It’s been a while, but I’ve kept them all the papers stored in a tab, nothing is lost. [OA] indcates open access papers. Feel free to request a detailed look at any of these.
General Interest, Important:
It’s no secret that I hold a low opinion of a lot of the human sexual selection and evolutionary psychology research, because I see a trend of insufficient sampling leading to overgeneralised statements that resemble “just-so stories” rather than evidence-backed claims. Here’s one paper that shows how to critically examine such papers.
Check out the whole range of additions, replies, and commentaries here, all [OA].
Tangentially-related, this review paper: Animal personality: what are behavioural ecologists measuring?
I always like to feature experimental evolution, especially when the results are as cool as this. Evolving multicellularity artificially isn’t anything new (e.g.), but more successful repetitions lead to us being able to identify all the potential evolutionary pressures that could have led to the convergent evolution of multicellularity, so such studies should always be encouraged.
Of course, studying things phylogenetically is also a good way: Development of ichthyosporeans sheds light on the origin of metazoan multicellularity [OA].
A point I made in my oft-read post on animal intelligence is that relative brain size is a fairly irrelevant criterion for intelligence. What matters more is organisation and connections between brain areas. While I was basing it on insects, the generality does also apply to mammals and vertebrates, as this paper shows: mosaic evolution is what leads to specialisations in the brain, and it’s what leads to the varying cognitive abilities of animals. Mosaic evolution in this case means a faster rate of evolution in some brain areas, which would automatically lead to novel connections. Relative brain size itself is irrelevant.
Some more on brains: Deep Homology of Arthropod Central Complex and Vertebrate Basal Ganglia.
I’ve written before on what I think of most genome sequencing projects: largely meh. This is a case of a non-meh genome sequencing project, since it showcases the depths of adaptation in obligate parasites. As an invertberate zoologist, I’m intimately familiar with their various morphological contrivances, but what this genome project shows is that they are accompanied by fancy genomic specialisations too. That’s my main interest, although less hedonistic scientists would be interested in the medical advances enabled by these discoveries.
Of course, the genome that everyone was concentrated on this week was the coelacanth. I have no idea why, it must be that idiotic “living fossil” myth. Whatever. Here’s a link to it: The African coelacanth genome provides insights into tetrapod evolution [OA].
It’s of narrow interest, but thought I’d highlight it as shameless self-promotion: this is the sort of thing I wanted to do with arthropods when I came to Cyprus, but failed as a result of never receiving any funding.
One of the points I tend to stick on when teaching evolutionary theory is the effect of population size. Very generally, the role of genetic drift (random evolution) gets larger as populations get smaller. Very large populations have their own wacky processes going, which this paper reviews and tells us to study deeper. I agree.
The Lessepsian migration is one of the more fascinating large-scale ecological phenomena happening nowadays. Since the Suez Canal was opened, the fauna of the Red Sea has been migrating naturally into the Mediterranean and, surprisingly, they’ve been outcompeting and displacing the native Mediterraneans. You can read some proposed reasons why in this paper. On a general note, I use this example to show that the distinction of “native” and “indigenous” ecosystems, while very useful for conservation, is not an evolutionary one. It’s a historical one, but just because species have evolved in the same place for centuries and millenia, it doesn’t mean they are a “perfect fit” – and this isn’t something we should expect anyway.
A slight ray of hope? Eh, depends on your perspective. Coral reefs may be among the most fragile of ecosystems, but this status is, in my opinion, very reflective of the disproportionate amount of attention that coral reefs get both from studies and from human anthropogenic disturbance – coral reefs get visited a lot, just look at any tropical tourism leaflet. This is what this paper shows, again in my opinion: leave coral reefs alone and they will rebound. Of course, ocean acidification is another problem altogether, but solving that is slightly more complex than slapping tourists and naughty fishermen around.
More coral research from this time period: Calcification by Reef-Building Sclerobionts [OA].
One of the biggest perks of being an invertebrate biologist is that you have the opportunity to learn and observe an enormous diversity of animal life. It’s much nicer than just being restricted to stupid mammals and birds and lizards and fish. It’s also great if you’re an educator, because kids tend to be informed only of charismatic animals: pandas, rabbits, cats. But this is a way too blinkered and narrow view of biodiversity, so introducing kids to the whole gamut of animal life is very satisfying. Here’s a review for the placozoans, the simplest animals yet known with only 5 cell types, with only one species officially described, Trichoplax adhaerens. It’s a marine 2mm large disc-shaped blob that constantly changes shape, and is more or less invisible in the wild – you need a stereoscope to see them properly. Go to www.trichoplax.com for pictures!
For another bunch of weirdo invertebrates: Molecular phylogeny of kinorhynchs; A complete three-dimensional reconstruction of the myoanatomy of Loricifera: comparative morphology of an adult and a Higgins larva stage [OA].
Another paper from this “Global Diversity” series from this time period, but involving stupid vertebrates: Global Taxonomic Diversity of Living Reptiles [OA].
I’ve already written about this very cool field of research, the study of plant-arthropod interactions through time and the useful info we get out of it. Here’s a review from the Grand Master of the field.
New genes can arise fortuitously, but their gaining a fitness-affecting function is a more advanced prospect, and their fixation a rare event indeed, since the new genes must be integrated into the whole of the organism where domino effects, pleiotrop, and general chaos rule. This paper sketches a pathway for all those.
One of my favourite aspects of developmental biology is the mechanical, physical basis for it: the effects of cells bumping into each other, the effect of cells moving through fluids, even the effect of gravity. Genes and developmental pathways are cool and all, but I have a special affinity for such holistic, big-picture perspectives that take external complicating factors into account. This paper provides an example of how important such things can be.
