Field of Science

The Butterflies Get All the Glory (Taxon of the Week: Gelechioidea)


Caterpillar of a parsnip moth, Depressaria daucella (Depressariidae or Oecophoridae). Depressaria moths are notable for feeding on toxic umbelliferous host plants that other animals (for instance, certain Greek philosophers) find distinctly unpalatable. Photo by Percherón.


The Lepidoptera, butterflies and moths*, are one of the most familiar groups of insects, and have the enviable advantage of tending to receive a more favourable response from the general public than other insects do. Some Lepidoptera, particularly the butterflies, are almost treated as honorary vertebrates - they receive a degree of attention and enthusiasm usually reserved for those animals of a more endoskeletal disposition. You might be forgiven, then, for assuming that the Lepidoptera are overall a well-known and studied order - but you'd still be wrong.

*Though in our lab, they tend to get referred to simply as "leps".

Traditionally, Lepidoptera have been divided into two, reasonably self-explanatory, groups - the microlepidoptera and macrolepidoptera. Though originally divided simply by size, the terms have been redefined in recent years on a phylogenetic basis - the name Macrolepidoptera has been attached to a particular clade, while leps outside this clade are dubbed microlepidoptera. The intuitive meanings of the names still work reasonably well - the majority of large Lepidoptera are indeed Macrolepidoptera (though the often very sizeable Hepialidae are, phylogenetically speaking, microlepidoptera). And, not surprisingly, it is the Macrolepidoptera that get most of the attention, while the microleps (which, just to make the point, probably constitute the greater part of lepidopteran diversity) tend to get shoved to one side.


Esperia sulphurella, Oecophoridae. Larvae of this species feed on rotting wood. Photo by Keith Edkins.


The Gelechioidea are a large microlepidopteran superfamily. They are spectacularly diverse - Hodges (1998) referred to there being well over 16,000 described species. As if this wasn't impressive enough, perhaps only about a quarter of the world's gelechioids have been described. Most of the Gelechioidea are extremely small - one of the largest, Cryptophasa setiotricha, is 25 mm long, while one of the smallest is Siskiwitia falcata, a mere two millimetres in length (Hodges, 1998). Like many other tiny moths, the wings often have a long fringe of hairs. The larvae of gelechioids are usually retiring herbivores, often concealing themselves in a web of silk or binding leaves to form a hide. Some are detritivores or fungivores, while a few have become carnivores of other insects such as scales (Kaila, 2004). The monophyly of the Gelechioidea is not certain - the morphological analysis of Kaila (2004) supported gelechioid monophyly, but three of the four supporting characters were homoplasious with other Lepidoptera, while the only character unique to Gelechioidea (antennae meeting mesally in the pupa) had been lost in a number of gelechioid subgroups.


Oecophora bractella (Oecophoridae), an atypically colourful gelechioid (yes, I know that means that all the photos are of oecophorids, but you see, most gelechioids can basically be described as "kind of brown"). Photo by Sean McCann.


Homoplasy was similarly rife within the superfamily itself. Kaila (2004) resolved two major clades, a "gelechiid lineage" including (among others) the Gelechiidae, Cosmopterigidae and Coleophoridae, and an "oecophorid lineage" with the Xyloryctidae, Oecophoridae and Elachistidae, but both were supported solely by homoplasious characters. Bucheli & Wenzel (2005) used molecular data as well as morphology, but included less taxa in their analysis than Kaila (2004) - they continued to support the oecophorid lineage, but resolved the gelechiid lineage as paraphyletic. Probably as a result of such rampant homoplasy, no two revisions have agreed on the best way to divide the gelechioids into families - the major families listed are fairly safe, but various minor "family-type groups" move in and out of them at will.

Relatively few gelechioids are of economic significance to humans. A few are plant pests (such as Pectinophora gossypiella, the cotton bollworm) or can feed on stored grain or textiles, but for the most part they are just as retiring as they look. There's still an awful lot of them, though.

REFERENCES

Bucheli, S. R., & J. Wenzel. 2005. Gelechioidea (Insecta: Lepidoptera) systematics: A reexamination using combined morphology and mitochondrial DNA data. Molecular Phylogenetics and Evolution 35 (2): 380-394.

