Sequence-based evidence for major histocompatibility complex-disassortative mating in a colonial seabird

Area of Science:

• Evolutionary biology
• Behavioral ecology
• Immunogenetics

Background:

• The Major Histocompatibility Complex (MHC) is crucial for immune defense and influences mate choice.
• The genetic compatibility hypothesis posits that females select mates with dissimilar MHC genotypes to avoid inbreeding and enhance offspring immunity.

Purpose of the Study:

• To test the genetic compatibility hypothesis in great frigatebirds (Fregata minor).
• To investigate mate choice based on Major Histocompatibility Complex (MHC) genotypes and microsatellite alleles.

Main Methods:

• Sequencing of the second exon of MHC class II B genes in great frigatebirds.
• Analysis of MHC allele sharing and amino acid sequence similarity between mated pairs.
• Comparison of MHC similarity with microsatellite allele sharing and size similarity.

Main Results:

• No significant difference in MHC similarity between pairs with and without extra-pair paternity.
• Significantly disassortative mating observed based on MHC amino acid sequence similarity.
• No evidence of mate choice based on MHC allele sharing or microsatellite alleles.

Conclusions:

• Great frigatebird females engage in mate choice favoring partners with dissimilar MHC amino acid sequences.
• This MHC-based mate choice does not appear to be driven by inbreeding avoidance.
• The findings suggest MHC influences mate selection through mechanisms beyond simple allele sharing or inbreeding avoidance.