A checklist of 916 lichenised taxa is reported from the Paneveggio-Pale di San Martino Natural Park and its surroundings (Trentino-Alto Adige, N Italy), based on 7351 records from: (a) 72 literature sources, (b) eight public and private herbaria and (c) field observations by some of the authors. The study area appears as a hotspot of lichen diversity, hosting 30.1% of the lichen biota of the Alps in a territory that has 0.064% of their total surface area. This is mainly due to its high climatical, geological and orographic heterogeneity, but also to the long history of lichenological exploration, that started in the 19^th century with Ferdinand Arnold and is still ongoing. The present work highlights the importance of detailed species inventories to support knowledge of biodiversity patterns, taxonomy and ecology and to properly address conservation issues. Fuscidea mollis var. caesioalbescens, Hydropunctaria scabra, Protoparmelia badia var. cinereobadia and Variospora paulii are new to Italy, 18 other taxa are new to Trentino-Alto Adige.

Alps, biodiversity, checklists, conservation, herbarium studies, historical records, lichen inventories

Basic information on the distribution, ecology and taxonomy of species is fundamental for revealing biodiversity patterns and providing effective conservation guidelines. Field species inventories carried out by specialists (Vondrák et al. 2016, 2018; Spribille et al. 2020) as well as survey of herbaria and literature records (Isocrono et al. 2007; Himelbrant et al. 2018) are fundamental for lichen biodiversity research, sometimes triggering taxonomic advances, including the description of new species (Spribille et al. 2020; Leavitt et al. 2021; Vondrák et al. 2022). Furthermore, temporal continuity of basic biodiversity data from a given region may allow comparison of biodiversity patterns across time, to track the effect of global changes (Hauck et al. 2013).

Unfortunately, basic biodiversity data on lichens are often missing, even for relatively well-explored areas, thus hampering conservation efforts (Hunter and Webb 2002; Rubio-Salcedo et al. 2013). However, some notable exceptions exist, as in the case of the Alps, which are amongst the lichenologically best known areas of the world, thanks to their long-lasting and accurate exploration. To date, 3046 lichenised infrageneric taxa are known from the area (Nimis et al. 2018a), but this number is likely to increase with the widening of exploration and the deepening of taxonomical knowledge.

Within the Alps, the historical region of Tyrol is certainly one of the best-explored, with one of the oldest known “checklists”: in their compilative monograph “Die Flechten (Lichenes) von Tirol, Vorarlberg und Liechtenstein”, Dalla Torre and Sarnthein (1902) summarised a huge amount of information on the lichen biota of the Tyrolean area, mainly based on original papers, based predominantly on multiple field explorations by Ferdinand Arnold (1828–1901) and Ernst Kernstock (1852–1900). These data largely contributed to the present lichen inventory of Trentino-Alto Adige, that is the lichenologically richest region of Italy, with 1573 infrageneric taxa of lichenised fungi reported to date (Nimis and Martellos 2022).

In particular, Arnold intensely explored the area of Paneveggio and Predazzo (Arnold 1879, 1880, 1887, 1897), whose localities are famous amongst lichenologists, due to the many specimens collected there and distributed in several public herbaria, as well as to the new species described from this area. Since 1967, the area of Paneveggio was included in the Paneveggio-Pale di San Martino Natural Park, that extends south of Paneveggio to incorporate almost all the Pale di San Martino dolomitic chain and a metamorphic mountain area at the orographic right side of the Vanoi River. Since its institution, this Park has attracted lichen research thanks to the fame resulting from Arnold’s explorations. In particular, since the mid-nineties the administration of the Park promoted a new phase of exploration that focused both on lichen floristics (e.g. Nascimbene and Caniglia 2003; Thor and Nascimbene 2007) and ecology (e.g. Nascimbene and Caniglia 1997, 1999; Nascimbene et al. 2008), expanding the research effort to almost all of the protected area.

In this work, we summarise about 150 years of lichenological exploration of the Paneveggio-Pale di San Martino Natural Park, providing an updated checklist of its lichenised fungi.

The checklist of the lichenised fungi of the Paneveggio-Pale di San Martino Natural Park includes 916 specific and infraspecific taxa (Suppl. material 1), corresponding to 58.4% of the lichen biota of Trentino-Alto Adige (Nimis and Martellos 2022), 35.2% of Italy (Nimis and Martellos 2022) and 30.1% of the Alps (Nimis et al. 2018a). Most records (4551, 731 taxa) were retrieved from literature, whereas a lesser amount refers to herbarium specimens (1325, 522 taxa) and field observations (1475, 180 taxa).

The species belong to 270 genera (most represented, with more than 20 species each: Cladonia, Lecanora, Lecidea s. lat., Rhizocarpon, Verrucaria, Rinodina; 128 genera with only one species each), 75 families (most represented, with more than 50 species each: Parmeliaceae, Lecanoraceae, Lecideaceae, Teloschistaceae, Verrucariaceae; 22 families with only one species each) and 26 orders (most represented, with more than 50 species each: Lecanorales, Verrucariales, Caliciales, Lecideales, Teloschistales, Peltigerales).

