Unusual evolution of tree frog populations in the Chernobyl exclusion zone

Research published in Evolutionary Applications explores the genetic status of Eastern tree frog (Hyla orientalis) populations in the Chernobyl exclusion zone (CEZ) following the 1986 nuclear accident.
Study examines how chronic ionizing radiation has influenced microevolution and genetic diversity over 30 years.

Clément Car, André Gilles, Olivier Armant, Pablo Burraco, Karine Beaugelin-Seiller, and other researchers from various institutions in France, Ukraine, the UK, and Sweden.
The study is open access, allowing for widespread dissemination of findings.

Genetic analyses of 19 Eastern tree frog populations collected from the Chernobyl region reveal:
- Absence of Genetic Erosion: No significant loss in genetic diversity due to radiation exposure.
- Higher Mitochondrial Diversity: Chernobyl populations exhibit greater mitochondrial genetic diversity compared to populations from other European regions.
Microevolutionary Processes: Researchers utilized nuclear and mitochondrial genetic markers to assess variations and trends in the evolutionary history of these frogs.
Haplotype Networks: Evaluation of haplotype networks suggests that Chernobyl's frogs have undergone unique evolutionary changes due to an increased mutation rate in their mitochondrial DNA.

Biodiversity loss has intensified over the past 50 years, impacted by pollution, habitat destruction, and climate change. Radioactive contamination post-Chernobyl presents a unique case for studying ecological impacts on wildlife.
Initial radiation effects led to marked concerns regarding ecosystem health and the long-term consequences on species.

Genetic Variation: Understanding genetic variation within and across populations helps in assessing the evolutionary impact of pollutants, particularly radiation.
Studies on Banks Voles: Research in Chernobyl has shown increased genetic diversity in species like the bank vole due to chronic radiation exposure, possibly explained by elevated mutation rates or demographic influxes into the CEZ.

Data collection involved:
- Capturing a total of 216 tree frog individuals across 19 populations between 2016 and 2018, covering a gradient of radioactive contamination.
- Used the cytochrome b gene as a mitochondrial marker alongside 21 nuclear microsatellites.
- The analysis also included measuring radiation levels at capture sites to assess dose exposure.

Mitochondrial vs. Nuclear Markers: Mitochondrial genetic biodiversity was significantly higher in CEZ populations. In contrast, nuclear diversity showed no significant differences.
Geographical Genetic Structure:
- Low differentiation indices for nuclear markers imply limited migration of these frogs, while high differentiation in mitochondrial markers reflects isolated evolutionary processes.

Unexpected Genetic Diversification: Higher mitochondrial diversity suggests a unique evolutionary trajectory in Chernobyl frogs, potentially driven by a higher mutation rate.
Mutation-Drift Dynamics: The findings propose that lower effective population sizes and increased mutation rates can lead to unexpected genetic diversity patterns in contaminated environments, contrary to classic expectations of genetic erosion.

The study illustrates how chronic exposure to ionizing radiation may lead to unique evolutionary adaptations in wildlife, emphasizing the importance of examining mitochondrial markers for ecological and evolutionary research.
Impacts on population viability underline the need for comparative studies across various contaminated regions to understand the broader ecological ramifications of such exposures.