ESTIMATING THE HERITABILITY OF FLUCTUATING ASYMMETRY IN FIELD DROSOPHILA

Some studies have found intermediate heritabilities for fluctuating asymmetry (FA) in traits, but almost all of these are flawed and/or based on laboratory experiments. We therefore tested if there was heritable variation for FA in bristle and wing traits in three field collections of Drosophila melanogaster by rearing F₁ s from field flies under laboratory conditions. One of the collections was reared to the F₂ generation in the laboratory to compare heritability estimates from the laboratory with those from the field-laboratory comparison. Trait means indicated an increase in size under laboratory rearing. FAs increased in one collection, decreased in another collection, and showed no changes in the third collection under laboratory rearing. FAs from the collections tended to converge under laboratory conditions. Morphological traits were heritable under field conditions. However, FA was not significantly heritable for any of the individual traits or when FA was determined by combining traits. Comparisons of the two laboratory generations showed that FA heritability was low under laboratory conditions, in contrast to the morphological traits themselves. These findings suggest a very low heritability for FA in field and laboratory Drosophila. FA in bristle and wing traits may therefore be a poor indicator of genetic quality in Drosophila.