Chlorolichens are the most frequent group (93.0%), followed by cyanolichens (6.0%) and cephalolichens (1.0%); amongst chlorolichens, most have a chlorococcoid photobiont (88.3%) and only a few a trentepohlioid photobiont (4.7%). Most numerous are crustose forms (68.8%), followed by foliose (15.5%), fruticose (11.2%); squamulose (3.4%) and leprose (1.1%) forms are far less represented. Most taxa reproduce sexually (76.5%), while 23.5% reproduce asexually, mainly by soredia (17.0%), followed by isidia (4.1%) and thallus fragmentation (2.4%).

The number of subcontinental taxa is 22 (2.4%), that of suboceanic taxa 80 (8.7%), while only two taxa can be considered as oceanic (0.2%).

Four taxa are new to Italy, i.e. Fuscidea mollis var. caesioalbescens, Hydropunctaria scabra, Protoparmelia badia var. cinereobadia and Variospora paulii. Eighteen other taxa are new to Trentino Alto Adige, i.e. Acarospora sphaerospora, Bacidina arnoldiana, Chrysothrix chlorina, Circinaria hoffmanniana, Dermatocarpon arnoldianum, Gyalecta erythrozona, Lecanora bicincta var. bicincta, Lecanora caesiosora, Lempholemma intricatum, Miriquidica plumbea, Myriolecis agardhiana subsp. sapaudica, Myriolecis invadens, Myriospora myochroa, Parmotrema arnoldii, Rhizocarpon geographicum subsp. arcticum, Sarcogyne urceolata, Staurothele sapaudica and Variospora macrocarpa. One species, belonging to genus Lecanora, still awaits a formal description as new to science (Nascimbene, pers. comm.). In previous, recent publications, several other species from the study area were recorded as new to Italy or Trentino Alto Adige (e.g. Thor and Nascimbene 2007; Nascimbene et al. 2021).

Ninety-one species are Red-listed: 62 epiphytic lichens (Nascimbene et al. 2013) and 25 terricolous lichens (Gheza et al. 2022), including four species of Cladonia subgen. Cladina (Ravera et al. 2016).

Only 57 taxa were recorded in all of the three exploration periods, whereas 271 were recorded in two of them, the largest overlap being between the 19^th and 21^st centuries, sharing 236 species (Fig. 2). Five hundred and ninety species were recorded only in one century (19^th: 284, 20^th: 24, 21^st: 281). Overall, 601 taxa (3794 records) were recorded in the 19^th century, 116 (186 records) in the 20^th and 585 (3371) in the 21^st century.

Figure 2. 

Number of lichen taxa recorded in the three exploration periods and their overlapping.

The spatial distribution of historical (Arnold’s) and recent (20^th and 21^th centuries) records reflects the exploration history, with Arnold’s localities concentrated in the northern part of the protected area (and its surroundings; Fig. 3) and recent records also scattered in the southern part of the Natural Park, both in the dolomitic and metamorphic areas where, however, some gaps still remain.

Figure 3. 

Georeferenced collection sites referred to the 19^th (yellow dots), 20^th (red dots) and 21^st (blue dots) centuries; the continuous black line indicates the borders of the Paneveggio-Pale di San Martino Natural Park.

The montane belt was the most explored, with 2654 records of 535 taxa, followed by the subalpine, (2296 records of 476 taxa) and the alpine belts (1852 records of 514 taxa) (Fig. 4). The nival belt was the less explored, with 109 records of 49 taxa (Fig. 4).

Figure 4. 

Number of lichen taxa in each altitudinal belt.

The highest number of records is from rocks (2351 records, 458 taxa), followed by bark (2003 records, 257 taxa) and soil (665 records, 116 taxa) (Fig. 5). Other substrates, such as deadwood, are less represented. Information about rock type, tree species and soil type was not always available. Amongst saxicolous lichens, most records are from magmatic and metamorphic siliceous rocks (1368 records, 287 taxa), while carbonatic rocks are poorer (873 records, 214 taxa). Epiphytic lichens were mainly collected on Picea abies (133 taxa, 730 records), followed by Abies alba (61, 174), Larix decidua (48, 527), Pinus cembra (34, 161), Alnus incana (24, 52), Rhododendron ferrugineum (24, 48) and Fraxinus excelsior (19, 19). Terricolous lichens were mainly from acidic soil (53 taxa), with 25 taxa from carbonatic soil.

Figure 5. 

Number of lichen taxa on the main substrate types.

The Paneveggio-Pale di San Martino Natural Park can be considered as a hotspot of both lichenological research, with more than 150 years of exploration, and of lichen diversity. Almost one third of the lichen biota of both the Alps and Italy occurs in this area, whose surface is ca. 0.06% of their total surface area. This highlights its importance for lichen conservation and lichenological research, with several regionally and nationally new taxa, the occurence of species that still await formal description or of taxa that are known from this area only, as in the case of Thelidium paneveggiensis. Moreover, lichen diversity is at least 60% of that of vascular plants, indicating that lichens strongly contribute to the biodiversity of the protected area.

