No evidence for MHC-based mate choice in wild giant pandas

Major histocompatibility complex genes (MHC), a gene cluster that controls the immune response to parasites, are regarded as an important determinant of mate choice. However, MHC-based mate choice studies are especially rare for endangered animals. The giant panda (Ailuropoda melanoleuca), a flagship species, has suffered habitat loss and fragmentation. We investigated the genetic variation of three MHC class II loci, including DRB1, DQA1, and DQA2, for 19 mating-pairs and 11 parent-pairs of wild giant pandas based on long-term field behavior observations and genetic samples. We tested four hypotheses of mate choice based on this MHC variation. We found no supporting evidence for the MHC-based heterosis, genetic diversity, genetic compatibility and "good gene" hypotheses. These results suggest that giant pandas may not use MHC-based signals to select mating partners, probably because limited mating opportunities or female-biased natal dispersal restricts selection for MHC-based mate choice, acknowledging the caveat of the small sample size often encountered in endangered animal studies. Our study provides insight into the mate choice mechanisms of wild giant pandas and highlights the need to increase the connectivity and facilitate dispersal among fragmented populations and habitats.