Bent-winged bats: wide ranges, very weird wings (vesper bats part III)

Welcome to part III of the vesper bat series though, as we'll see, the bats I'm covering here are not really vesper bat at all (anymore, and in the strictest sense of the term 'vesper bat'). They are the extremely strange, highly widespread long-winged bats, long-fingered bats or bent-winged bats (Miniopterus). Of these vernacular names, I prefer 'bent-winged bats'. As you can see from the simplified cladogram shown below, they're consistently found as the sister-group to virtually all other lineages conventionally included within Vespertilionidae [adjacent photo, from wikipedia, shows Common bent-winged bat M. schreibersii].

If you've been reading the previous episodes, you'll already be familiar with the basics of vesper bat diversity and phylogeny: if not, part I is here, and part II here.

So, on to bent-winged bats. These short-snouted, thick-furred bats occur from southern Europe, across Africa and Madagascar, throughout Asia, and to Australia, Vanuatu and New Caledonia. Or, as Miller-Butterworth et al. (2007) said "Their range extends through the majority of the Afrotropic (sub-Saharan Africa), Palearctic (north Africa and Eurasia), Indomalayan (southern and southeastern Asia) and Australasian (including Australia, New Guinea and neighboring islands) ecozones" (p. 1553) [old illustration below, of the Common bent-winged bat subspecies M. s. dasythrix; from wikipedia, but illustrated in Andrew Smith's 1838 Zoology of South Africa].

Bent-winged bats are typically small (total length c. 10 cm, wingspans 30-35 cm, mass less than 20 g); the muzzle is broad and short and the cranium is bulbous, being much taller than the shallow snout. A notably bulbous cranium that's much taller than the snout is present in bent-winged bats, woolly bats (kerivoulines) and mouse-eared bats (Myotis) and hence is likely to represent the ancestral or 'primitive' kind of skull shape for vesper bats. Bent-winged bats have short, rounded ears. A peculiar, unique feature is the presence of one or two tiny, relictual premolars located between the upper canine and first large premolar. They're also unusual in lacking the tendon-locking mechanisms present in the toes of other bats: quite what this means for how their toes work I'm not sure, as tendon-locking is typically said to be an essential energy-saving feature for animals that spend lots of time hanging from their claws.

The reason they have the common names that they do is because the super-elongated third finger (the second phalanx of which is about three times longer than the first) folds back on itself when the wing is folded [adjacent wing diagram from Parnaby (1992)]. In flight, this particularly long finger gives these bats extremely long, narrow wings. They're fast (though not particularly manoeuvrable) fliers in open spaces, and are also good long-distance colonisers: some species are long-distance seasonal migrants. In Australia, some populations travel about 300 km every spring to their traditional nursery caves, while there are African species suspected of covering distances of about 560 km to get to their wintering caves (Miller-Butterworth et al. 2003).

Some of their colonies are huge. Koegelbeen Cave in South Africa was estimated in 1985 (and again in 1997) to be home to as many as 60,000 individuals of a population identified at the time as M. natalensis (Herselman & Norton 1985). The cave was only home to about 2000 of the bats in a 2008 count, presumably due to seasonal migration (Monadjem et al. 2008). Mass die-offs of populations identified at the time as of the Common bent-winged bat (read on) have been recorded from across Europe and also Australia and possibly Iran. These were perhaps caused by bad weather, not by the fatal fungal infections now killing bats across North America. [A selection of bent-winged bats are shown in the montage below. Clockwise from top left: M. africanus, M. magnater, M. majori and M. gleni. These images are from the vesper bat page at Professor Paul's Guide to Mammals. I'm unsure about their origins and hope it's ok to use them. I originally wanted to use neat photos of bent-winged bat colonies, like this one on Wild Wonders of Europe].

Oh, another peculiarity of bent-winged bats is that they have the smallest reported genome of any mammal: it's about half average size.

More bent-winged bats... and more... and more...

Until about 2005, about 11 species were recognised in this group, one of which - the Schreiber's long-fingered bat or Common bent-winged bat M. schreibersii - was said to have colonised the entirety of this group's gigantic geographical range by itself. This was never as widely recognised as it should have been: whenever people talk about widespread mammal species, it's always house mouse, wolf, brown bear, human.

