Potential trouble for the endangered Udzungwa red colobus monkey

Recent genetic analysis of the Udzungwa red colobus monkey (Procolobus gordonorum) indicates the species might be in trouble in the future. This endangered monkey is endemic to the Udzungwa Mountains in Tanzania with population numbers currently in decline due to habitat loss and fragmentation (Struhsaker et al., 2008).

Udzungwa red colobus monkey, credit:Stevage

Ruiz-Lopez and colleagues (2015) did genetic analyses on 121 individuals using DNA collected from fecal samples. Samples were collected from populations living in five forest fragments of varying size. Scientists then used what is termed, "landscape genetics," combining genetic analysis with geographic-information-science (GIS). Ruiz-Lopez and colleagues (2015) specifically looked at how fragmentation affects P. gordonorum's genetic variation and what landscape features explained genetic differences.

Results showed that the greatest genetic differences were found between monkeys that are separated by villages and/or by areas of land that experienced high densities of fires. Given that the red colobus monkey is arboreal, Ruiz-Lopez and colleagues were surprised forest coverage is not a significant factor contributing to genetic variation. Despite differences in forest fragment size and in population density of the monkeys themselves, genetic variation is not significantly affected by the forest fragment individuals inhabit. Forest fragmentation in this area is relatively new (Marshall, 2007), thus these populations have only recently been genetically isolated from each other. Perhaps not enough time has passed for differences to manifest.

Ruiz-Lopez and colleagues (2015) are careful in their conclusions though and state that their findings do not necessarily prove that human activities are the main cause of this genetic variation. Human habitation and human-caused fires are likely contributing to the genetic differences, but these differences may be natural in origin, with humans simply reinforcing and maintaining genetic variation (Ruiz-Lopez et al., 2015).

Although Ruiz-Lopez and colleagues are unable to show a direct cause-and-effect relationship, this work does highlight the importance of human activity on the landscape and its impact on genetic changes in primate populations. As of today, inbreeding is not a problem for the Udzungwa red colobus monkeys, but it could be in the future, given this new evidence suggests human impacts are contributing to genetic differentiation. This is one of the few studies to use landscape genetics in this region.

Links of interest:
IUCN Redlist Page
Why we need corridors

Works cited:
Marshall AR. (2007) Disturbance in the Udzungwas: Responses of monkeys and trees to forest degradation. PhD thesis University of York: UK.
Struhsaker, T, Butynski, T.M. & Ehardt, C. 2008. Procolobus gordonorum. The IUCN Red List of Threatened Species 2008: e.T40015A10302163. http://dx.doi.org/10.2305/IUCN.UK.2008.RLTS.T40015A10302163.en . 

Ruiz-Lopez, M. J., Barelli, C., Rovero, F., Hodges, K., Roos, C., Peterman, W. E., & Ting, N. (2015). A novel landscape genetic approach demonstrates the effects of human disturbance on the Udzungwa red colobus monkey (Procolobus gordonorum). Heredity.