosting the Q23 Habitat, then the whole diagnosis of this Habitat will need to be revised.

EUNIS Habitat Q45 includes several of the species and communities we detected, although its diagnosis and current distribution “Fens developed on open substrates constantly flushed by icy, base-rich water alongside small rivers, springs or glaciers in the alpine belt of European mountains and in the Arctic” would not support its occurrence in a Mediterranean mountain range such as the Apennines. However, the presence in our samples of Q45 diagnostic bryophytes, such as Ptychostomum pseudotriquetrum, Palustriella commutata, Campylium stellatum, together with several diagnostic vascular plant species, testifies to the importance of the Laga Mountains for the conservation of boreal species during the post-glacial period. This statement is particularly supported by the finding of Schljakovia kunzeana which is currently considered as diagnostic for extreme glacial habitats, such as S11 “Shrub tundra” and S12 “Moss and lichen tundra”, both limited to the northern sector of Scandinavia.

Our attempts to find a correspondence between the bryophytes found in the study area and the diagnostic species lists occurring in Annex I, of the EUR 23 interpretation manual of Directive 92/43/EEC, reveal that the information obtained from Annex I is limited and partially indeterminate. This is probably due to the lower degree of detail used in Annex I in evaluating both the numerical consistency of the pools of species typical of a given Habitat and, more specifically, the ecological (and coenological) role of the bryophyte component within each habitat type. Habitat 7160 (Fennoscandian mineral-rich springs and springfens) is the one showing the highest number of diagnostic bryophyte species, among those we collected during our sampling. This evidence is quite surprising, even just considering the diagnosis of Habitat 7160 and the geographical distribution declared in it. However, this Habitat would not seem like a good reference for the communities we sampled also from a floristic point of view, since only Epilobium alsinifolium was found in our surveys among all the vascular plant species reported as diagnostic for 7160 in the Manual of interpretation. It is no coincidence that, the Italian Manual for Habitats Directive (Biondi et al. 2009) excludes the presence of this habitat from the whole Italian territory.

The Habitat types exhibiting the greatest coherence with the cryptogamic and vascular flora occurring in our sampled sites, according to the EUR 28 Manual, are certainly Habitats 7220* (Petrifying springs with tufa formation) and 7230 (Alkaline fens). Both these habitats share numerous diagnostic species (e.g. Ptychostomum pseudotriquetrum, Parnassia palustris, Pinguicula vulgaris, Saxfraga aizoides, Tofieldia calyculata). However, the environments characterized by the two aforementioned habitats appear to be very different from each other, as can be deduced even just by considering the phytosociological alliances proposed as syntaxonomic reference in the Manual. Habitat 7220* is characterized by communities mainly developed near springs and dripping walls, normally in shady locations, which are generally classified in the alliance Cratoneurion commutati. This type of vegetation does not correspond, if not very partially, to the communities we detected. In fact, at least in Italy, Habitat 7220 is not linked to the mountain environment, but is widely distributed in all the Italian administrative Regions, including Sicily and Sardinia.

However, as emerged from our samples, the bryophytes listed as diagnostic for Habitat 7220* (Eucladium verticillatum, Philonotis calcarea, Hamatocaulis vernicosus, Ptychostomum pseudotriquetrum, Scorpidium cossonii) show high frequency and coverage values also in a completely different environment, such as the Caricion davallianae meadows. This grassland type closely matches Habitat 7230, which, accordingly, is to be considered the most suitable reference for the communities we sampled, both considering their ecology and structure, and the syntaxonomic classification provided in the diagnosis itself (i.e. small sedge and brown moss mire communities belonging mainly to Caricion davallianae developed on soils permanently waterlogged with the water table at, or slightly above or below, the substratum).

