Tetrapod Zoology

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ResearchBlogging.org

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].

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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.

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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].

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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.

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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 (Wołoszyn 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.

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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…

And for previous Tet Zoo articles on bats, see…

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

- ., Tunç, Ö., 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.

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

Comments

  1. #1 Anonymous
    March 19, 2011

    “house mouse, wolf, brown bear, human”

    I wonder how well these taxa qualify for having really big ranges, seeing as the house mouse mostly spread worldwide as a result of humans, and it has been suggested that the gray wolf and brown bear previously had a Eurasian-Beringian distribution before the Late Pleistocene extinctions. Although if bent-winged bats only expanded their range in the last 15,000 years, one could make an argument that their range expansion is the result of human expansion as well. Though if we include Pleistocene taxa in the running, I suppose one would have to include the lion on that list.

  2. #2 Tim Morris
    March 20, 2011

    http://browse.deviantart.com/?qh=&section=&q=albino+bat#/d37qxi2

    Found this and thought of you, certainly rare.

  3. #3 Dartian
    March 20, 2011

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

    Interesting; I didn’t know that. Can you give a reference?

  4. #5 David Marjanović
    March 20, 2011

    A peculiar, unique feature is the presence of a small additional tooth located between the upper canine and first premolar.

    How many upper premolars have other bats got?

  5. #6 Darren Naish
    March 20, 2011

    On genome size in bent-winged bats, Miller-Butterworth et al. (2007, p. 1554) wrote…

    Furthermore, Miniopterus schreibersii has the smallest genome reported for any mammal. Mammalian C values average 3.5 pg or 3423 Mb (Gregory et al. 2007), whereas the M. schreibersii genome (C-value 5 1.73 pg or 1692 Mb) is approximately half that size (Capanna and Manfredi Romanini 1971; Gregory 2006; Gregory et al. 2007).

    The references cited there are:-

    Capanna, E. & Manfredi Romanini, M. G. 1971. Nuclear DNA content and morphology of the karyotype in certain palearctic Microchiroptera. Caryologia 24, 471-482.

    Gregory, T. R. 2006. Animal genome size database [Internet]. Available from: http://www.genomesize.com. Accessed 2007 June 1.

    - ., Nicol, J. A., Tamm, H., Kullman, B., Kullman, K., Leitch, I. J., Murray, B. G., Kapraun, D. F., Greilhuber, J. & Bennett, M. D. 2007. Eukaryotic genome size databases. Nucleic Acids Research 35, D332–D338.

    On the dentition, I made a mistake and will now go correct. It isn’t that bent-winged bats have unique supernumery teeth: rather, it’s that a variable mumber of inconspicuous, vestigial post-canines seems to be P1 and/or P2, making the ‘normal sized’ upper premolar P3 or P4. Upper premolar count in bats varies between 1 and 4: a quick check indicates that the possession of three upper premolars is most widespread (with P2 being most frequently absent).

  6. #7 David Marjanović
    March 21, 2011

    with P2 being most frequently absent

    Not P1? That’s interesting, because — by showing losses don’t have to start from an end of the series — it supports the idea that, of the five premolars that are plesiomorphic for therians, the one missing in most placentals and a few other eutherians is the third.

  7. #8 Darren Naish
    March 21, 2011

    Well, premolar identification in bats has been notoriously controversial: for a discussion see Giannini & Simmons (2007) (this was on fruit bats, but includes a discussion relevant to the crown as a whole). The missing upper premolar is most likely P2, but the way in which this has been established is rather complex. So, there are typically two big, posterior premolars – they are surrounded in the sequence by teeth that don’t have deciduous predecessors. The premolar anterior to the two big premolars is thus presumably P1 (in general, a deciduous P1 is absent*), and the molar posterior to the two big premolars is thus presumably M1. Not only does this suggest identification of the ‘two big premolars’ as P3 and P4, it indicates that P2 is missing. There’s a large literature on this subject, however, and other possibilities have been published.

    * Whales are one exception.

    Ref – -

    Giannini, N. P. & Simmons, N. B. 2007. Element homology and the evolution of dental formulae in megachiropteran bats (Mammalia: Chiroptera: Pteropodidae). American Museum Novitates 3559, 1-27.

  8. #9 David Marjanović
    March 21, 2011

    I see, thanks!

  9. #10 metridia
    March 22, 2011

    Interesting discussions on a group that is perhaps the most morphologically diverse & interesting groups of mammals..
    What is the deal with the Bent-winged bat cranium? Is that just like a cetacean melon analogue, or is that the braincase?

