Human-induced pressures such as climate and land-use changes in the Anthropocene disproportionately threaten island ecosystems and the endemic species they host. Shedding light on the ecological needs of island species is key to the conservation of these fragile ecosystems and their unique species. Here we present the ecological needs of a bat species endemic to Sardinia, the long-eared bat Plecotus sardus, and analyse the relationship between this Critically Endangered species and the insular environment at different spatial scales to inform action for its conservation. We show that besides displaying a unique phenology and roost use, the species is closely associated with the dry broadleaf forests of native oaks Quercus ilex and Quercus suber at all scales and, in contrast, is negatively affected by coniferous stands, open pastures and urban environments. Our results not only provide key information for the conservation of P. sardus but also provide insights into the unique adaptations of insular endemic species to the fragile island ecosystems, highlighting the importance of ecological studies to informing conservation in biodiversity hotspots. We also demonstrate that protection and restoration of key habitats, particularly within 2 km of roosts, are key to protecting the few known reproductive colonies.

Islands host high numbers of endemic species, and the latter are especially exposed to human-driven habitat alteration because their population size is constrained by the limited space and resources found in insular systems. Extreme events linked with climate change and direct anthropogenic stressors may synergistically affect endemic species, and even push them to the brink of extinction. Bats include many insular endemics whose life traits make them excellent candidates to test the effects of both climate-change driven events and direct human disturbance. The Mediterranean island of Sardinia is home to the endemic long-eared bat Plecotus sardus . Within the island, this recently described species is restricted to a limited range where suitable habitat is present. This makes the species extremely vulnerable to human action. Here we use Plecotus sardus as a model to assess the response of insular endemic bats to climate change and human disturbance, exploring demographic trends across two decades. Overall, roost count data for all known reproductive sites showed a steep (-63.4% between 2003 and 2020) population decline, so that the current estimated population size is only 36.5% of that observed in 2003. Colony growth rates are strongly affected by recurring wildfires around reproductive sites, summer precipitation and temperature extremes, pointing to climate change as a primary threat to the species along with direct human interference. Such anthropogenic pressures may therefore rapidly expose island endemic bats to a high extinction risk. Based on our analysis, Plecotus sardus is among the most threatened mammals, and likely the rarest bat species, in Europe. Thus, we urge that (1) similar assessments are conducted on other insular endemic bats in Mediterranean Europe, (2) IUCN Redlist categories are revised according to new analyses, and (3) recovery action plans are immediately developed and implemented to revert the current population trends.

Circoviruses are small circular DNA viruses causing severe pig and poultry disease, recently identified in various bat species worldwide. We report the detection and full-genome molecular characterization of a novel bat-associated Circovirus identified in faecal samples of Miniopterus schreibersii bats (Schreiber's bent-winged bats) from Sardinia, Italy. Full-genomic sequencing revealed a new putative member of Circoviridae family, with a genome size of 2063 nt. Sequencing allowed the characterization of the two major ORFs, inversely arranged, encoding replicase and capsid proteins, as well as the finding of a polythymidine tract within the genome, and highlighted phylogenetic relationships of the novel virus. This is the first report of circovirus in European bats. Giving the high level of genetic diversity of bat circoviruses, it is paramount to further investigate the relationships between these viruses and bats.

Characterizing the genetic outfit of a species is fundamental to evaluate its status and devise optimal conservation plans to maintain or enhance the viability of its populations. The greater horseshoe bat (Rhinolophus ferrumequinum) underwent declines across Europe over the 20th century and was thus listed in the EU Habitat Directive and the species protection legislation of EU countries. To understand what is the state of the species in Italy, we described the genetic variability and population structure derived from 327 bats sampled in twenty-two Italian colonies. The analysis of the first part of the mitochondrial DNA control region (525 bp) and a panel of 12 microsatellite loci revealed high genetic variability throughout the study area and the presence of two genetically distinct groups: the Sardinian and the peninsular pools. We could also identify indications of a genetic substructure within the peninsular population, with a significant divergence concerning colonies located at the northern borders. Notably, the relevant genetic differentiation between Italian and Sardinian colonies should be carefully taken into account for conservation planning.

