Long-time readers (i.e., “for more than one week”) of The Molecular Ecologist will notice that this is the 2nd post on the socio-genetics of a primate multi-level society. The first being Melissa’s post last week that covered my recent paper on the genetics of the multi-level society of the gelada monkey. Now, there’s a new paper on the multi-level genetic structure of the gelada monkey’s close relative, the hamadryas baboon.
Hamadryas social structure
Multilevel societies are identified by two or more nested levels of organization. Hamadryas baboon society has four levels of organization. The smallest level, and core group, is the one-male unit (OMU), which is composed of (you guessed it) one-male and multiple females. OMUs aggregate to form groups of increasing size from clans, the smallest aggregation of OMUs, to bands to troops, the largest aggregations of OMUs, which can contain several hundred baboons. So, at least on the surface of things, this society appears to be strikingly similar to that of the gelada monkeys. But are the genetic underpinnings the same?
Researchers at the Max Planck Institute for Evolutionary Anthropology and the Filoha Hamadryas Project set out to address this question. They genotyped 244 baboons at 1 Y-linked and 23 microsatellite loci and also sequenced part of the mitochondrial d-loop (HVR-1). These genetic data, in combination with years of behavioral data on association patters, revealed that females dispersed farther than males, which suggests that it is closely related males that are the “glue” keeping clans together. Interestingly, they also found some evidence for limited dispersal among females, suggesting that they maintain bonds with close kin before and after dispersal.
We speculate that male philopatry at the clan level and female dispersal across one-male units and clans may enable both kin-based cooperation among males and the maintenance of kin bonds among females after dispersal.
So it appears that the closely related geladas and hamadryas baboons have converged on superficially similar, but fundamentally different multilevel societies.
Fun fact: Geladas and hamadryas baboons are sympatric in the the highlands of Ethiopia. Here’s a photo that I took of a mixed herd of geladas and hamadryas baboons. A male hamadryas is walking away in the background and two female geladas are in the foreground:
I wonder what their hybrid socio-genetic structure would be?