To the list of special issues dealing with the evolution of eyes (E:EO, Phil Trans R Soc B), you can now add one on nervous systems in Nature Reviews Neuroscience.

Nature Reviews Neuroscience

Vol. 10, Oct. 2009

Charles Darwin’s theory of descent with modification by means of natural selection has stood the test of time, with new discoveries in genetics and the mathematical basis of natural selection providing ever growing evidence for the theory. This focus issue of Nature Reviews Neuroscience — sponsored by the Wellcome Trust — celebrates the contribution of Darwin’s ideas to our current understanding of the evolution of the nervous system. The articles in this special issue discuss the molecular, cellular and structural changes that have contributed to CNS evolution and their functional consequences.

The origin and evolution of synapses

Tomás J. Ryan & Seth G. N. Grant

Nature Reviews Neuroscience 10, 701-712 (2009)

Tracing the phylogeny of the molecular components of synapses, Ryan and Grant speculate on the core components of the last common ancestor of all synapses and posit that the diversification of upstream signalling components contributed to increased signalling complexity later in evolution.

• Abstract
• Full Text
• PDF (1,249 KB)
• Supplementary information

Considering the evolution of regeneration in the central nervous system

Elly M. Tanaka & Patrizia Ferretti

Nature Reviews Neuroscience 10, 713-723 (2009)

What allows some species, but not others, to regenerate their nervous system? In this Review, the authors compare CNS regeneration among vertebrates looking for clues that might explain how this ability might have emerged or been restricted through evolution.

• Abstract
• Full Text
• PDF (848 KB)

Evolution of the neocortex: a perspective from developmental biology

Pasko Rakic

Nature Reviews Neuroscience 10, 724-735 (2009)

Focusing on mammalian species, Pasko Rakic uses evo–devo studies to model how gene mutations may have affected neuron number and neuronal migration, which in turn may have contributed to the species-specific expansion and elaboration of the cerebral cortex.

• Abstract
• Full Text
• PDF (840 KB)

Chordate roots of the vertebrate nervous system: expanding the molecular toolkit

Linda Z. Holland

Nature Reviews Neuroscience 10, 736-746 (2009)

By comparing developmental gene expression and neuroanatomy of vertebrates and the basal chordate amphioxus, Linda Holland sheds light on the molecular changes that may have facilitated the evolution of the vertebrate brain.

• Abstract
• Full Text
• PDF (743 KB)

HT: Evolving Thoughts

Some time ago, I put together a list of websites for the journals I am most interested in. It occurred to me that this could be useful for others. (I am also planning to post some information on how to aggregate journal tables of contents, automatic index searches, and science news).

General

Evolution

Genome biology and evolution

Zoology

Education

It is always a nice feeling to have a paper published, especially when it is a first paper for a student. It is an even nicer feeling when that paper is featured on the journal cover (i.e., when you submit a cool picture that the editor likes). As it happens, two of our papers appeared on covers in the last month, joining two that I had before.

Ardila-Garcia and Gregory (2009).
Photo by Jay Cossey.

Smith and Gregory (2009).
Photo by Oliver Lucanus.

Hebert and Gregory (2005).
Image by T.R. Gregory.

Gregory and Shorthouse (2003).
Photo by David Shorthouse.

The online journal Genome Biology and Evolution is now publishing its initial set of articles, so be sure to have a look and watch for some good stuff in the future.

I notice that there’s a paper on mammalian genome sizes planned for the first issue. It looks interesting, though I note the following intriguing quotes:

“The evolutionary patterning of genome architecture by nonadaptive forces is supported by population-genetic theory, estimates of the relative power of the major forces of evolution, and comparative analyses of whole-genome sequences. Nevertheless, some biologists still adhere to the idea that even the most arcane aspects of genome evolution, including expansions of genome size by mobile-element proliferation, are direct products of natural selection (e.g., Gregory 2005; Kirschner and Gerhart 2005; Caporale 2006)”.

“our results challenge the notion that genome size reflects a finely tuned structural determinant of the adaptive phenotypes of organisms (Cavalier-Smith 1978; Hughes and Hughes 1995; Gregory 2005).”

Readers of this blog can probably answer the issue of whether I believe all aspects of genome expansion are adaptive.

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Update:
I have looked at the article in more detail, and it is indeed interesting. However, as is common with this kind of analysis, there are some questions. Here are the species they examined to claim that no reductions in genome sizes occurred in plants or invertebrates:

Plants — Arabidopsis thaliana (thale cress, genome size 125Mb, one of the smallest in plants), Populus trichocarpa (cottonwood, 500Mb), and Oryza sativa (rice, 420Mb). The average genome size for flowering plants is 6,400Mb based on more than 4,000 species, ranging from around 60Mb to 124,000Mb.

Invertebrates — Strongylocentrotus purporatus (sea urchin, 870Mb), Anopheles gambiae (mosquito, 280Mb), Drosophila melanogaster (vinegar fly, 175Mb), Caenorhabditis elegans (nematode, 100Mb), Ciona intestinalis (tunicate, 195Mb), and Daphnia pulex (water flea, 230Mb). I would not want to suggest a mean genome size for “invertebrates”, but I can say that even in mosquitoes they range at least 8-fold.

If people who work on genome size do not immediately accept the population size explanation for differences among taxa, it’s not because they don’t understand the argument. It’s because the data are based on a tiny and non-random subsample of genomes, and because predictions don’t seem to be upheld when we examine genome sizes. Being miscited doesn’t help.

I received notification today that the most recent article from my lab has been accepted by BioScience. I am feeling a bit sentimental about it because this marks my 50th peer-reviewed paper. It’s also something new for me, a study on grad student conceptions of evolution. I have now officially been all over the map — experimental, comparative, synthetic, reviews, methods, and educational. Thanks to all my colleagues and students who have been co-authors to date!