Does Sex Trade with Violence among Genotypes in Drosophila melanogaster?

Abstract

The evolutionary forces shaping the ability to win competitive interactions, such as aggressive encounters, are still poorly understood. Given a fitness advantage for competitive success, variance in aggressive and sexual display traits should be depleted, but a great deal of variation in these traits is consistently found. While life history tradeoffs have been commonly cited as a mechanism for the maintenance of variation, the variability of competing strategies of conspecifics may mean there is no single optimum strategy. We measured the genetically determined outcomes of aggressive interactions, and the resulting effects on mating success, in a panel of diverse inbred lines representing both natural variation and artificially selected genotypes. Males of one genotype which consistently lost territorial encounters with other genotypes were nonetheless successful against males that were artificially selected for supernormal aggression and dominated all other lines. Intransitive patterns of territorial success could maintain variation in aggressive strategies if there is a preference for territorial males. Territorial success was not always associated with male mating success however and females preferred ‘winners’ among some male genotypes, and ‘losers’ among other male genotypes. This suggests that studying behaviour from the perspective of population means may provide limited evolutionary and genetic insight. Overall patterns of competitive success among males and mating transactions between the sexes are consistent with mechanisms proposed for the maintenance of genetic variation due to nonlinear outcomes of competitive interactions.

Socially-Responsive Gene Expression in MaleDrosophila melanogasterIs Influenced by the Sex of the Interacting Partner

“…However, male-male interactions such as those involved in aggressive encounters may have greater effects on gene expression than male-female interactions. Males of many Drosophila species, including D. melanogaster, compete for mates and territories, and aggressive behavior is correlated with mating success (Dow and von Schilcher 1975); both factors correlated with genotype (Cabral et al 2008). Social experience with other males reduces aggressive behavior during competition for territories, and experienced males are more likely to regain territories (Hoffmann 1990).…”

Quantitative Trait Loci for Aggressive Behavior inDrosophila melanogaster

“…Theoretical modeling has suggested that frequency-dependent selection could be generating genetic variation in aggression (Maynard Smith and Harper 1988). The observation that many behavioral phenotypes vary widely in a population is often attributed to life history trade-offs (Cabral et al 2008;Maney 2008); recent work also suggests that animal ''personalities'' within a population might be adaptive (Wolf et al 2007). Another potential explanation is that the pleiotropic nature of many genes affecting aggressive behavior subjects them to opposing or multidirectional selective pressures, maintaining variation.…”

Genetic variation in social environment construction influences the development of aggressive behavior in Drosophila melanogaster

“…Aggression is heritable in at least four natural populations of Drosophila (Hoffmann, 1988;Edwards et al, 2006;Cabral et al, 2008). Natural genetic variation in aggressiveness influences group formation, including group size (Saltz and Foley, 2011), through processes that are not yet fully understood (Foley et al, 2015).…”

“…Natural genetic variation in aggressiveness influences group formation, including group size (Saltz and Foley, 2011), through processes that are not yet fully understood (Foley et al, 2015). Males from natural genotypes modulate their aggressive behavior in response to local ecology and sex ratio (Cacoyianni and Hoffmann, 1990), and natural genotypes show indirect genetic effects, whereby the aggressiveness of a male depends on the genotype of his opponent (Cabral et al, 2008;Saltz, 2013). Complementary work on laboratory genotypes has shown that prior exposure to males (Yurkovic et al, 2006;Wang et al, 2008) and females (Yuan et al, 2014;Baxter et al, 2015) can influence males' later aggression.…”

“…The day 2 arena was identical to the one on day 1, except for the addition of a ball of live yeast on the food patch. The live yeast was included, because it is common in studies of Drosophila aggression (for example, Nilsen et al, 2004;Cabral et al, 2008;Wang and Anderson, 2010;Baxter et al, 2015) and because it provided a cue that could indicate to the flies that the day 2 environment was different from the day 1 environment (Figure 2). …”