Wednesday, January 2, 2013

First lab-meeting 8 January 2013: Evolution of sex differences in canalization and plasticity

Male pheasant (Phasanius colchicus), a sexually very dimorphic bird. 
Photo: Erik Svensson

Posted by Erik Svensson

It is time for the first lab-meeting of 2013, and since it will be my birthday (8 January), I will bring a cake. I want to dedicate this lab-meeting to two papers about sex differences in plasticity and its opposite (canalization). You will find the Abstracts below, and you can download these two papers here and here.

I do also want to take the opportunity to briefly (15-30 minutes) present some ongoing work that I have been doing with Machteld, Maren and Anna Runemark about sex-differences in learned mate preferences and responses to heterospecifics, based on some experiments we have done on male and female banded demoiselles (Calopteryx splendens). This is also related to some of Machtelds ongoing work on the developmental plasticity of preference curves and mate preference learning, which we can also discuss a bit. Hopefully, there will then be a smooth transition between this short presentation and the papers we will discuss.

For the rest of the semester, Machteld Verzijden ( is responsible for setting up a "Google Docs"-link soon so that we can all sign up for lab-meetings and take the opportunity to arrange at least one lab-meeting during next semester (including picking 1-2 papers and/or prepare a presentation, bring fika, writeup a blog post, post it on the Facebook group).

Details about the lab-meeting next week:

Time: 8 January 2013 at 10.30
Place: "Argumentet", 2nd floor, Ecology Building

Sex Differences in Phenotypic Plasticity Affect Variation in Sexual Size Dimorphism in Insects: From Physiology to Evolution

Annual Review of Entomology

R. Craig Stillwell, Wolf U. Blanckenhorn, Tiit Teder, Goggy Davidowitz, and Charles W. Fox  
Males and females of nearly all animals differ in their body size, a phenomenon called sexual size dimorphism (SSD). The degree and direction of SSD vary considerably among taxa, including among populations within species. A considerable amount of this variation is due to sex differences in body size plasticity. We examine how variation in these sex differences is generated by exploring sex differences in plasticity in growth rate and development time and the physiological regulation of these differences (e.g., sex differences in regulation by the endocrine system). We explore adaptive hypotheses proposed to explain sex differences in plasticity, including those that predict that plasticity will be lowest for traits under strong selection (adaptive canalization) or greatest for traits under strong directional selection (condition dependence), but few studies have tested these hypotheses. Studies that combine proximate and ultimate mechanisms offer great promise for understanding variation in SSD and sex differences in body size plasticity in insects.

Author(s): Ord, T.J.; King, L, Young, A.R. 
Evolution Volume: 65   Issue: 9   Pages: 2572-2591   DOI: 10.1111/j.1558-5646.2011.01319.x   Published: SEP 2011

Abstract: We tested hypotheses on how animals should respond to heterospecifics encountered in the environment. Hypotheses were formulated from models parameterized to emphasize four factors that are expected to influence species discrimination: mating and territorial interactions; sex differences in resource value; environments in which heterospecifics were common or rare; and the type of identity cues available for species recognition. We also considered the role of phylogeny on contemporary responses to heterospecifics. We tested the extent these factors explained variation among taxa in species discrimination using a meta-analysis of three decades of species recognition research. A surprising outcome was the absence of a general predictor of when species discrimination would most likely occur. Instead, species discrimination is dictated by the benefits and costs of responding to a conspecific or heterospecific that are governed by the specific circumstances of a given species. The phylogeny of species recognition provided another unexpected finding: the evolutionary relationships among species predicted whether courting males within species-but not females-would discriminate against heterospecifcs. This implies that species recognition has evolved quite differently in the sexes. Finally, we identify common pitfalls in experimental design that seem to have affected some studies (e.g., poor statistical power) and provide recommendations for future research.

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