Friday, April 3, 2009

Thoughts from a sexual selection workshop and presentation of an article idea.

As Erik mentioned earlier, I and Josefin met Janne Kotiaho during his visit here for a short discussion on biases in sexual selection/sexual conflict research. We actually met Janne already at the workshop on gender biases in sexual selection research in Uppsala last October, which some of you may remember that we, and Åsa Lankinen, participated in. The workshop in Uppsala was organised by Malin Ah-King and Ingrid Ahnesjö, who are both evolutionary ecologists, but also have an interest in gender issues. Malin Ah-King has done a post doc at GenNa, which is a centre at Uppsala University where researchers from different fields study what kind of “knowledge about gender and gendered knowledge are produced in the intersection between the natural and cultural sciences”. Also Ingrid Ahnesjö has been involved in GenNa, at least for a shorter period. Invited speaker at the one day workshop was Patricia Gowaty from UCLA who is a feminist evolutionary ecologist. During the workshop she gave two talks on the history of sexual selection and on a neutral sexual selection model she and Steve Hubbell have been (and still are) working on (see Gowaty and Hubbell 2005). The rest of the day was devoted to group discussions.

Participants came from mainly Sweden and Finland but also Switzerland, working with sexual selection and sexual conflict in animals (either with conventional sex roles or with reversed sex roles) and in hermaphrodites (animals and plants). Although the cause for joining the meeting, and the idea of what gender bias in research actually is, differed between participants (which, to be honest, made the discussions sometimes a bit vague) some main problems were outlined. These mainly concerned the sex roles we assign our study objects. E.g. why conventional (active male/passive female) sex roles are applied in sexual selection research and the impact this has on how we perform science, if we have to use conventional sex roles, how sexual selection theory should be applied on hermaphrodites including plants, and how we can overcome our possible preconceptions of how males and females “should” behave.

Our, and Janne’s, impressions from the workshop was that it was indeed interesting and inspiring and especially Janne had received a new way of thinking. What in particular opened Janne’s eyes was how and why we nominate systems that do not behave as “normal” as sex role reversed – because what is actually the “normal” state in nature? We thought that Janne would continue on this topic for his Thursday seminar during his visit to Lund, but instead he gave a very interesting talk on the history of sexual selection, publication biases and how researchers strive towards fitting in the “format” which at the moment leads to publications. He exemplified this with his own critical studies on the lek paradox (paradoxes can’t exist!).

With Janne, besides reflecting on the workshop, we discussed an idea of an article that we are working on. Now we’d also like to present our thoughts here to get your opinions, if any, and receive some (critical) feedback! Emerging from the Uppsala workshop, but also from the recent criticism on sexual selection theory, (see e.g. Clutton-Brock 2007, Kokko and Jennions 2008), we would like to write a comment or a discussion article on potential biases in sexual conflict research. We’d like to ask the question whether some parts in a conflict dynamics may be left out by us researchers (compare e.g. male mate choice) due to our potential preconceptive view of how the sexes should act. For example, in sexual conflict theory both sexes are striving for their own optimum when it comes to mating and reproduction, and if this is made at a cost for the opposite sex there will be a conflict. However, our impression is that it is mainly a female cost that is being searched for in sexual conflict research and that the terminology used, although stemming from a neutral theory, implies that males make the offensive act and females barely defend themselves, without any impact on the male. But if the males are not affected why should they continue an arms-race?

Thus, by starting off with the recent progress and criticism in sexual selection research, we want to investigate and discuss three main issues in sexual conflict research. First, we will investigate what terminology is used in the most cited articles in “sexual conflict” and “sexually antagonistic coevolution”. By doing that we will know which terms have the widest impact in the field. Second, we will discuss how semantics may influence our perception and how it thus may form our thoughts and ideas, and third, we survey all theoretical models made on sexual conflict to see what parameters are incorporated – and thus are given the potential to affect the result; if male cost is never incorporated it will never be of significance and may furthermore not stimulate to empirical research.

We are just at the starting point, currently surveying the litterature, but we’d love to hear your thoughts on this project. We are not saying that our impression is correct (and we don’t even know what we will find yet!), but we’d like to open up for discussions or at least implant some thoughts on this topic. And, as we are speaking of biases, yes, we may be biased as well! J By being interested in gender issues in the human society we may be more prone to think of these topics also in evolutionary science, however, our aim is not a feminist inflammatory speech and hope that it will not be considered as such. We are not aiming for equality in the animal/plant world – it doesn’t matter if conventional sex roles actually are the truth and that all female individuals are coy, that is not the point. Instead we think that by considering these questions and potential preconceptions one may discover interesting evolutionary aspects that otherwise may be overlooked.

Have a nice weekend and enjoy the sun!


