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A Noninvasive Hair Sampling Technique to Obtain High Quality DNA from Elusive Small Mammals

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Historical sampling reveals dramatic demographic changes in western gorilla populations.

Olaf Thalmann¹, Daniel Wegmann, Marie Spitzner

¹Max Planck Institute for Evolutionary Anthropology, Deutscher Platz 6, 04103 Leipzig, Germany. olatha@utu.fi

BMC Evolutionary Biology

|April 5, 2011

Summary

Cross River gorillas diverged from western gorillas over 17,000 years ago, but gene flow ceased recently, leading to a severe population bottleneck and genetic diversity loss. This history is linked to climate change and human impact.

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Area of Science:

Genetics
Evolutionary Biology
Conservation Biology

Background:

Many large mammal populations are fragmented, with unclear origins of subdivision.
Demographic modeling and temporal genetic sampling help infer population history.
Western gorillas (Gorilla gorilla), especially the Cross River subspecies (G. g. diehli), face conservation challenges.

Purpose of the Study:

To investigate the long-term and recent population dynamics of Cross River gorillas.
To compare genetic variation in contemporary samples with historical museum specimens.
To understand the factors driving population divergence and decline in great apes.

Main Methods:

Microsatellite genotyping of museum specimens and contemporary Cross River gorilla samples.
Demographic modeling to infer population size changes and gene flow.
Comparison of heterozygosity between historical and modern genetic data.

Main Results:

Cross River gorillas diverged from ancestral western gorillas approximately 17,800 years ago.
Gene flow ceased around 420 years ago, followed by a bottleneck starting 320 years ago, reducing effective population size by 60-fold.
A significant loss of genetic variation was observed in the last 100 years.

Conclusions:

Climatic oscillations likely caused population expansions and isolation, leading to the divergence of Cross River gorillas.
Recent population decline is attributed to anthropogenic pressures over the last few hundred years.
Prolonged gene flow with eventual isolation, rather than secondary admixture, characterizes African great ape population histories.