I think Easter is happening around now, not sure though. But I do remember writing a popular post on regeneration one year for Easter. Planarians feature heavily in it, and this review is useful if you want more details on why planarians are useful for the study of regeneration, and a historical perspective.
Horned beetles are a classic model system for evolutionary ecology and evo-devo (and later will be for eco-evo-devo, or whatever the abbreviation will be). The interest arises because beetle horns are completely novel structures that arose convergently 6 times in beetles and were meaintained. Development informs us of how a novels tructure can arise in the first place; ecology tells us what they’re used for; evolution tells us how they remain. Put all that together, and you have a fascinating model system you can with hundreds of studiable species and permutations. This paper reviews all this potential.
If the meshing of evolution and ecology interests you, then so will this: Special Issue: A Critical Look at Reciprocity in Ecology and Evolution.
Crazy people with an agenda call us who follow the science on global warming “alarmists”. Here’s a paper to shove in their faces. Although the assumption that they know how to read is unwarranted and not backed up by the evidence.
China is the gift that keeps on giving in palaeontology. Some more amazing fossils.
But hey, other countries with cool fossils still exist: A ten-legged sea spider (Arthropoda: Pycnogonida) from the Lower Devonian Hunsrück Slate (Germany); A troodontid dinosaur from the latest Cretaceous of India; Original spotted patterns on Middle Devonian phacopid trilobites from western and central New York; A Large Accumulation of Avian Eggs from the Late Cretaceous of Patagonia (Argentina) Reveals a Novel Nesting Strategy in Mesozoic Birds [OA].
There’s been much fuss made about this in the popular science news. I took care of it on request some time ago on the Facebook page of the blog, so I’ll just copy-paste the text from there. It’s a solid phylogenetic study of mites whose main result is that dust mites are belong to a group of mites parasitic on vertebrates. In other words, house mites evolved from a parasitic ancestor. This is deemed surprising because parasites are rightly considered to be highly-specialised, so while a transition from generalist to specialist is easy to envision, the opposite is more implausible. But implausible is not impossible, as this study shows. The way the article is reported on belies the true nature of the advance here, especially witht he invocation of Dollo’s Law (which, to be fair, was done by the original authors as well). Dollo’s Law, as understood today (which is a far cry from Dollo’s original formulation), refers to a proposition that single complex characters, once lost, cannot be regained. But its validity as a law is increasingly being called into question, as more and more evidence piles on against its validity (see this paper, for example, which shows that fingers revolved in several liazrds even after they were evolutionarily lost). Saying that this paper puts “a new piece in the evolution puzzle” is just plain wrong. That piece has been known for ages. And in any case, a violation of Dollo’s Law is emphatically not “reversible evolution”, because that implies that evolution has a direction. The discovery is that the linear evolution to the free-living dust mite went like this: Free-living mites -> parasitic mites -> free-living dust mites. Does this mean that, somehow, dust mites have suddenly gone back in evolution? Absolutely not, because that would imply that they are now identical to those free-living ancestors of the parasitic mites. They’re not. They’ve gone their own way in evolution. So, to summarise: the awesome finding here, beside the details about mite evolution, is that free-living organisms can evolve from specialised parasitics. It’s not a reversal in evolution, except in the sense that their ecology is now similar to that of their distant ancestors. There is no such thing as “devolution”.
Those with a memory good enough for two years will remember the huge splash from two years ago from the description of Australopithecus sediba. For the uninitiated, enjoy a description I had written that time: They found pieces from two individuals: a 12-13 year old male, and an adult male. The age of the find is 1-98 – 1.75 million years, a time when there were many other hominins running around. The one closest to A. sediba, morphologically, is A. africanus: the body is very similar, with both being bipedal, but still having long arms (adaptation to trees). The face is also pretty much identical, besides A. sediba having slightly smaller teeth and more flattened cheeks. This is excellent, because A. africanus disappears from the fossil record before 2 Ma, so A. sediba fills in perfectly as their descendant, and so we get some more resolution of the australopithecine tree. A. sediba‘s hips have some feature found in Homo erectus, but not found in H. habilis and H. rudolfensis. The authors interpreted that as meaning that A. sediba is either ancestral to Homo (or very close to the ancestor), and that H. habilis and rudolfensis are not Homos, but actually australopithecines. Maybe I missed it when skimming through the paper, but I didn’t see them discuss the possibility that it’s convergence. After all, the hips are both adapted to bipedalism. It’s not far-fetched to think that they will look similar, and come up with the same mechanisms, to enable that. They then go into various arguments about Homo habilis not being a human ancestor, bringing in punctuated equilibrium to the mix. The whole issue has to do with how early Homos and australopithecines fit together – something that will always be controversial.
In any case, another big splash has been made, with another special issue devoted to A. sediba, with more papers with more detailed analyses and claims. Take your time poring through them, this is pretty critical stuff!
The phylogenetics and classifications of unicellular eukaryotes is something that invertebrate biologists are supposed to be familiar with, but I never had the interest in the microthings and don’t keep as close an eye on the advances as I should. Good thing reviews exist.
Something for the archaeologists.
Only putting this here because it has personal significance for me: the Nördlinger Ries is the very first impact crater I went to as a student. Long-time readers should also be familiar with it: it’s the big brother of the Steinheim crater, where the lake that contained the Steinheim snails was. In fact, that post is a simplification of the field trip report I had to write when we visited the Nördlinger Ries. Ah, to be 6 years younger again. Good old days. Hmm. Read the rest of this entry »