Bats may be natural reservoirs for a large variety of emerging viruses, including mammalian coronaviruses (CoV). The recent emergence of severe acute respiratory syndrome-associated coronavirus (SARS-CoV) and Middle East respiratory syndrome coronavirus (MERS-CoV) in humans, with evidence that these viruses may have their ancestry in bats, highlights the importance of virus surveillance in bat populations. Here, we report the identification and molecular characterization of a bat β-Coronavirus, detected during a viral survey carried out on different bat species in the island of Sardinia (Italy). Cutaneous, oral swabs, and faecal samples were collected from 46 bats, belonging to 15 different species, and tested for viral presence. Coronavirus RNA was detected in faecal samples from three different species: the greater horseshoe bat ( Rhinolophus ferrumequinum ), the brown long-eared bat ( Plecotus auritus ), and the European free-tailed bat ( Tadarida teniotis ). Phylogenetic analyses based on RNA-dependent RNA polymerase (RdRp) sequences assigned the detected CoV to clade 2b within betacoronaviruses, clustering with SARS-like bat CoVs previously reported. These findings point to the need for continued surveillance of bat CoV circulating in Sardinian bats, and extend the current knowledge on CoV ecology with novel sequences detected in bat species not previously described as β-Coronavirus hosts.

During the last decades, the important role of bats in ecosystems and the threats to many bat species were increasingly recognized, and bats were integrated into several conservation acts. Protected areas like national parks may play a major role in bat conservation if species requirements are included in management plans. With its high bat diversity and many unexplored off-shore islands, Sardinia has a high potential for the protection of European bats and for research on their ecology. We conducted the first survey of the bat fauna on the Sardinian off-shore island and National Park Asinara, a formerly inhabited island. We applied a multi-method approach over two years to create a proper species inventory and to obtain data on the use of man-made structures by the bats. We recorded bat calls at different sites in summer and winter, captured bats via mist-netting, and performed roost surveys of man-made structures. Ten species were identified, three of them are highly protected, namely Rhinolophus hipposideros, R. ferrumequinum and Miniopterus schreibersii. Thirty-nine day roosts and 14 night roosts of, in total, five species were found in man-made structures. Many structures provided day and night roosts for different bat species. Although forest and water bodies are limited, and intensive grazing has created several open areas on the island, a remarkably high bat diversity developed, making Asinara an important offshore retreat area for bats in Italy. Our findings indicate an essential role of the abandoned buildings, and artificial ponds, of the island for bat conservation. The results of this study provide a basis for future bat conservation measures on Asinara Island.

Islands are biodiversity hotspots, often containing numerous endemic species. This makes them also hotspots for conservation. Within the Mediterranean region, Sardinia is known for its comparatively high degree of endemism, including cryptic diversity. In this paper we aim to elucidate the variability of pipistrelles (Pipistrellus and Hypsugo) on Sardinia. More specifically, we ask which species occur on Sardinia and we describe the geographic affiliations of these evolutionary lineages. We sequenced ca. 560 bp of the 16S rRNA gene from 36 pipistrelle specimens representing 17 localities from all major parts of Sardinia. For comparison we added samples from the entire Mediterranean region as well as sequences stored at GenBank. We constructed Bayesian phylogenetic trees and minimum spanning networks to identify which species occur on Sardinia and to infer their genetic affiliation to lineages occurring throughout the Mediterranean and the Canary Islands. We identified five pipistrelle lineages on Sardinia: Pipistrellus pipistrellus (haplolineage II), P. pygmaeus, P. kuhlii/desertii, Hypsugo savii s.str. and H. cf. darwinii. Colonization of Sardinia occurred at different times from different geographical sources, namely Europe and Africa. Some lineages may have invaded Sardinia recently. The Sardinian H. cf. darwinii may be endemic to the island. Our results highlight the importance of Sardinia as a major Mediterranean hotspot for bat biodiversity. The island harbours a pipistrelle diversity that is higher than that on any other Mediterranean island. Lying geographically at the interface between Europe and Africa, Sardinia combines elements from both continents.

