Feather chemicals contain information about the major histocompatibility complex in a highly scented seabird

Abstract

Mate choice informed by the immune genes of the major histocompatibility complex (MHC) may provide fitness benefits including offspring with increased immunocompetence. Olfactory cues are considered the primary mechanism organisms use to evaluate the MHC of potential mates, yet this idea has received limited attention in birds. Motivated by a finding of MHC-dependent mate choice in the Leach's storm-petrel ( Oceanodroma leucorhoa ), we examined whether the chemical profiles of this highly scented seabird contain information about MHC genes. Whereas previous studies in birds examined non-volatile compounds, we used gas chromatography–mass spectrometry to measure the volatile compounds emitted from feathers that potentially serve as olfactory infochemicals about MHC and coupled this with locus-specific genotyping of MHC IIB genes. We found that feather chemicals reflected individual MHC diversity through interactions with sex and breeding status. Furthermore, similarity in MHC genotype was correlated with similarity in chemical profiles within female–female and male–female dyads. We provide the first evidence that volatile chemicals from bird feathers can encode information about the MHC. Our findings suggest that olfaction likely aids MHC-based mate choice in this species and highlight a role for chemicals in mediating genetic mate choice in birds where this mode of communication has been largely overlooked.

No evidence for a role of MHC class II genotype in the chemical encoding of heterozygosity and relatedness in Antarctic fur seals

“…Our results are not consistent with either of these mechanisms, as we were unable to detect any effects of the MHC on chemical similarity or diversity, regardless of whether we tested for relationships in isolation or after controlling for the genomic background. Broadly speaking, our results stand in contrast to several recent studies of wild vertebrate populations reporting links between the MHC and odour [ 66 – 70 ]. However, in support of our results, Slade et al .…”

“…Our results are not consistent with either of these mechanisms, as we were unable to detect any effects of the MHC on chemical similarity or diversity, regardless of whether we tested for relationships in isolation or after controlling for the genomic background. Broadly speaking, our results stand in contrast to several recent studies of wild vertebrate populations reporting links between the MHC and odour [66][67][68][69][70]. However, in support of our results, Slade et al [68] also found no relationship between MHC heterozygosity and the chemical diversity of preen wax in song sparrows, even though chemical distance was associated with MHC dissimilarity in male-female but not same sex dyads.…”

“…[ 67 ] did not find odour differences among mandrills carrying different MHC supertypes, although MHC similarity and chemical similarity were correlated. Moreover, associations between the MHC and odour often appear to be context-dependent, varying for example by sex or breeding status [ 66 , 68 , 69 ]. However, there is no indication of strong context-dependence in our study as comparable results were obtained for breeding females and offspring.…”

House sparrows do not exhibit a preference for the scent of potential partners with different MHC-I diversity and genetic distances

“…However more recently, two bodies of evidence support olfactory mediated MHC-based mate choice in birds. Firstly, there is an increasing number of studies showing that the chemical profile of bird odour is correlated with MHC-II allelic diversity [41][42][43]. Secondly, behavioural experiments testing the olfactory preferences of birds have found that olfactory preferences for other conspecifics is based on MHC-II genes [28,29].…”