Myotis nustrale: A new species of Mouse-eared Bat from Corsica.

During the past three decades, the application of genetic methodologies to taxonomy has revolutionised our understanding of the world's biodiversity, with many widespread 'species' now recognised as groups of closely related, but nevertheless distinct, cryptic species, with much more restricted distributions. This in turn has implications for the ecology and conservation of these species, with species thought to be widespread and environmentally tolerant turning out to be groups of species, each of which has a limited distribution and a narrow ecological range.

One group for which this has been found to be true are Mouse-eared Bats, Myotis spp., which were once thought to be a single species, ranging from Western Europe and North Africa through the Middle East and Central Asia as far east as Korea and Japan, but which have now been shown to be a series of morphologically similar species with more limited populations.

In a paper published in the journal Revue suisse de Zoologie on 18 October 2023, Sébastien Puechmaille of the University of Montpellier, the Institut Universitaire de France, the Groupe Chiroptères de Midi-Pyrénées, and the Zoological Institute and Museum at the University of Greifswald, Serena Dool, also of the Groupe Chiroptères de Midi-Pyrénées, and the Zoological Institute and Museum at the University of Greifswald, Gregory Beuneux of the Groupe Chiroptères Corse, and Manuel Ruedi of the Muséum d’histoire naturelle de Genève, describe a new species of Mouse-eared Bat from Corsica.

The new species is named Myotis nustrale, where 'nustrale' means 'ours' in the Corsican language. It is described largely on the basis of inspection of living specimens, and comparison of genetic material taken from tissue samples to that of Mouse-eared Bats from other populations. The designated holotype is a female specimen found dead by Julien Barataud in July 2006 and preserved in alcohol, although this is noted to be in a poor state. Physically, all examined specimens of Myotis nustrale were identical to examined specimens of Myotis nattereri and Myotis crypticus in that a small black spot on the lower lip was retained into adulthood, while it was present only in juvenile members of the other species.

External characters of Myotis nustrale. 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. 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. Puechmaille et al. (2023).

Despite its morphological similarity to other species, Myotis nustrale is clearly genetically distinct, forming a sister taxon to a clade which includes Myotis escalerai, Myotis zenatius, Myotis schaubi, Myotis tchulliensis, Myotis nattereri, Myotis hoveli, and Myotis crypticus. Myotis nustralei shows signs of long genetic isolation from other species, which at first sight might be connected to its island endemic status, although this is actually difficult to relate to our current understanding of the behaviour of Bats of the genus Myotis. Corsica, with its own species of Myotis is 50 km from the island of Elba, which in turn is 10 km from the Italian mainland. Ireland is 78 km from the island of Great Britain, which is in turn 33 km from the European mainland, but specimens of Myotis nattereri from Ireland, Great Britain, and Europe show little genetic differentiation. Similarly, Myotis hoveli is found on the Anatolian Peninsula and the island of Cyprus, separated by 69 km, and Myotis escalerai is found on the Iberian Peninsula, and the islands of Ibiza, 86 km from the mainland, Mallorca, 81 km from Ibiza, and Menorca, 36 km from Mallorca.

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) lower than 60 are not shown, neither are within species BPP values. The holotype of Myotis nustrale (sample number MNA008_CO_ALB) is indicated by a white arrow. Puechmaille et al. (2023).

Several female Myotis nustrale were equipped with radio transmitters, and tracked during spring and summer. They spent most of their time in mountainous regions more than 500 m above sealevel, although they did occasionally come close to sea level. Hunting was carried out within 8 km of the Bat's roosts, in dense maquis scrubland with stands of Evergreen Oak, Quercus ilex, and Ash, Fraxinus spp., or open forests with Corsican Pines, Pinus nigra, surrounded by Ferns.

Portraits and hind feet (dorsal view) of an adult female Myotis nustrale caught near Bavella, in southern Corsica (left) and an adult female Myotis 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. Puechmaille et al. (2023).

Myotis nustrale is restricted to the island of Corsica, and apparently to a small region within the Parc Naturel Régional de Corse, largely at altitudes of between 500 m and 2000 m above sealevel. The limited distribution and small population of the species would seem to make it particularly vulnerable to climate change, as the only response the Bats would have to a warming climate, would be to move upwards, leading to increased population fragmentation. 

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