Robert John Lechmere Guppy (born August 15, 1836 in London; died August 5, 1916 in San Fernando, Trinidad and Tobago) discovered this tiny fish in Trinidad in 1866, and the fish was named Girardinus guppii in his honour by Albert C. L. G. Gunther later that year.

However, the fish had previously been described by Wilhelm Peters in 1859 on material collected from South America. Although Girardinus guppii is now considered a junior synonym of Poecilia reticulata, the common name “guppy” still remains. Over time guppies have been given a variety of taxonomic names, although Poecilia reticulata is the name currently considered to be valid.

Distribution:
Guppies are native to Trinidad and parts of South America, specifically Antigua and Barbuda, Barbados, Brazil, Guyana, Netherlands Antilles, Trinidad and Tobago, the US Virgin Islands, and Venezuela.

However, guppies have been introduced to many different countries on all continents, except Antarctica. Sometimes this has occurred accidentally, but most often as a means of mosquito control, the hope being that the guppies would eat the mosquito larvae slowing down the spread of malaria. In many cases, these guppies have had a negative impact on native fish faunas.

Ecology & Behavior:
There is a great deal of variety between the populations, many with distinctive coloring or patterning. Those that live in habitats where predators are common tend to be less vividly decorated as a protective measure. Populations that deal with fewer predators are much more colorful. Recent studies suggest that vividly colored males are favored via sexual selection (Handicap principle) while natural selection via predation favors subdued tones. As a result, the dominant phenotypes observed within a reproductively isolated community are a function of the relative importance each factor has in a particular environment.

Occasionally male guppies may behave aggressively towards each other, engaging in fin-nipping and other bullying behaviour. Guppies live in complex social networks, choosing social partners and remembering them.

Guppies are a seminal species for evolutionary biologists because predation often varies over small geographic areas. Both historical work and recent studies are summarised in Anne Magurran’s Evolutionary Ecology: the Trinidadian Guppy.

Reproduction:
Guppies are highly prolific livebearers. The gestation period of a guppy is 22-30 days, with an average of 28 days. After the female guppy is inseminated, a dark area near the anus, known as the gravid spot, will enlarge and darken. Guppies prefer water temperatures of about 28 °C (82 °F) for reproduction. The female guppy has drops of between 2-200 fry, typically ranging between 30 and 60. After giving birth, the female is ready for conception again within only a few hours. Guppies are known to exhibit superfetation, that is, the maintenance of batches of embyros at various states of development. As a result, a female guppy can continue to give birth for over a month after any males have been separated from the tank.

Source : http://www.guppies.com/index.php?option=com_content&task=view&id=50&Itemid=71