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Yes, the busy-ness has captured me. I am working on an entry right now about Triassic reptile trackways in Germany, but it’s going to take some time and I don’t want to screw it up by rushing. So I will try to get that to you tomorrow, and in the meantime you can stop by Catalogue of Organisms to read about aquatic sloths (!!), Tetrapod Zoology to read about crested porcupines, and test your knowledge of evolutionary relationships at Bayblab (discovered by way of Sandwalk).

I think the Bayblab quiz is a good example of some of the tendencies that we have that I mentioned in my entry on understanding evolutionary trees. Appearances can be deceptive–if we get tricked into thinking of evolution as a linear process rather than branching, we might classify some apparently simple creatures as distantly related that are actually just on the next branch over.

ResearchBlogging.orgTHE VERTEBRATE coagulation system is a complicated cascade of enzymes, yet it evolved by the gradual addition of enzymes. It is thought that this complex system evolved by the repeated duplication and divergence of two ancestral genes. We are most familiar with the prothrombin activators as essential clotting cascade elements, yet some snakes have weaponized these enzymes.

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ResearchBlogging.orgHUMANS CAN live to over seventy years old, yet female fertility begins a precipitous decline after about forty years of age. This is unusual since most other species continue reproducing into old age. Some have proposed our extension of life past reproductive years is due to a survival benefit for grandchildren with grandmothers who contribute to their care. However, this benefit is not enough to explain the initial cessation of reproduction.

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ResearchBlogging.orgIN THE PAST week or so I’ve been writing about the attine ants, which have a complicated mutualistic network combining cultivated fungi and actinomycete bacteria, and are parasitized by Escovopsis fungi and perhaps black yeasts as well! Today I’m writing about the attine ants again, but along a very different angle. In this case this paper examines the influence of evolution upon reproductive behavior. I actually ran across the paper by accident, having previously planned to write about a paper on evolution and reproductive behavior in humans. This paper nicely transitions between these two themes.

Among organisms in general it is a bad idea evolutionarily to abandon breeding in favor of helping another individual raise its offspring. There are examples of social cheaters among groups as different as myxobacteria, slime molds, vertebrates, and insects. The myxobacteria and slime molds are bacteria and eukaryotes respectively that have converged upon a similar lifecycle. These are organisms capable of lone existence, but which mass together during unfavorable conditions to produce a stalk that launches spores. Ideally every strain in the group will be represented equally in the spores produced, but some cheater strains are able to produce more than their share of spores. Among vertebrates, there are examples in many groups of species that parasitize the nests of others, foisting off their young upon an unsuspecting individual. Cowbirds and cuckoos are well known among the birds, and cuckoos gave their name to the cuckoo catfish, which parasitizes cichlids. A similar parasitism is seen among insects where some wasp species will infiltrate another species nest and lay their eggs. The ants take this type of parasitism even further, with some species going to war against others to capture their larvae, which are raised in their captor’s colony and tend their brood. But the type of reproductive cheating occurring in attine ants is different from all of these!

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ResearchBlogging.orgATTINE ANTS have been a theme at my blog recently. They first showed up in a discussion of their evolutionary tree, then in a post examining their relationship with the actinomycete bacteria that help protect their fungal gardens from parasites. In my reading I stumbled across the article that I will write about today, which seems to have discovered another part to the attine ant symbiosis. As of now this is the sole report on the occurrence of black yeasts living apparently parasitically on the attine ants, reliant upon the cuticular crypts that normally house helpful actinomycetes.

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ResearchBlogging.orgWHILE THE ATTINE ants are not well-studied, I posted this week about a study into their evolution that revealed the history of innovations in their cultivation of fungus. The attine ants are part of a symbiotic network between the ants, their fungal cultivars, the parasitic fungus Escovopus, and actinomycete bacteria that serve to suppress this parasite. These bacteria are members of Pseudonocardia and grow in filamentous mycelia on the insects’ integument, where the ants have evolved cuticular crypts to house the bacteria and glandular secretions that support their growth.

The actinomycetes are an order of bacteria that are know to produce a wide range of biologically active molecules, many of which are active against other bacteria and against fungi. Some of these natural products are now used clinically, such as the antibacterial antibiotics streptomycin, erythromycin, and tetracycline, anticancer drugs daunorubicin and doxorubicin, and antifungal drugs amphotericin B and natamycin. Actinomycetes inhabit a variety of environments, but many are ubiquitous soil bacteria.

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WHILE CNIDARIA are considered to have radial symmetry, a new article proposes that the cnidaria had a bilaterian ancestor and may properly be placed in Bilateria.1

Whoa.

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ResearchBlogging.orgI HAVE ALREADY mentioned one type of selfish genetic element. These are mobile elements that can move about and reproduce within the genome, and include the transposon and retrotransposons. A second similar type of selfish genetic element are the homing endonucleases. These come in two forms, as introns which are spliced out of RNA and then translated into protein instead of being discarded, or as inteins that splice out of the protein once it has been synthesized. In both cases the homing endonuclease then during meiosis attacks the allele that does not contain the homing endonuclease intron or intein and triggers DNA repair that duplicates the homing endonuclease’s sequence. Since mobile elements and homing endonucleases either attack at a wide variety of sites or duplicate onto both of a pair of chromosomes, they are passed on according to Mendelian inheritance patterns. But there are other selfish genetic elements that are passed on preferentially, and a new paper in Genetica focuses on the effects of these selfish elements upon fertility in carrier males.

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ResearchBlogging.orgTHERE IS A new article published online at PNAS reporting the results of a 36-year experiment on the Italian wall lizard Podarcis sicula. A population of lizards was already living on a small islet called Pod Kopiste, and the authors moved five females and five males to the nearby islet Pod Mrcaru. This was originally an experiment in “competitive exclusion”, as the islet was already inhabited by the Dalmatian wall lizard, Podarcis melisellensis, which was apparently outcompeted and is now extinct on that islet.

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THIS WEEK I’ve been covering some interesting instances of new gene evolution. The one I’m covering today is hard to boil down into a short title. This is a case of a new gene in hominoids as the result of retrotransposition of an aberrant mRNA transcript. Transposons showed up in the last post as well, but here they play a different role. That example involved a class II transposon, a segment of DNA that can jump around the genome. This case involves a class I transposon, a retrotransposon that transcribes itself into RNA, then copies that transcript back into DNA, and inserts it elsewhere in the genome. Here the retrotransposon accidentally retrotransposed a gene transcript instead of a retrotransposon transcript. This is not an especially rare event, but this case is unusual because the transcript itself is unusual.

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