Are giant panda populations separated genetically across human disturbance features?

By: Liz Audie, Mike Lane, Samantha Morand, and Jackie Shuttleworth (Stonehill College, BIO323: Evolution, Spring 2019)

Ailuropoda melanoleuca, more commonly known as the giant panda, is facing serious population decline and is one of the many species conservationists are trying to save by protecting the areas where they live. While road development has been a huge advancement for us as humans, it has disrupted these pandas because it separates them from other pandas, causing subpopulations to form. This decreases the genetic diversity, which then reduces the probability that the given population will last. In the research done by Qiao et al. (2019), they chose to focus on the pandas from the Wolong Mountains. This region is heavily trafficked by tourists and is divided by a main highway (national road G350). Tourism is a possible threat to the giant panda population as it increases the isolation between pandas, and therefore the genetic composition.

Two captive giant pandas in Wolong
Figure 1 from Qiao et al.: “Two captive giant pandas in Wolong. Photo credit to Bo Luo of the China Conservation and Research Center for the Giant Panda.”

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The main objective of this research was to compare the genetics of the two populations of giant pandas north and south of the main road through Wolong. The populations’ genetic diversity was studied, as well as their size and distribution. Qiao et al. wanted to test the gene flow between the populations to see the impact of the road on the giant panda populations. The researchers also wanted to use a more reliable way of testing population size by using spatially explicit capture–recapture (SECR) methods to avoid experimental errors that have been found in previous research. They hypothesized the genetic diversity would be high as the pandas would have most likely spread out due to the road bisecting the populations.

The methods used in this research involved randomly distributed fecal sample collection from as many pandas in the population as possible. These samples were then used for DNA extraction and amplification in order to investigate the population size, health, and connectivity of pandas within the habitat of the Wolong Nature Reserve in Sichuan, China. In order to ensure the quality of the genetic data, all fecal samples were amplified at least three times. Individual genotypes were identified, and these records were able to estimate the total population size via capture-mark-recapture methods. A pairwise relatedness value (r) was used to relate kinship, with a larger positive value suggesting closer kinship and a smaller negative value suggesting distant kinship. Offspring of two individuals that have a high r value have a high risk of inbreeding deficiencies and low genetic variation, so this value was also measured in the population.

Map of Wolong Nature Reserve where fecal samples were collected
Figure 3 from Qiao et al.: “Map of Wolong Nature Reserve where fecal samples were collected.”

Researchers found that there seems to be no significant genetic boundaries within the populations of pandas they studied. This may be due to migration across the national road G350 that passes through the reserve. Although migration seems to be occurring across the road, other studies have shown that less migration is occurring across other roads with more traffic. These findings suggest that there may be more gene flow between subpopulations than was originally thought. Even so, these populations are still in danger of becoming more isolated as development, tourism, and traffic increases in less populated areas. To promote diversity and to preserve gene flow between populations, it is important to allow habitat corridors for individuals to migrate to different populations. In further studies, we would suggest that researchers analyze to what extent migration is occurring between subpopulations in other areas within these mountain ranges, and what can be done to maintain gene flow and genetic diversity. Research should also look closer at the effect of traffic and human disturbances on migration, as migration is one of the most important aspects of maintaining genetic diversity and reducing inbreeding.

Citation: Qiao, M., T. Connor, X. Shi, J. Huang, Y. Huang, H. Zhang, and J. Ran. 2019. Population genetics reveals high connectivity of giant panda populations across human disturbance features in key nature reserve. Ecology and Evolution 9: 1809–1819.

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