Morph specific selection in Proc B

posted May 24, 2018, 12:38 AM by Bruno Buzatto   [ updated May 24, 2018, 12:40 AM ]

Today Proc B published a paper I wrote with Huon Clark and Joe Tomkins (both at UWA) about our ambitious artificial selection experiment with the mite Rhizoglyphus echinopus. The experiment ran for about a year and a half, so we put a lot of our work (and lives!) into that experiment. The goal was simple — I wanted to test whether selection acting exclusively on one male morph (males of this species can conditionally be one of 2 morphs: fighters or scramblers) would affect the evolution of the other morph. Phenotypic plasticity theory predicts some level of developmental decoupling between morphs, and therefore potential for independent evolution, but we suspected the story was a bit more complicated than that. So we imposed selection for thicker (and thiner) legs on 6 lines of mites, always applying selection to fighter males only, focusing on their fighting legs.

After 9 generations we found that scrambler males (and females!) presented correlated evolution in the same direction as shown by fighters. This is not very surprising, as we already knew there were genetic correlations for this trait between male morphs and sexes. However, our approach is a powerful demonstration of a genetic constraint for the evolution of dimorphisms (between sexes and morphs), and goes one step beyond predicting correlated evolution through genetic correlations — we showed that correlated evolution in the lab! Now we know that, despite these constraints, the morphs did evolve (prior to the experiment!) very different morphologies, so what we demonstrated just shows that somehow male morphs overcame the genetic constraints (that are truly there!) to evolve divergent morphologies. But now we need to figure out how!

Move to Macquarie University!

posted Feb 11, 2018, 10:07 PM by Bruno Buzatto   [ updated Feb 11, 2018, 10:09 PM ]

I am extremely happy to announce that I just moved to Sydney to take a lecturer position at Macquarie University! I really wanted to announce this here and in social media a bit earlier, but the last few weeks have been so busy with the move that I am only 'pausing' to breathe and do 'less urgent' stuff now... After a long drive across the country (done in 9 days!), I am in Sydney for just over a week now, and currently in my second week here at Macquarie Uni. The place is amazing and the people fantastic, so I am sure this will be a great personal and professional experience. Macquarie Uni is beautiful and has an amazing infra structure, and Sydney is incredibly green (and hilly when compared to Perth!).

I already dearly miss Perth and all the amazing friends I have on the west side of the country, where I had the honour and pleasure to be part of the Centre for Evolutionary Biology at UWA for almost 9 years! But who knows, maybe I'll be back one day — my contract at MQ goes till mid-2019, so I'll be back to the job market after that. For now I hope I can make the most of this amazing opportunity here at Macquarie. By the way, I think there will be plenty of scuba diving, rock climbing, hiking, kiting, sailing, and kayaking to do around here as well ;)

Intralocus tactical conflict in JEB

posted Jun 12, 2017, 11:35 PM by Bruno Buzatto   [ updated Jun 12, 2017, 11:37 PM ]

The latest issue of the Journal of Evolutionary Biology features an article by Kyana Pike, Joe Tomkins and myself on a topic that I am fascinated about — the evolutionary conflict between different male phenotypes. In some species, alternative male phenotypes are linked to different tactics for securing matings, where large male morphs express weapons used to defend females or territories (like the thick legs of bulb mites or the forceps of earwigs displayed on the left), whereas small male morphs have reduced weaponry and sneak copulations. In these systems, theory predicts that the evolution of male dimorphism is facilitated if morphs are genetically uncoupled and free to evolve towards their phenotypic optima; however there is little evidence for male morphs responding independently to selection.

One way of investigating the potential for independent or correlated evolution between male morphs is by using quantitative genetics to estimate
the heritability and the intrasexual genetic correlations (between male morphs) of dimorphic and monomorphic traits, and comparing them. We did that with two different model systems, and found two contrasting patterns: earwigs exhibited low intrasexual genetic correlations for the dimorphic trait, suggesting that the conflict between male phenotypes is moving towards a resolution. Meanwhile, bulb mites exhibited high and significant intrasexual genetic correlations for most traits, suggesting that morphs in the species may be limited in evolving to their optima. It is surprising, however, that intrasexual dimorphism can evolve to be so evident in this system, despite such strong genetic constraints.

Another very cool aspect of this project is that it emerged from a short project in the unit 'Evolutionary Biology', here at the University of Western Australia. The lead author, Kyana, was at the time doing her honours at UWA with magpies, but Joe and I 'highjacked' her talent and hard work to our bulb mite project, and the result was this beautiful paper!

