Limia is a genus of livebearing fish in the family Poeciliidae, native to the Caribbean — the atlas's species are concentrated on the island of Hispaniola (Haiti and the Dominican Republic), with others on the Cayman Islands and a mainland population in Venezuela. Like their poeciliid relatives the mollies and guppies, Limia give birth to free-swimming young rather than laying eggs, and most species are small, deep-bodied fish under 3 in found in streams, spring-fed pools, and crater lakes. The atlas covers 13 species.
Limia is one of the most conservation-critical genera in the atlas: most of its assessed species are listed as critically endangered, and ten of the genus's thirteen atlas species carry CARES conservation-priority status. Hispaniola's spring- and lake-dwelling Limia have been squeezed by habitat loss, water extraction, and introduced fish such as tilapia and Gambusia, and several species are now known from only one or a handful of localities. In the hobby the blackbarred limia (Limia nigrofasciata) is the classic, widely kept species, with the ornate limia (L. ornata) and Venezuela molly (L. heterandria) also occasionally available; captive populations held by hobbyist conservation groups are an important backstop for the rarer species.
Limia is closely allied to the mollies (genus Poecilia), and some taxonomists have argued the two lineages should be merged, since molecular studies have repeatedly found Limia nested within a broader Poecilia-Limia group rather than standing apart from it. The atlas follows the traditional separate-genus treatment still used across most of the current literature and hobby references.