  1. These are some very interesting and important issues that would probably require a lab-meeting to discuss. I have a few reflections though:

    1. The possibility of male costs of mating should definitely be discussed more, and not as now focus on only female costs. For instance, males might actually have HIGHER costs of mating, e. g. if they are more conspicuous to predators. I also vaguely remember an antelope study in Current Biology where they discussed male costs and female harassment that could be of interest. In one of the latest issues of "Evolution" (I think), there was a comparative study on spider genital morphology which indicated that males might also have costs of mating due to "lock-and-key"-phenomena of genitalia.

    2. Another issue is whether sexually antagonistic selection actually leads to co-evolutionary arms races always? Frankly, the evidence is not that strong and mainly comes from Göran Arnqvist's comparative studies on water striders and W. R. Rice's experimental evolution assays of Drosophila in the laboratory. But apart from these classical cases, how common IS it actually with these open-ended co-evolutionary arms races? Frankly, I am getting more and more sceptical, and I feel that other possibilities (stable equilibria, female polymorphisms etc) should be considered more seriously. Arms races have been "sexy" but that does not mean that they are true (always)! It might also be quite common in nature that female BENEFIT from mating with males (e. g. nuptial gifts).

    3. Another interesting possibility, that I have discussed with Lars Råberg in a recent review (under consideration in Ecology Letters) is that females might instead evolve fitness tolerance to male mating harassment, rather than resist. Thus, females might instead of resisting evove counteradaptations to minimize the fitness impact of matings ("buffer"). The evolution of tolerance, as opposed to resistance, has been discussed A LOT by plant biologists (e. g. Rausher 2001, Nature). If there is genetic variation in tolerance, and not only resistance, the evolution of tolerance WILL WEAKEN SELECTION PRESSURES TO INCREASE RESISTANCE. This, in turn, might "halt" the co-evolutionary arms race, which is usually built on the assumption that the "victim" (females in this case) mainly defend themselves by resistance, not tolerance. I can give you copy of this paper when you get back, if you are interested.

  2. This was indeed an interesting post, which I think we discussed briefly in a wednesday meeting. Although I agree that it is important to assess the impact of society on science, we should also take into consideration the history of the subject and how it has lead to current thinking. Sexual selection was first proposed by Darwin to explain away seemingly maladaptive traits (which are mainly found in males) in light of his new theory of natural selection.
    Therefore you could argue that the current roles of males and females in science have come from a need to explain secondary sexual traits in males. This then begs the question "why do (mainly) males display for females". Again, this has lead to the idea that females carry higher costs in reproduction than males, which leads to females being more selective and males having to prove their worth for access to the goods, which, as Erik mentioned, could lead to high costs in males. The next step is males trying to "cheat and steal" for what they need (to avoid these costs). Of course this could be influenced by society, but you could equally argue that the theory of sexual conflict (first proposed in the late 70's, yet still a relatively new theory) has been hindered by the sensibilities of the liberal west. I agree with Erik that SAC may not be the "normal" outcome from conflict, but at the same time, suggesting that SAC came about due to the bias of a male dominated world seems a little over the top.

    Male mating costs is currently quite a hot topic, the recent am nat paper by roger and i is testament to that. I would be interested to read your findings, as I will hopefully be examining the correlation between male and female preferences.

    A very recent paper might also be of interest to you both. Check the march issue of evolution; Whitlock and Agrawal, where they examine male mating success and how this results in the purging of the male genome (i've only read the abstract.....what do you expect!).

    Finally, Erik, I'd like to take a look at the ecol let paper, even if it is to make sure that you cite our new am nat paper in your review (as well as the PLOS paper)

  3. Tom & Others:

    Will send you this review, when it is accepted (IF it gets accepted!). Two more thoughts:

    1. It might be worth thinking about male mating costs in sexually cannibalistic systems, where males are smaller than females and hence are likely to pay a higher cost (probably in many spider species). There could then be a race between female fecundity selection driving up female size and male "hanging on" to avoid becoming eaten. I think this might have been the message in that spider-paper in Evolution, I mentioned.

    2. Sexually transmitted diseases (STD:s): if the costs of getting a disease (e. g. risk of sterility???) is higher in one sex than the other, I can imagine situations where it is not necessarily females who pay the highest costs.

    I general, I think it is good to question conventional wisdom that females mainly pay the highest cost and the traditional gamete-asymmetri arguments a la Bateman. So the idea of male costs is certainly worth exploring.

  4. My comments were not saying that mate mating costs don't exist or that they are any less interesting, but rather that the reason for the slow pick up is, in my opinion, unlikely to be solely due to a male dominated society dictating how we as scientists think. In fact you could argue the opposite that the reason it has taken us so long to get round to studying male costs is due to sexual conflict as a theory being hindered by societies liberal thinking. The comments by Kristina Hultman about our PLoS one paper is a testament to that. It is important to think about how we got to our current thinking, the ideas and evolution of the theory itself. Of course society effects our thinking, monogamy in birds is an example of that, but how and what you pin on society is hard and unquantifiable.

