Birds of the Sun

Handsome sunbird Aethopyga bella, photographed by Tonee Despojo. This species was only recently separated at species level from the lovely sunbird Aethopyga shelleyi; one of the distinguishing features of the two is the purple ear-patch in A. bella.

The sunbirds are definitely forerunners in the tally of the world's most brilliantly coloured birds. This family of long-billed nectar-feeders, found in tropical regions of the Old World, is often compared to the New World hummingbirds. Like hummingbirds, the males of most sunbirds shimmer with brilliant iridescent colours (the exceptions are the spiderhunters of the genus Arachnothera); the females are much more restrained, generally shades of olive-green or brown. However, though hummingbirds are committed aerialists (as befits their relationship with the swifts and nightjars), sunbirds are, as Passeriformes, more likely to feed while perched on a stem alongside their chosen flower. Also, while sunbirds are primarily nectar feeders, they also feed to a fair extent on small insects (this is also true of hummingbirds).

Male (above) and female (below) of fork-tailed sunbird Aethopyga christinae. Male photographed by Frankie Chu, female by Neil Fifer.

Sunbirds are also a rather less diverse group than hummingbirds, both in number of species and in external appearance. Because of their structural similarity, authors have differed in the number of genera recognised in the family, but one group that has generally been differentiated is the Aethopyga sunbirds of southern Asia. Aethopyga species tend to be smaller than other sunbirds, with relatively short but strongly downcurved bills. The male has the central tail-feathers elongate (Ali & Ripley 1999). Aethopyga species are also distinguished from other sunbirds by the structure of the tongue. As with other sunbirds, the tongue is elongate, with the sides curved inwards to form a double tube. Differing from others, the end of the tongue is divided into two inwardly open tubes but with a basal bifurcated plate connecting the tubes:

Tongues of sunbirds of different genera showing differences in morphology, from Cheke & Mann (2001).

Cheke & Mann (2001) listed seventeen species of Aethopyga, with an eighteenth species being added by Mann (2002). Several of these species are also currently recognised as polytypic, with multiple subspecies. Though Mann's (2002) 'new' species was simply derived from the elevation of previously-recognised subspecies, one entirely new species of Aethopyga, A. linaraborae from Mindanao in the Phillippines, was only described as recently as 1997. No large scale analysis of the interrelationships between Aethopyga species appears to have been published as yet, but centres of diversity are the Philippines and the Himalayas.

Elegant sunbird Aethopyga duyvenbodei, photographed by Marc Thibault. Having been informed by their vernacular names that Aethopyga sunbirds are, in turn, handsome, lovely and elegant, it is all the sadder to say that this last species from Sangihe, near Sulawesi, is regarded as endangered.

REFERENCES

Ali, S., & S. D. Ripley. 1999. Handbook of the Birds of India and Pakistan, together with those of Bangladesh, Nepal, Sikkim, Bhutan and Sri Lanka, 2nd ed., vol. 10. Flowerpeckers to Buntings. Oxford University Press.

Cheke, R. A., & C. F. Mann. 2001. Sunbirds: A Guide to the Sunbirds, Flowerpeckers, Spiderhunters and Sugarbirds of the World. A & C Black Publishers.

Mann, C. F. 2002. Systematic notes on Asian birds. 28. Taxonomic comments on some south and south-east Asian members of the family Nectariniidae. Zool. Verh. Leiden 340: 179-189.

Linguipolygnathus Redux

Upper (left in each case) and lower (right, do.) views of representative Pa elements of polygnathids from Bardashev et al. (2000): (upper left) 'Linguipolygnathus' anastasiae; (upper right) 'Eolinguipolygnathus' nothoperbonus; (lower) 'Costapolygnathus' inversus. Bardashev et al. (2002) classify L. anastasiae closer to C. inversus despite regarding it as phylogenetically closer to E. nothoperbonus.

There are some things that you find yourself returning to like an itching scab. Yes, it's time for me to once again wade into the unsettling world of polygnathid conodont taxonomy.

Previous comments on the subject can be found here and here. To briefly recap: Bardashev et al. (2002) divided the Devonian conodonts of the Polygnathidae, most of them previously assigned to a single genus Polygnathus, between a number of families and genera. However, they explicitly represented a number of both families and genera as extensively polyphyletic. Later, Weddige (2005) responded to criticisms of the divided taxonomy by claiming that it represented a form taxonomy only. In my first post on the subject, I expressed confusion at what exactly Weddige meant by that claim.

On closer examination, I'm somewhat more inclined to take Weddige's claim at face value. Despite proposing detailed phylogenetic relationships between the species studied, Bardashev et al.'s (2002) taxonomy is supposed to prioritise identification above all. The primary division, Polygnathidae vs 'Eopolygnathidae', is based on a single character: the development of the basal cavity on the underside of the Pa element of the polygnathid apparatus. Presence of a basal cavity is the ancestral condition; within the 'eopolygnathids', the margins of the basal cavity become progressively closed in a number of lineages until, in the 'polygnathids', there is only a small basal pit remaining. So, for instance, the genera Eolinguipolygnathus and Linguipolygnathus are placed in separate families, despite the facts that (a) they differ in no other characters (the diagnoses provided for the two genera by Bardashev et al. are effectively identical), (b) 'Linguipolygnathus' is proposed to have arisen no less than five separate times from 'Eolinguipolygnathus' ancestors (and is not directly connected phylogenetically to other genera in its own family), and (c) relative to the other polygnathids examined, the two 'genera' supposedly share a clear and (more significantly) phylogenetically coherent character in the formation of the posterior part of the Pa element into a transversely ridged tongue.

