Myotis nustrale, Puechmaille & Dool & Beuneux & Ruedi, 2023

Puechmaille, Sébastien J., Dool, Serena, Beuneux, Gregory & Ruedi, Manuel, 2023, Newly described and already endangered: a new mammal species endemic to Corsica, Revue suisse de Zoologie 130 (2), pp. 335-351 : 342-346

Myotis nustrale sp. nov. Ruedi, Beuneux & Puechmaille

Figs 4-6

ZooBank Life Science Identifier ( LSID): urn:lsid:zoobank.org:pub:6804EDB9-2337-4253-9381-D1DDBFD239FE

Holotype: One adult female ( MNHN-ZM-2023-12 , with field number SP.C.37 and sample number MNA008_CO_ALB ) found dead by Julien Barataud on the 25th of July 2006. The whole carcass has been preserved in alcohol but is currently in a poor state, with large portions of the dorsal and ventral fur missing and the patagium of the left wing torn apart. Epiphyses are fully fused. The skull has been removed and preserved separately; it is intact, except for the right zygomatic arch that is broken ( Fig. 4 ); teeth are only slightly worn. External measurements (in mm; Table 2 ) were taken on the fluid-preserved carcass: FA 39.5, HB 42, TL 40; HF 7.8, TIB 17.0, EAR 18.5, TRA 10.9. Skull measurements (in mm; Table 3 ) are: GTL 15.62; CBL 14.49; CCL 13.47; CM3 5.77; M3M3W 6.26; CCW 3.92; ZB 9.64; BCW 7.86; MAB 7.94; POC 3.93; ROL 4.79; M1M3 3.50; ml 11.14; cm3L 6.04; m 1m 3L 3.81; coh 3.29. Tissue samples from this specimen are stored in alcohol at -20°C. DNA sequences from this specimen are deposited in the European Nucleotide Archive and include regions of the nuclear introns SLC38A7 ( OX958065 ), ABHD11 ( OX958096 ), ACOX2 ( OX958129 ) and ROGDI ( OX958185 ). Type locality: Albertacce , Haute-Corse, France (42°16’42”N, 8°54’43”E), ca. 1100 m a.s.l.

Paratypes: No paratypes are designated.

Distribution: This species is endemic to the island of Corsica ( France), in the Mediterranean Sea ( Fig. 1 ).

Diagnosis: Medium sized Myotis (W 5.5-9.5 g; FA 38.4-41.3 mm) with relatively long, unnotched ears; tragus straight, reaching beyond half the length of the conch ( Fig. 5 ). The long, unkeeled and S-shaped calcar running along the proximal half of the uropatagium, as well as the stiff hairs visible on the trailing edge of the uropatagium are typical features of all taxa in the Myotis nattereri species complex. Stiff hairs of the uropatagium occur in two rows, with only few hairs being reflected backwards ( Fig. 5 ).

Wing membrane (plagiopatagium) attaching to the base of the toe, as in M. nattereri s. str. or M. crypticus ( Fig. 6 ), but unlike in M. escalerai or M. zenatius which attaches to the base of metatarsus ( Puechmaille et al., 2012). Pelage greyish-brown above and whitish below, with a sharp demarcation line running along the sides of the body. Feet relatively small, half or less the length of tibia. Wing and tail membranes essentially naked and ochraceous-brown. Face hairy, except around eyes. Muzzle relatively flat and pointed. A prominent darkpigmented chin spot is visible on the lower lip in adult individuals ( Figs 5 and 6 ) which distinguish them from all other European Myotis in this group.

Skull and dentition ( Fig. 4 ) like that of other members of the M. nattereri species complex ( GLS 15.62 mm; CM 3 5.77 mm; ml 11.14 mm). Neurocranium globose without visible crests. The frontal part raises sharply above the orbits and becomes relatively flat near apex. Rostrum nearly flat. Teeth strong, uncrowded, with long canines, third premolars and molars. All premolars in-line with the tooth row; the second premolar (both upper and lower jaw) much smaller than the first ( Fig. 4 ). Lower molars myotodont.

