Field of Science

South American Mites

Diagnostic views of Charassobates cavernosus (clockwise from left: dorsum; prodorsum with covering lamellae removed; venter) from Schuster (1969).

For this week's random taxon, I drew the oribatid mite family Charassobatidae. This has proved to be something of a challenge: info on the charassobatids seems a little hard to come by. It doesn't help that the 'Charassobatidae' has haemorrhaged taxa somewhat. Balogh & Balogh (1992), in their invaluable (if not entirely unproblematic) identification guide to oribatids, listed three genera in the Charassobatidae: Charassobates, Topalia and Ametroproctus. The main reason for associating these genera appears to have been the presence of massively expanded lamellae on the prodorsum (the 'head' part of the mite). However, Behan-Pelletier (1988), in transferring Ametroproctus to the family Cymbaeremaeidae, argued that this feature had probably arisen convergently as similar large lamellae are known from other oribatid families. Topalia has also since been removed from Charassobatidae, which is now redundant with Charassobates. Norton & Behan-Pelletier (2009) placed Charassobates in the superfamily Licneremaeoidea, but the monophyly of that group has been questioned (Schäffer et al. 2010).

Charassobates is a strictly South American group of mites (with an outlying species in the Galapagos). They have pelopsiform (very long and slender) chelicerae, possibly indicating a liquid diet, that are also somewhat unusual among oribatids in lacking an articulation between the chelicerae and the underside of the 'head'. Some species, such as the type Charassobates cavernosus, also possess deep fossae on the dorsal surface of the main body. The nymphs are wrinkly (unlike humans, some oribatids become less wrinkly as they get older) and apheredermous (i.e. they do not carry the shed skins of former instars as protective scalps) according to Norton & Behan-Pelletier (2009) and Behan-Pelletier & Walter (2007), indicating that their description as eupheredermous (carrying scalps) by Behan-Pelletier (1988) was probably an error.


Balogh, J., & P. Balogh. 1992. The Oribatid Mites Genera of the World. 2 vols. Hungarian Natural History Museum.

Behan-Pelletier, V. M. 1988. Systematic relationships of Ametroproctus, with modified definition of Cymbaeremaeidae (Acari: Oribatida). In: Channabasavanna, G. P., & C. A. Viraktamath (eds) Progress in Acarology vol. 1 pp. 301-308. E. J. Brill: Leiden.

Behan-Pelletier, V. M., & D. E. Walter. 2007. Phylleremus n. gen., from leaves of deciduous trees in eastern Australia (Oribatida: Licneremaeoidea). Zootaxa 1386: 1-17.

Norton, R. A., & V. M. Behan-Pelletier. 2009. Suborder Oribatida. In: Krantz, G. W., & D. E. Walter (eds) A Manual of Acarology pp. 430-564. Texas Tech University Press.

Schäffer, S., S. Koblmüller, T. Pfingstl, C. Sturmbauer & G. Krisper. 2010. Ancestral state reconstruction reveals multiple independent evolution of diagnostic morphological characters in the “Higher Oribatida” (Acari), conflicting with current classification schemes. BMC Evolutionary Biology 10: 246.

Schuster, R. 1969. Die terrestrische Milbenfauna Südamerikas in zoogeographischer Sicht. In: Fittkau, E. J. (ed.) Biogeography and Ecology in South America vol. 2 pp. 741-763. Dr W. Junk N. V.: The Hague.


So what was the bird in Wednesday's photo? It didn't take long for it to be recognised for what it was, a coscoroba.

The coscoroba Coscoroba coscoroba, photographed by Christopher Valentine at the Jardin des Plantes, Paris. Photographing this animal was not entirely easy: it was in the process of preening, and every time that we tried to get a photo, its head would dive back into its feathers and we'd have yet another photo of a headless coscoroba.

The coscoroba (its name refers to the sound of its call) is a waterbird of coastward parts of southern South America, with its range having extended over the past century as far north as Uruguay (Kear 2005). In general appearance, it resembles a small swan (and is often called the 'coscoroba swan'). The most obvious difference between a swan and a coscoroba is that the latter lacks a bare patch of skin between its eyes and its beak. Coscorobas also have a flatter, more 'duck-like' beak than swans. Another significant difference can be seen in their behaviour: swans and geese are characterised by what is called a 'triumph ceremony', where a male approaches his partner (swans form life-long pair bonds), raising and lowering his head while calling, and is answered by her in kind. This behaviour is particularly common after the male has seen off a potential rival (hence the name), and probably serves to maintain the pair bond. Coscorobas, it seems, are far too refined for such brazen posturing, and limit themselves to a little quiet murmuring of their eponymous call (Johnsgard 1965).

