Quantitative genetic variation in an island population of the speckled wood butterfly (Pararge aegeria)

Abstract

Evidence of changes in levels of genetic variation in the field is scarce. Theoretically, selection and a bottleneck may lead to the depletion of additive genetic variance (VA) but not of nonadditive, dominance variance (VD), although a bottleneck may converse VD to V A. Here we analyse quantitative genetic variation for the Speckled Wood butterfly Pararge aegeria on the island of Madeira about 120 generations after first colonisation. Colonisation of the island involved both a bottleneck and strong natural selection, changing the average value of traits. Several life history and morphological traits with varying levels of change since colonisation were analysed. In accordance with expectations, all traits except one showed relatively low levels of VA, with an average heritability (h2) of 0.078. Levels of VD for these traits were relatively high, 20-94% of total variance and on average 80% of VG. The exception was a morphological trait that probably had not experienced strong natural selection after colonisation, for which a h2 of 0.27 was found. Another interesting observation is that the population seems resistant to inbreeding effects, which may be the result of purging of deleterious alleles.