The bryophytes that the Manual EUR 28 reports as diagnostic for the Habitat 7230 are Campylium stellatum, Calliergonella cuspidata, Ctenidium molluscum, Ptychostomum pseudotriquetrum, Scorpidium cossonii. However, compared to Habitat 7220*, there is a significantly higher number of diagnostic vascular plant species. What is apparently not entirely consistent comparing the study area with the Habitat diagnosis, is that Habitat 7230 is normally associated with calcareous substrates with neutral alkaline pH values, and dominated by calciphilous small sedges. This is actually not exactly in line with the soil characteristics of the Laga Mountains, which especially in the highest bioclimatic belts are characterized by typical acidophilous communities, such as the Nardus stricta L., and Patzkea paniculata (L.) G.H.Loos communities among the grasslands, the acidophilic beech forest of the upper montane belt with Veronica urticifolia Jacq. and Gymnocarpium dryopteris (L.) Newman and of the Vaccinium myrtillus L. heathlands throughout the lower subalpine belt (see Pedrotti, 1982; Biondi et al. 2009; Blasi et al. 2003; Di Pietro 2007; Di Pietro et al. 2007). A plausible explanation for this apparent contradiction could be that vascular plants are more affected by the influence of the bedrock than bryophytes because they are characterized by roots that penetrate the soil at greater depths. Having rhizoids anchored to the substrate to a depth of only a few millimeters and absorbing nutrients directly from the atmosphere, bryophytes are less strongly influenced by the type of substrate. This weak influence is likely to be more pronounced in environments such as those investigated in this study (mires developed at the bottom of subalpine north facing gullies), where the upper soil layers tend to lose part of their acidity being washed away by rain or snow.

If only the type of substrate and the pH values are considered, Habitat 7240 (Alpine pioneer formations of Caricion bicoloris-atrofuscae) would be the most suitable to be used as reference, as it refers to a neutral or slightly acidic pH. However, in neither the EUR23 Interpretation Manual, nor the Italian version of it, is there a list of diagnostic bryophyte species for this habitat, apart from a coenological reference to a “Scorpidium revolvens-Carex saxatilis community”. Instead, there are several vascular plant species listed as diagnostic for Habitat 7240, including some occurring as dominant in the communities we sampled (e.g. Carex frigida, Juncus alpinoarticulatus, J. arcticus).

The remaining habitats as hosting some of the bryophyte species detected in the sampled area (i.e. 7140; 7310) cannot be taken into consideration, as they are both strictly related to the peatbogs of Northern Europe and characterized by the absolute dominance of Sphagnum species in their bryophyte component. Finally, Habitat 9050, which includes among its diagnostic species Brachythecium rivulare, Plagiomnium undulatum, P. cuspidatum, actually concerns open coniferous forest vegetation totally unrelated to the fen and mires communities we investigated.

It emerges that the choice of the habitat to which to assign the communities we detected may not be unambiguous, depending on whether the interpretations are made using the EUNIS Habitats factsheets or the EUR28 Habitat Interpretation manual. If we refer to the EUNIS factsheets it is possible to identify two different habitats (i.e. Q41 for the small pools dominated by small sedge communities and Q43 for the larger pools characterized by bigger size sedge species). Instead, if we refer to the EUR28 Interpretation Manual there would seem to be only a single Habitat type (7230) to which to assign both of the above-mentioned community types. At the same time, however, it is evident that EUNIS habitats Q41 and Q43 are partially overlapping from both a floristic and an ecological point of view so that the choice to consider them as two separate habitats may not be fully shared by the scientific community. Consequently, the uncertainty on which of the two interpretations should be considered the most correct, the one proposed by the EUNIS factsheets or the one proposed by the EUR28 Manual. This paper does not have necessary research data to provide a solution to this question. Apparently, at least in our study case, the EUNIS classification is able to identify two distinct habitats as it uses greater detail than the EUR 28 Manual in the resolution and description of the environmental pattern of the mires and fen occurring in the study area. It seems that the EUNIS classification interpreted the communities using a higher detail scale than that adopted by the EUR 28 Manual. However, the issue of the scale adopted may not be the one to be called into question and the differences between the two aforementioned classification systems have to be attributed to other factors. In fact, in the EUNIS terrestrial habitat classification with crosswalks to Annex I (Schaminée et al. 2012), as reported by the European Environment Agency updated to 2021 (EUNIS 2021), Habitat Q41(D4.2a) corresponds to Annex I 7230 while Habitat Q43 (D4.2b) corresponds to Annex I 7210. Therefore, rather than a simple “quantitative” issue attributable to the scale of observation, there would seem to have been real “qualitative” differences which gave rise to such an interpretation of the aforementioned Habitats.