Benefits of polyandry in Molecular Ecology

posted May 12, 2017, 2:08 AM by Bruno Buzatto   [ updated May 12, 2017, 2:09 AM ]

Molecular Ecology just published a paper on dung beetles that Erin McCullough (the lead author), Leigh Simmons and I conducted here at the University of Western Australia. In a nutshell, we collected mated females of the dung beetle Onthophagus taurus from the field, allowed them to breed (make brood balls and lay eggs) in the lab, and then genotyped their offspring and used microsats (thanks to Erin's amazing molecular skills!) to estimate the (minimum) number of males each female mated with, and their relative fertilization success in each clutch. We found that females of the species are highly polyandrous (88% of them were, some having mated with at least 5 males in the field!!). We also found significant paternity skew (some males sired more offspring than others), suggestive of sexual selection in the field. Finally, the coolest thing was that paternity skew (the amount of sexual selection) was correlated with the number of offspring produced, suggesting a benefit of polyandry and a benefit of sexual selection! Dung beetles are just the coolest...

Conditional trimorphism in the J Theor Biol

posted Mar 22, 2017, 12:03 AM by Bruno Buzatto   [ updated Mar 22, 2017, 12:04 AM ]

A few years ago, my interest in male dimorphism led me to a collaboration with professors Mark Rowland and Clifford Qualls, from the University of New Mexico. Our collaboration had the purpose of putting forward a model for conditional trimorphisms, which is an extension of the 'environmental threshold model' from quantitative genetics, designed to account for trimorphisms with two thresholds, and compatible with the 'rock-paper-scissors model' of evolutionary game theory. Unfortunately, I was devastated to hear that Mark passed away in early 2015, at the very start of our collaboration. Publishing this paper then became a mission where Clifford and I joined forces (Clifford on the side of the maths, and myself with the evolutionary biology perspective) to make sure Mark's ideas would be published and available in the literature for anyone working on the rare but incredibly interesting cases of trimorphism in nature. The Journal of Theoretical Biology has just published this paper, and you can find it here.

Multiple male spawnings in a frog

posted Feb 14, 2017, 1:52 AM by Bruno Buzatto

This month's issue of Evolution features my latest paper on sperm competition in the Australian quacking frog Crinia georgiana, which I co-authored with Evan Thyer, Dale Roberts and Leigh Simmons. For this paper we video-recorded over thirty multiple male amplexus in this species, and then collected the offspring for molecular paternity analyses. We found that amplexus time and position were very important for fertilization success of males under competition (amplexing dorsally resulted in higher success!), and that testis size also had a positive effect on fertilization success, but only for males amplexing the female in the ventral position. It seems that in this species larger testes are an advantage in high population densities, where more multiple male spawnings occur and where males more commonly end up in a non-ideal amplexus position, such as holding on to the female in a ventral or lateral position.

Best published paper award

posted Dec 21, 2016, 12:38 AM by Bruno Buzatto   [ updated Dec 21, 2016, 12:39 AM ]

Last week I was awarded the 'Best 2015 Published Paper' award from the School of Animal Biology, here at UWA. The prize came with 250$, a very nice Christmas gift, so thanks so much, SAB! The paper that won this award was my 2015 Evolution paper on sperm competition and the evolution of arm strength in a frog with multimale amplexus, which I co-authored with Dale Roberts and Leigh Simmons. The next chapter on this story has just been published as another paper in Evolution, this time with paternity data and videos of the multimale amplexus to make the story more complete! This second paper also has the honours student Evan Thyer as another author.

Friends' paper on parental harvestmen

posted Nov 30, 2016, 7:18 PM by Bruno Buzatto   [ updated Nov 30, 2016, 7:19 PM ]

I was very excited to see this paper published in J Evol Biol on Serracutisoma proximum, a species that I have very close to my heart as I did my MSc thesis on it :) Males of this harvestman defend harems of females, who normally guard their eggs for over a month. If a female dies, males can guard the eggs for short periods of time. My friends Louise, Danilo and Glauco, from the University of São Paulo, showed that attractive males guarded eggs less often, but their attendance increased with perceived paternity, which is super cool.

There is also a great post about it by a science journalist which you can see here.

Encyclopedia of Evolutionary Psychological Science

posted Oct 31, 2016, 11:36 PM by Bruno Buzatto   [ updated Oct 31, 2016, 11:42 PM ]

I had the privilege to co-author the chapter/entry  'precopulatory intrasexual competition' for the recently published Encyclopedia of Evolutionary Psychological Science, which is an interdisciplinary and comprehensive reference for evolutionary psychology. Interestingly, I can update the chapter at any time, so it's online version is 'alive', which is very cool. Also, my co-author on this was my office mate Renée Firman, who normally works with postcopulatory sexual selection, which made the interaction even more interesting!

Macroecology of sexual selection in Am Nat

posted Oct 13, 2016, 8:13 PM by Bruno Buzatto   [ updated Oct 13, 2016, 10:25 PM ]

One of my most pleasant collaborations, with Glauco Machado, Rogelio Macías-Ordóñez and Solimary García Hernández, has recently been published in The American Naturalist. It is about a macroecological perspective of sexual selection, proposing an approach for large-scale (global!) variation in mating systems and sexual dimorphism. We used harvestmen (Arachnida: Opiliones) as a proof of concept of the proposed framework, and
it all started with a chapter entitled 'The macroecology of harvestmen mating systems' published in 2014 in the book Sexual Selection: Insights from the Neotropics

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