Because of its 'not-quite-swannish' nature, the coscoroba has often been seen as a link between swans and some other group of waterfowl, such as geese or whistling ducks. Molecular studies (e.g. Donne-Goussé et al. 2002) have placed it as sister to the Cape Barren goose Cereopsis novaehollandiae of Australia, with the two together sister to the swans. This does seem a little counter-intuitive, as superficially Cereopsis does not appear very coscoroba-like, but it is relatively well-supported. The purported similarities between the coscoroba and whistling ducks, on the other hand, are quite possibly plesiomorphies retained from the ancestral waterfowl.

The Cape Barren goose Cereopsis novaehollandiae, potential sister to the coscoroba. Photographed by Norm Hanson.


Donne-Goussé, C., V. Laudet & C. Hänni. 2002. A molecular phylogeny of Anseriformes based on mitochondrial DNA analysis. Molecular Phylogenetics and Evolution 23: 339-356.

Johnsgard, P. 1965. Handbook of Waterfowl Behavior. University of Nebraska: Lincoln.

Kear, J. 2005. Ducks, Geese and Swans. Oxford University Press.

Name the bug # 57

So the last round of Name the Bug ended in a tie (well, effectively it did, because I say it did) between Adam Yates and Neil. So how am I going to decide the winner?

This is a photo that Christopher took recently. Neil and Adam both have an opportunity to provide an identification. As usual, points will be given for pizzazz (or however you spell pizaz) and supporting arguments as much as a real ID. And because this is supposed to be a showdown, I expect claws, lads!

Update: Identity now available here.

From Tree Moss to Tree Ferns

Close-up of Davallia canariensis frond showing terminal sori. Photo from here.

Epiphytes seem to be the way to go here at CoO lately: after having covered a family of epiphytic mosses last week, I'm going to move on to a family of epiphytic ferns. The Davalliaceae are found in tropical and warm-temperate parts of the Old World. A few species are terrestrial but the majority are good old tree-huggers, either climbing up a suitable tree from roots attached to the ground or living entirely free of the tyranny of soil.

Habitus of Araiostegiella perdurans. Photo from here, where it is identified as 'Araiostegia' perdurans. Members of the previously recognised genus Araiostegia were redistributed by Kato & Tsutsumi (2008) between the genera Davallodes and Araiostegiella.

As a group, Davalliaceae are characterised by their elongate sori (spore-pouches) in marginal positions on the fronds at the junction of branching veins. The sori are covered by an indusium prior to maturity. Like other epiphytic ferns, the Davalliaceae also have creeping rhizomes covered by closely appressed scales. The most recent generic revision of the family recognises five genera (Kato & Tsutsumi 2008) but this aspect of Davalliaceae has always been unsettled. Phylogenetically, the Davalliaceae seem to belong in a clade that also includes the families Polypodiaceae and Grammitidaceae (Tsutsumi & Kato 2006). As these families are also primarily epiphytic, it seems likely that this lifestyle was ancestral for this clade. This would make the polypodioid-davallioid clade the largest assemblage of epiphytes among the ferns. It is also worth noting that these families probably diverged from each other some time in the early Tertiary (Schneider et al. 2004). Something that really does not get enough appreciation is that, despite the linear presentation of plant evolution that plagues most textbooks (bryophytes being replaced by ferns, which are shoved aside by conifers, that bow down before the all-conquering flowering plants), a significant percentage of the major fern lineages around today are actually much younger than the major flowering plant lineages.

Humata pectinata. Photo from here.

One final detail that's of patriotic interest to me: fossil Davalliaceae are known from the Miocene of New Zealand (Conran et al. 2010). These days Davalliaceae hang on in New Zealand by the skin of their rhizomes, with only a single species represented in the northernmost part of the country by asexually-reproducing individuals only (many fern species are able to survive by reproducing asexually in habitats where conditions do not permit sexual reproduction). This means that, along with coconuts, cone shells and crocodiles, Davalliaceae were part of a diverse biota that inhabited New Zealand during the balmy Miocene, only to decline and disappear as conditions became cooler.


