First lab-meeting for autumn 2015: ESEB summary and group selection

Posted by Erik Svensson 

It is time to kick off the EXEB labmeetings for this coming semester, and what would be better than do it this coming Tuesday (August 18)? Especially when several of us have been to the ESEB Congress and we can have a nice brief discussion about our impressions of where the field of evolutionary biology might be going.

In the same general spirit, I suggest we discuss a paper in Nature from last year on the prospects for group selection in a socially polymorphic spider system. This work has been performed by Jonathan Pruitt and Charles Goodnight, the latter being a long-term champion of group selection. 

As group selection has historically been a very controversial topic in evolutionary biology, I hope we will have a stimulating discussion about this paper. See also the "News & Views"-article in the same issue of Nature, which can be found here. 

Note different meeting time!

When: Tuesday August 18 at 10.00

Where: "Argumentet", 2nd floor, Ecology Building 

Site-specific group selection drives locally adapted group compositions

Pruitt, JN (Pruitt, Jonathan N.)^{[ 1 ]} ; Goodnight, CJ (Goodnight, Charles J.)^{[ 2 ]}

NATURE 514: 359+ (2014)

 

Abstract

Group selection may be defined as selection caused by the differential extinction or proliferation of groups(1,2). The socially polymorphic spider Anelosimus studiosus exhibits a behavioural polymorphism in which females exhibit either a 'docile' or 'aggressive' behavioural phenotype(3,4). Natural colonies are composed of a mixture of related docile and aggressive individuals, and populations differ in colonies' characteristic docile: aggressive ratios(5,6). Using experimentally constructed colonies of known composition, here we demonstrate that population-level divergence in docile: aggressive ratios is driven by site-specific selection at the group level-certain ratios yield high survivorship at some sites but not others. Our data also indicate that colonies responded to the risk of extinction: perturbed colonies tended to adjust their composition over two generations to match the ratio characteristic of their native site, thus promoting their long-term survival in their natal habitat. However, colonies of displaced individuals continued to shift their compositions towards mixtures that would have promoted their survival had they remained at their home sites, regardless of their contemporary environment. Thus, the regulatory mechanisms that colonies use to adjust their composition appear to be locally adapted. Our data provide experimental evidence of group selection driving collective traits in wild populations.

Interesting interview with Richard Dawkins on the political implications of "The Selfish Gene" and the "God Delusion"

Here is an interesting interview with popular science writer and evolutionary biologist Richard Dawkins, famous for his book "The Selfish Gene" from 1976, which revolutionized the general public's view about the evolutionary process, in particular the role of gene selection, as opposed to naive group selection.I found this video as I was looking for material for an undergraduate course that I am teaching entitled "Human Biology & Evolution". 

It is worth watching, particularly since Richard Dawkins clearly explains what selfish genes are, and what they are not. In particular the crucial notion that selfish genes do not imply that individuals must be selfish, but rather the converse: selfish genes might often results in altruistic individuals. This crucial point has apparently been missed by the many right-winged libertarians and free-market ideologists, who wrote many letters to Richard Dawkins after the publication of his book to express their admiration and support. In this video, Richard Dawkins is very clear about his own view about such political idéas, which are strong in the right-wing segment of the US population: he does not support them at all.

As Dawkins states in the video above: "I have voted to the left in Britain in  my whole life". Selfish genes do thus by no means justify unregulated marked capitalism, although many wishful thinkers on the right side of the political spectrum have tried to exploit the title of his book for their own ideological purposes. As a matter of fact, Richard Dawkins have even stated that an alternative title of his book could very well have been "The Altruistic Organism".

It is important to be fair to Richard Dawkins, as there is actually some serious criticism that can be directed to both his idéa about the overall importance of gene selection, and his rather dogmatic dismissal of higher-level selection, such as at the level of groups, populations or species. Here, I think he is wrong, and there are many leading evolutionary biologists and population geneticists who would agree that group selection can indeed work in many ecological situations, including David Sloan Wilson and Michael J. Wade. 

There are many conceptual problems with Richard Dawkins strict separation between "replicators" (genes) and "vehicles" (organisms) that forms the basis of his whole argumentation that gene selection will always outpower higher-level selection, and some of these problems and logical pitfalls are discussed here.

Personally, I do als think that Dawkin's stance on religion is both unproductive and not very sophisticated, in terms of the nature of the criticism, as expressed in his too hyped book "The God Delusion". Apparently, Dawkinshas also recently stated that he partly regrets that he wrote this book (or should I say pamphlet?). The God that he describes in that book is more of a charicature of religion as he perceives it, than actually depicting the true beliefs of most religous people.

My own personal view, as an atheist, is again much closer to my fellow atheist David Sloan Wilson's view that religion has evolved for some reason, and hence can be treated as a problem that one can study in the light of evolutionary theory. That view strikes me as being a more intellectually fruitful and interesting approach towards understanding religion than just pointing fingers and treating it as a disease, which Dawkins tends to do.

Reinventing species selection with molecular phylogenies

When I was a PhD-student in Sweden in the nineties, one of the most ugly words you could say was "group selection", and the so-called "selfish-gene paradigm" of Richard Dawkins was taken as almost a religious truth. These were the days when behavioural ecology ruled much of of the scentific activities in biology in Scandinavia and Britain. Lower-level selection of selfish genes was assumed to be either the only or at least the major evolutionary force that would explain all adaptation and biological diversity. Higher-level selection, on goups, demes, populations or species, was either deemed impossible or dismissed as unimportant.

This remarkable dogmatic reductionism in Scandinavian behavioural ecology seems, in the aftermath, as both dogmatic and not very well supported by either theory or empirical evidence. Even the great population geneticist R. A. Fisher did actually believe in group selection, and for him it was mainly an empirical issue how strong it was, compared to lower-level selection of individuals and genes.

However, one thing is certain: scientific paradigms change, and clearly group-selection (or rather multi-level selection) is on the rise again. This week's lab-meeting (Wednesday May 4), we will discuss a relatively recent TREE-paper on how molecular phylogenies might be used to study the process of species selection in a statistically rigorous and empirical way. Increasing evidence suggest that macroevolutionary trends, such as increases or decreases in diversity, speciation and extinction can simply not be extrapolated from lower-level selection processes, challenging the selfish-gene paradigm. Below, you will find an abstract and a link to the paper.

Time as usual: 13.30 on Wednesday (May 4) afternoon. Place: Probably "Argumentet".

Rabovsky, M. L. & MacCune, A. R.


Trends Ecol. Evol. 25: 68-74


Abstract: Species selection as a potential driver of macroevolutionary trends has been relegated to a largely philosophical position in modern evolutionary biology. Fundamentally, species selection is the outcome of heritable differences in speciation and extinction rates among lineages when the causal basis of those rate differences can be decoupled from genotypic (within-population) fitnesses. Here, we discuss the rapidly growing literature on variation in species diversification rates as inferred from molecular phylogenies. We argue that modern studies of diversification rates demonstrate that speciesselection is an important process influencing both the evolution of biological diversity and distributions of phenotypic traits within higher taxa. Explicit recognition of multi-level selection refocuses our attention on the mechanisms by which traits influence speciation and extinction rates.