Halfway Through Ex Situ Population Genetic Lifespan: The Case of Cochlearia polonica

TL;DR

A study on the endangered plant Cochlearia polonica shows that cultivating it outside its natural habitat led to a rapid loss of genetic diversity, increasing its risk of extinction.

Contribution

The study highlights the genetic risks of ex situ conservation in a critically endangered plant species.

Findings

The ex situ population of C. polonica lost about half its genetic diversity compared to the wild source population.

The cultivated population became genetically homogenized and went extinct within 5–6 generations.

The remaining wild population is now more threatened than previously thought.

Abstract

Cochlearia polonica is a critically endangered plant species naturally occurring in a limited area of Poland. After its original habitat was destroyed, conservationists established a cultivated population in a PAS Botanical Garden CBDC. This study compares the genetic profile of the last remaining wild population and the now extinct cultivated population. Although the cultivated group initially increased in number, it experienced a significant loss of genetic variation over a short time. The analysis reveals a divergence in genetic structure between the two populations, despite their shared origin. These results demonstrate the risks associated with cultivating endangered species outside their natural environment, especially when the starting population is small. Reduced genetic diversity can limit a species’ ability to adapt and survive. The findings emphasise the importance of maintaining genetic health in conservation efforts. To prevent further decline, it is essential to collect seeds from the remaining wild population and store them under secure, long-term conditions. This strategy could help conserve the species and support future restoration efforts.

Although the usage of genetic data for the conservation management of threatened species is growing rapidly, the assessment of the trajectory and persistence of ex situ and in situ populations suffers from a lack of monitoring of genetic indicators. To fill this gap, we conducted a comparative analysis of the genetic structure ex situ and its source population of Cochlearia polonica to improve conservation outcomes for this species. C. polonica, as a range-restricted endemic species in Poland, exists in the wild in a single reintroduced population, which was the source for establishing an ex situ population in the botanical garden, and both populations have been well studied in abundance time series until the extinction of artificial populations due to genetic constraints. We collected AFLP data from individuals sampled after the peak recovery phase following the founder effect in the ex situ population, as well as from the source population, to assess the genetic consequences of long-term cultivation. The genetic profile of both populations suggested their strong differentiation. The genetic variation in the ex situ population expressed by Shannon’s Information Index and expected heterozygosity (He) was approximately half that of the source population. While ex situ population growth was high, the gene pool was homogenised, and genetic diversity waned, leading to its extinction across merely 5–6 generations. Thus, the only reintroduced population of C. polonica left in the wild is more threatened with extinction than previously thought, and conservation action should be taken immediately.

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