Anyway, the discovery of new species in the field (like M. gleni Peterson et al., 1995, M. sororculus Goodman et al., 2007, M. petersoni Goodman et al., 2008 [shown here], M. mahafaliensis Goodman et al. 2009 and M. aelleni Goodman et al. 2009, all from Madagascar) and the discovery that many traditional 'species' - and some of those recently discovered ones! (Goodman et al. 2010) - are in fact paraphyletic species complexes has increased the species count to the high twenties. Supposedly super-widespread M. schreibersii has proved to represent a species complex: the population that should be associated with this name is actually restricted to southern Europe, northern Africa and the coastal regions of Asia Minor while the 'M. schreibersii' populations of eastern Asia, Australasia and elsewhere warrant their own species names (M. fuliginosus, M. natalensis, M. majori and M. oceanensis among them) (e.g., Appleton et al. 2004, Tian et al. 2004, Furman et al. 2010a, b).

Across at least part of the Common bent-winged bat's range, colonisation has occurred rapidly - apparently within the last 15,000 years (Furman et al. 2010c). Fossils show that bent-winged bats once occurred across the whole of Europe: two Miocene species (M. fossilis and M. zapfei) are known from France (Mein & Ginsburg 2002) and another (M. rummeli) from Germany; a Pliocene species (M. approximatus) is known from Poland (WoÅoszyn 1987). By the Pleistocene, bent-winged bats were gone from northern Europe, but still present in Spain and south of the Carpathians. Pleistocene fossils of certain extant bent-winged bat species have been reported from China, Tanzania and elsewhere (you might be slightly sceptical of the conclusion that these fossils are definitely conspecific with the extant populations, though there's no reason why they shouldn't be), and there's also an extinct Pleistocene species (M. tao) from China.

Miniopterids, not miniopterines

Molecular phylogenetic studies have agreed that bent-winged bats are outside the clade that contains all other vesper bats, and that these two lineages diverged approximately 45 Ma ago, in the Eocene (Eick et al. 2005, Miller-Butterworth et al. 2007) [the cladogram below shows the position of bent-winged bats in the vesper bat tree: for discussion of the topology shown here, see The vesper bat family tree]. This ancient divergence, combined with the many unique features of bent-winged bats, has led to the suggested that they should be excluded from Vespertilionidae and given their own 'family-level' clade, Miniopteridae. This proposal has been fairly widely (though not universally) supported by bat workers (e.g., Van Den Bussche & Hoofer 2004, Eick et al. 2005, Miller-Butterworth et al. 2007), and note that Hoofer & Van Den Bussche (2003) even found bent-winged bats to be closer to molossids than to vesper bats sensu stricto.

The idea of a separate Miniopteridae has, however, been rejected by Gu et al. (2008) and some other authors, mostly because they didn't find the lineage to be 'distinct enough' from other vesper bats to warrant recognition as a 'family' (after all, it was already a 'subfamily').

Here we come back to the old and familiar problem of 'how distinct' a taxon needs to be before you give it its own 'family', or 'order', or whatever. Given that bent-winged bats seem to be about as old as various other bat clades conventionally regarded as 'families' (like Megadermatidae, Noctilionidae and Phyllostomidae), you could argue that raising the bent-winged bat lineage to 'family' level brings proper attention to its long independent history and respectable list of apomorphies. I don't have a problem with this suggestion and am more than happy to talk of 'miniopterids' rather than 'miniopterines'. But I don't really see the need for it, especially given that many other divergences within 'family-level' clades are as old or even older. Miniopterines or miniopterids, what's the difference?

For previous Tet Zoo articles in the vesper bats series, see...

• Introducing the second largest mammalian 'family': vesper bats, or vespertilionids
• The vesper bat family tree: of myotines, plecotins, antrozoins, and all those cryptic species (vesper bats part II)

And for previous Tet Zoo articles on bats, see...

