MHC GENETIC VARIATION INFLUENCES BOTH OLFACTORY SIGNALS AND SCENT DISCRIMINATION IN RING-TAILED LEMURS

Diversity at the Major Histocompatibility Complex (MHC) is critical to health and fitness, such that MHC genotype may predict an individual′s quality or compatibility as a competitor, ally, or mate. Moreover, because MHC products can influence the components of bodily secretions, an individual′s body odor may signal its MHC and influence partner identification or mate choice. To investigate MHC-based signaling and recipient sensitivity, we test for odor-gene covariance and behavioral discrimination of MHC diversity and pairwise dissimilarity, under the good genes and good fit paradigms, in a strepsirrhine primate, the ring-tailed lemur ( Lemur catta ). First, we coupled genotyping with gas chromatography-mass spectrometry to investigate if diversity of the MHC-DRB gene is signaled by the chemical diversity of lemur genital scent gland secretions. We also assessed if the chemical similarity between individuals correlated with their MHC similarity. Next, we assessed if lemurs discriminated this chemically encoded, genetic information in opposite-sex conspecifics. We found that both sexes signaled overall MHC diversity and pairwise MHC similarity via genital secretions, but in a sex- and season-dependent manner. Additionally, both sexes discriminated absolute and relative MHC-DRB diversity in the genital odors of opposite-sex conspecifics, supporting previous findings that lemur genital odors function as advertisement of genetic quality. In this species, genital odors provide honest information about an individual′s absolute and relative MHC quality. Complementing evidence in humans and Old World monkeys, our results suggest that reliance on scent signals to communicate MHC quality may be important across the primate lineage.