[HELICONIUS] Two cool new papers on Heliconius: Estrada et al on antiaphrodisiacs and Walters et al. on seminal fluid proteins

[James Mallet]

1) Estrada C, Schulz S, Yildizhan S, Gilbert LE. 2011. Sexual selection 
drives the evolution of antiaphrodisiac pheromones in butterflies. 
Evolution 65: 2843-2854.
http://dx.doi.org/10.1111/j.1558-5646.2011.01352.x
email: estradac at si.edu
Abstract: Competition for mates has resulted in sophisticated mechanisms 
of male control over female reproduction. Antiaphrodisiacs are 
pheromones transferred from males to females during mating that reduce 
attractiveness of females to subsequent courting males. Antiaphrodisiacs 
generally help unreceptive females reduce male harassment. However, lack 
of control over pheromone release by females and male control over the 
amount transferred provides males an opportunity to use antiaphrodisiacs 
to delay remating by females that have returned to a receptive state. We 
propose a model for the evolution of antiaphrodisiacs under the 
influence of intrasexual selection, and determine whether changes in 
this signal in 11 species of Heliconius butterflies are consistent with 
two predictions of the model. First, we find that as predicted, 
male-contributed chemical mixtures are complex and highly variable 
across species, with limited phylogenetic signal. Second, differences in 
rates of evolution in pheromone composition between two major clades of 
Heliconius are as expected: the clade with a greater potential for 
male-male competition (polyandrous) shows a faster rate of divergence 
than the one with typically monoandrous mating system. Taken together, 
our results provide evidence that for females, antiaphrodisiacs can be 
both honest signals of receptivity (helping reduce harassment) and 
chastity belts (a male-imposed reduction in remating)

2) Walters JR, Harrison RG. 2011. Decoupling of rapid and adaptive 
evolution among seminal fluid proteins in Heliconius butterflies with 
divergent mating systems. Evolution 65: 2855-2871.
http://dx.doi.org/10.1111/j.1558-5646.2011.01351.x
email: jw663 at cam.ac.uk
Abstract: Reproductive proteins often diverge rapidly between species. 
This pattern is frequently attributed to postmating sexual selection. 
Heliconius butterflies offer a good opportunity to examine this 
hypothesis by contrasting patterns of reproductive protein evolution 
between clades with divergent mating systems. Pupal-mating Heliconius 
females typically mate only once, limiting opportunity for postmating 
sexual selection. In contrast, adult-mating females remate throughout 
life. Reproductive protein evolution is therefore predicted to be slower 
and show little evidence of positive selection in the pupal-mating 
clade. We examined this prediction by sequencing 18 seminal fluid 
protein genes from a dozen Heliconius species and a related outgroup. 
Two proteins exhibited dN/dS > 1, implicating positive selection in the 
rapid evolution of at least a few Heliconius seminal fluid proteins. 
However, contrary to predictions, the average evolutionary rate of 
seminal fluid proteins was greater among pupal-mating Heliconius. Based 
on these results, we suggest that positive selection and relaxed 
constraint can generate conflicting patterns of reproductive protein 
evolution between mating systems. As predicted, some loci may show 
elevated evolutionary rates in promiscuous taxa relative to monandrous 
taxa resulting from adaptations to postmating sexual selection. However, 
when monandry is derived (as in Heliconius), the opposite pattern may 
result from relaxed selective constraints


-- 
James Mallet
Professor of Biological Diversity, GEE
University College London
LONDON WC1E 6BT
+44 (0)20 7679 7046
www.ucl.ac.uk/taxome/jim