Even with no males present, release of a single female pet fish into the wild can generate entire new populations. The guppy's prolific reproduction abilities have earned it the reputation as one of the world's most invasive fish.
A joint study conducted by biologists at Scotland's St Andrews University and West Indies University experts has revealed that an entire population of guppies can be generated by the release of a single female fish. Biologists have confirmed the two primary means for the fish ending up in wild are the escape of ornamental fish and deliberate introductions designed to control mosquito larvae that spread malaria.
In places such as Southern India, guppies are routinely released into water troughs, wells and small ponds to control mosquito populations. Although initially self-contained, heavy rains and flooding enable the fish to eventually find their way into streams and rivers, where they come into contact with native fish.
According to Dr Amy Deacon, lead researcher at St Andrews University, "We know that the vast majority of species introduced to a new habitat in this way are unable to survive, let alone establish a population, which left us with a huge question mark."
To solve the mystery, the researchers conducted an experiment where single wild female guppies were put into outdoor tanks. After two years, it was discovered that nearly all of the tanks contained populations of guppy populations, each founded by a solitary female.
"Sperm storage is an excellent adaptation for living in constantly changing habitats, and it might also explain the guppies' global success,” stated Dr Deacon. "Female guppies can store sperm in their reproductive tracts for many months after mating, and this enables single fish to establish populations, even when no males are present. Seemingly harmless activities such as a child freeing a few pet fish or a concerned householder using guppies to control mosquitoes, can ultimately contribute to the reduction of biodiversity”, she added.
The popular ornamental fish, whose native home is Trinidad and the northeastern fringe of South America, is now present in more than 70 countries worldwide.
The research, published in the journal PLoS ONE, was funded by the Natural Environment Research Council and the European Research Council.