• Desmodontines: the amazing vampire bats
• Giant extinct vampire bats: bane of the Pleistocene megafauna
• Camazotz and the age of vampires
• Dark origins: the mysterious evolution of blood-feeding in bats
• A new hypothesis on the evolution of blood-feeding: food source duality involving nectarivory. Catchy, no?
• Oh no, not another giant predatory flightless bat from the future
• The most terrestrial of bats
• I stroked a pipistrelle
• Red bats
• We flightless primates
• Big animalivorous microbats
• Hidden in plain sight: discovering cryptic vesper bats in the European biota
• PROTOBATS: visualising the earliest stages of bat evolution

Refs - -

Appleton, B., McKenzie, J., & Christidis, L. (2004). Molecular systematics and biogeography of the bent-wing bat complex Miniopterus schreibersii (Kuhl, 1817) (Chiroptera: Vespertilionidae) Molecular Phylogenetics and Evolution, 31 (2), 431-439 DOI: 10.1016/j.ympev.2003.08.017

Eick, G. N., Jacobs, D. S. & Matthee, C. A. 2005. A nuclear DNA phylogenetic perspective on the evolution of echolocation and historical biogeography of extant bats (Chiroptera). Molecular Biology and Evolution 22, 1869-1886.

Furman, A., Ãztunç, T. & Ãoraman, E. 2010b. On the phylogeny of Miniopterus schreibersii schreibersii and Miniopterus schreibersii pallidus from Asia Minor in reference to other Miniopterus taxa (Chiroptera: Vespertilionidae). Acta Chiropterologica 12, 61-72.

- ., Postawa, T., Ãztunç, T. & Ãoraman, E. 2010a. Cryptic diversity of the bent-winged bat, Miniopterus schreibersii (Chiroptera: Vespertilionidae), in Asia Minor. BMC Evolutionary Biology 2010, 10: 121

- ., Tunç, Ã., Tomasz, P. & Emrah, C. 2010c. Shallow genetic differentiation in Miniopterus schreibersii (Chiroptera: Vespertilionidae) indicates a relatively recent re-colonization of Europe from a single glacial refugium. Acta Chiropterologica 12, 51-59.

Goodman, S. M., Maminirina, C. P., Bradman, H. M., Christidis, L. & Appleton, B. R. 2010. Patterns of morphological and genetic variation in the endemic Malagasy bat Miniopterus gleni (Chiroptera: Miniopteridae), with the description of a new species, M. griffithsi. Journal of Zoological Systematics and Evolutionary Research 48, 75-86.

Gu, X.-M., He, S.-Y. & Ao, L. 2008. Molecular phylogenetics among three families of bats (Chiroptera: Rhinolophidae, Hipposideridae, and Vespertilionidae) based on partial sequences of the mitochondrial 12S and 16S rRNA genes. Zoological Studies 47, 368-378.

Herselman, J. C. & Norton, P. M. 1985. The distribution and status of bats (Mammalia: Chiroptera) in the Cape Province. Annals of the Cape Provincial Museums (Natural History) 16, 1-126.

Hoofer, S. R. & Van Den Bussche, R. A. 2003. Molecular phylogenetics of the chiropteran family Vespertilionidae. Acta Chiropterologica 5, 1-63.

Mein, P. & Ginsburg, L. 2002. Sur l'âge relatif des différents karstiques miocènes de La Grive-Saint-Alban (Isère). Cahiers scientifiques, Muséum d'Histoire naturelle, Lyon 2, 7-47.

Miller-Butterworth, C. M., Jacobs, D. S. & Harley, E.H. 2003. Strong population substructure is correlated with morphology and ecology in a migratory bat. Nature 424, 187-191.

- ., Murphy, W. J., O'Brien, S. J., Jacobs, D. S., Springer, M. S. & Teeling, E. C. 2007. A family matter: conclusive resolution of the taxonomic position of the long-fingered bats, Miniopterus. Molecular Biology and Evolution 24, 1553-1561.

Monadjem, A., Higgins, N., Smith, T. & Herrmann, E. 2008. Bats recorded from Koegelbeen Cave and selected other sites in the northern cape, South Africa. African Bat Conservation News 18, 2-4.

Parnaby, H., 1992. An interim guide to identification of insectivorous bats of south-eastern Australia. Technical Reports of the Australian Museum 8, 1-33

Tian, L., Laing, B., Maeda, K., Metzner, W. & Zhang, S. 2004. Molecular studies on the classification of Miniopterus schreibersii (Chiroptera: Vespertilionidae) inferred from mitochondrial cytochrome b sequences. Folia Zoologica 53, 303-311.

Van Den Bussche, R. & Hoofer, S. R. 2004. Phylogenetic relationships among recent chiropteran families and the importance of choosing appropriate out-group taxa. Journal of Mammalogy 85, 321-330.

WoÅoszyn, B. W. 1987. Pliocene and Pleistocene bats of Poland. Acta Palaeontologica Polonica 32, 207-325,