Conran, J. G., U. Kaulfuss, J. M. Bannister, D. C. Mildenhall & D. E. Lee. 2010. Davallia (Polypodiales: Davalliaceae) macrofossils from Early Miocene Otago (New Zealand) with in situ spores. Review of Palaeobotany and Palynology 162 (1): 84-94.

Kato, M., & C. Tsutsumi. 2008. Generic classification of Davalliaceae. Acta Phytotaxonomica et Geobotanica 59 (1): 1-19.

Schneider, H., E. Schuettpelz, K. M. Pryer, R. Cranfill, S. Magallón & R. Lupia. 2004. Ferns diversified in the shadow of angiosperms. Nature 428: 553-557.

Tsutsumi, C., & M. Kato. 2006. Evolution of epiphytes in Davalliaceae and related ferns. Botanical Journal of the Linnean Society 151 (4): 495-510.

Name the Bug #56

Anyone recognise this one?

Attribution to follow.

Update: Identity available here. Photo from here.

The Trials and Tribulations of Tree Moss

Weymouthia cochlearifolia, photographed by Juan Larraín.

The Lembophyllaceae are a family of mosses found most abundantly in the Australasian region, though species are also found in other parts of the world such as Asia and South America. Most members of the family are epiphytic (growing on trees) or epilithic (growing on rocks). The composition of the family has varied significantly over the years, and as currently circumscribed the various Lembophyllaceae lack any reliable shared morphological characters and are united on the basis of molecular data (Olsson et al. 2009). Lembophyllaceae usually have concave leaves, loosely appressed to terete shoots, that lack a clearly differentiated leaf margin (Olsson et al. 2009).

Capsules of Isothecium alopecuroides, photographed by Hermann Schachner.

In the broader context, Lembophyllaceae are placed among the pleurocarpous mosses of the order Hypnales ('pleurocarpous' means that the reproductive structures are produced on small side branches rather than at the top of the main stalk), probably as the sister group to the bulk of the Neckeraceae (Olsson et al. 2009). Merget & Wolf (2010) reported finding Lembophyllaceae as polyphyletic but a closer look at the supplementary figures shows that only two of their four clades ('Lembophyllaceae III' and 'IV') actually correspond to the current concept of the family established by Quandt et al. (2009); the remainder represent genera removed to other families. More to the point, Merget & Wolf were using that most wretched of molecular methods, neighbour joining, and despite their use of a large number of source taxa it is difficult to accord their results much significance.

Spruce trees with a covering of Isothecium myosuroides in Olympic Natural Park, USA. Photo from here.

One genus of Lembophyllaceae, Weymouthia, contains two species found in Australia, New Zealand and South America. Such disjunct distributions have been the subject of much debate in moss biogeography. Some authors attribute them to a Gondwanan ancestry, indicating that the modern species must have arisen prior to the separation of these landmasses through continental drift. Others would see them as the result of post-separation dispersal. Supporters of the former explanation point to the supposed inability of moss spores to survive extended environmental exposure, and the correlation of numbers of shared species with age of geological separation rather than current distance (Blöcher & Frahm 2002; e.g. South America shares more species with New Zealand than southern Africa, despite being closer geographically to the former). Supporters of the latter point to the low levels of morphological and molecular differentiation between individuals from disjunct populations.


Blöcher, R., & J.-P. Frahm. 2002. A comparison of the moss floras of Chile and New Zealand. Tropical Bryology 21: 81-92.

Merget, B., & M. Wolf. 2010. A molecular phylogeny of Hypnales (Bryophyta) inferred from ITS2 sequence-structure data. BMC Research Notes 3: 320.

Olsson, S., V. Buchbender, J. Enroth, S. Huttunen, L. Hedenäs & D. Quandt. 2009. Evolution of the Neckeraceae (Bryophyta): resolving the backbone phylogeny. Systematics and Biodiversity 7 (4): 419-432.

Quandt, D., S. Huttunen, R. Tangney & M. Stech. 2009. Back to the future? Molecules take us back to the 1925 classification of the Lembophyllaceae (Bryopsida). Systematic Botany 34 (3): 443-454.

Name the Bug # 55

So, did anyone miss me?

Attribution to follow (and this one will be really easy if you've been paying attention).

Update: Identity available here. Photo from here.