It was at the XIV international meeting of the International Union for the Study of Social Insects in 2002 that the “gang of four” decided to join forces to reconstruct the phylogenetic history of ants using molecular data. Four years later Brady et al. 2006 was published.
Familiar to many, you can know how old a tree is and how fast it has grown by counting the number of rings in a cross section. Well, you can do the same with the long bones of vertebrates.
Now Gregory M. Erickson and co-workers published a paper in which they did just that to a specimen of one of the most famous fossil forms around: Archaeopterix. Watch Mark Norell, paleontologist from the American Museum of Natural History and co-author of the paper, explain the results:
Can someone please tell me if August 28th is the equivalent of “April’s fool day” somewhere in the world? This paper just published online in the Proceedings of the National Academy of Sciences (USA) reads like something coming out straight from The Onion:
Published online before print August 28, 2009, doi: 10.1073/pnas.0908357106
Donald I. Williamson
Marine Biology, University of Liverpool, Liverpool L69 7ZB, United Kingdom
I reject the Darwinian assumption that larvae and their adults evolved from a single common ancestor. Rather I posit that, in animals that metamorphose, the basic types of larvae originated as adults of different lineages, i.e., larvae were transferred when, through hybridization, their genomes were acquired by distantly related animals. “Caterpillars,” the name for eruciforms with thoracic and abdominal legs, are larvae of lepidopterans, hymenopterans, and mecopterans (scorpionflies). Grubs and maggots, including the larvae of beetles, bees, and flies, evolved from caterpillars by loss of legs. Caterpillar larval organs are dismantled and reconstructed in the pupal phase. Such indirect developmental patterns (metamorphoses) did not originate solely by accumulation of random mutations followed by natural selection; rather they are fully consistent with my concept of evolution by hybridogenesis. Members of the phylum Onychophora (velvet worms) are proposed as the evolutionary source of caterpillars and their grub or maggot descendants. I present a molecular biological research proposal to test my thesis. By my hypothesis 2 recognizable sets of genes are detectable in the genomes of all insects with caterpillar grub- or maggot-like larvae: (i) onychophoran genes that code for proteins determining larval morphology/physiology and (ii) sequentially expressed insect genes that code for adult proteins. The genomes of insects and other animals that, by contrast, entirely lack larvae comprise recognizable sets of genes from single animal common ancestors.
I think Lynn Margulis went too far this time…
GenBank, the standard database for genetic information maintained by National Center for Biotechnology Information, has been accumulating DNA sequences for some three decades now. Since its creation in the late 1980s, it has become the de facto repository for genetic information– genetic data must now be submitted to GenBank for a paper to be accepted for publication. Most sequence data accumulated are the result of the sum of many “local” taxonomic studies that have targeted a particular group of organism for a relatively small, but well-known collection of genes. It contents now span over hundreds of genes across all of life’s domains. So, what would happen if you were to take all the sequence information contained in GenBank and analyze it phylogenetically all together in a single, one-step study? Well, that is what Pablo A. Goloboff and coworkers just did, the results of which were published in last week’s online early edition of Cladistics, the international journal of the Willi Hennig Society.
The metapleural gland is the definitive character of ants. It is unique to the family. Nothing homologous or similar is found anywhere else in insects. Within the tree of life of Hymenoptera, myrmecologists agree that the appearance of this gland provides a good cutting point to marks-out ants as a monophyletic group1. You have it? You are an ant. You don’t? Sorry, you don’t qualify, get the hell out of here lousy wasp2. It is the ultimate ant synapomorphy.
- Grimaldi, D. and D. Agosti (2000). The Oldest Ants are Cretaceous, Not Eocene: Comment. Canadian Entomologist 132(5):691-693. ↩
- Yes, one can insult insects by calling them members of the Order Phthiraptera ↩
This is an excellent example of the way systematic papers should be. In the latest issue of the Proceedings of the National Academy of Sciences (USA), Blackledge and coworkers assembled a comprehensive data set for cladistic analysis of orb web spiders that includes six different molecular loci, 143 morphological characters and behavior in the form of characters derived from web architecture.
The recent description of the new and unusual ant species from Brazil Martialis heureka, caused furor in the popular media. It was entertaining to watch how, like the children’s game of Chinese whispers, the report rapidly deteriorated and became increasingly sensationalistic as it spun through news agencies around the globe. Reports ranged from accurate and informative to down right silly, with some newspapers almost claiming that the species actually originated in Mars (You can read more about it at Myrmecos blog and comments therein).
I have to say, I appreciate the medias attention to insect science no matter how distorted it gets. But now that the news storm has settle we can point out some other good news about Rabeling, Brown, and Verhaagh’s paper. News that may not make for a good newspaper headline but that are nevertheless relevant to specialists in ant systematics. › Continue reading
- Tom Waits