Genetic study shows human influence in northward spread of European wall lizards
A study of the mitochondrial DNA of the common wall lizard shows that their spread from Italy into southeastern Europe was probably aided by human influence.
A study of the mitochondrial DNA of the common wall lizard shows that their spread from Italy into southeastern Europe was probably aided by human influence.
The alternative explanation is that the species (Podarcis muralis) survived in refuges during the periodic advance and retreat of European ice sheets over the past 2 million years of the Pleistocene epoch.
But the research published online Sept. 30 in Biodiversity Data Journal presents data based on analysis of the lizards’ mitochondrial DNA that argues for a human-assisted spread of their natural range.
Lead author Oleksandra Oskyrko is affiliated with Universidade do Porto, Portugal, and Charles University, Prague, Czech Republic.
Origin and range of the species
The genus Podarcis is hypothesized to have originated in the Oligocene epoch (34 million to 23 million years ago) and diversified into the main lineages found today during the Miocene (23 million to 5 million years ago).
The species muralis, the common wall lizard, has the widest known range of all members of the genus, making it a prime candidate for evaluating the evolution of local adaptation to climate changes, particularly in the northern limit of its present ranges.
The current distribution of the species ranges from the Iberian peninsula to Asia Minor. It is notably present in more northern, extra-Mediterranean regions of Western, Central and Eastern Europe.
The study of its spread in present-day Europe can shed light on the likelihood of the survival of a variety of species in today’s changing climatic conditions, as well as elaborate the dynamic nature of species ranges and the role of micro-evolutionary processes.
Determining regional differentiation
Previous studies based on mitochondrial DNA had suggested that the wider than expected distribution of P muralis was accompanied by regional differentiation into more than 20 distinct genetic linkages. More recent work showed an origin in Italy during the Miocene, followed by expansion into Iberia and the Balkans, and subdivision into lineages.
To verify and elaborate these earlier hypotheses, researchers examined the protein cytochrome b commonly found in the mitochondria of eukaryotic cells. Some of their samples were taken for the first time from wall lizards in new regions of southeastern Europe.
The new research added to the previously limited data from southeastern Europe, particularly the region of the Danube River that forms the Romanian-Bulgarian border. Human-mediated colonization had already been identified in a nearby region of Ukraine.
The researchers sampled individuals from 28 locations in Bulgaria and Romania by capturing the lizards and gently removing a tiny piece of the outer tip of their tails for later laboratory examination.
New connection to Italy discovered
All of the samples fell into five distinct haplogroups or clades, and no new clades were found. Of the 50 new DNA sequences taken from lizards found in Bulgaria and Romania, 45 fell into three clades previously known from Bulgaria, Serbia, Romania, and Ukraine, known as the Central Balkan clade.
Five samples collected from Bucharest, Romania, however, were found not to be part of that Central Balkan grouping. Analysis of the mitochondrial DNA sequences “revealed close affiliation with the Southern Alps clade which has its main distribution in northern Italy,” the authors write.
This points to the presence of a non-native population, previously known only in northeastern Italy, and suggests human introduction of the Southern Alpine clade followed by possible admixture with native Central European populations.
The authors suggest this is “most likely . . . a result of human-mediated transport on inland waterway vessels with construction materials, plants or other goods, as was discovered in other countries.”
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Oleksandra Oskyrko et al. Unravelling the origin of the common wall lizards (Podarcis muralis) in south-eastern Europe using mitochondrial evidence. Biodiversity Data Journal (20 Sep 2022).
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