Inheritance of behavioural differences between two interfertile, sympatric species, Drosophila silvestris and D. heteroneura

Abstract

The Hawaiian fly species, Drosophila silvestris and D. heteroneura, are sympatric and interfertile but show strong behavioural isolation and major differences in male aggressive behaviour and the associated morphology. As a first step in elucidating the genetic control of the differences between these species, we examined the mating and aggressive behaviour of their reciprocal F 1 hybrids. The latency to the first wing vibration and the latency to copulate did not differ significantly between the parental species. However, D. heteroneura females had a very low tendency to copulate with D. silvestris males, rarely mating during the observation period. The duration of copulation also differed significantly: same-species pairs of D. silvestris had copulations that lasted about 50% longer than those of same-species pairs of D. heteroneura. The hybrids were intermediate between the parental species for both the tendency to copulate with D. silvestris males and the duration of copulation, suggesting codominance or polygenic inheritance for those traits. The aggression traits that we scored were the leg posture and wing extension during early aggression, and the leg posture and head position during escalated aggression. The parental species showed clear differences for each of these traits. The F 1 hybrids resembled one parent or the other, without showing intermediate values, suggesting single-gene dominance or threshold expression of many genes for those traits. None of the courtship or aggressive traits showed X-chromosomal effects, although the head shape of hybrids is influenced by genes on the X chromosome. It is difficult to reconcile the patterns of inheritance of aggressive behaviour and the lack of an X-chromosomal effect with the hypothesis that these traits are influenced by a coadapted gene complex.

The genetic architecture of insect courtship behavior and premating isolation

“…Although such measures are useful in quantifying premating isolation as a whole, they integrate a large collection of traits, including male activity, mate recognition, male choice, female resistance, female choice, and the complexity of courtship, making these measures relatively uninformative about what specific traits underlie isolation. Moreover, as pointed out by Boake et al (1998), as such summary traits likely represent several characters, they are predisposed to reveal a polygenic architecture, biasing studies of the genetics of reproductive isolation towards detection of such effects. In this review, I thus concentrate on the genetic bases of the specific phenotypic traits involved in courtship and reproductive isolation.…”

Fighting fruit flies: A model system for the study of aggression

“…Despite its importance, relatively little is known of the neural and humoral mechanisms that are its proximate causes. Given the near ubiquity of aggression, it is not surprising to find aggression and territorial behavior in fruit flies (3-10), particularly among a selection of Hawaiian taxa (4,5,8) that have proven difficult to study in the laboratory. The existence of these behaviors in common strains of Drosophila melanogaster is not widely known, however.…”

Serotonin circuits and anxiety: what can invertebrates teach us?

“…As mentioned, we focus our discussion to one such behavior, a fighting response to an environmental stressor. Drosophila exhibits aggressive behavior (Jacobs 1978), which is ethologically (Skrzipek et al 1979; Lee and Hall 2000) and evolutionarily well established (Boake and Hoikkala 1995; Boake et al 1998). Male flies under appropriate conditions will occupy a food patch and defend it against other males (Hoffman and Cacoyianni 1989; Hoffman and Cacoyianni 1990).…”