In the dramatic karst landscapes of southwest China, giant sinkholes known as tiankeng harbor isolated microhabitats that shelter rare plant species from extreme environmental stresses. A recent genomic study has illuminated the dual nature of these enigmatic ecological refuges: while they provide critical sanctuary from heat and drought, they also impose genetic constraints on an endangered tree species, Magnolia aromatica.
Researchers from the South China Botanical Garden and Guangxi Institute of Botany sequenced the genome of Magnolia aromatica and analyzed 112 individuals across 26 populations distributed inside and outside these karst tiankeng. Their population-level genomic analyses unveiled four major evolutionary lineages, two of which are tightly linked to the unique environmental conditions within the Leye Tiankengs. These sinkholes create cool, humid enclaves at their bases by buffering harsh climatic variability typical of karst mountains.
Intriguingly, the study revealed a genetic paradox. On a macro scale, populations inside tiankeng exhibited moderate genetic diversity and mutation loads, confirming their role as vital microrefugia that sustain species persistence. However, at finer spatial resolution, populations confined within tiankeng showed diminished genomic diversity coupled with an increased burden of deleterious mutations relative to neighboring exterior populations. This genomic erosion suggests that while tiankeng offer short-term protection, their geographic isolation may limit gene flow and thus suppress evolutionary potential over time.
Functional genomic analyses further demonstrated local adaptation of Magnolia aromatica to the shaded, dim forest interiors of tiankeng. Genes associated with photosynthesis and carbon fixation exhibited strong signatures of positive selection in these populations. Experimental shading confirmed these adaptations: seedlings endured and thrived under deep shade, but succumbed rapidly to full or intense sunlight, underscoring their ecological dependence on the sinkholes’ buffered light environments.
Climate change projections introduced additional concern. Modeling future habitat suitability indicated spatial shifts in viable ranges and increased maladaptation risks for some populations. More alarmingly, the accumulation of harmful mutations is predicted to intensify, exacerbating genomic deterioration and compounding challenges to long-term survival under rapidly shifting environmental conditions.
This pioneering study provides compelling genome-scale evidence that karst tiankeng simultaneously serve as refuges that preserve endangered trees and as evolutionary traps that constrain their adaptive capacity. It prompts a paradigm shift in conservation strategies, emphasizing that protecting isolated refuges alone may not safeguard the evolutionary futures of vulnerable species.
Lead author Kang Ming highlights the necessity of maintaining genetic connectivity by protecting not only tiankeng interiors but also adjacent exterior populations and dispersal corridors. This integrated approach aims to preserve gene flow, fostering resilience and adaptive potential necessary for enduring environmental change.
As rapid climate dynamics threaten biodiversity worldwide, these findings underscore the crucial balance between ecological shelter and genetic exchange. The karst tiankeng of southwest China, with their unique geomorphology and biotic communities, vividly illustrate the complex interplay between habitat isolation and evolutionary viability.
Subject of Research: Conservation genomics and evolutionary biology of Magnolia aromatica in karst tiankeng habitats
Article Title: Karst Tiankengs preserve but constrain evolutionary potential in the endangered tree Magnolia aromatica
News Publication Date: 14-Jul-2026
Web References: http://dx.doi.org/10.1016/j.cub.2026.06.051
Image Credits: Image by TANG Jianmin
Keywords: Evolutionary biology, conservation genomics, karst tiankeng, Magnolia aromatica, microrefugia, genetic diversity
