Do your friends and family make you sick? Sociality and immunity in hyenas

Katy Califf and colleagues’ recent paper in The Journal of Mammalogy examined how sociality affects the variation and evolution of immunity in hyena populations.

Hyenas are an important large carnivore in the ecosystems they inhabit and are exposed to many diseases, however different hyena species show different degrees of sociality.  This makes them ideal for studying how sociality impacts the level of variation or the rate of evolution of immune gene families, specifically the major histocompatibility complex (MHC).

“More social animals [are likely to] have more opportunities to pick up pathogens [from other members of their species],” Califf says, and previous studies have some found evidence to support this.  Therefore, it was expected that these two hyena species would differ in the amount of variation in their immune system genes.  However, when comparing the diversity of 3 MHC genes in spotted (social) & striped hyenas (solitary), Califf and colleagues found both species to be equally diverse in genes within the MHC and that variation also changes, or evolves, quickly within each species. Furthermore, at each MHC locus, the team found several instances of shared versions of the genes between the species.

These findings suggest that the same evolutionary pressures, “including a common ancestral pattern of carrion-feeding,” has influenced MHC diversity more strongly in these hyena species than have more recent pressures like sociality.

Read more here: Califf K, Ratzloff EL, Wagner A, Holekamp KE, Williams BL, “Pervasive gene duplication and positive selection at MHC loci in two hyena species”, Journal of Mammalogy. 2013.94(2): 282-294.

[This is a reposted excerpt from my work in the BEACON Buzz]

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