Barring snake has crossed the Alps

Forum Science Barring snake has crossed the Alps

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    Barring snake has crossed the Alps

    Invader from the south: the Italian barn snake has recently also appeared in Bavaria. This snake species, originally only native to southern climes, has successfully crossed the Alps, which are actually considered a natural barrier, as studies have shown. These meandering immigrants were only stopped when they came across the related grass snake in southern Bavaria. Today there is a zone with hybrids of the two species.

    More and more animal species are now finding their way into regions where they were not originally native. For example, the Burmese pythons from Southeast Asia settled in Florida and the Asian ladybird came to Europe from Japan and China. And the Italian ring snake (Natrix helvetica sicula) has recently been found not only in Italy and the southern Alps, but also in southern Bavaria – despite the Alps being considered a natural barrier.

    Where does the adder come from?

    How did the snake get to Germany? A research team led by Marika Asztalos from the Senckenberg Natural History Collections in Dresden has now got to the bottom of this question. “We wanted to know how the snakes came to Bavaria, how widespread they are and whether they mix with the other grass snakes there,” explains Asztalos.

    Using around 1000 genetic samples from grass snakes from Central Europe, around 200 of which came from Bavaria, the scientists examined which representatives of this species of snake occur in southern Bavaria. From this, they derived the distribution and mixture of the grass snake native to Bavaria (Natrix natrix) and the Italian bar snake.

    Held up by the local snake

    It turned out that the Italian ring snake actually occurs in southern Bavaria and thus seems to have crossed the Alps. “Our study shows that the Italian ring snake spread over Alpine passes to Tyrol and Bavaria in the post-Ice Age,” explains Asztalo’s colleague Uwe Fritz. According to the research team, the range of the non-local snake has so far only been limited to the river valleys of the Inn, Isar and Loisach.

    At the points where the rivers settled by the immigrants pour into the plains from the Alpine valleys, however, their range ends quite abruptly, according to Asztalos and her team. A few kilometers further north, the researchers discovered only the native grass snake. Accordingly, the Alps apparently could not stop the grass snake from spreading, but the strong presence of grass snakes further north could, the scientists conclude.

    Hybrid formation in Bavaria

    Interesting: Of the approximately 200 samples from Bavaria, the researchers were able to assign 90 animals to the Italian barn snake. Most of them were hybrids between the immigrants and the native grass snake. “We are already familiar with similar hybridization processes from the Rhine region, but in southern Bavaria these are limited to a hybrid zone that is just a few kilometers wide, in which the parent species also live,” explains Asztalos.

    A subspecies of the invasive snake, the western barren grass snake (Natrix helvetica helvetica), which has been known for a long time in West Germany, came to Germany via a different route. “In West Germany there is another subspecies of the barnnake in the Rhine area that took a different route,” explains Fritz. “She immigrated to Central Europe from France.”

    Asztalos and her colleagues also discovered traces of this western barring snake for the first time in Bavaria, especially in the Lake Constance region and in Lower Franconia. However, these were exclusively mixed breeds of the western barn snake and the native snake species in Bavaria.

    Invaders advance

    According to the scientists, the hybrids of the two alien grass snake species and the native species could be an indication that future research could also reveal pure populations of immigrants in western Bavaria. (Journal of Zoological Systematics and Evolutionary Research, 2021, doi: 10.1111 / jzs.12471)

    Source: Senckenberg Society for Nature Research

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Forum Science Barring snake has crossed the Alps