Amazing stuff!
"Deep in the heart of China's karst landscapes, scientists have discovered immense sinkholes that appear to contain ancient forests that are teeming with life ...
These sinkholes are known as karst tiankengs — and they appear to be a hotbed of genetic diversity and home to endangered species like the Manglietia aromatica.
A recent study was published in the March issue of Forests, which appeared to provide evidence that these sinkholes have conserved long lost DNA. ...
In the introduction to the study, researchers stated: "China has the most extensive distribution of karst terrain globally, covering an area of 344 km2. The unique development process of karst landforms has resulted in the formation of distinctive landscapes, including peak clusters, peak forests, caves, and karst sinkholes." ...
In 2022, the UNESCO Courier reported that the Dashiwei "tiankeng is the largest of its kind and yet has only been known to the outside world since 1998. It is part of the Dashiwei Tiankeng Group, a rare geological wonder with 29 sinkholes distributed in an area of 20 square kilometers. The scene down there was stunning: an underground pristine forest with no trace of human activities, with 40 metre-high ancient trees and a group of endangered wild plants from the times of dinosaurs." ..."
In the introduction to the study, researchers stated: "China has the most extensive distribution of karst terrain globally, covering an area of 344 km2. The unique development process of karst landforms has resulted in the formation of distinctive landscapes, including peak clusters, peak forests, caves, and karst sinkholes." ...
In 2022, the UNESCO Courier reported that the Dashiwei "tiankeng is the largest of its kind and yet has only been known to the outside world since 1998. It is part of the Dashiwei Tiankeng Group, a rare geological wonder with 29 sinkholes distributed in an area of 20 square kilometers. The scene down there was stunning: an underground pristine forest with no trace of human activities, with 40 metre-high ancient trees and a group of endangered wild plants from the times of dinosaurs." ..."
From the abstract:
"Karst tiankengs in China are globally significant locations for studying ecological environments and plant diversity. However, there are few reports on how the unique geographical environment of tiankengs affects plant genetic diversity and genetic structure. This study used Hyper-seq gene sequencing technology to develop large-scale genomic SNPs of Manglietia aromatica, both within and outside the tiankengs. Its aim was to investigate the impact of tiankengs on the genetic diversity and genetic structure of the M. aromatica population. The analysis results indicate that the genetic diversity of the populations within the tiankeng (π = 0.2044) is higher than that of the populations outside of it (π = 0.1671), indicating that the tiankengs have a positive impact on species diversity. The genetic differentiation coefficient (FST) between the populations inside and outside the tiankeng was 0.0534 and the FST values of populations within the tiankeng were 0.077, 0.082, and 0.141, meaning that the genetic variation in the tiankengs is very high. The genetic similarity outside the tiankengs is also very high, indicating that the tiankengs are effectively preserving the genetic diversity of M. aromatica. Furthermore, the gene introgression analysis results gave no proof of gene flow between the three tiankeng populations. This suggests that the tiankengs not only protect species diversity, but also hinder gene flow between populations to some extent. However, this hindrance may gradually subside with the evolution of the tiankengs. The genetic structure analysis revealed that the M. aromatica population in Guangxi, China, can be classified into three subpopulations. The first is the tiankeng subpopulation, including all the populations in tiankengs. The second subpopulation consists of populations surrounding the tiankengs. These two subpopulations are distributed in Leye County in northwestern Guangxi, China, and are very close to each other. The third is the Huanjiang subpopulation, which is located far away from the tiankengs. Considering the direction of gene flow and genetic structure, it is speculated that the populations in the tiankengs evolved from the populations near the pit mouth. This study confirms that the tiankengs are shelters and provide a suitable habitat for the endangered plant M. aromatica, because its genetic diversity is well conserved and the species is well adapted to the habitat within the tiankengs."
Figure 1. The distribution map of 10 populations of Manglietia aromatica. Note: The orange points represent the populations of M. aromatica inside the karst tiankeng and the blue points represent the populations of M. aromatica outside the karst tiankeng.
Xiaozhai Tiankeng seen from the southern rim in 2005.
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