Bardashev et al. argued that this division was necessary because the restricted basal cavity was the original character used to establish the Polygnathidae, so the inclusion of taxa with an open basal cavity violated the original diagnosis of the family. The possibility of revising the family diagnosis is not raised, despite their own research apparently showing that it does not diagnose a coherent group. The underlying motivation for this prioritisation of diagnostic characters over phylogeny seems to be the use of conodonts as markers in biostratigraphy. For instance, the type of Eolinguipolygnathus, Polygnathus dehiscens, has been proposed as the marker for the beginning of the section of the Devonian known as the Emsian. But does this emphasis on diagnostic features truly serve even biostratigraphy? Carls et al. (2008), for instance, claim that emphasis on characters of the ventral side of the conodont Pa element has lead to a number of distinct taxa being confused under the name 'Polygnathus dehiscens', leading to misdiagnosis of the Emsian boundary.

Just as I have stated before that a key should not be a taxonomy, a taxonomy should not be a key. Both are important, but both have their own roles to play.

REFERENCES

Bardashev, I. A., K. Weddige & W. Ziegler. 2002. The phylomorphogenesis of some Early Devonian platform conodonts. Senckenbergiana Lethaea 82 (2): 375-451.

Carls, P., L. Slavík & J. I. Valenzuela-Ríos. 2008. Comments on the GSSP for the basal Emsian stage boundary: the need for its redefinition. Bulletin of Geosciences 83 (4): 383–390.

Weddige, K. 2005. Contra Ruth Mawson’s critizising Bardashev, Weddige & Ziegler 2002, e.g. in SDS Newsletters 20 (2004). Subcommission on Devonian Stratigraphy Newsletter 21: 51-52.

The Coral-lovers

The free-living (but, from the look of it, not particularly mobile) coralliophiline Latiaxis mawae, photographed by Merlin Charon.

While the subjects of today's posts, the gastropods of the Coralliophilinae, might have a name that translates as 'lovers of coral', it seems likely that the corals do not love them. Members of the Coralliophilinae are a group of about 250 species of specialised predators/parasites of corals and other cnidarians. They vary in habits from free-living grazers to species that live embedded within their coral host, and as a result they vary in external appearance. However, their internal anatomy is fairly consistent, with all species lacking a radula and having a similar gut anatomy. As far as is known, they are all protandrous hermaphrodites, maturing from males to females as they grow larger. The females brood their eggs within the mantle cavity. Phylogenetic analysis has indicated a relationship with the subfamilies Rapaninae (the oyster drills) and Ergalataxinae in the Muricidae, and the recent tendency has been to treat the coralliophilines as a subfamily of the latter (Barco et al. 2010).

The endobiotic Magilus striatus, with a close-up of the coiled juvenile shell, photographed by Femorale.

Like other muricids, many of the free-living coralliophilines (such as species in the genera Latiaxis and Babelomurex) are strikingly ornamented with spiny shells. Those that live in closer association with their coral hosts, however, show a corresponding reduction in ornamentation. Members of the genus Rapa, feeding on soft corals, have inflated, relatively flat-spired shells. Most derived of all, perhaps, is the boring genus Magilus, in which the shell, after an initial coiled section, becomes uncoiled and tubular to form a channel to the outer wall of the host coral. The simplified shell morphology of the endoparasitic forms means that species can be exceedingly difficult to distinguish. A study of the genus Leptoconchus, internal parasites of mushroom corals, by Gittenberger & Gittenberger (2011) identified fourteen molecularly distinct species, each associated with a different species of coral. However, morphological variation between specimens did not reliably correlate with molecular and host-association data and could not be used to distinguish species. In comparison, a study of the host-nonspecific free-living species Coralliophila meyendorffii found that, despite the clear distinction of a larger form feeding on sea anemones vs a smaller form feeding on corals, the two forms were not resolved as molecularly distinct and there was inadequate support for the recognition of the forms as separate species (Oliverio & Mariottini 2001).

The bubble turnip Rapa rapa, photographed by Eddie Hardy.

REFERENCES

Barco, A., M. Claremont, D. G. Reid, R. Houart, P. Bouchet, S. T. Williams, C. Cruaud, A. Couloux & M. Oliverio. 2010. A molecular phylogenetic framework for the Muricidae, a diverse family of carnivorous gastropods. Molecular Phylogenetics and Evolution 56: 1025-1039.

Gittenberger, A., & E. Gittenberger. 2011. Cryptic, adaptive radiation of endoparasitic snails: sibling species of Leptoconchus (Gastropoda: Coralliophilidae) in corals. Organisms Diversity & Evolution 11: 21-41.

