I’m going to Cyprus!

Phycomorph_logo3

I’m heading to Limassol, Cyprus at the end of September to talk about Volvox morphology and evolution. Phycomorph is a European group studying seaweed development and reproduction, with a large focus on cultivation. I have an extra day after the meeting, so hopefully I’ll get to explore a bit.

The organizers were initially worried about the high cost of transportation from Missoula, but I had good news for them: I won’t be flying from Missoula but from Atlanta, which is (seriously) half as expensive. The timing of the flights is a bit unfortunate, though, so I’ll have a couple of very long layovers in Heathrow (17 and 20 hours).

 

The preliminary list of confirmed speakers is:

Phycomorph speakers

 

Problems with major transitions: Maureen O’Malley & Russell Powell respond

The Great Oxidation Event by Adelle Schemm.

The Great Oxidation Event by Adelle Schemm.

In a recent series of posts, I reviewed Maureen O’Malley and Russell Powell’s paper in Biology and Philosophy, “Major Problems in Evolutionary Transitions: How a Metabolic Perspective Can Enrich our Understanding of Macroevolution.” Although they made several good points, I thought that some of their criticisms were off the mark and that their proposed solution to the real and perceived problems with the major transitions framework was unsatisfying.

Drs. O’Malley and Powell are both heavy hitters in the philosophy of biology, and as I usually do when I dig deeply into someone else’s paper, I invited them to respond to my criticisms. They kindly provided a thoughtful rebuttal and permitted me to post it here. I’ll have more to say later, but for now I’ll just say that they make some good points and (most importantly) fairly represent my arguments. As usual for guest posts, I have made no edits to the content of their response, only formatted and added links:

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The evolution of undifferentiated multicellularity: the Gonium genome

Blogging took a backseat to the wedding of two dear friends two weekends ago and to morel hunting last weekend, so I’m only now getting around to a post that should have been written weeks ago (I promised on April 22 that it would be out the following week). Last month, Erik Hanschen and colleagues published the Gonium pectorale genome, filling in some crucial bits of the transition to multicellular life in the volvocine algae. This was a big project, taking several years and involving over 20 authors from over a dozen institutions. The final paper is open access in Nature Communications.

I did post an effort to explain some aspects of the paper to the cdesign proponentsists at Evolution News and Views, who, by their own admission, failed to understand it (“After reading this paper, we’re none the wiser.”). I also complained of the science media’s tendency to refer to all algae as ‘pond scum.’ The lead author of the genome paper kindly followed up with a guest post addressing some of ENV‘s other misunderstandings, such as the purpose of model organisms in biology and the difference between ‘assertion’ and ‘evidence’. But now it’s time to dig into what the genome paper actually says.

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Please stop calling them pond scum

Gonium pectorale. Credit: Kansas State University.

Gonium pectorale. Credit: Kansas State University.

Yes, they live in ponds; no they don’t form any kind of scum. The press release from Kansas State on the Gonium genome paper, which is reprinted here, here, and here, is titled “Pond scum and the gene pool: One critical gene in green algae responsible for multicellular evolution, understanding of cancer origin.” Gonium forms planktonic colonies of (usually) 8, 16, or 32 cells that swim under their own power and exhibit phototaxis (they’ll swim toward a light source). They are not pond scum. ‘Algae’ and ‘pond scum’ are not synonyms, dig? Leaving aside the distinction between algae and cyanobacteria, calling Gonium pond scum is like saying pineapples are lemons (because both are fruits).

Also…cancer origin, really? You went there? The word ‘cancer’ does not appear in the paper except in the funding acknowledgements (Bradley Olson is partly funded by the KSU Johnson Cancer Center).

Heads I win; tails you lose: Evolution News & Views on Gonium, part 2: Model systems and gene duplication

Figure 2 from Hanschen et al. 2016. (a) Predicted number of genes in each phylostratum (PS1–PS9) for Chlamydomonas, Gonium and Volvox. (b) Heatmap of transcription factor abundance for all green algae. Significant over- (+) and under-representation (−) in colonial/multicellular lineages (Gonium and Volvox) is denoted (G test of independence, α=0.05). Rows are clustered (left), an accepted phylogeny is depicted (top). (c) Phylogenetic analysis of gene family evolution. Bars to the left and right of the vertical axis denote the lost and gained gene families respectively, relative to its parental node. (d) Venn diagram of the species distribution of Pfam A domains unique to the volvocine algae.

Figure 2 from Hanschen et al. 2016. (a) Predicted number of genes in each phylostratum (PS1–PS9) for Chlamydomonas, Gonium and Volvox. (b) Heatmap of transcription factor abundance for all green algae. Significant over- (+) and under-representation (−) in colonial/multicellular lineages (Gonium and Volvox) is denoted (G test of independence, α=0.05). Rows are clustered (left), an accepted phylogeny is depicted (top). (c) Phylogenetic analysis of gene family evolution. Bars to the left and right of the vertical axis denote the lost and gained gene families respectively, relative to its parental node. (d) Venn diagram of the species distribution of Pfam A domains unique to the volvocine algae.

