Data from: Male biased sex ratio reduces the fecundity of one of three female morphs in a polymorphic damselfly

Females of the damselfly Ischnura graellsii display 3 color morphs, a
male-like androchrome morph and 2 other morphs, infuscans and aurantiaca,
which are not male-like. Previous research has suggested that male
harassment has a negative effect on female fitness in many different
insect species. Studying how male harassment affects fitness of the
different female color morphs is key to a better understanding of how
these morphs are maintained in natural populations. This study evaluated
the response of female morphs of I. graellsii to contrasting sex ratios
under controlled laboratory conditions. In our experiments, male
abundance, through increased harassment, affected differentially the
fecundity of females of the 3 color morphs. A male biased (3:1) sex ratio
drastically decreased the average fecundity of infuscans females but had
no effect on androchrome and aurantiaca females. Taking into account our
results and previous studies that indicate that males prefer infuscans
females, we propose a mechanism for the maintenance of this polymorphism.
In this scenario, within-generation fluctuations in male abundance produce
2 regimes: One in which male abundance disfavors infuscans females by
decreasing their fecundity and other in which a low male abundance results
in androchromes that do not mate because of their low appeal to males. By
studying a simple population genetics model, we found that the mechanism
that we propose may contribute to maintain a stable female-limited
polymorphism under a wide range of parameter combinations.