Variation in morphological traits and trait asymmetry in field Drosophila serrata from marginal populations

Drosophila serrata occurs along the eastern coast of Australia with a south ern range boundary near Sydney. To compare levels of phenotypic variation i n marginal and central populations, we examined morphological variation in populations of this species from the southern range boundary and two more n ortherly populations. The populations differed for wing traits and there wa s an increase in wing size in the marginal locations which persisted under laboratory culture. The means of wing and bristle traits increased under la boratory culture, whereas wing trait coefficients of variation and variance s decreased. Heritability estimates for wing size traits tended to be lower in the field compared with the laboratory, whereas bristle and crossvein l ength heritabilities were similar across environments. There was evidence f or heritable variation in wing and bristle traits in both the marginal and more northern populations, suggesting that genetic variation was not limiti ng in marginal populations. Fluctuating asymmetry (FA) was also assessed as a measure of genomic and environmental stress. There were no consistent di fferences among populations for the FA of individual traits, or for a total FA score summed across traits. FA levels in field parents and laboratory-r eared progeny were similar. Overall, the results do not support the conject ure that levels of phenotypic and genetic variability differ between centra l and marginal D. serrata populations.