Advanced molecular and computer modeling has revealed that the titi monkey - one of the world's most diverse primate groups - has a more complicated evolution than previously thought.
Rather than grouping these New World monkeys together under the genus Callicebus, scientists from the University of Salford found that the primates warrant a more precise classification. They suggest redefining the monkeys as three distinct genera: Callicebus, Chaeracebus and Plecturocebus.
The study also revealed that the species Callicebus dubius should be reclassified as Callicebus caligatus, lowering the number of recognized species from 34 to 33.
"By dividing the titi monkeys into three new genera we are better describing biodiversity by acknowledging the evolutionary uniqueness of these old lineages," explained Jean Boubli, reader in animal ecology at the University of Salford. He described the findings as the "culmination of his 20 year quest for the origins of titi monkey diversity."
Having spent three years in the northern Amazon, Boubli and his Ph.D. student Hazel Byrne - who also spent months in the jungle - constructed the largest know array of titi monkey DNA sequences. This, researchers say, sheds new light on key evolutionary events of the monkeys' past.
Working alongside zoologists from Brazil and the U.S., the team ran hundreds of genetic codes through computer programs in order to simulate the evolution of titi monkeys over millions of generations.
One key evolution event was identified 11 million years ago, at which time Plecturocebus and Callicebus diversified as two unique genera. Researchers also found an evolutionary split between Callicebus and Cheracebus 8 million years ago.
"Historically taxonomy (the classification of animals) has been largely based on morphology - color, shape, size, features - rather than genetic diversity. However, things can be very closely related and look quite different, or be genetically distinct and look the same," Byrne said.
Researchers describe taxonomy as "the road map of conservation." In other words, identifying the monkeys in greater detail will allow for improved, targeted protections, as conservationists will be able to better assess the needs and threats of individual species.
"Each of the three genera can now be recognized as unique, important lineages, giving governments and NGOs a clearer focus for conservation programs," Boubli said. "It makes sense that before you say 'we're going to dedicate our resources to this, you need to know what 'this' is."
Titi monkeys are currently listed as critically endangered on the International Union for Conservation of Nature's Red List of Threatened Species. It is estimated that 80 percent of titi monkey populations have declined within the last 25 years, largely due to massive deforestation and mounting pressure from human population encroachment.
Next, researchers plan to further investigate the biogeographical evolution of titi moneys. Learning more about how the animals diversified over time and space could ultimately reveal how the Amazon was formed.
The findings were published in the March 1 issue of the journal Frontiers in Zoology.
