Trait loss is a widespread phenomenon with pervasive consequences
for a species’ evolutionary potential. The genetic changes
underlying trait loss have only been clarified in a small number of cases. None of these studies can identify whether the loss of the trait
under study was a result of neutral mutation accumulation or negative selection. This distinction is relatively clear-cut in the loss of
sexual traits in asexual organisms. Male-specific sexual traits are not expressed and can only decay through neutral mutations,
whereas female-specific traits are expressed and subject to negative selection. We present the genome of an asexual parasitoid
wasp and compare it to that of a sexual lineage of the same species.
We identify a short-list of 16 genes for which the asexual lineage
carries deleterious SNP or indel variants, whereas the sexual lineag
e does not. Using tissue-specific expression data from other insects,
we show that fifteen of these are expressed in male-specific reproductive tissues. Only one deleterious variant was found that is
expressed in the female-specific spermathecae, a trait that is
heavily degraded and thought to be under negative selection in
L. clavipes
. Although the phenotypic decay of male-specific sexual traits in asexuals is generally slow compared with the decay of
female-specific sexual traits, we show that male-specific traits do indeed accumulate deleterious mutations as expected by theory.
Our results provide an excellent starting point for detailed s
tudy of the genomics of neutral and selected trait decay.