Oliverio, M., & P. Mariottini. 2001. Contrasting morphological and molecular variation in Coralliophila meyendorffii (Muricidae, Coralliophilinae). Journal of Molluscan Studies 67: 243-246.

Brachymeria perflavipes and Beyond

Male of a Brachymeria species, possibly B. hammari, photographed by John Hallmén.

For the subject of today's post, the wheel-spin brought up the parasitic wasp Brachymeria perflavipes. This is a species of the family Chalcididae described by our old friend Alexander Arsene Girault in 1913 from a female specimen collected in the Dandenong Mountains in Victoria, Australia. He described it under the name of Tumidicoxa flavipes; when that genus was later synonymised by Girault in 1915, the species name was replaced by perflavipes as there was already a Brachymeria flavipes. Girault's description of this species was, thankfully, more detailed than some of his later productions, though the species was not illustrated (not an uncommon state of affairs at the time) and, to the best of my knowledge, never has been. Girault (1915) later also recorded a male from Brisbane in Queensland, collected from a lepidopteran host. And that, except for an extra host record by Bouček (1988), is pretty much the sum total of our knowledge of this species.

Brachymeria calliphorae, a parasitoid of blow fly larvae, photographed by C. Bento.

Brachymeria is a large genus of Chalcididae, with over a hundred species worldwide. The Chalcididae are, in my opinion, one of the more instantly recognisable families of Chalcidoidea, with hind femora distinctly larger than those on other legs and with a ventral row of teeth. These large hind femora enable the wasp to jump, and I can confirm from personal observation that they are adept pingers. Most Chalcididae are black with coarse punctation over most of the body, though an interesting find on one of our recent field trips was a bright electric blue chalcidid. However, despite their recognisability, a recent major molecular phylogenetic analysis of Chalcidoidea failed to recover the Chalcididae as monophyletic. Brachymeria is distinguished from other chalcidid genera by features such as a short petiole, short postmarginal vein (but even shorter stigmal vein), distinct malar suture, and hind tibia with a distinct apical spine (Bouček 1988). Attempts have been made to subdivide Brachymeria into subgenera but, as we saw with Ormyrus, proposed subgeneric divisions have been based on species found within a restricted biogeographic area (e.g. Burks 1960; Bouček 1988) and a broad worldwide survey of Brachymeria still hasn't been conducted.

Brachymeria ovata on pupa of crow butterfly Euploea core, from Brisbane Insects.

Most Brachymeria species (including B. perflavipes) are parasitoids of lepidopteran pupae, but some attack dipteran larvae or pupae (more on that in a moment). Though more than one egg may be laid within a single pupa, Dowden (1935) found that in the case of B. intermedia, a parasitoid of the gypsy moth Lymantria dispar, only one wasp would develop to maturity in a single host. Indications are that the wasp larvae themselves kill any would-be competitors within the host: the mandibles of the larva are strongly sclerotised even in the first instar, and Dowden found that dead larvae dissected out from a host invariably bore signs of injury from the mandibles. Larvae dissected out from a host and placed together would quickly attack each other.

Diagram of distinguishing characters of Brachymeria intermedia vs B. compsilurae, from Dowden (1935).

Brachymeria species also include a good example of the potential importance of reliable taxonomic identifications. The aforementioned B. intermedia has been the subject of deliberate introductions outside its native range in attempts to control its host, the gypsy moth (or, more accurately, one of its wide range of hosts). Another Brachymeria species, B. compsilurae, closely resembles B. intermedia and also appears to lay its eggs in gypsy moths. However, the target of B. compsilurae is not the gypsy moth itself, but the larvae of tachinid flies that are parasitising the moth and are themselves used in its control. Programs to introduce B. intermedia to New England had to be careful to eliminate B. compsilurae (Burks 1960), whose release would have the opposite effect of that intended.

REFERENCES

Bouček, Z. 1988. Australasian Chalcidoidea (Hymenoptera): A biosystematic revision of genera of fourteen families, with a reclassification of species. CAB International: Wallingford (UK).

Burks, B. D. 1960. A Revision of the genus Brachymeria Westwood in America north of Mexico (Hymenoptera: Chalcididae). Transactions of the American Entomological Society 86 (3): 225-273.

Dowden, P. B. 1935. Brachymeria intermedia (Nees), a primary parasite, and B. compsilurae (Cwfd.), a secondary parasite, of the gypsy moth. Journal of Agricultural Research 50 (6): 495-523.

Girault, A. A. 1913. On several new genera and species of Australian Hymenoptera Chalcidoidea. Canadian Entomologist 45: 101-106.

Girault, A. A. 1915. Australian Hymenoptera Chalcidoidea—XIV. The family Chalcididae with descriptions of new genera and species. Memoirs of the Queensland Museum 4: 314-365.

Munro, J. B., J. M. Heraty, R. A. Burks, D. Hawks, J. Mottern, A. Cruaud, J.-Y. Rasplus & P. Jansta. 2011. A molecular phylogeny of the Chalcidoidea (Hymenoptera). PLoS One 6 (11): e27023. doi:10.1371/journal.pone.0027023.