Erik Hanschen, the lead author on the Gonium genome paper, is also an old friend of mine from when we were both in Michael Doebeli’s lab at the University of British Columbia. He kindly agreed to write a guest post responding to Evolution News and Views‘ misunderstandings of his paper. Everything below the fold was written by Erik:

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Heads I win; tails you lose: Evolution News & Views on Gonium, part 1

Figure 6 from Hanschen et al. 2016. Multicellularity hinges on the evolution of cell cycle regulation in a multicellular context with subsequent evolution of cellular differentiation (here, cell size-based) and increased body size.

Figure 6 from Hanschen et al. 2016. Multicellularity hinges on the evolution of cell cycle regulation in a multicellular context with subsequent evolution of cellular differentiation (here, cell size-based) and increased body size.

Remember how I said they’re prolific? Before I’ve even had a chance to write up my thoughts on the Gonium genome paper, Evolution News & Views has already published theirs. The story has also been picked up by the Washington Post, New Historian, GenNews, and ScienceDaily (that last one looks like just a reprint of the press release from University of the Witwatersrand). By the way, the genome paper is open access, so you don’t need a subscription to see it for yourself.

We already know that cdesign proponentsists are not fans of research into the evolution of multicellularity, and that they have trouble understanding it. In an unsigned article on the Gonium genome at ENV, they admit that

After reading this paper, we’re none the wiser.

That’s too bad. I’m here to help.

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Gonium genome published

Figure 1 from Hanschen et al. 2016. (a) Evolution of cell cycle control (C), expanded ECM (E) and somatic cells (S) are denoted. (b) Micrographs of Chlamydomonas (green; scale bar, 10 μm), Gonium (blue; scale bar, 10 μm) and Volvox (black; scale bar, 25 μm) show morphological differences.

Figure 1 from Hanschen et al. 2016. (a) Evolution of cell cycle control (C), expanded ECM (E) and somatic cells (S) are denoted. (b) Micrographs of Chlamydomonas (green; scale bar, 10 μm), Gonium (blue; scale bar, 10 μm) and Volvox (black; scale bar, 25 μm) show morphological differences.

I haven’t read it yet and won’t have time today, but the Gonium pectorale genome paper just came out in Nature Communications! Erik Hanschen is the lead author, and the article is open access. I previously reported on Erik’s talk at Volvox 2015:

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Time for a revision? Maureen O’Malley and Russell Powell on Major Transitions, part 1

The so-called ‘Major Transitions’ framework is an attempt to explain the hierarchical structure of life on Earth: genes within chromosomes, chromosomes within cells, cells within cells (eukaryotic cells), individuals within sexual partnerships, cells within multicellular organisms, and organisms within societies. The best-known attempt to unify the origins of these relationships is a book by John Maynard Smith* and Eörs Szathmáry, The Major Transitions in Evolution.

MajorTransitionsCover

First published in 1995, the book focused on the origins of these hierarchical levels, connecting them with the unifying theme that

…entities that were capable of independent replication before the transition can replicate only as part of a larger whole after it.

For example, after a transition from unicellular to multicellular organisms (there were several), cellular reproduction either contributes to the growth of the organism or to production of new multicellular organisms.

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Pleodorina starrii

32- and 64-celled colonies of Pleodorina starrii.

32- and 64-celled colonies of Pleodorina starrii. Not to scale. Creative Commons License
Pleodorina starrii by Matthew Herron is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.

I spent a year in graduate school trying to cross male and female strains of the volvocine green alga Pleodorina californica. A year. I did some other stuff in that time, but I spent an awful lot of it trying to convince these algae to get busy. I threw everything I could think of at them: four different mating media, different temperatures, different lighting conditions…nothing worked. I never recovered a single viable zygote. I needed to cross them to generate some genetic variation for an ambitious artificial selection study, my ‘official’ dissertation project. Eventually, my advisor suggested I ask Hisayoshi Nozaki for advice.

There is little doubt that Dr. Nozaki is the world’s leading expert on volvocine biodiversity, having described about half of the known species (see for example New Volvox Species, Volvox ovalis, and African Volvox in Montana). He responded that the strains of Pleodorina californica I had been failing to breed had been collected many years ago and had probably lost the ability to reproduce sexually (a problem I mentioned in Why don’t we revise volvocine taxonomy?). I had been spinning my wheels, never realizing that I had no hope of success. I should have contacted Dr. Nozaki about eleven months earlier.

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