Support the Molecular Ecologist with all-new evolution and ecology-themed merch!

We don’t often make a big deal about it, but The Molecular Ecologist has long offered merchandise for purchase to help cover our operating expenses, which are chiefly web hosting and small stipends for contributors. The platform we’d used for that was less than ideal, though — and we’ve finally set up shop on Redbubble, which offers a wider range of products at better pricing.

Molecular Ecologist-supporting shirts, images by Redbubble

You can now purchase our “heliboot” logo on a wide array of apparel, mugs, and other accessories, get a poster print of the Molecular Ecology Flowchart, or pick a side in the eternal struggle between genetic drift and natural selection. Prices start at less than $20 for a tee (before shipping and sales tax), and all proceeds benefit the blog — so check out the whole range.

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Population genetic simulation … in Lego

Julien Yann Dutheil, of the Institut des Sciences de l’Évolution de Montpellier, has a long track record of work in population genetics and genomics methods, particularly in the C++ programming language. He recently posted a video to YouTube, though, which suggests he’s trying out a new simulation platform: Lego bricks.

The video shows a robot built using the Lego Mindstorms system, which connects a programmable computing unit to motors and sensors built into Lego bricks. The robot moves along a rack of colored balls representing a population of haploid, clonally reproducing individuals bearing one of two possible color genotypes. The robot randomly selects individuals to remove, simulating their deaths, and draws colored balls from two hoppers to replace dead individuals with ones “cloned” from one of the balls neighboring the empty space in the population. This is a physical model of Patrick Moran’s 1958 description of evolution by drift in a fixed, finite population, and while it’s not very computationally efficient, Dutheil speeds up the video to show how the random birth-death process eventually leads to the loss of diversity, and that this loss happens more quickly when the population is smaller. I’ll definitely be keeping this one in my pocket for my fall evolutionary biology class.

Hat tip to Will Shoemaker, who posted the video to Twitter.

Reference

Moran P. 1958. Random processes in genetics. Mathematical Proceedings of the Cambridge Philosophical Society, 54(1), 60-71. doi: 10.1017/S0305004100033193

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Nominations open for the Harry Smith Prize in Molecular Ecology

Posted on behalf of the Harry Smith Prize Selection Committee.

The editorial board of the journal Molecular Ecology has established a new prize to recognize the best paper published in Molecular Ecology in the previous year by graduate students or early career scholars with no more than five years of postdoctoral or fellowship experience. The prize comes with a cash award of US$1000 and an announcement in the journal. The winner will also be asked to join a junior editorial board for the journal to offer advice on changing research needs and potentially serve as a guest editor. As with the Molecular Ecology Prize, the winner of this annual prize will be selected by an independent award committee.

The prize is named after Professor Harry Smith FRS, who founded the journal and served as both its Chief and Managing Editor during the journal’s critical early years. He continued as the journal’s Managing Editor until 2008, and he went out of his way to encourage early career scholars. In addition to his editorial work, Harry was one of the world’s foremost researchers in photomorphogenesis, where he determined how plants respond to shading, leading to concepts such as “neighbour detection” and “shade avoidance”; which are fundamental to understanding plant responses to crowding and competition. More broadly his research provided an early example of how molecular data could inform ecology, and in 2008 he was awarded the Molecular Ecology Prize that recognized both his scientific and editorial contributions to the field.

Please send your nomination with a short supporting statement (no more than 250 words; longer submissions will not be accepted) directly to Rose Andrew (randre20@une.edu.au) by Tuesday 31 July 2018.

With thanks on behalf of the Harry Smith Prize Selection Committee

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500 Queer Scientists

When I heard the first time about 500 Queer Scientists (@QueerSci, #QueerSTEM) I thought for myself ‘Why do we need to support STEM scientists based on their sexual orientation?’. This is how ignorant and clumsy I am. We got sensitized against antisemitism at school. We were not taught much about minorities. We joked about them. We bullied. Nobody stopped us. I had to leave my home country to become a minority. I see many Europeans experiencing the same. I know about discrimination against women in leader roles and against parents in academia because I have experienced it, but I did not know about discrimination against members of the LGBTQ community. I assume the majority of us is as ignorant as I am. This is why I am writing this post – to inform you.

