(Probably not) Precambrian Volvox

A new(ish) paper in National Science Review evaluates the evidence for various interpretations of Ediacaran microfossils from the Weng’an biota in South China (Xiao et al. 2014. The Weng’an biota and the Ediacaran radiation of multicellular eukaryotes. Natl. Sci. Rev., 1:498–520.). I recommend checking it out; it’s open access, and there’s a lot of interesting stuff in there that I’m not going to address.

These fossils are undoubtedly multicellular, probably eukaryotic, and extremely enigmatic. Their age (582-600 million years) means they could have important implications for the evolution of multicellularity, and their exceptional preservation in great numbers creates the potential for reconstructing their life cycles in great detail. Some of the Weng’an fossils have been interpreted as volvocine algae, an interpretation that I find highly unlikely.

Some of the Weng’an fossils are thought to represent red algae, and this would not be terribly surprising, since red algae have been around for at least 1.2 billion years. Others, for example the tubular fossils, are more problematic, with interpretations as diverse as cyanobacteria, eukaryotic algae, crinoids, and cnidarians.

Fig. 8 from Xiao et al. 2014

Figure 8 from Xiao et al. 2014: Schematic diagram showing diagnostic features of the five recognized species of tubular microfossils in the Weng’an biota.

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Evolution of eusociality

Last month, two papers on the evolution of eusociality were published in high-profile journals: one by Karen M. Kapheim and colleagues in Science, the other by Sandra M. Rehan and Amy L. Toth in Trends in Ecology & Evolution (TREE). Social and eusocial insects are an attractive system for studying major transitions, sharing some of the key features that make the volvocine algae so good for this purpose: multiple, independent origins of traits thought to be important to the transition and extant species with intermediate levels of sociality. These features make the social insects, like the volvocine algae, well-suited for comparative studies.
Figure 1 from Rehan & Toth: (A) Overview of phylogeny of aculeate Hymenoptera (with the nonhymenopteran but eusocial termites as an outgroup), highlighting independent origins of sociality (colored branches), groups with species ranging from solitary to primitively social (green), primitively social to advanced eusocial (orange), solitary to advanced eusocial (blue), and all species advanced eusocial (grey). (B) The full range of the solitary to eusocial spectrum (blue) and predictions of which genomic mechanisms are hypothesized to operate at different transitional stages of social evolution (broken arrows).

Figure 1 from Rehan & Toth: (A) Overview of phylogeny of aculeate Hymenoptera (with the nonhymenopteran but eusocial termites as an outgroup), highlighting independent origins of sociality (colored branches), groups with species ranging from solitary to primitively social (green), primitively social to advanced eusocial (orange), solitary to advanced eusocial (blue), and all species advanced eusocial (grey). (B) The full range of the solitary to eusocial spectrum (blue) and predictions of which genomic mechanisms are hypothesized to operate at different transitional stages of social evolution (broken arrows).

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An Ode to Unicellularity

Biosphere 2

Biosphere 2, the site of the First International Volvox Meeting in 2011.

This year’s Volvox meeting, as with the previous two, will feature an image/video/arts competition. Erik Hanschen, a graduate student in the Michod lab, has kindly granted me permission to post the winning entry in the poetry contest at the first Volvox meeting: a sonnet in honor of Chlamydomonas.

An Ode to Unicellularity – Erik Hanschen

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Actin evolution in the Volvocales

Kato-Minoura Figure 1

Fig. 1 from Kato-Minoura et al. 2015: Genomic structure of volvocine actin and NAP genes. For comparison, previously identified sequences are also shown. Filled boxes, putative coding exons; open boxes, putative 5′ and 3′ untranslated regions. Intervening sequences are shown by solid lines. Intron positions are indicated by codon and phase numbers with reference to the three alpha-actins of vertebrates (377 amino acids) (Weber and Kabsch 1994). The conserved intron positions are linked with dotted lines. ATG, translation start codon; TAA or TGA, stop codon.

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Evolution is evidence against evolution (?)

Intelligent Design blog Uncommon Descent thinks Betül Kacar’s microbial evolution experiments somehow support their agenda (“E coli hybrid copes with 700 mya engineered gene“). The post quotes extensively from a recent article in Quanta Magazine, which in turn reports on Dr. Kacar’s presentation at AbSciCon (which I briefly covered here).

I’m really not sure what the logic is here. The blog post quotes extensively from the Quanta article (really the post just is quotes from the article, with two short comments added), including sections that make clear that Dr. Kacar observed evolution in action in these experiments:

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New Scientist article on experimental evolution of multicellularity

On the second day of AbSciCon, members of the Ratcliff lab and I met with a reporter, Bob Holmes, from New Scientist. We had all given our talks on the first day of the meeting. The resulting article came out yesterday.

I’ve dealt with New Scientist before, and I find them among the better science news outlets. They make a real effort to understand the science behind their stories, a refreshing change from sites that slap misleading headlines onto barely reworded university press releases. Aaaand I’m going to wrap this up before it turns into a rant.

Peter Conlin, Jennifer Pentz, Bob Holmes, and Will Ratcliff

Peter Conlin, Jennifer Pentz, Bob Holmes, and Will Ratcliff enjoying some sushi in a Chicago park.

Volvox 2015 poster deadline extended

The deadline for poster abstracts for the Third International Volvox Conference has been extended to July 25th (the website says June 25th, but the organizers assure me that it is July). Registration is open until July 15th, so there is still time if you’d like to join us in Cambridge!

The preliminary program is here.

AbSciCon day 4: Mars, life, and Mars life

marvinmartian

I stepped out of my comfort zone a bit this morning and went to a session on Mars (okay, there weren’t any biology talks). This is far outside of my expertise, so if I say something outrageously wrong, feel free to set me straight in the comments (actually, you can always do that). I’ve never really given up on the idea of life on Mars. I remember the Viking missions and the ambiguous* results of their biological experiments, and I’m still surprised that none of the subsequent robotic missions have followed them up. I think there are better candidates further out in the Solar System, but Mars is a lot easier to get to.

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