Wednesday, October 14, 2015

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.
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.

Monday, October 5, 2015

Gregarious chimps have more grey matter in specific region of the brain

Chimpanzees with offspring, Photo credit: flickr user Valerie
As one of our closest living relatives, studying the behavior, ecology, and anatomy of chimps provides a look back in time as to what the last common ancestor of chimpanzees and humans may have been like. A recent study examined the brain structure of over one hundred chimpanzees to understand how personality and the brain are connected.

Latzman and colleagues (2015) studied 107 captive chimpanzees by using MRIs and an assessment composed of 41 questions about each individual chimp's personality that was conducted by staff members who care for the animals. The article did not state how long these staff members worked with the chimpanzees, only that they felt they could assess their personalities.

Latzman and colleagues (2015) showed that the volume of gray matter and asymmetry of various regions of the frontal cortex are correlated. Grey matter, found mainly on the outside of the brain, is composed on neuronal cells and unmyelinated axons. (To learn more about grey matter, click here.) Chimpanzees ranked as more dominant, open, and extraverted have greater average grey matter in the frontal cortex of their brains. Extraversion in this article is defined as "energetic approach orientated." Their research also shows that frontal cortex asymmetry, or lack of equality/symmetry, is associated (but not correlated) with dominance, extraversion, and unpredictability.
Source: Biological Psychology 6e via Wikipedia

There are limitations to this study, as Latzman and colleagues (2015) mention. It is impossible to determine the causal relationship. Do personality differences create these structural differences in the brain? Or do structural differences in the brain create these personalities differences? As of right now, we can't answer this question. Interpretations of these findings are also limited by our own understanding of the brain, and we have much to still learn about the structure and function of this complex organ.

Yet, because of this study we have a greater understanding of the biological bases of behavior and personality.  Latzman and colleagues (2015) are the first to study the frontal cortex of the brain and personality in chimpanzees. As we know, chimpanzees are an excellent model for human behavior and personality because they are so closely related to humans. Studies such as this one allow us to refine our understanding of the evolution of our own species.

Food for thought: Would we expect to see the same results in bonobos? Orangutans? Lemurs?

Links of interest:
Cooking chimpanzees
Female friendship in chimpanzees
Differences in tool use between males and females

Works cited:

Robert D. Latzman, Lisa K. Hecht, Hani D. Freeman, Steven J. Schapiro, William D. Hopkins. Neuroanatomical correlates of personality in chimpanzees (Pan troglodytes): Associations between personality and frontal cortex. NeuroImage, 2015; 123: 63 DOI: 10.1016/j.neuroimage.2015.08.041