Popularly requested tweak: Choice quotes from abstracts now included!
These are papers that may be of general interest published this week, with commentary as necessary. No specific case studies, overly specialised research, or taxonomic papers. Papers ordered only by their appearance in my inbox. For PDFs, e-mail me, I get most of them. You can request an in-depth analysis of any paper and I’ll do it as I get the time.
Open-access papers, those that are free to read/download even without an academic connection, are tagged with [OA] for easy finding with your browser’s text search (Ctrl+F).
19 papers this week, 5 of them open access.
Index:
- Arthropods [3]
- Botany [1]
- Ecology [2]
- Evolution [3]
- Palaeontology [4]
- Phylogenetics [2]
- Zoology [4]
From the abstract:
Myrmica ruginodis workers are able to distinguish black or white circles from black or white squares, black or white ellipses from black or white rectangles as well as hollow circles or ellipses from hollow squares or rectangles. They can also distinguish differently oriented elements as well as objects containing a various number of elements.
- A Total-Evidence Approach to Dating with Fossils, Applied to the Early Radiation of the Hymenoptera. [OA]
I would normally put this paper in the phylogenetics or palaeontology section, because that’s where its true significance is – the study shows just how important fossils are in reconstructing dated phylogenies (this is one of my pet convictions that I try to shove down the throat of molecular phylogeny fetishists at any chance I get). But for the sake of keeping it interesting, this paper does also provide some useful prospective dates for divergence times of the Hymenoptera.
With respect to the early radiation of Hymenoptera, our results suggest that the crown group dates back to the Carboniferous, ∼309 Ma (95% interval: 291-347 Ma), and diversified into major extant lineages much earlier than previously thought, well before the Triassic.
From the abstract:
Our results demonstrate that a simple but experimentally tractable visual system can distinguish complex images and that processing in the relatively large central brain may compensate for the simple input.
The only text you’ll need about collenchyma. Has handy diagrams and pictures too, useful for teaching plant anatomy.
This paper really doesn’t need to be written, because it’s really kind of obvious. I can personally attest to the point made in the paper about funding stability, since my own attempts at setting up a long-term ecology study at my vernal ponds all fail miserably because the cost of regular check-ups of the ponds are prohibitive.
Among the skeptic and freethinking circles I hang around in, “correlation doesn’t imply causation” is a pretty overused sentence. There is a validity to it, but the flipside is that foten, correlation does suggest causation at least. There was a good Slate article on this, there’s this article, and there’s a whole load of papers to consult too. This paper is very relevant:
We introduce a method, based on nonlinear state space reconstruction, that can distinguish causality from correlation.
I mentioned fig pollination as an example of co-evolution in my insect-flower co-evolution post, and this spectacularly thorough paper reinforces the example’s status as the best and most widespread coevolutionary scheme known.
Overall, our findings indicate that the fig-pollinator mutualism represents an extreme case among plant–insect interactions of coordinated dispersal and long-term codiversification.
Interesting because this is exactly what I need to apply in my own research. From the abstract:
Recognition of evolutionary units (species, populations) requires integrating several kinds of data, such as genetic or phenotypic markers or spatial information in order to get a comprehensive view concerning the differentiation of the units.
Cheaters are everywhere in life, and they also suck everywhere in life.
We found that: (i) QS cheating occurs in biofilm populations owing to exploitation of QS-regulated public goods; (ii) the thickness and density of biofilms was reduced by the presence of non-cooperative cheats; (iii) population growth was reduced by the presence of cheats, and this reduction was greater in biofilms than in planktonic populations; (iv) the susceptibility of biofilms to antibiotics was increased by the presence of cheats; and (v) coercing cooperator cells to increase their level of cooperation decreases the extent to which the presence of cheats reduces population productivity.
The science news has probably gone ahead and abused this paper already, since this topic is second only to new hominid fossils in the “palaeontological stuff the public finds inexplicably fascinating” section. I will only quote the abstract.
Here we report a new stem-tetrapod (Tungsenia paradoxa gen. et sp. nov.) from the Lower Devonian (Pragian, ~409 million years ago) of China, which extends the earliest record of tetrapods by some 10 million years. Sharing many primitive features with stem-lungfishes, the new taxon further fills in the morphological gap between tetrapods and lungfishes. The X-ray tomography study of the skull depicts the plesiomorphic condition of the brain in the tetrapods. The enlargement of the cerebral hemispheres and the possible presence of the pars tuberalis in this stem-tetrapod indicate that some important brain modifications related to terrestrial life had occurred at the beginning of the tetrapod evolution, much earlier than previously thought.