    For example, you could argue that sexual conflict models have only recently started taking into consideration male costs due to the theory evolving as we discover more about the potential conflict between the sexes.
    There are a plethora of reasons for males to have higher costs, including those you mentioned Erik, as well as simple searching costs. I have been discussing with Steve how underrated these costs could be in Drosophila, who in the lab get everything they what but in nature how common are the food resources they seek? (easy in a banana plantation!!)

    I don't disagree that gender issues in humans are important, but I get a little uncomfortable when they are transposed onto other theories.

  5. Erik and Tom, thanks a lot for all your input and interesting discussion! I’m just sorry that I haven’t replied earlier, partly this is due to my computer screen collapsed last week (but now I’m back – wide screen)! First of all maybe I should clarify that we’re not saying that sexually antagonistic coevolution was founded due to a male dominated world. At least this is not what we are thinking and I’m sorry if the text could be interpreted like that. On the other hand, this may well be what some of the future critique may concern so it is good that it came about! What we were trying to saywas instead that, although the sexual conflict theory suggests adaptations and counteradaptations and a strive of each sex to reach their own optimum, at a cost for the opposite sex, there are still not many studies on e.g. male conflict costs. We’re sort of asking why research has not taken all aspects of the quite neutral theory into account and wonders if this to some extent has to do with our preconceptive view of how the sexes should act and what features the conventional sex roles entail. I think it may be very easy to unconsciously project ones own opinions on the study species of interest, and just as unconsciously decide what would be interesting to study after what one expects to find. For example, when studying the isopods I prefer not knowing if the individual I’m observing comes from the reed or the stonewort as I know that I have a certain picture of how the reed ecotype behaves and in what aspects the stonewort ecotype may differ. I guess that we all have this inherent picture of how the sexes behave and in what aspects males and females may differ and, as least as long as we are studying systems with males and females, this picture may be difficult to escape from. Thus maybe it would be worth looking into this topic to see if there seem to be some biases in sexual conflict research and if so, consider our biases and hopefully gain some new insights in our study systems or rediscover some overlooked aspects of the theory.

    I also think that theory and research may have sprung from what is most elaborate and conspicuous in nature, who can foresee the tail of a peacock?! And maybe this is also what is the most common, and as I said before, that doesn’t matter; we’re not interested in demanding equality in nature or having affirmative actions for either sex. But if theory should be general, and maybe also just because it shouldn’t be kept inside the box, it may be good to take it a step further and ask what is going on in the not so conspicuous cases. Or in the cases with hermaphrodites, plants etc where conventional sex role thinking may be difficult or even useless. Perhaps we are getting there, as you point out male cost may have started to be considered and male mate choice is another “hot topic”, and probably the process is naturally very slow when research evolves but maybe by studying the potential bias aspect we may at least gain some insight in by what research may affected and how science develops.

    As for the question whether SAC is common is sexual conflicts I agree with both of you that I don’t think it is the most common scenario. And actually not the most interesting either, despite it may create elaborate traits. I’ve also been thinking on the male cost (and I think this is suggested in the isopod literature, but I may be wrong), that in some cases it may for the male be a question of mating or not but for females it may be only a question of a good or a bad mating. I suppose that males then may suffer a bigger cost than females if the conflict is solved in favour of their partner? (Or does it sound more like an “ordinary” sexual selection scenario?) I also think that the STD-thought you had Erik, was interesting, have you read anything on that? As for your article suggestions, I’ll look them up, and Erik, I’m also looking forward to read your review!

  6. A good retort Tina, I may well have gone off the line a bit, it is harder having discussions like this than in person as they take a lot longer and go off in tangents.

    My main point was that the pattern you are looking for can be attributed to many things, preconceptions about the role of the sexes, new theory taking time to evolve, social backdrop hindering the advancement of an idea etc..
    Also, the probing of the curious nature of sexual interactions is not new, questions regarding the evolution of the sexes have been around for a while, including models such as Maynard-Smith's two-fold cost of sex from the early 80's.

    Sexual conflict, as a theory, emerged from sexual selection so therefore there was already baggage, regarding the views of "how things work". I disagree that scientists tend to stick within the box, nothing will get you further than a novel finding in a high ranking journal. Why do you there is a constant search for the next "hot topic"

    Of course most of what is discussed in this framework is conjecture, but if it leads to a break through in the field it will all be worth it, which ever side of the coin it lands. Good luck with the paper.

  7. As an aside, our review was rejected in "Ecology Letters", unfortunately, so we will now try to send it elsewhere. Any suggestions?

    Damned journal editors: first invite to write a review, invite to revise it and then reject it...