Adaptive wing asymmetry in males of the speckled wood butterfly (Pararge aegeria)?

Proceedings of the Royal Society B: Biological Sciences (Impact Factor: 5.05). 05/2013; 266:1413-1418. DOI: 10.1098/rspb.1999.0795
Source: PubMed Central


We analysed asymmetry in the wings of the speckled wood butterfly (Pararge aegeria)by measuring area, length and width of fore- and hindwings. The type of asymmetry is fluctuating except for fore- and hindwing area, and forewing width in males, where asymmetry is directional. The amount of asymmetry (variance of the left wing minus the right wing) is less in males than in females. Within males asymmetry was directional and less in pale, predominantly territorial males than in melanic, predominantly non-territorial males. Asymmetry was negatively related to growth rate within females, but not within males. Females grew faster than males, but had higher asymmetry, whereas the more asymmetrical melanic males grew more slowly than pale males. The differences in the type and amount of asymmetry between the sexes and colour classes suggest a relationship with sex-specific flight patterns such as the territorial spiralling flight of males. We hypothesize that slightly asymmetrical males turn faster, and therefore are superior in territorial disputes over more symmetrical or extremely asymmetrical males. This implies that sexual selection via male–male competition influences the type and amount of asymmetry. The existence of more extremely asymmetrical individuals in females, and to a lesser extent in non-territorial males, may indicate that there are costs in reducing asymmetry.

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    • "However, these ecological associations with the direction of bias have not involved subtle asymmetries, which are thought to arise due to errors made during development. There is a paucity of investigations that move beyond considering these slight departures from symmetry as nonheritable " errors " into considering them as new phenotypes with which to exploit new niche space (but see Seligmann 1998; Windig and Nylin 1999). Such information could identify ecological mechanisms that underlie the fitness and biomechanical consequences of subtle asymmetry in phenotype. "
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    ABSTRACT: Slight departures from bilateral symmetry are usually associated with reduced fitness. Here we show that an insular freshwater population of Gasterosteus aculeatus exhibits spatial and temporal segregation according to the incidence and direction of asymmetry in the number of bony lateral plates, which are important predator-defense structures. We analyzed 11,263 fish collected from 19 full lake transects over three years, and found that signed asymmetries for plate number were slightly left-side biased. Asymmetries occurred in 55% of the stickleback with more asymmetrics found during cold weather, and more left-biased individuals found during windy conditions, possibly due to environmentally driven activity levels that differ among asymmetric forms. Absolute plate asymmetries were randomly distributed in the lake, but there was a strong shift in signed plate asymmetry from a mean of zero in littoral zones to left-side bias in limnetic zones, probably due to microhabitat choices among asymmetric forms. Video data of avian piscivores on the lake show laterality in prey handling, providing a potential mechanism for asymmetric prey morphology. Our results imply a complex relationship between slight asymmetries and niche space that is relevant to the broader literature on the evolutionary implications of developmental instability and intrapopulation variability.
    Evolution 10/2008; 63(1):115-26. DOI:10.1111/j.1558-5646.2008.00520.x · 4.61 Impact Factor
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    • "Loss of wing area is not the only problem faced by wingworn organisms. Events that cause wing wear, such as failed predator attacks or collisions with solid objects, can result in asymmetric wings, for example in butterflies (Carpenter 1937; Windig and Nylin 1999) and in solitary bees (Mueller and Wolf-Mueller 1993). Asymmetry complicates flight because an individual must compensate for the differential lift and thrust created by each wing. "
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    ABSTRACT: We lack a mechanism that links wing wear with mortality in foraging social insects. This study tests the hypothesis that wing wear strongly degrades foraging flight performance, thereby providing a biomechanical explanation for the wing wear-mortality relationship. We examine the effect of simulated win(, wear wing area reduction and asymmetry on the flight behaviour of bumble bee (Bombus flavifrons Cresson, 1863) workers moving between vertically oriented flowers spaced 30 cm apart and arranged in a two-dimensional horizontal grid. Flight behaviour was measured in three dimensions as total flying distance, mean velocity, variability of velocity, maximum acceleration, maximum deceleration, percentage of time spent accelerating, and displacement from a straight line path between flowers. Loss of wing area had Surprisingly little effect on flight behaviour. Viewed multivariately, bees with low asymmetry and low loss of mean area, or with high asymmetry and high loss of mean area, differed from the other three treatment groups. When bees were burdened with both high asymmetry and high loss of wing area, their between-flower flight path was less direct. Overall, flight behaviour of bumble bees was highly resilient to major changes in wing area and asymmetry in this simple foraging environment. The wing wear-associated causes of increased mortality remain elusive.
    Canadian Journal of Zoology 06/2008; 86(7):668-675. DOI:10.1139/Z08-034 · 1.30 Impact Factor
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    • "Other potential costs include the risk of sustaining injury and the opportunity cost of lost mate locating time. One persistent suggestion in the literature, based upon the observation that butterfly contests present elaborate aerial manoeuvres, is that flight performance attributes, such as acceleration ability and/or manoeuvrability, may be important determinants of RHP (Baker 1972; Berwaerts et al. 2002; Hernández and Benson 1998; Karlsson 1994; Stjernholm and Karlsson 2000; Wickman 1992; Windig and Nylin 1999). Relative flight performance could prove routinely decisive in aerial wars of attrition if more agile individuals are better able to manage the risk of injury and/ or death (through collision with their opponent, vegetation and other objects, or predatory attack), thus affording them a relatively lower rate of cost accrual. "
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    ABSTRACT: Although contemporary animal contest theory emphasises the importance of physical asymmetries in resolving disputes, such asymmetries do not obviously settle fights in all groups. Territorial male butterflies, for example, compete via elaborate non-contact aerial interactions in which success is determined by relative persistence. Prior research suggests that the resolution of these contests is not clearly related to physical variables such as body size or energy reserves. However, given that the contests involve elaborate aerial manoeuvres, one long-standing suggestion is that asymmetries in flight performance, and thus flight morphology, may be important. We addressed this hypothesis via a manipulative investigation into the biophysical correlates of contest success in the speckled wood butterfly, Pararge aegeria. This species possesses the ability for significant adaptive phenotypic plasticity in relevant flight morphological parameters. We took advantage of this plasticity to rear 90 individuals of markedly varying flight morphologies, which we then pitted against each other in a semi-controlled experimental fashion. Multiple logistic and lognormal analyses provided little evidence for the relevance of morphological parameters, including relative flight musculature, wing loading and wing aspect ratio (wing length relative to area), to the outcome and/or duration of experimental contests. Instead, we found a positive effect of age upon contest success. Given that ability for high acceleration is strongly linked to variation in these morphological parameters, our findings suggest that flight performance is not a strong determinant of resource-holding potential in this notably territorial butterfly.
    Behavioral Ecology and Sociobiology 01/2005; 59(3):403-411. DOI:10.1007/s00265-005-0064-1 · 2.35 Impact Factor
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