Seems like we’ll need to update even more dinosaur reconstruction:
Here we report the occurrence of feathers in ornithomimosaurs, a clade of non-maniraptoran theropods for which fossilized feathers were previously unknown. The Ornithomimus specimens, recovered from Upper Cretaceous deposits of Alberta, Canada, provide new insights into dinosaur plumage and the origin of the avian wing. Individuals from different growth stages reveal the presence of a filamentous feather covering throughout life and winglike structures on the forelimbs of adults. The appearance of winglike structures in older animals indicates that they may have evolved in association with reproductive behaviors. These specimens show that primordial wings originated earlier than previously thought, among non-maniraptoran theropods.
Arthrodization refers to one of the critical steps in the evolution of arthropods: the sclerotisation of the body (i.e. the formation of the exoskeleton). The species described here from the Burgess Shale is very basal, and has weak sclerotisation but also a bivalved carapace – meaning that the exoskeleton didn’t evolve as a protective measure.
I talked about wood-feeding in the deep sea in this post. Now we have the very cool preservation of the digestive system of a fossil wood-boring bivalve. It’s a shame there isn’t enough preserved to see just how similar the system was to modern wood-feeding bivalves – it would make for an interesting case of convergence if they looked the same.
Dendroscope is one of the most intuitive programs for visualising phylogenetic trees, and now has a new version, downloadable for free here. I include this in the compilation because if you’re a high school teacher, you could conceivably try and teach your students some systematics with it – just get trees for the ToL and play around.
Lateral gene transfers are usually viewed as anathema for phylogenetic reconstructions, a source of unreliable signal and data. But, of course, they can be used as a source for dating, and this is what this paper sets out to demonstrate successfully:
Our results demonstrate that lateral gene transfers, detected by probabilistic models of genome evolution, can be used as a source of information on the timing of evolution, providing a valuable complement to the limited prokaryotic fossil record.
A very, very interesting paper if you’re into animal cognition and intelligence. In the author’s words:
Here I will review experimental results suggesting that these difficulties, arising from the animal’s morphology, have imposed the evolution of unique brain/body/behavior relationships best explained as intelligent behavior which emerges from the octopus’s embodied organization. The term ‘intelligent embodiment’ comes from robotics and refers to an approach to designing autonomous robots in which the behavior emerges from the dynamic physical and sensory interactions of the agent’s materials, morphology and environment. Consideration of the unusual neurobiology of the octopus in the light of its unique morphology suggests that similar embodied principles are instrumental for understanding the emergence of intelligent behavior in all biological systems.
Cycliophora is the most recent animal phylum to have been described, by Funch & Kristensen (1995), on the basis of a single species, Symbion pandora, found in the mouthparts of a lobster. There’s not much I can tell you about them – they deserve their own post – except that they’re very enigmatic, as evidenced by this paper which finds that they only live in specific lobster mouthparts, namely just three species of lobster.
Slime molds aren’t animals, but I won’t make a brand new category for this paper. It’s relevant to animals anyway, by showing that intelligence isn’t even something for which a brain is needed, which is one of the things I try to convince everyone of. Heck, it goes even further, since slime molds don’t even have a nervous system. These guys have an external memory thatm allows them to travel through complex environments. Amazing.
Besides creationists and other typical pseudoscientists, Ray Kurzweil and his Singularity cult are one of the frequent targets of my debunking ire. While I don’t mind the futurism, I do mind Ray Kurzweil’s absurd predictions about brain simulation and uploading because they are taken seriously, even though Kurzweil demonstrates a very thorough ignorance of neurobiology. Specifically, the notion that we will one day replicate a brain is stupid, because we can’t even replicate a single neuron. As this paper shows, there are a lot of changes that happen in neurons, both physical, chemical, and morphological ones. We haven’t even begun to characterise these, let alone quantify them. And this Kurzweil guy expects to have billions of neurons made artificially and interacting together to make an artificial brain so close to the biological one that you can just upload your brain to it. It’s idiocy, through and through.
