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.
Panov AA. 2012. Leaf beetles (Coleoptera: Chrysomelidae): Mushroom body simplification in the course of progressive evolution of the family. Biology Bulletin 39, 35-42.
As I mentioned in this post, one of the most important parts of an insect’s nervous system is the musroom body. To summarise, in most insects (i.e. the Neoptera), the mushroom body is composed of a calyx connected to the α and ß lobes by a peduncle; the lobes interact with the protocerebrum, while the calyx interacts with the peripheral nervous system. Many functions have been assigned to the mushroom body, all of them related to insects’ learning and memorisation abilities – the mushroom body is often referred to as the center for insect intelligence. In general, the evidence for these associations comes from the observation that the most active insects – those that need to memorise most, those that need to have the most flexible behaviour – have more highly-developed mushroom bodies. I may summarise these studies in a future post; this paper brings up a factor I’ve never thought of before regarding mushroom body development. It reviews the structure of the mushroom bodies of species of Chrysomelidae (leaf beetles) spanning the whole group. They find that in the more derived chrysomelids, the mushroom body’s complexity decreases, and that the most probably correlation isn’t ecological, it’s morphological: the more derived chrysomelids just don’t have the space for a larger mushroom body. I’d be interested to see if space is a limiting factor in other insect groups.
Ménez B, Pasini V & Brunelli D. 2012. Life in the hydrated suboceanic mantle. Nature Geoscience 5, 133-137.
In the last post of my deep-sea series, I wrote an elaborate, but ultimately unsourced, scheme for how abiogenesis could occur at hydrothermal vents. Granted, I would only be confident about it as far as origination of biologically-active molecules are concerned. Anyway, I emphasised there that serpentinisation is key – serpentinisation is when the mantle gets hydrated, resulting in both the formation of different minerals, and in hot water saturated in elements getting pumped into the ocean. This paper supports my emphasis, but that’s not important – it’s a great piece of work that shows that there is plenty of organic matter to be located in serpentine-derived areas, and the analysis they did shows that this organic matter is potentially sourced from microbial activity. It’s impressive, and it leaves plenty of ground for future research to identify the components of this so-far unresearched realm of the biosphere.
Ratcliff WC, Denison RF, Borrello M & Travisano M. 2012. Experimental evolution of multicellularity. PNAS 109, 1595-1600.
Unicellular organisms have been made to become multicellular in previous experiments. They gain mutations in their surface proteins to allow them to stick together, leading to a clump of clonal cells. This study goes further and evolves not only multicellularity, but also division of labour: once the clonal aggregate forms, some cells can then turn to performing tasks other than reproduction, since their genes will be passed on by cloning anyway. The study further goes to show how some cells begin differentiating in their cycle, all under the influence of natural selection. It’s a brilliant piece of work, and one which I will definitely be using in any relevant presentation. It also helps that it’s open access ;)
Winguth C & Winguth AME. 2012. Simulating Permian–Triassic oceanic anoxia distribution: Implications for species extinction and recovery. Geology 40, 127-130.
I’ve already explained the basics of the PT extinction at the end of this post. I especially put the blame on anoxia, as supported by extensive geological and geochemical evidences from around the world. This paper adds another line of evidence in the form of a thorough model of oxygen circulation at the PT boundary. The most important find is that at the boundary, an already-large anoxic zone expanded greatly – corroborating the geological and -chemical evidence for a superanoxic event – and that it took a while for the oceans to go back to “normal”, hence why the recovery was so protracted. It’s safe to say that by now, we have a fairly solid framework of the situation during the PT extinction.
Hart BW. 2012. Watching the ‘Eugenic Experiment’ Unfold: The Mixed Views of British Eugenicists Toward Nazi Germany in the Early 1930s. Journal of the History of Biology 45, 33-63.
A bit of a topical pick for this week, since I’ve been having a half-a-week-long argument about the utility of evolution with a creationist. It’s like discussing Goedel’s Theorem with an eroded brick wall. Anyway, one of his main discussion points (actually, the only one besides whining and crying persecution) is that evolution leads to eugenics (which is wrong from a historical perspective – eugenics was a movement borne out of a notion of genetic purity, and evolution as we understand it today was largely derided by biologists of the time). So this paper caught my attention, and it’s a pretty interesting one. It’s well-known that the USA had a large amount of eugenicists, but from the British of the time, only R. A. Fisher sticks out prominently. This paper argues that eugenicist views were much more common than supposed in 1930s Britain, but that it was all recontextualised in the aftermath of World War II and the exposition of eugenics as the perfect trolley to slide down the slippery slope with. It’s fairly convincing.
Harvey THP, Vélez MI & Butterfield NJ. 2012. Exceptionally preserved crustaceans from western Canada reveal a cryptic Cambrian radiation. PNAS 109, 1589-1594.
It’s no secret that I love exceptionally-preserved stem-group arthropods – after all, that’s what my Bsc. thesis was about. So this paper’s a natural pick. It’s an awesome find from a formation I was only vaguely aware of before – I know it as a place to find random trace fossils and brachiopods from a nearshore facies, but that’s it. It turns out that it impeccably preserves organisms at the microscale, kind of like small shelly fossils. Among these are cuticles of crustaceans, including the oldest representatives of extant branchiopods, and stem-group copepods and ostracods. And this is end-Cambrian crustacean diversity we never knew existed, and which had much of the same adaptations that modern counterparts do.
Thomas GH & Freckleton RP. 2012. MOTMOT: models of trait macroevolution on trees. Methods in Ecology and Evolution 3, 145-151.
This seems like a great R package for macroevolution. I’ll be test-driving it soon.
Conus snails are somewhat of a model system for both evolution and pharmacology – their diverse toxins are investigated to see if they can serve as the basis for new drugs. Ont he evolutionary side, we’re interested in their shell patterning, which is readily simulatable. Since the pattern is developmentally-determined (some is genetic, some is environmental), it’s possible to see how evolution is reflected on the shell’s colouring. And this is what this study does, by plotting the patterning on a phylogeny of a well-known segment of the Conus tree (Conus is a hyperdiverse genus as far as molluscs go). The most exciting finding from my point of view is the evidence for developmental canalisation. What they did was do an ancestral trait reconstruction to figure out how the pattern was on the hypothetical last common ancestor of these Conus species, and they find that it’s unlike anything in its descendants, but that all the descendants just take bits and pieces of that ancestor’s developmental program and expand on it, and that’s how they diversify. It’s an elegant piece of work (it’s one of those where I wish I’d have thought of doing the work myself!).