  10. #11 Allen Hazen
    March 22, 2011

    Re the small genome (#4, ref given in #6):
    Am I right in thinking I remember that smaller genomes correlate with smaller cell size? In which case… a small genome might allow more cells to be packed into a given volume. Bats are tiny, but lead complicated lives: flying, using sonar… So could this be an adaptation to allow a larger number of neurons in a small braincase?

  11. #12 Darren Naish
    March 22, 2011

    metridia: bent-winged bats are similar to quite a few other vesper bat lineages in having a particularly bulbous cranium. This explains the prominent convexity you’re seeing. I’m not sure why their skulls are shaped like this: maybe a consequence of enlarging the brain and reducing the olfactory apparatus?

    Allen: it’s been suggested that small genome size in birds is related to weight reduction (though, can someone demonstrate that the weight loss is really that significant? No bird is such a finely honed flying machine that it can’t deal with an additional 5, or 10, or 20% or more of its normal weight and still fly just fine. And this proposal is negated by work indicating that small genomes evolved in Saurischia long prior to the origin of birds). In view of this, weight reduction is another interesting proposal… but why, then, is it limited to bent-winged bats alone? The same point applies to any other proposal, like denser packing-in of neurons.

    PS – has anyone noticed that Tet Zoo is being PANNED with spam at the moment. I remove it as soon as I see it, but can hardly keep up. It’s, like, 15 messages a day or something.

  12. #13 Allen Hazen
    March 22, 2011

    Re: genome sizes.
    http://www.genomesize.com (link provided by Darren in #6) has links to abstracts of some papers. One (by Smith and Gregory) has the intriguing line
    “It has long been recognized that bats and birds contain less DNA in their genomes than their non-flying relatives. It has been suggested that this relates to the high metabolic demands of powered flight, a notion that is supported by the fact that pterosaurs also appear to have exhibited small genomes.”

    So, maybe the bent-wing bats are the most extreme, but small genomes are widespread in bats?

  13. #14 David Marjanović
    March 23, 2011

    Smaller cells have a higher ratio of surface to volume and thus a higher maximum metabolism. This must be why cell size decreased in dinosaurs long before the origin of birds.

  14. #15 Allen Hazen
    March 23, 2011

    David Marjanovic (#14)– In all the posts of yours I have read, on this site and at DML, I think this is the first time I have seen you use the word “must” (at least in this sense, as an evidential marker for inferentiality)!
    But thanks– I hadn’t thought of why cell size might be relevant to metabolic rate.

  15. #16 David Marjanović
    March 24, 2011

    I think this is the first time I have seen you use the word “must” (at least in this sense, as an evidential marker for inferentiality)!

    *blink*

    Interesting.

  16. #17 David Houston
    March 24, 2011

    “a notion that is supported by the fact that pterosaurs also appear to have exhibited small genomes”
    ??? we have even the remotest idea what pterosaur genomes were like!?!?

  17. #18 Owlmirror
    March 25, 2011

    ??? we have even the remotest idea what pterosaur genomes were like!?!?

    Huh. The paper from the abstract being cited is available for free,
    (Smith, J.D.L. and T.R. Gregory (2009). The genome sizes of megabats (Chiroptera: Pteropodidae) are remarkably constrained. Biology Letters, 23 June 2009 vol. 5 no. 3 347-351. )
    as is the paper that that paper is citing
    (Organ C.L. Shedlock A.M. 2008 Palaeogenomics of pterosaurs and the evolution of small genome size in flying vertebrates. Biol. Lett. 5, 47–50. )

    But nothing is known about the genomic characteristics of pterosaurs, which took to the air over 70 Myr before birds and were the first group of vertebrates to evolve powered flight. Here, we estimate genome size for four species of pterosaurs and seven species of basal archosauromorphs using a Bayesian comparative approach. Our results suggest that small genomes commonly associated with flight in bats and birds also evolved in pterosaurs, and that the rate of genome-size evolution is proportional to genome size within amniotes, with the fastest rates occurring in lineages with the largest genomes.

    “Estimate”. Bah.

    Oh, for a time-machine and a gene-sequencer.

  18. #19 David Marjanović
    March 25, 2011

    ??? we have even the remotest idea what pterosaur genomes were like!?!?

    Yes. Genome size is strongly correlated to cell size, bone cells leave holes in fossil bone, and the size of these holes can simply be measured.

  19. #20 metridia
    March 25, 2011

    maybe a consequence of enlarging the brain and reducing the olfactory apparatus

    (not sure if HTML markup correct)

    Not to turn this in to another discussion on encephalization quotient, but does this mean vesper bats are more intelligent? Or is it just that integrating sound signals to form a coherent mental image takes a lot of brain mass?

  20. #21 metridia
    April 3, 2011

    Anyone? Anyone? Bueller? Bueller?

  21. #22 David Marjanović
    April 3, 2011

    When nobody knows an answer, you won’t get one…

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