Hodges, R.W., 1998. The Gelechioidea. In Lepidoptera: Moths and Butterflies (N. P. Kristensen, ed.) pp. 131–158. Walter de Gruyter, Berlin and New York.

Kaila, L. 2004. Phylogeny of the superfamily Gelechioidea (Lepidoptera: Ditrysia): an exemplar approach. Cladistics 20 (4): 303-340.

10 comments:

  1. Sorry, I'm not sure I got the reference: Umbelliferous plants that certain Greek philosophers found unpalatable?
    Socrates and Hemlock, or ???

    ReplyDelete
  2. That's the one - though I suppose that one could argue that he found it entirely palatable, but only the once.

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  3. This was a fantastic post!

    ReplyDelete
  4. I was surprised, upon reading Plato, to find that Socrates drank hemlock not because he had no choice, but just to spite the people who had sentenced him. They were all sure he would leave town, and then they could forget all about him. The joke was on them, I guess.

    Not that this has anything to do with L..

    I wonder why anyone does taxonomy based on anything other than molecular or DNA-sequence data, any more. (Paleontologists excepted, of course.) Haven't there been enough embarrassments yet?

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  5. I wonder why anyone does taxonomy based on anything other than molecular or DNA-sequence data, any more. (Paleontologists excepted, of course.) Haven't there been enough embarrassments yet?

    Are you perhaps referring to the Haematothermia scenario? Or Marsupionta?

    People still do morphology-based phylogenetics because there's absolutely no reason not to. Morphology is no less useful a data source now than it was fifty years ago - in fact, it's more so, because techniques have not stood still in that time. Cases where morphology and molecules disagree do not automatically mean that the latter is right and the former wrong. It could be the other way around, or both could be wrong. Fortunately, though, the two are probably in agreement more often than not.

    End rant.

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  6. Sorry to make you rant. I was thinking of Accipitriformes, and of your harvestmen, and of mosses, and of all the myriads of tiny things that aren't necessarily distinguishable by reliable, visible phenotypic characters. There's no objective reason, in principle, why there should be any such, or enough. Why shouldn't a whole clade be distinguishable only by odor, or by preferred mating temperature?

    Apologies if this taps into your more distressing dreams.

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  7. I Spotted your Ciliate Post some time ago and replied ..

    Why does your Email not work ?

    CHICHI .. UK ?

    gerarus at westnet.com.au.

    I Live in the UK and am a "Fish-Keeper" .. I read one of your Bloggs on Ciliate Mutation and wondered whether you might Possibly be in a position to Help ?

    I have an Unclassified at least in the Fish "Parasitology" Dept critter which has Killed many of my Fish to date and does not respond to the Most Aggressive Treatments Levied at it to Date ..
    In a bid to ID this over two years I have Trawled the length and Breadth of Protist identification .... All to No Avail

    ReplyDelete
  8. This comment has been removed by a blog administrator.

    ReplyDelete
  9. That's the correct e-mail - don't forget that you have to remove the " at " and replace it with the "@" symbol (like many people on the internet, I'm not putting my e-mail address down exactly as written because then spam robots could lift it from the website and bombard me daily with 5000 offers of penis extensions).

    Unfortunately, I'm not in a position to help you with your ID problem. Try searching for "ciliate researcher" or "protistologist" - they're out there, and they may be able to help.

    ReplyDelete
  10. So, like, I am a YEAR late, but whatever...

    I never thought that anything regarding Gelechioidea systematics would end up on anyone's blog ever for any reason!

    I had to limit the sample size to accommodate the combination of the two data matrices. I had more in each but they were not necessarily overlapping.

    Entomologists rely heavily on morphology because it is a very rich source of data -- the problem with Gelechioidea is the divergent evolution of the "tried and true" morphological characters (wings; genitalia; venation.) @80 my of evolution + much speciation events = difficulty in homologizing morphology across taxa. I argue that morphology should not thrown out a priori, though. Give it a shot. Why not? Also, I am not embarrassed to have someone challenge my work. Maybe they can teach me something.

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