Size, Symmetry, and Sexual Selection in the Housefly, Musca domestica

Abstract

Relationships between measures of body size, asymmetry, courtship effort, and mating success were investigated in the housefly, Musca domestica (Diptera: Muscidae). A previous study indicated that both male and female flies with low fluctuating asymmetry enjoyed enhanced mating success. The aim of our investigations was to determine whether the greater success of symmetrical males is due to variation in male mating effort or to female choice and whether males exhibited mate choice. However, our study found directional rather than fluctuating asymmetry, with both male and female flies having, on average, longer left wings than right. Also, asymmetry was not related to mating success in either sex. Rather, both males and females appeared to exhibit choice on the basis of the size of potential mates, with males preferring females with long bodies and females preferring heavy males. Possible benefits from choice of large mates are discussed. The initial mating strikes (in which the male leaps onto the back of the female) did not appear to be targeted according to female morphology, and their frequency did not vary according to male morphology. This indicates that mate choice by both sexes according to size probably occurs during the later stages of courtship, when the flies are in intimate contact. Possible reasons for the absence of choice according to asymmetry are discussed.

SIZE AND FLUCTUATING ASYMMETRY OF MORPHOMETRIC CHARACTERS IN MICE: THEIR ASSOCIATIONS WITH INBREEDING AND t-HAPLOTYPE

“…In any event, size rather than FA in morphometric characters such as those used here may be a better indicator of (inbreeding) stress, as sometimes has been proposed on the basis of findings in other experimental studies that have used various stressors (Woods et al 1999). In addition, larger size may be an advantage in the sexual selection process, at least as measured by mating success (Goulson et al 1999).…”

“…Møller (1997) used metaanalysis techniques on a number of studies that suggested FA is negatively correlated with fitness, although these data and the analysis were criticized from several standpoints (see Clarke 1998). Many of these studies found a relationship between FA and sexual selection characteristics such as mat-ing success (Møller 1993;Møller and Pominakowski 1993;Møller and Thornhill 1998), but it turns out that more asymmetrical individuals are not always disadvantaged in the mating process (Markow 1995;Goulson et al 1999;Bjorksten et al 2000). Furthermore, there is at least some evidence that character size may be the more important indicator of mating success than the degree of asymmetry (Goulson et al 1999).…”

“…Many of these studies found a relationship between FA and sexual selection characteristics such as mat-ing success (Møller 1993;Møller and Pominakowski 1993;Møller and Thornhill 1998), but it turns out that more asymmetrical individuals are not always disadvantaged in the mating process (Markow 1995;Goulson et al 1999;Bjorksten et al 2000). Furthermore, there is at least some evidence that character size may be the more important indicator of mating success than the degree of asymmetry (Goulson et al 1999). Clearly, therefore, additional studies that compare the size and asymmetry of characters to traditional natural selection fitness characteristics such as viability and fecundity are needed if we are to properly sort out the role that FA plays in the overall fitness of organisms.…”

The Quantitative Genetics of Fluctuating Asymmetry

“…This model predicts that mate choice for symmetrical males will be rewarded by genetic factors (good genes) passed to offspring that confer superior developmental stability and thus elevate offspring survival (Møller and Pomiankoski 1993;Møller and Swaddle 1997). Mate choice in favor of symmetry has been documented in some taxa (reviewed by Møller and Thornhill 1998), such as in barn swallows (Hirundo rustica; Møller 1992) and wolf spiders (Schizocosa ocreata; Uetz and Smith 1999), but not in earwigs (Forficula auricularia; Radesäter and Halldó rsdó ttir 1993;Tomkins and Simmons 1998) and house flies (Musca domestica; Goulson et al 1999).…”

How Well Do Mating Frequency and Duration Predict Paternity Success in the Polygynandrous Water Strider Aquarius Remigis?

“…Sexual selection was originally defined as differential reproduction owing to variation in the ability to obtain mates (Darwin 1871). Hence, most studies of sexual selection have focused on the effects of particular traits on mating success, with the latter usually defined as the number of mates or matings obtained by each male (for example, Houck et al 1985;Harvey 1990;Arnqvist 1992a,b;Sih and Krupa 1992;Krupa and Sih 1993;Andersson 1994;Petrie and Halliday 1994;Preziosi and Fairbairn 1996;Weigensberg and Fairbairn 1996;Arnqvist et al 1997;Abell et al 1999;Goulson et al 1999;Savalli and Fox 1999;Shine et al 2000). This approach assumes a simple, direct relationship between the number of matings and reproductive success.…”