Genetic Patterns of Pond Turtles at the Northern Edge of the Pannonian Basin

Jim Crocker
19th July, 2024

Genetic Patterns of Pond Turtles at the Northern Edge of the Pannonian Basin

Mitochondrial DNA analysis shows that northern Pannonian populations of the European pond turtle (Emys orbicularis) primarily belong to the native lineage II derived from postglacial expansion (inset map), but also reveals the presence of non-native lineages I and IV in specific populations, indicating recent introductions (main map and haplotype network).

Image adapted from: Mikulíček et al. / CC BY (Source)

Key Findings

  • The study focused on the genetic diversity of European pond turtles in the northern Pannonian Basin (Slovakia, Hungary, Austria)
  • Contrary to expectations, these peripheral turtle populations showed high genetic diversity
  • A mixed population in Austria's Donau Auen National Park revealed hybridization between different turtle lineages
Understanding the genetic diversity of populations at the edge of their geographical range is crucial for conservation biology. Often, these peripheral populations are thought to have lower genetic diversity due to historical and contemporary factors such as postglacial dispersal, low effective population size, and genetic drift. This study, conducted by researchers at Comenius University, analyzed the genetic structure of the European pond turtle (Emys orbicularis) in the northern part of the Pannonian Basin (Slovakia, Hungary, Austria) to investigate this issue[1]. The researchers employed mitochondrial DNA (mtDNA) and microsatellite markers to assign individuals and populations into phylogeographic lineages and to determine genetic variation and population structure. They found that most individuals from natural populations belong to mtDNA lineage II, which includes the widely distributed haplotype IIa and likely endemic haplotypes IIl and IIo. Interestingly, non-native haplotypes were detected in one Slovak population (haplotype Ib) and in the Austrian Donau Auen National Park (haplotype IVa). These findings challenge the long-standing assumption that peripheral populations exhibit lower genetic diversity. Previous studies have suggested that peripheral populations often show reduced genetic diversity and increased differentiation due to smaller effective population sizes and greater geographical isolation[2]. However, the high variability found in microsatellite markers in this study indicates that marginal populations of Emys orbicularis in the Pannonian Basin may not necessarily have reduced genetic diversity. Moreover, the study uncovered a genetically mixed population in the Donau Auen National Park, consisting of turtles from mtDNA lineage II and lineage IV. This admixture suggests intense hybridization and introgression between the two lineages, which are taxonomically assessed as subspecies E. orbicularis orbicularis and E. orbicularis hellenica, respectively. This finding is significant as it highlights the potential for gene flow between different subspecies in peripheral populations, adding another layer of complexity to our understanding of genetic diversity at range margins. The use of both mtDNA and microsatellite markers in this study is noteworthy. Mitochondrial DNA is often used in phylogeographic studies because it is inherited maternally and can provide insights into historical population structures. Microsatellite markers, on the other hand, are highly polymorphic and can reveal fine-scale genetic variation within and between populations. This dual approach allowed the researchers to obtain a comprehensive picture of the genetic structure of Emys orbicularis in the Pannonian Basin. This study also ties into previous research on the genetic differentiation of Emys populations in different geographic regions. For example, a study on inland and coastal populations of Emys in Turkey found that these populations tend to preserve their allelic richness while continuing to differentiate[3]. The current study expands on this by showing that peripheral populations in the Pannonian Basin also maintain high genetic variability, despite their marginal location. In terms of methodology, the researchers employed Bayesian clustering algorithms to analyze the genetic data. This approach, while computationally intensive, is effective in identifying genetic clusters and assigning individuals to populations. However, as the size of genetic datasets continues to grow, there is a need for less computer-intensive methods. One such method is the Discriminant Analysis of Principal Components (DAPC), which has been shown to perform better than Bayesian clustering algorithms in some cases[4]. While DAPC was not used in this study, it represents a promising tool for future research on genetic population structure. In conclusion, this study by Comenius University provides valuable insights into the genetic diversity of peripheral populations of Emys orbicularis in the Pannonian Basin. Contrary to the expectation of reduced genetic diversity at range margins, the study found high genetic variability and evidence of hybridization between different lineages. These findings underscore the importance of considering both historical and contemporary factors in studies of genetic population structure and highlight the need for further research to fully understand the dynamics of peripheral populations.

GeneticsAnimal ScienceEvolution

References

Main Study

1) Population genetic structure of the European pond turtle (Emys orbicularis) at the northern edge of the Pannonian Basin

Published 18th July, 2024

https://doi.org/10.1007/s10592-024-01624-8

Related Studies

2) Genetic variation across species' geographical ranges: the central-marginal hypothesis and beyond.

https://doi.org/10.1111/j.1365-294X.2007.03659.x

3) Population structure and gene flow of the syntopic turtles Emys and Mauremys from coastal and inland regions of Anatolia (Turkey): results from mitochondrial and microsatellite data.

https://doi.org/10.1007/s11033-021-06429-3

4) Discriminant analysis of principal components: a new method for the analysis of genetically structured populations.

https://doi.org/10.1186/1471-2156-11-94


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