Posts Tagged 'selection'

Mutual sexual selection in dinosaurs and pterosaurs

As of last night my latest paper has come out, coauthored with Darren Naish and Innes Cuthill. Those with access to the journal Lethaia can get it here. Believe it or not I’ve been juggling with the idea as to whether or not to blog about this for quite some time. This is, I think, the most significant paper that I’ve produced and it’s the product of literally years of work (though at least part of that was as a result of very difficult editors and referees at various times, this was started back in 2007!) and I’m really rather proud of it.
Then why not blog it? Well the short answer is that this is a long and complex paper and it ultimately deals with a huge range of difficult issues (and not in the length we’d have liked, it had to be cut down severely to fit the journal and we still incurred page charges). It touches at various times on pterosaurs, sauropod body size, various ornithischian lineages, theropod sociality, the origins of feathers among other themes. All of this means that it’s very hard to blog about and cover the salient points for a non-expert audience without writing thousands upon thousands of words and, well, I did that for the paper.

This is obviously counterintuitive for a blog that is effectively about science communication, but I can’t do everything all the time (I certainly haven’t blogged all of my papers of the last few years). Moreover, in my experience, a paper like this which rather stomps a bit over some much cherished hypotheses of people tends to attract huge number of comments along the lines of “but what about *this* contrived example!” which I can assure you gets very annoying when people won’t let it drop.

None of this means I *won’t* be blogging it at length. But I know it’s likely to be covered a bit elsewhere on the web and thus it’ll look odd that I’m not doing it right away and it seemed sensible to provide an explanation up front. What I will at least talk about it mutual sexual selection – it’s right there in the title and the abstract and is, I suspect, a concept unfamiliar to most, perhaps nearly all, readers. it is after all, something almost entirely absent from the literature on dinosaurs and pterosaurs, Darren and I could only find two other references to it ever and one of those was what we put into the Taylor et al. paper on sauropod necks and the other sprang from Portsmouth. So it’s something that’s only really just coming into the literature.

Sexual selection is probably familiar – the idea that some traits are selected for by the opposite sex and can drive the development of bight colours, crests. displays and all manner of other things. The obvious one that’s endlessly used is the train of a peacock, that makes the male look very different to the drab female. This is typically coupled with sexual dimorphism (again, like the peacock) where the male is bigger than the female and has the extra ornaments etc. and males compete for females, with the best ornaments males advertising their fitness through the size and quality of their fitness (though in some cases like jacanas, this is reversed with bigger females).

So far, so simple. Mutual sexual selection is simply an extension of this into both genders. Both males *and* females are ornamented (or rather, have sexually selected traits) and just as males are competing with other males for the best females, so too the females are competing with each other for the best males. This means that dimorphism is limited or even absent – both genders having such traits. This is in fact, well known for quite a number of bird species and the number of papers on the subject in living species is increasing in leaps and bounds.

In the paper we hypothesis that this may have been common in the ornithodirans. It explains (potentially) quite a lot and solves a couple of previous paradoxes about crests evolution and development. Critically it means that you *don’t need* dimorphism of a feature for it to be sexually selected – both genders can have a crest and it can still be a sexually selected feature. This needs testing, this paper does little more than lay out all the conceptual issues and evolutionary biology and ecology behind the hypothesis, but at the same time, I think we do have some pretty good support for our ideas.

But as ever, what really needs to happen is for you to go and read the paper! And yes, I do have a PDF if you want it.

 

HONE, D. W., NAISH, D. and CUTHILL, I. C. (2011), Does mutual sexual selection explain the evolution of head crests in pterosaurs and dinosaurs?. Lethaia. doi: 10.1111/j.1502-3931.2011.00300.x


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