As the only examined specimen is a female, the shape of the baculum is unknown.

Etymology: The specific epithet nustrale is a pronoun in apposition meaning “ours - le notre” in the Corsican language.

Description: The new species of Myotis from Corsica shares external morphological characters with all other members of the Myotis nattereri species complex, including a long straight tragus, unnotched ears ( Fig. 5 ), a long, S-curved, unkeeled calcar and the presence of stiff hairs along the trailing edge of the uropatagium. However, its wing insertion at the base of the toe ( Fig. 6 ) and double row of stiff hairs bordering the uropatagium on the ventral side classify the Corsican species into the morpho-group comprising M. nattereri s. str. and M. crypticus . Morphological comparisons will therefore concentrate on the distinction of M. nustrale from M. nattereri s. str. and M. crypticus , all three being distributed exclusively in Europe and western Turkey ( Çoraman et al., 2019; Uvizl & Benda, 2021). Except for the genetically very distinct but similarsized M. hoveli from the Levant, Asian members of this species complex are indeed larger in most respects ( Uvizl & Benda, 2021). Externally, M. nustrale is very similar to M. nattereri s. str. and M. crypticus and probably cannot be reliably distinguished from them, except by the presence of a conspicuous blackish spot present on the lower lip of all adult individuals examined in Corsica ( Figs 5 and 6 ). Such a pigmented spot is present in the lower lip of young individuals of a few other Myotis species (e.g. in M. daubentonii , M. dasycneme ) but vanishes when they attain adulthood ( Richardson, 1994; Haarsma & Van Alphen, 2009). M. nustrale has relatively longer ears and tragus than M. nattereri s. str. or M. crypticus ( Table 2 ), but because a single individual has been measured for these characters so far, individual variation may blur these apparent differences. The same applies to the shape of the tragus, the margins of which appear slightly more linear in the Corsican species than in the other continental taxa; tragus shape in these taxa, however, are subject to substantial individual variation. Fur colouration, greyish-brown above and whitish below, is also similar in all three species. Although craniodental dimensions of all three species are again largely overlapping ( Table 3 ), the general shape of the skull of M. nustrale is more similar to that of M. crypticus than to the slightly larger and more robust skull of M. nattereri s. str. Sequences of the mitochondrial cytochrome b gene, forming a strongly supported monophyletic group, are unique in the Corsican species and diverge by an average 7.5 % Kimura-2-parameter distance from its closest relative M. crypticus ( Puechmaille et al., 2012) . Nuclear genes and microsatellite data for M. nustrale also differ considerably from other taxa in the M. nattereri species complex ( Figs 2 and 3 ) and suggest that M. nustrale may be basal to other members of this clade ( Fig. 2 ). Recordings of echolocation calls of M. nustrale in Corsica show the typical acoustic signature of members of the M. nattereri species complex ( Russo & Jones, 2002), i.e. short and strongly frequency modulated calls dominated by sweeps ranging from>105 kHz down to ca. 25 kHz frequencies, but again these calls are too plastic to serve for species identification.

Proposed vernacular names: Korsican Mausohr (German), Corsican myotis (English) , murin de Corse (French), murin nustrale (Corsican) , murciélago ratonero de Córcega (Spanish).

Natural history: Several females equipped with transmitters were radio tracked in spring and summer in two mountainous areas of central Corsica: Ghisoni and Bavella ( Groupe Chiroptères Corse, 2019). Most records were gathered from forested areas above 500 m a.s.l., although a few observations have been recorded near sea level ( Fig. 1 ). These animals were hunting in various habitats located within 8 km of their day roosts. Hunting territories were used regularly by single individuals and were either located in dense maquis populated with evergreen oak ( Quercus ilex ), ash ( Fraxinus spp. ) and abundant undergrowth, or in more open forests with Corsican pines ( Pinus nigra ) surrounded by ferns. The bats were hunting both high in the canopy and closer to the ground. All known day roosts ( Fig. 1 ) were in cliffs, rocky outcrops, stone bridges or in an artificial tunnel (where the only recorded nursery colony of ca. 60 individuals was established), denoting a strong rupicolous roosting behaviour for this Corsican myotis. This clear affinity for rocky habitats is similar to the roosting behaviour of M. escalerai , but is distinct from the typical treeroosting behaviour of M. nattereri or M. crypticus ( Agirre-Mendi & Ibáñez, 2012) .

