Researchers from New York University and University of Exeter have discovered that some Old World monkeys (Cercopithecidae) have developed distinctive facial traits in order to avoid interbreeding with related species. The group of guenon monkeys mainly lives in Central and West Africa. It contains more than 25 species which spend times together during their travels or sleeping, increasing the risk of interbreeding. Let’s see what the scientist say about how monkeys avoid interbreeding.
Departing from a common sense hypothesis, the authors posed the question “what mechanisms keep closely related species that overlap geographically from inter-breeding, so that they are maintained as separate species”? (James Nigham, NYU). The common sense hypothesis has been developed in the 1980’s by Jonathan Kingdon, who tried to explain the differences in monkeys’ faces, but has never been tested. Among the distinctive facial features which help the monkeys identify each other are “differently colored eyebrow patches, ear tufts, nose spots, and mouth patches”
Monkeys avoid interbreeding with close-by species
To answer the question, the researchers went in a fieldwork in Central and West Africa, where various species of guenon monkeys live close to each other. They even went to zoos in the US and UK in an effort to gather 1400 standardized photographs for a total period of 18 months. Through the algorithmic technique called eigenface, they managed to identify the different facial features between the species. The characteristic is found to apply in the case of geographically overlapping species, as an effort to avoid hybridization. The species of monkeys living side by side have this mechanism to protect them from having infertile offspring by enforcing genetic separation.
“In other words, how you end up looking is a function of how those around you look. With the primates we studied, this has a purpose: to strengthen reproductive isolation between populations” James Nigham, NYU, stated.
According to BBC, it is not the first example of ‘character displacement’. Other scientists have provided so far illustrations of other means of differentiation by acoustic and electric signals. The authors claim that to date this is the best example of research on how monkeys avoid interbreeding.
The paper called “Character displacement of Cercopithecini primate visual signals” appeared in Nature Communications on the 26th on June.