This level of knowledge of the lichen biota is rare in protected areas of the European Alps. Arnold himself stated that, thanks to the repeated and careful investigations he carried out “from the valleys to the highest heights”, the upper Val di Fiemme could be considered as the lichenologically best known area of Tyrol at the time (Arnold 1887). A similar situation is perhaps that of the High Tauern National Park, in which over 1100 species have been recorded since the times of Arnold (Türk 2016) on an area which is, however, larger by a factor of ten. In the Italian Alps, other checklists are available, as in the case of a sector of the Stelvio National Park (Nascimbene et al. 2012) or for the Sciliar Natural Park in South Tyrol (Nascimbene 2008), but these are far less exhaustive and the number of species will certainly increase with further exploration. In the case of lichens, not easily detectable and often with a rarefied distribution (Nimis et al. 2018b), it is difficult to provide exhaustive checklists. However, when exploration is concentrated on relatively small and environmentally heterogeneous areas, the number of species can be surprisingly high (Vondrák et al. 2022). At a national level, in the absence of comparable knowledge on other protected areas, the Paneveggio-Pale di San Martino Natural Park is certainly a priority area for lichen conservation, which should be amongst its main management aims.

This small Natural Park has a great climatic, geological and orographical heterogeneity that likely enhances lichen diversity (Vondrák et al. 2022). For example, Passo Rolle, located in the central part of the study area, is a boundary between oceanic (south) and continental (north) climates, as well as a geological and tectonic boundary. The climatical heterogeneity determines the occurrence of many species with different phytoclimatic affinities, i.e. 22 subcontinental and 82 suboceanic/oceanic taxa. Geological diversity as well plays an important role in shaping and enriching lichen diversity, at least with regard to saxicolous and terricolous species: the checklist includes many specialists of either siliceous or carbonatic rocks and soils, whose co-occurrence in the study area is allowed by the high variety of rock types. Finally, the wide altitudinal range offers favourable conditions for montane, subalpine, alpine and nival species. This also implies different tree species available for epiphytic lichens along the gradient, from broadleaved forests at lower altitudes to coniferous stands in the highest forested belts.

The other component of this lichen hotspot is its exploration history, starting from the 19^th century. It should be noticed that, at the times of Arnold, explorations were much more difficult: although he spent a long time in the study area, the investigations carried out in the last decades covered an overall longer timespan and also took into account several areas not explored by Arnold. Nevertheless, a high number of taxa was recorded only either by Arnold or by Nascimbene, but it is hard to say whether the species recorded only in the 19^th century could actually have disappeared today. In some cases, the lack of recent records is probably due to merely overlooking the widespread and common taxa in recent surveys, as in the cases of Athallia pyracea, Circinaria calcarea and Physconia grisea that surely still occur. It is also difficult to understand how several widespread or locally common species that likely already occurred at the times of Arnold went unnoticed in historical times and were recorded only in the 21^st century, as in the cases of Athallia cerinella, Cladonia symphycarpa, Evernia prunastri and Lecidella elaeochroma. On the other hand, some species were recorded only in recent times, because they were described recently (e.g. Absconditella lignicola, Anaptychia bryorum, Calicium pinicola and Variospora paulii) or were recognised later as independent taxa (e.g. Cetrelia cetrarioides, C. monachorum and C. olivetorum). Even when the same locality was visited across the three periods, as in the case of Mt. Castellazzo, the overlapping of records was relatively low, differences being mainly related to poorly detectable species, such as small crustose and endolithic lichens and perhaps also the the bias related to the effect of different collectors. Under these circumstances, the checklist is likely more an image of lichen diversity taken with a long exposure time rather than a generalised framework for directly assessing changes of the lichen biota across time, that can be only achieved with resampling of small and clearly localised plots. Only in the case of some easily-detectable species, sensitive to environmental changes (e.g. Nephroma laevigatum, Sticta fuliginosa and Usnea longissima) that were not recorded in recent years, we could hypothesise that they actually disappeared due to global changes (i.e., climate, land-use, forest management).

The checklist of the lichens of the Paneveggio-Pale di San Martino Natural Park contributes to a better knowledge of the lichen biota at a broader level than a mere local checklist. It has: (1) a biogeographical value, including a high number of records useful to better elucidate the distribution of many rare and/or poorly known taxa; and (2) a value for biodiversity conservation, providing a framework on which further research can be based. Such detailed floristic information is useful to plan new explorations for assessing the occurrence of the rarest species, which is of paramount importance for planning future conservation actions. Focusing on this topic with a targeted sampling could help to understand the effects of environmental changes in the last 150 years (Hauck et al. 2013), including increased human impact and the ongoing climate change.

Last but not least, this checklist is a remarkable demonstration that even the best-studied areas can still reveal many novelties and should not be considered as “accomplished missions”, but should be monitored continuously.

We are grateful to Matteo Barcella, Luca Di Nuzzo, Camilla Frascari and Angelica Riciputi for help in managing the dataset and to Holger Thüs for checking (also with molecular approach) specimens of some freshwater lichens.