Top Papers of the Week: 13.02-19.02

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The master list for this week is here. Only those categories with more than one paper will be considered. Taxonomy will be exempt, because new species descriptions isn’t the kind of thing I can choose between.

Arthropods:

Vogt G. 2012. Ageing and longevity in the Decapoda (Crustacea): A review. Zoologischer Anzeiger 251, 1-25.

There were several really cool arthropod papers the past week, for example Fischer et al. (2012), Rehm et al. (2012), or Lancet & Dukas (2012), but this paper wins out for sheer amount of information – it’s a review on how long decapods live and how they age, a sorely underresearched field of crustacean biology. This is very surprising given just how important decapods (incl. shrimps and crabs) are – they’re worth over $20 billion in aquaculture. Given just how diverse, both systematically (10000 spp.!) and ecologically, the decapods are, it’s no surprise that very little generalisations can be made – lifespans between different species can vary by an order of magnitude (1 to 10 years), with cold-water, deep-water, and cave taxa generally living longer, most likely due to their much slower metabolism and way of life. The decapods are also rather unique among the animals for being very resistant to cancer. This isn’t just an artefact of the lack of research, they actually have various mechanisms from the cellular to the physiological level to prevent the formation of neoplasias; not even environmental carcinogens seem to be very successful in causing tumour formation. As such, the author suggests studying the Decapoda and their ageing to find inspiration for anti-ageing and anti-cancer breakthroughs, and I agree.

Developmental:

Kimelman D & Martin BL. 2012. Anterior–posterior patterning in early development: three strategies. WIREs Developmental Biology 1, 253-266.

The anterior-posterior (AP) axis is the most important for animals, and as such, there’s an enormous amount of literature on the subject from all sorts of model organisms. This paper handily summarises its specification in Tribolium, Drosophila, and the zebrafish. The only thing missing is Strongylocentrus, the sea urchin model, but you can’t have everything. If you’re at all interested in animal development, this paper is a must-have as a reference.

Ecology:

Gilman RT, Fabina NS, Abbott KC & Rafferty NE. 2012. Evolution of plant–pollinator mutualisms in response to climate change. Evolutionary Applications 5, 2-16.

I’ve written before about the effect of climate change on marine ecosystems, but obviously, climate change has a large impact on terrestrial ones as well. The most important expected and observed effects are changes in phenology (time of year when organisms are active, e.g. flowering time or migration time), population densities, community structures, and species ranges. The latter two are of most importance to this paper, as the paper involves the interaction of two mutuaistic species. In order for the mutualism to persist, the species have to overlap geographically, and they have to be able to survive in their ecosystem. There is a certain equilibrium in ecosystems in that these two conditions are fulfilled, but the potential of the interacting species remain different. A plant can have a high tolerance for temperatures, while its pollinator can only tolerate a narrow temperature band, and the ecosystem where they coexist is at that temperature. With the abrupt climate changes happening now, this balance will be disrupted. There will be no suitable ecosystem where the plant and pollinator can coexist, either due to the abiotic factors becoming different, or due to the migration of new predatory/herbivore species. The effect on phenology can be especially strong in the case of pollination systems. In the most extreme scenarios, extinction will result; however, if the mutualism can be achieved with other species, the results are not too dire. This paper basically formalises all this with nifty calculations.

Environmental:

Brévault T, Nibouche S, Achaleke J & Carrière Y. 2012. Assessing the role of non-cotton refuges in delaying Helicoverpa armigera resistance to Bt cotton in West Africa. Evolutionary Applications 5, 53-65.

I love GMOs and go out of my way to support them. To me, it’s the only way forward in this era of high population and climate change. One of the best advances in GMOs in agriculture is the use of Bt crops. These are the regular crops, modified so they express a ð-endotoxin from the bacterium Bacillus thuringiensis. It’s especially used for cotton, and gets rid of pest insects, and thus has effectively reduced the amount of insecticides needed, thus reducing the amount of poison in the environment. However, a problem was soon realised: pests develop resistance to the Bt toxin, as they are wont to do. So now the biggest area of research is figuring out how to delay or prevent the acquisition of this resistance. This paper makes a contribution by quantifying how providing non-Bt ecosystems adjacent to the crops delays the evolution of resistance of this caterpillar to Bt cotton.

Evolution:

Song Y, Scheu S & Drossel B. 2012. The ecological advantage of sexual reproduction in multicellular long-lived organisms. Journal of Evolutionary Biology 25, 556-565.

I’ve written about the evolutionary theory behind the dominance of sexual reproduction before, unequivocally supporting the Red Queen model. This paper is a mathematical exploration of sexual reproduction, and it manages to bridge this model with another model where resource availability is the most important factor. I haven’t checked the maths in detail, but I’m assuming it’s okay since it passed review.

Palaeontology:

Tapanila L & Robert EM. 2012. The Earliest Evidence of Holometabolan Insect Pupation in Conifer Wood. PLoS ONE 7, e31668.

Several pupation chambers are known in the fossil record, including from the critical Cretaceous period when insect biodiversity exploded. I can’t give a list of how many insects pupate in wood, but all holometabolous orders have at least one representative that does it, including the beetles, lepidopterans, and hymenopterans. Whatever the case, this is the earliest evidence of wood pupation, suggested by the authors to be done by a cupedid beetle.

Phylogenetics:

Mariadassou M, Bar-Hen A & Kishino H. 2012. Taxon Influence Index: Assessing Taxon-Induced Incongruities in Phylogenetic Inference. Systematic Biology 61, 337-345.

I’ve written about the importance of taxon sampling before. Most of the talk about taxon sampling revovles around the need to have a complete taxon sampling for our purposes, in other words, to be as comprehensive as possible – this involves a trade-off with computational time and researcher effort. What has been missing so far is a good index or calculation to allow us to identify which taxa are the most important to include. This paper is a first step towards such an algorithm. First of all, it shows that not all taxa affect a phylogenetic tree equally, with a small number having an unproportionate pull on the topology of the overall tree. By identifying such taxa, we can make sure to place a particular emphasis on them when building our character matrices/sequencing our genes.

Systematics:

Kawauchi GY, Sharma PP & Giribet G. 2012. Sipunculan phylogeny based on six genes, with a new classification and the descriptions of two new families. Zoologica Scripta 41, 186-210.

The Sipuncula, long thought to be a phylum, are now known to be highly-derived annelids. However, their internal systematics is still a mess. I can’t give any perspective on whether this paper is a step forward or a molecular screw-up. Six genes seems pretty flimsy, but the tree is robust, and apomorphies could be found for all the rearranged clades. So if you’re looking for the latest tree of sipunculids, this is the one.

Zoology:

Arkhipkin AI, Bizikov VA & Fuchs D. 2012. Vestigial phragmocone in the gladius points to a deepwater origin of squid (Mollusca: Cephalopoda). Deep Sea Research I 61, 109-122.

The phragmocone is the gas-filled chamber of the ammonite or the Nautilus. The gladius is an internal support structure found in squid (if you ever dissect one, it’s the soft/squishy bit that most of them have), and is also the vestigial remnant of the molluscan shell. What the researchers did was investigate the microstructure of gladiuses (gladii?) from a variety of squids, and what they found was that in the rear part of the gladiuses, one can find rows of walls – much like the walls in the phragmocone of an ammonite. This is pretty damn cool just for the fact that we know that the gladius is actually two vestigial organs, and is nonetheless still in use. The rest of the paper is necessarily more speculative, as the authors attempt to convince you that this points to an evolutionary origin of squid in the deep sea.