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Field notes from city streets

White clover in the lawn of North Hollywood Park (jby)

I spent this morning in Los Angeles city parks, pulling up clover. This attracted less attention than you might expect. Angelenos are, as a group, not inclined to bother people who aren’t doing anyone else any obvious harm, and honestly the range of activity in a typical LA park includes behaviors that are objectively odder (group yoga) and more damaging to the turf (pickup soccer games). The single fellow who shouted good morning to me followed up only with “happy hunting!” He may have thought I was looking for a lucky charm.

In fact I wasn’t counting leaflets, but trying to make sure I got to twenty more-or-less distinct patches of Trifolium repens, white clover. White clover is native to Europe, but it loves lawns, and it’s been introduced all over the world. Recently Ken Thompson, Marie Renaudin, and Marc Johnson reported something interesting about white clover populations in Toronto, New York, and Boston: close to the centers of those cities, clover samples were less likely to respond to injury by producing toxic hydrogen cyanide, HCN. HCN production has a simple genetic basis, so parallel loss of the phenotype is likely an evolved response. The HCN reaction defends against herbivores — but it’s also triggered by freezing damage, so HCN-producing plants in cold climates risk poisoning themselves. Thompson et al. hypothesized that winter road plowing in built-up urban areas exposes roadside clover to sharper cold than it would cope with in the countryside, insulated under snow cover. And it turns out that in a fourth city, Montreal, where there were below-freezing days with no snow cover at the sampling sites, clover populations didn’t show the pattern of reduced HCN production.

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What is DAS? A new tool to recover genomes from metagenomes

There are a lot of data out there, and if you haven’t already noticed the ‘omics train has steadily stayed its path through the fruitful (but challenging) world of metagenomics. Metagenomics offers the chance to unravel complex microbial communities without the need for individual cell sequencing or the isolation and cultivation of each and every member of the uncultured majority.

If you think of deciphering metagenomes as trying to complete wildly complex puzzles that have all been jumbled together into one box, (as Sieber and colleagues suggested recently) it makes sense that it would be hard to sort them all out. This would be challenging because you (a) don’t know what the final pictures should be (b) aren’t sure how many full puzzles are in the box, and (b) are pretty dang certain there are pieces missing. To make pulling out pieces of interest (sequences) and completing one entire puzzle (genome) more feasible, bioinformatic tools have been developed. These tools put contigs from a metagenome into bins, which essentially means putting all the contigs that seem to be from one thing together, making it possible to eventually assemble (completely…or mostly…or partly) entire genomes.

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La vie en rouge … l’algue rouge

Best laid plans of a #NewPI … what happens to them?

Well, they often get triaged for more urgent things that were triaged earlier for more urgent things that were also triaged even earlier for more urgent things … and well you get the drift.

My lab and I have embarked on a summer of field work (not unlike the summer of 2015 that was highlighted on TME).

First leg of Summer 2018 was to France, for field work bookended by two evolutionary conferences. I will follow up this post with several posts on the work presented at the Conférence Jacques Monod Sex Uncovered: the evolutionary biology of reproductive systems held at the Station Biologique de Roscoff and then Marine Evolution 2018 in Strömstad, Sweden.

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Is the neutral theory dead?

Motoo Kimura. Source: WikimediaCommons

You might have noticed how the world of genetics was shaking as the giants of theoretical population genetics started discussing some of the most fundamental questions in the arena of Twittersphere. This happened after the publication of Andrew Kern and Matthew Hahn’s paper titled “The Neutral Theory in Light of Natural Selection“.

For the sake of all the early career scientists who might be under the false impression that they don’t understand anything, while all the fancy last authors have it figured out, I have decided that at least some of the Twitter gems shall be recorded.

I’m not going to walk into the lion’s den and try to argue for or against neutral theory or even comment on the new paper. I’m merely providing a record of what’s been said by others, and by the end of this post you might be more confused about neutral theory than ever (#sorrynotsorry).

I think this could be the best summary of the whole thing:

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Nominations Open for 2018 Molecular Ecology Prize

We are soliciting nominations for the annual Molecular Ecology Prize. The field of molecular ecology is young and inherently interdisciplinary. As a consequence, research in molecular ecology is not currently represented by a single scientific society, so there is no body that actively promotes the discipline or recognizes its pioneers. The editorial board of the journal Molecular Ecology therefore created the Molecular Ecology Prize in order to fill this void, and recognize significant contributions to this area of research. The prize selection committee is independent of the journal and its editorial board. The prize will go to an outstanding scientist who has made significant contributions to Molecular Ecology. These contributions would mostly be scientific, but the door is open for other kinds of contributions that were crucial to the development of the field. The previous winners are: Godfrey Hewitt, John Avise, Pierre Taberlet, Harry Smith, Terry Burke, Josephine Pemberton, Deborah Charlesworth, Craig Moritz, Laurent Excoffier, Johanna Schmitt, Fred Allendorf, Louis Bernatchez, and Nancy Moran. Please send your nomination with a short supporting statement (no more than 250 words; longer submissions will not be accepted) directly to Deborah Charlseworth (Deborah.Charlesworth@ed.ac.uk) by Friday 29 June 2018. With thanks on behalf of the Molecular Ecology Prize Selection Committee
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Chromosomal inversions and the maintenance of species barriers

