Data from: Experimental evolution reveals balancing selection underlying coexistence of alternative male reproductive phenotypes

Heritable alternative reproductive phenotypes (ARPs), which differ in traits associated with competition for mates, occur across taxa. If polymorphism in the genes underlying ARPs is maintained by balancing selection, selection should return ARP proportions to their equilibrium if that equilibrium is perturbed. Here, we used an experimental evolution approach to directly test this prediction in male Rhizoglyphus robini, in which two heritable morphs occur: armoured fighters and more female-like, benign scramblers. Using selection lines nearly fixed for male morph, we constructed replicate populations consisting of 50% or 94% fighters, and allowed them to evolve for 14 generations in two types of environment: simple or spatially complex. We found that in both types of populations, the proportion of fighters converged on values within a narrow range of 0.70-0.83, although the rate of convergence was slower in the complex environment. Our results thus demonstrate balancing selection acting on polymorphism(s) underlying ARP

Data from: Age, experience and sex – do female bulb mites prefer young mating partners?

In species where advancing sire age is associated with decreased progeny fitness, female resistance to mating with old partners can be expected to evolve. In polyandrous species, such resistance may be contingent on female mating experience: virgins should be relatively indiscriminate to ensure egg fertility, whereas non-virgins can be expected to base their re-mating decisions on the age of their previous versus potential new partners, and ‘trade up’ if previously mated with old males. Here, we tested these predictions using a promiscuous and relatively long-living bulb mite (Rhizoglyphus robini), in which old sire age is associated with decreased fecundity of daughters. In a fully factorial design, we applied two male treatments: young and old, and three female treatments: virgin, previously mated to an old male and previously mated to a young male. Consistent with earlier studies, we observed a reduced mating success of old males. However, we found no support for attributing this result to female discrimination, as female behaviour in response to male mounting attempts was not affected by the age of the suitor, or by its interaction with the age of the female’s previous mate. Interestingly, females were passive during 93% of male mounting attempts observed, suggesting that once they are located by a male, they exert little control over copulation. Old males had lower mate searching activity and were less efficient in obtaining matings (lower success rate per mounting attempt), suggesting a decreased mate securing ability due to aging. Overall, our results suggest that in bulb mites, male ability to secure mates declines with age, whereas they do not support the prediction that females actively discriminate against old partners

Data from: Mating system affects population performance and extinction risk under environmental challenge

Failure of organisms to adapt to sudden environmental changes may lead to extinction. Mating system, by affecting fertility and the strength of sexual selection, may have a major impact on a population’s chances to adapt and survive. Here, we use experimental evolution in bulb mites (Rhizoglyphus robini) to examine the effects of mating system on population performance under environmental change. We demonstrate that populations in which monogamy was enforced suffered a dramatic fitness decline when evolving at an increased temperature, whereas the negative effects of change in thermal environment were alleviated in polygamous populations. Strikingly, within 17 generations, all monogamous populations experiencing higher temperature went extinct, whereas all polygamous populations survived. Our results show that mating systems may have dramatic effects on the risk of extinction under environmental change

Male age and female preferences in bulb mite

Male age and female preferences in bulb mit

plesnar_et_al_2012_data

Data from fecundity, fertility and trans-generation effects assays on the experimental evolution lines of R. robin

Mate choice and post-zygotic isolation indexes for monogamous and promiscuous mating system.

<p>Mean mate choice and post-zygotic isolation indices for monogamous and promiscuous mating system calculated from the mean indices for male lines. Indices values lower than 0.5 indicate that a female from the same line as a male produces on average more offspring than a female from a different line. Bars indicate 95% confidence intervals.</p

Schematic representation of the design of Assay I.

<p>Schematic representation of the design of Assay I and the way of calculating pre-zygotic isolation mechanisms under male competition index on the example of a female’s line 1. Procedures are described in the text.</p

Schematic representation of the design of Assay II.

<p>Schematic representation of the design of Assay II and the way of calculating mate choice and post-zygotic reproductive isolation on the example of a male’s line 1. Procedures are described in the text.</p