Other bat species recorded in the same hunting habitats as those frequented by the Corsican myotis included Eptesicus serotinus , Hypsugo savii , Nyctalus leisleri , Pipistrellus pipistrellus, Rhinolophus ferrumequinum and Plecotus austriacus , but not other Myotis species ( Groupe Chiroptères Corse, 2019).

Conservation: This endemic species is apparently very rare ( Courtois et al., 2011) and owing to its limited distribution range in the mountains of Corsica ( Fig. 1 ), should be considered as globally endangered. Based on our current knowledge, the species has an area of occupancy of 1,300 km 2 and an extent of occurrence of 2,400 km 2. For the present and given its broad tolerance for diverse forested habitats as hunting grounds, humaninduced habitat change is not foreseen as a threat for the species. Forest fires might, however, temporarily limit hunting habitats. Rocky outcrops used as day roosts do not appear to be limiting factors in Corsica, but they could be subject to disturbance from rock climbing or abseiling and associated activities.

Figures

Fig. 4. Lateral and occlusal views of the skull and mandible of the holotype female Myotis nustrale sp. nov. (MNHN-ZM-2023-12). The scale is 5 mm.

Fig. 5. External characters of Myotis nustrale sp. nov. Panels are close-ups of the female holotype (MNHN-ZM-2023-12), except the lower right one which is a picture from a released adult individual (Photo © Yann Le Bris). The upper left panel illustrates the stiff hairs running along the uropatagium, viewed from below. The upper right panel is the right foot with wing insertion to the base of the outer toe, in ventral view. The lower left panel illustrates the long and straight tragus and unnotched ear of the female holotype. On the portrait of the live individual, notice the black chin spot on the lower lip.

Fig. 6. Portraits and hind feet (dorsal view) of an adult female M. nustrale sp. nov. caught near Bavella, in southern Corsica (left) and an adult female M. crypticus from the Jura mountains in Switzerland (right). Notice that the latter individual has a faint line bordering the lower lip, while the former has a much more conspicuous chin spot. Wing insertion to the outer toe is, however, identical in both species. For the left individual, the wing was not stretched while it was stretched for the right individual.

Fig. 1. Topographic map of Corsica (France) showing the current records of M. nustrale sp. nov. on this Mediterranean island (Courtois et al., 2011; Groupe Chiroptères Corse, 2019). The black dots represent capture sites, while the red stars indicate the presence of lactating females, including those living in the only known nursery roost of Ghisoni. A double circle indicates the location where the holotype of M.nustrale sp. nov. was found. Shades of grey represent areas above 100 m a.s.l.

Fig. 2. Bayesian topology based on five partitioned nuclear introns (SLC38A7, ABHD11, ACOX2, COPS7A and ROGDI). The outgroup (Pipistrellus pipistrellus) is not shown. Bayesian posterior probabilities (BPP) <60 are not shown, neither are within species BPP values. The holotype of Myotis nustrale sp. nov. (sample number MNA008_CO_ALB) is indicated by a white arrow.

Fig. 3. PCA showing (A) the clear separation between M. crypticus (Mcry; green circles) and M. nustrale sp. nov. individuals (Mnus; blue squares), and (B), the differentiation between populations within M. nustrale sp. nov. Horizontal and vertical axis explain 23.9 and 8.5% of the variance, respectively, in (A) and 17.1 and 13.9% of the variance in (B).