Chromosomal inversions have long fascinated evolutionary biologists for their role in adaptation and speciation. These structural variants are abundant in natural populations and can have diverse evolutionary consequences. They can cause reproductive isolation through hybrid sterility or protect sets of co-adapted alleles from recombination, while inversions in genes or promoters can disrupt gene expression.

A recent review paper by Maren Wellenreuther and Louis Bernatchez published in TREE comprehensively summarises what is known about the biology of inversions. Wellenreuther & Bernatchez (2018) include a list of about two dozen species where inversions have been characterised in the wild, and come to some interesting conclusions about inversion size (important inversions are often large), age (they’re often old and pre-date speciation), and the evolutionary processes that act on them (balancing selection may be important).

 

Representative examples of taxa with well-characterised chromosomal inversions, and their evolutionary consequences. From Wellenreuther & Bernatchez (2018).

This paper is a clear reminder of the importance of inversions  in evolution. Reading the review, however, made me wonder just how common inversions are in speciation, adaptation, and the maintenance of species differences, or whether their perceived importance is biased by their ease of detection. In many genetic analyses inversions stand out like a sore thumb. They can be spotted in genome-wide alignments, or may be seen as large regions of divergence in outlier scans. Inversions are also obvious in genetic maps where you see clusters of markers with reduced recombination. Making a causal link between inversions and adaption is harder, but there are many cases where quantitative trait loci (QTL) co-occur with inversions and implicate their role in adaptation (e.g. Lowry & Willis, 2010).

This question about the ubiquity of inversions in speciation studies is partly addressed in a recent paper by Davey et al. published in Evolution Letters. Davey et al. (2017) investigated whether species barriers between closely-related hybridizing taxa are always maintained by inversions, and answered this with a resounding “no”. While this shouldn’t come as much of a surprise, it is useful case study that brings balance to the recent inversion-heavy evolutionary literature.

In their study, Davey et al. (2017) use genetic mapping, genome assemblies, and long-read sequencing to look for inversions that differ between two sympatric species of the widely studied butterfly genus Heliconius. They showed hybridising H. cydno and H. melpomene completely lack any large inversions (over 50Kb in length) that are likely to be involved in maintaining co-adapted gene complexes. Their use of high quality genome assemblies and long-read sequence data make it unlikely that any large inversions would be overlooked. The authors conclude that: “This suggests that hybridization is rare enough and mate preference is strong enough that inversions are not necessary to maintain the species barrier”.

So, how often are inversions involved in speciation? Clearly we need more studies investigating the genomic basis of species differences in order to answer this question. But we should also remember that the prevalence of studies that implicate inversions in adaptation and speciation are likely (at least in part) to be due to the ease of detecting inversions, and the methodological constraints in finding individual loci underlying divergence. In Heliconius butterflies, and no doubt many other organisms, divergence has occurred in the face of homogenizing gene flow despite lacking major inversions. Future studies investigating the genetics of speciation and adaptation should broaden the search to other genic modifiers of recombination rate (reviewed in Ortiz-Barrientos et al. 2016), to more fully understand how the recombination landscape influences speciation, while also continuing the search for elusive speciation genes.

References

Davey JW, Barker SL, Rastas PM, et al. (2017) No evidence for maintenance of a sympatric Heliconius species barrier by chromosomal inversions. Evolution Letters 1, 138-154.

Lowry DB, Willis JH (2010) A widespread chromosomal inversion polymorphism contributes to a major life-history transition, local adaptation, and reproductive isolation. PLoS Biol 8, e1000500.

Ortiz-Barrientos D, Engelstädter J, Rieseberg LH (2016) Recombination rate evolution and the origin of species. Trends in Ecology & Evolution 31, 226-236.

Wellenreuther M, Bernatchez L (2018) Eco-evolutionary genomics of chromosomal inversions. Trends in Ecology & Evolution 33, 427-440.

 

 

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