Flight metabolic rate andPgigenotype influence butterfly dispersal rate in the field

Abstract

Dispersal is a key life-history trait, especially in species inhabiting fragmented landscapes. The process of dispersal is affected by a suite of morphological, physiological, and behavioral traits, all of which have a more or less complex genetic basis and are affected by the prevailing environmental conditions. To be able to identify genetic and phenotypic effects on dispersal, movements have to be recorded over relevant spatial and temporal scales. We used harmonic radar to track free-flying Glanville fritillary butterflies (Melitaea cinxia) released in the field and reconstructed their flight tracks for several hours. Flight track lengths for individual butterflies ranged from tens of meters to several kilometers. Butterflies were most mobile at midday and in intermediate temperatures. Flight metabolic rate (MR), measured prior to the tracking, explained variation in mobility at all scales studied. One-third of the variation in the distance moved in one hour could be attributed to variation in flight MR. Heterozygous individuals at a single nucleotide polymorphism in the phosphoglucose isomerase (Pgi) gene moved longer distances in the morning and at lower ambient temperatures than homozygous individuals. A similar genotype x temperature interaction was found to affect the metabolic rate. Our results establish connections from molecular variation in a single gene to flight physiology and movement behavior at the landscape level. These results indicate a fitness advantage to the heterozygous genotype in low temperatures and suggest a mechanism by which varying environmental conditions maintain genetic polymorphism in populations.

Thermal biology of flight in a butterfly: genotype, flight metabolism, and environmental conditions

“…2008) and longer distances in low ambient temperatures in the field (Niitepõld et al. 2009) than the alternative SNP genotypes. The AC heterozygotes also have higher flight metabolic rates at low ambient temperatures (Haag et al.…”

“…Butterflies are especially dependent on flight for most activities during adult life, including foraging, escaping predation, locating mates, searching for host plants, and dispersal (Kingsolver 1983; Saastamoinen and Hanski 2008; Niitepõld et al. 2009; Gibbs 2010). However, insect flight is energetically very costly, and thoracic muscles of flying insects exhibit the highest rates of metabolism known for any locomotor tissue (Dudley 2000; Suarez 2000), exceeding metabolism at rest by up to two orders of magnitude (Kammer and Heinrich 1978).…”

“…2005; Niitepõld et al. 2009; Niitepõld 2010), and indeed, flight metabolic rate correlates positively with dispersal rate in the field, explaining up to one‐third of the variation in flight distances (Niitepõld et al. 2009).…”

“…2009; Niitepõld 2010), and indeed, flight metabolic rate correlates positively with dispersal rate in the field, explaining up to one‐third of the variation in flight distances (Niitepõld et al. 2009). Finally, the AC heterozygotes have on average higher T b as recorded in butterflies caught during flight (Saastamoinen and Hanski 2008).…”

“…2005; Niitepõld et al. 2009; Niitepõld 2010), it is feasible that it could influence the thermal dynamics of flight.…”