Aims Because rhinolophids have been hypothesized to use echolocation call frequency to recognize conspecifics, sympatric species calling at similar frequencies should be subject to acoustic character displacement, i.e. a drift in frequency values to minimize the risk of misidentification of conspecifics. However, it has been proposed that insufficient geographical separation between populations in sympatry and allopatry may counter the establishment of frequency differences by character displacement. Here we tested the hypothesis that insular populations should exhibit acoustic divergence, and this should be revealed by comparing call frequencies with those observed in mainland, allopatric populations of conspecifics. We also tested whether the evolutionary pressure towards acoustic divergence should be especially strong at sites where rhinolophid species emitting similar call frequencies roost together in order to minimize interspecific frequency overlap. Location Sardinia and southern Italy (Campania, Lazio, Abruzzo). Methods Time-expanded echolocation calls and body size were recorded from Sardinian populations of Rhinolophus mehelyi Matschie, Rhinolophus hipposideros (Bechstein) and Rhinolophus euryale Blasius. Both call frequencies and forearm length of insular R. hipposideros and R. euryale were compared with those of populations from mainland areas of Italy where R. mehelyi is absent, to explore the hypothesis that the presence of the latter species (which calls at frequency values intermediate between the other two) may determine acoustic divergence in the other species. For Sardinian R. mehelyi and R. euryale, we also carried out intraspecific comparisons of call frequencies between bats from monospecific colonies and those from mixed colonies. Results As hypothesized, Sardinian R. hipposideros and R. euryale called at frequencies higher and lower, respectively, than in the peninsula. In this way, overlap with R. mehelyi is avoided. Body size showed no difference between insular and peninsular populations, i.e. frequency differences are not a by- product of difference in body size determined by insularity. Frequency values in Sardinian R. euryale from monospecific colonies did not differ from those of bats roosting together with R. mehelyi. However, R. mehelyi showed frequency values significantly higher when associated with R. euryale, possibly to minimize the risk of species misrecognition.

Aims Because rhinolophids have been hypothesized to use echolocation call frequency to recognize conspecifics, sympatric species calling at similar frequencies should be subject to acoustic character displacement, i.e. a drift in frequency values to minimize the risk of misidentification of conspecifics. However, it has been proposed that insufficient geographical separation between populations in sympatry and allopatry may counter the establishment of frequency differences by character displacement. Here we tested the hypothesis that insular populations should exhibit acoustic divergence, and this should be revealed by comparing call frequencies with those observed in mainland, allopatric populations of conspecifics. We also tested whether the evolutionary pressure towards acoustic divergence should be especially strong at sites where rhinolophid species emitting similar call frequencies roost together in order to minimize interspecific frequency overlap.Location Sardinia and southern Italy (Campania, Lazio, Abruzzo).Methods Time-expanded echolocation calls and body size were recorded from Sardinian populations of Rhinolophus mehelyi Matschie, Rhinolophus hipposideros (Bechstein) and Rhinolophus euryale Blasius. Both call frequencies and forearm length of insular R. hipposideros and R. euryale were compared with those of populations from mainland areas of Italy where R. mehelyi is absent, to explore the hypothesis that the presence of the latter species (which calls at frequency values intermediate between the other two) may determine acoustic divergence in the other species. For Sardinian R. mehelyi and R. euryale, we also carried out intraspecific comparisons of call frequencies between bats from monospecific colonies and those from mixed colonies.Results As hypothesized, Sardinian R. hipposideros and R. euryale called at frequencies higher and lower, respectively, than in the peninsula. In this way, overlap with R. mehelyi is avoided. Body size showed no difference between insular and peninsular populations, i.e. frequency differences are not a by-product of difference in body size determined by insularity. Frequency values in Sardinian R. euryale from monospecific colonies did not differ from those of bats roosting together with R. mehelyi. However, R. mehelyi showed frequency values significantly higher when associated with R. euryale, possibly to minimize the risk of species misrecognition.Main conclusions At least under geographical isolation, character displacement may be a causal mechanism for shifts in call frequency of sympatric rhinolophids. Species recognition and facilitation of intraspecific communication (with possible implications for mate recognition) constitute the best candidate factors for the phenomenon we observed.

We describe a new species of long-eared bat, genus Plecotus, from the island of Sardinia (Italy). The new species is clearly distinguishable from other European Plecotus species by its mitochondrial 16S rRNA gene (4.1-9.6% sequence divergence) as well as by a unique combination of morphological characters such as brownish colour of dorsal pelage, a relatively large thumb and thumb claw, an almost cylindrical form of the penis and the characteristic shape of the baculum. The most important morphological diagnostic character is a relatively long (greater than or equal to 18 mm) and wide (greater than or equal to 6 mm) tragus. The new species is currently known from three localities on Sardinia. In addition to the new species we discovered a lineage of P. auritus, which is substantially differentiated from continental P. auritus at subspecific level (1.2-2.7% of sequence divergence of the 16S rRNA gene). The existence of these two endemic bat taxa on Sardinia highlights the island's importance in the conservation of the European bat community.

A study in the mining area of Montevecchio-Ingurtosu, in territory of Guspini and Arbus (South western Sardinia), found 8 species of bats were present: Rhinolophus ferrumequinum, Rhinolophus hipposideros, Myotis myotis, Myotis capaccinii, Pipistrellus pipistrellus, Pipistrellus kuhlii, Hypsugo savii, Tadarida teniotis, 17 roosts were localized, 11 in subterranean cavities and 6 in building.