The evolution of empty nuptial gifts in a dance fly, Empis snoddyi (Diptera: Empididae): bigger isn't always better

Ornamental traits function by improving attractiveness and are generally presumed to experience directional selection for mating success. However, given the greater investment of females in offspring than males, female-specific ornaments can in theory signal fecundity yet be constrained by fecundity costs. Theoretical work predicts that such constraints can lead to stabilizing selection via male choice for intermediately ornamented females. Female dance flies Rhamphomyia longicauda (Diptera: Empididae) display two female-specific ornaments in mating swarms - inflatable abdominal sacs and pinnate tibial scales. We investigated the intensity and form of sexual selection on female traits including ornaments and found no evidence for directional sexual selection. Instead, we found marginally nonsignificant quadratic selection for all three measures of ornament expression. Canonical analysis confirmed that the strongest vectors of nonlinear selection were associated with ornamental traits, although the significance of the quadratic coefficients associated with these vectors depended on the statistical approach. Direct Mitchell-Olds and Shaw tests for the location of the maximum fitted fitness value for both raw morphological traits and canonical axes revealed only one marginally nonsignificant result for the multivariate axis loading most heavily on pinnate leg scales. Together, these results provide the first tentative support for stabilizing selection on female-specific ornaments

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“…Like many other assessments of sexual selection in insects including dance flies (Sadowski et al. , 1999; LeBas et al.…”

Section: Discussionmentioning

confidence: 99%

Stabilizing sexual selection for female ornaments in a dance fly

Wheeler

Gwynne

Bussière

2012

J of Evolutionary Biology

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“…The copulating pair then rest on nearby vegetation while the female probes the nuptial gift with her proboscis (Cumming 1994; Preston‐Mafham 1999). A diverse range of nuptial gifts are found in the Empidinae, from unwrapped, edible insect prey, edible prey in a silken ‘balloon’, balloons containing dried insects or inedible algae, to empty and inedible balloons made of bubbles or silk strands secreted by the male (reviewed by Cumming 1994; Vahed 1998; Sadowski et al. 1999, see also Young & Merritt 2003).…”

Section: Sensory Bias and Nuptial Gift Compositionmentioning

confidence: 99%

All that Glisters is not Gold: Sensory Bias, Sexual Conflict and Nuptial Feeding in Insects and Spiders

2007

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It is becoming increasingly clear that the evolutionary interests of the sexes are often in conflict when it comes to mating. Sexual encounters involving nuptial gifts, however, have often been viewed as prime examples of sexual co-operation, rather than conflict. In this review, I explore the proposition that nuptial gifts act as sensory traps: by exploiting the female's gustatory responses, the male may be able to entice females to accept superfluous matings and/or transfer greater volumes of ejaculate than are in the female's reproductive interests. Evidence suggests that the females' sensory biases may have played an important role in shaping gift characteristics in at least four different systems, although relatively few forms of nuptial feeding have so far been examined from this perspective. I argue that gift composition is more likely to be tailored to increasing the attractiveness of the gift to the female and/or maximizing gift handling time than to suit the female's nutritional needs and that the fecundity-enhancing benefits of nuptial gifts are often questionable and have been over-stated in the literature. Fertilization biases associated with the female's attraction to the nuptial gift, however, could lead to in-direct benefits for the female. On the other hand, nuptial feeding may also lead to significant costs to the female. Evidence suggests that some types of gift entice the female to mate, but it is not clear whether the resultant degree of polyandry is higher than optimal for the female. In other cases, evidence suggests that the gift enables the male to overcome the resistance of the female to accepting an extra large ejaculate and that large ejaculates are associated with longer post-mating sexual refractory periods in the female. This could represent a cost to the female by delaying or preventing her from receiving the genetic benefits of polyandry. At present, it is not clear, however, whether such costs outweigh the potential benefits of nuptial feeding for the female

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“…Presumably as a consequence, females in many species compete intensely for the food gifts provided by males, and females have evolved a series of remarkable secondary sex characters that appear to improve their attractiveness to males (Collin, ; Cumming, ; Funk & Tallamy, ; LeBas, Hockham, & Ritchie, ; Murray, Wheeler, Gwynne, & Bussiere, ; Wheeler, Gwynne, & Bussière, ). In spite of the strong predicted covariance between sexual trait expression and mating success, studies of sexual selection on female dance flies report remarkable variation in the form and strength of selection (Bussière, Gwynne, & Brooks, ; Funk & Tallamy, ; LeBas et al., ; Sadowski, Moore, & Brodie, ; Wheeler et al., ). Whereas some studies have shown mating advantages for females with large ornaments (e.g.…”

Section: Introductionmentioning

confidence: 99%

The role of functional constraints in nonrandom mating patterns for a dance fly with female ornaments

Murray

Gwynne

Bussière

2019

J of Evolutionary Biology

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Most hypotheses to explain nonrandom mating patterns invoke mate choice, particularly in species that display elaborate ornaments. However, conflicting selection pressures on traits can result in functional constraints that can also cause nonrandom mating patterns. We tested for functional load‐lifting constraints during aerial copulation in Rhamphomyia longicauda, a species of dance fly that displays multiple extravagant female‐specific ornaments that are unusual among sexual traits because they are under stabilizing selection. R. longicauda males provide females with a nuptial gift before engaging in aerial mating, and the male bears the entire weight of the female and nuptial gift for the duration of copulation. In theory, a male's ability to carry females and nuptial gifts could constrain pairing opportunities for the heaviest females, as reported for nonornamented dance flies. In concert with directional preferences for large females with mature eggs, such a load‐lifting constraint could produce the stabilizing selection on female size previously observed in this species. We therefore tested whether wild‐caught male R. longicauda collected during copulation were experiencing load‐lift limitations by comparing the mass carried by males during copulation with the male's wing loading traits. We also performed permutation tests to determine whether the loads carried by males during copulation were lighter than expected. We found that heavier males are more often found mating with heavier females suggesting that whereas R. longicauda males do not experience a load‐lift constraint, there is a strong relationship of assortative mating by mass. We suggest that active male mate choice for intermediately adorned females is more likely to be causing the nonrandom mating patterns observed in R. longicauda.

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The evolution of empty nuptial gifts in a dance fly, Empis snoddyi (Diptera: Empididae): bigger isn't always better

Cited by 38 publications

References 23 publications

Stabilizing sexual selection for female ornaments in a dance fly

Stabilizing sexual selection for female ornaments in a dance fly

All that Glisters is not Gold: Sensory Bias, Sexual Conflict and Nuptial Feeding in Insects and Spiders

The role of functional constraints in nonrandom mating patterns for a dance fly with female ornaments

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