As already been mentioned where wild guppies originate from, wild type and wild guppies have also been introduced within Europe. This would be in artificial thermal water bodies. This could be in free nature or basins. But no matter wild type (fancy guppies reverted to wild type) or wild guppy, we're talking about "feral populations" in this case. Most of them are Poecilia reticulata. But even Poecilia wingei has been introduced to these non endemic locations.

Depending on the location and when fancy guppies have been introduced to non endemic spots, their phenotypes can differ a lot. From still visible traits of breeding forms to reverted to wild types.

Above: Locations where wild type and wild guppies are to be found in Europe.

Illustration above & below courtesy :

Paper: European thermal waters as hotspots for aquarium dumping: insights into feral guppies and other pet-traded species from Southern France

Above: Updated feral populations of Poecilia reticulata across Europe

Gillbach

Below: An illustration of the area in Germany where guppies are to be found. To be precise, in the Gillbach river, near a power plant. The Gillbach is a 28.5-kilometer-long right tributary of the Erft in North Rhine-Westphalia, Germany. This watercourse is exceptional because, particularly in its upper reaches, it maintains a water temperature of over 20°C year-round, thereby providing a habitat for a community of flora and fauna that wouldn't otherwise occur naturally in Germany. This is caused by the discharge of warm cooling water from the Niederaußem lignite-fired power plant.

Above: Niederaußem power plant.

The Gillbach has got the nickname "Guppybach" because of the many guppies that are found overthere. But besides guppies, also other tropical and subtropical fish are introduced in the Gillbach by man. Some of those fish are cichlids, mollies, catfish, etc...

Euphrates Basin

The first location in Turkey where feral guppies were found alongside green swordtails was in a hot spring in Eastern Turkey (38°34′32″N, 37°29′21″E) in the Euphrates River Basin near the Tohma river drainage (in Darende-Malatya, in the Eastern Turkey).
am (Malatya, in the Eastern Turkey). Feral guppies have also been recorded in the Çeşme-Ildır aquifer in İzmir, indicating that these ornamental fish have also become established in the Aegean region of Turkey. Nowadays, feral guppies are now established in multiple regions of Turkey.

Warmbach

Warmbach" (Warm Creek), a unique thermal stream where the water temperature hits 24 -30°C (depending on the location). This is a creek in the Alps of Villach, Austria. All kinds of tropical and subtropical fish are to found overthere. -