This study made it possible to fill some knowledge gaps on the presence and distribution of relict bryophyte species of boreal origin in the high altitude bioclimatic belts of the Central Apennines. Nine species of bryophytes were found to be new records for the Lazio administrative Region and one species for the Abruzzo administrative region. For some of these species (e.g. Hamatocaulis vernicosus, Schljakovia kunzeana and Scorpidium cossonii), the new findings have led to an extension of the southernmost limit of their distribution range (at the national and global scale). Of particular interest are the new records of Hamatocaulis vernicosus, a species currently included in Annex II of the Habitats Directive, which was still unknown for the Apennines.

The correspondence between the bryophyte species identified and the Habitats available using the EUNIS factsheet and the 92/43/EEC Directive Interpretation Manual led to results that were not completely in agreement in terms of number of species considered and Habitat type involved. The EUNIS classification highlighted two possible Habitats to be used as reference (Q41 and Q43), whereas the Habitat directive Manual highlighted just one Habitat (7230).

The amount of information provided by the EUNIS expert classification system was found to be greater and more complete than that provided by the Habitats Directive Interpretation Manual overall. Based on a continuously updated database of phytosociological surveys and syntaxonomic framework (EuroVegChecklist), the EUNIS factsheets prove to be more effective in providing useful qualitative and quantitative information regarding the cenological role of bryophytes. In contrast, the information provided by the EUR28 interpretation Manual was found to be a little flatter, especially owing the fact that it was not directly derived from statistically-derived diagnostic species. Moreover, the EUR 28 Manual was sometimes found to be deficient in providing information on the ecological role of the diagnostic species and lacking in updated syntaxonomic references to be used for the correct identification of Habitats.

The importance of the Habitats Directive in the management of the environment is clearly recognized in all the European Union countries. All the implications, not only scientific, but also administrative, bureaucratic, and legal linked to the identification, monitoring and assessment of EU Habitats are also recognized. Updated taxonomic, syntaxonomic and ecological information deriving from a robust basis of georeferenced field surveys and validated through publications in scientific journals would therefore be an essential and indispensable help for all the bodies responsible for the management and conservation of the Natura 2000 sites. The need for effective tools which could help in procedures of habitat identification and interpretation (see Bonari et al. 2021) is extremely pressing for the high-altitude habitats of the Mediterranean mountains. Indeed, these are concretely at risk of extinction as a consequence of progressive and increasingly intense global warming and of greater competition from the plant communities normally developed at lower altitudes. The new floristic, chorological, and coenological data provided by our study confirm the importance of undertaking field sampling campaigns, which are the only way of creating deeper knowledge usable for developing an increasingly efficient network of measures to safeguard biodiversity.

The research was in part supported by private funds of the authors and in part by: i) National Recovery and Resilience Plan (NRRP), Mission 4 Component 2: Investment 1.4 - Call for tender No. 3138 of 16 December 2021, rectified by Decree n.3175 of 18 December 2021 of Italian Ministry of University and Research; Award Number: Project code CN_00000033, Concession Decree No. 1034 of 17 June 2022 adopted by the Italian Ministry of University and Research, Project funded by the European Union – “NextGenerationEU NBFC”. A) R. Di Pietro: CUP B83C22002950007, Project title “National Biodiversity Future Center; ii) Ateneo Sapienza progetti medi: prot. RM123188F7AAEE40 Resp. Romeo Di Pietro.