Decay of Sexual Trait Genes in an Asexual Parasitoid Wasp.
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 lineage 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 study of the genomics of neutral and selected trait decay.
Animal Ecology, Department of Ecological Sciences, VU University Amsterdam, The Netherlands.|Leiden Genome Technology Center, Department of Human Genetics, Leiden University Medical Center, Leiden, The Netherlands.
Ken
K
Kraaijeveld
Leiden Genome Technology Center, Department of Human Genetics, Leiden University Medical Center, Leiden, The Netherlands.
Seyed Yahya
SY
Anvar
Leiden Genome Technology Center, Department of Human Genetics, Leiden University Medical Center, Leiden, The Netherlands.
Jeroen
J
Frank
Leiden Genome Technology Center, Department of Human Genetics, Leiden University Medical Center, Leiden, The Netherlands.
Arnoud
A
Schmitz
Department of Ecology and Evolution, University of Lausanne, Lausanne, Switzerland.
Jens
J
Bast
Zoological Research Museum Alexander Koenig, Center for Molecular Biodiversity Research, Bonn, Germany.
Jeanne
J
Wilbrandt
Zoological Research Museum Alexander Koenig, Center for Molecular Biodiversity Research, Bonn, Germany.
Malte
M
Petersen
Zoological Research Museum Alexander Koenig, Center for Molecular Biodiversity Research, Bonn, Germany.
Tanja
T
Ziesmann
Zoological Research Museum Alexander Koenig, Center for Molecular Biodiversity Research, Bonn, Germany.
Oliver
O
Niehuis
Department of Human Genetics, Leiden University Medical Center, Leiden, The Netherlands.
Peter
P
de Knijff
Leiden Genome Technology Center, Department of Human Genetics, Leiden University Medical Center, Leiden, The Netherlands.
Johan T
JT
den Dunnen
Animal Ecology, Department of Ecological Sciences, VU University Amsterdam, The Netherlands.
Jacintha
J
Ellers
D000818:Animals; D005260:Female; D017344:Genes, Insect; D008297:Male; D009154:Mutation; D010641:Phenotype; D010802:Phylogeny; D020641:Polymorphism, Single Nucleotide; D012100:Reproduction, Asexual; D014863:Wasps / Q000235:genetics* / Q000502:physiology
Leptopilina clavipes; Wolbachia; parthenogenesis; deleterious variants; sexual trait decay