Aquarist Atlas
Livebearers · waters

The regions behind the fish

Livebearers are not one fauna but several, each shaped by its own water: the cool spring-fed lakes of the Mexican plateau that cradle the threatened splitfins; the warm Atlantic-slope rivers of Mexico where the swordtails radiated; the isolated island streams of the Greater Antilles; the Orinoco Llanos that gave the world the guppy; and, half a world away, the forest streams of South-East Asia where the halfbeaks went live-bearing on their own. Here are the 10 freshwater regions that shaped 382 of the 383 species in this atlas.

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Mexican Plateau & Mesa Central

44 species

The cool, high-altitude endorheic lakes and spring-fed rivers of central Mexico — the Lerma–Santiago system, Lago de Pátzcuaro, Chapala and the Mesa Central. This is the cradle of the Goodeidae, the matrotrophic 'splitfins' (Xenotoca, Skiffia, Ameca, Characodon, Ilyodon, Zoogoneticus), many of them now critically endangered as the plateau's waters are drained and invaded.

Atlantic-slope Mexico · Pánuco & Veracruz

92 species

The warm Atlantic-slope drainages of eastern Mexico — the Río Pánuco–Tamesí, Papaloapan, Coatzacoalcos and the rivers of Veracruz. Heartland of the swordtails and platies (Xiphophorus), alongside Poecilia, Heterandria and Pseudoxiphophorus, with sharp upstream/downstream species turnover that has made the genus a model for speciation studies.

United States & the Rio Grande

22 species

The Gulf and south-eastern United States plus the Rio Grande / Río Bravo borderlands — the only livebearers native north of Mexico. Gambusia (the mosquitofishes), the sailfin molly Poecilia latipinna and the least killifish Heterandria formosa range across coastal marshes, springs and slow lowland creeks; several desert-spring Gambusia are among North America's most endangered fishes.

Central America · Pacific & Atlantic slopes

76 species

The twin-slope rivers of the Central American isthmus, from the Usumacinta and Grijalva down through Honduras, Nicaragua, Costa Rica and Panama. A hotbed of poeciliid endemism — Alfaro, Brachyrhaphis, Phallichthys, Priapichthys, Neoheterandria and the regional Poeciliopsis — shaped by the slope-to-slope barrier of the continental divide.

Greater Antilles & the Caribbean

48 species

The island freshwaters of the Greater Antilles, where livebearers radiated in isolation: Limia across Hispaniola, Cuba and Jamaica, plus Girardinus, Quintana, Gambusia and Cubanichthys on Cuba. Limestone springs, sinkholes and short coastal streams hold a string of single-island endemics, several confined to one cave or lagoon.

Orinoco Llanos, Trinidad & Lake Maracaibo

15 species

The Llanos floodplains of the Orinoco, the Maracaibo basin and the island of Trinidad — the native homeland of the guppy (Poecilia reticulata) before it became the world's most translocated fish. Alongside it swim Poecilia, Micropoecilia and Priapichthys in warm, weedy lowland ditches, lagoons and piedmont streams.

Trans-Andean Colombia · Magdalena & Pacific

8 species

The drainages west of the Andes — the Magdalena–Cauca, Atrato and Pacific-slope rivers of Colombia and Ecuador, cut off from the Amazon by the cordilleras. Poecilia caucana, Pseudopoecilia and trans-Andean Priapichthys occupy these warm lowland and piedmont waters, a fauna distinct from the Orinoco–Amazon livebearers to the east.

Amazon & the Guianas

19 species

The vast Amazon basin and the coastal Guianas, where livebearers are a quiet understory of the great characin- and catfish-dominated fauna. Poecilia and the diminutive Micropoecilia haunt blackwater margins and coastal swamps, while the egg-scattering Tomeurus gracilis — the most 'primitive' poeciliid — bridges live-bearing and egg-laying.

La Plata & southern South America

53 species

The subtropical Paraná–Paraguay–Uruguay system, the Río de la Plata and the Atlantic-Forest coastal rivers of southern Brazil. Home to the southern poeciliid line — Cnesterodon, Phalloceros, Phalloptychus and Jenynsia (the one-sided livebearing Anablepidae) — adapted to cooler, seasonal waters at the family's southern frontier.

South-East Asia · the halfbeak livebearers

42 species

The one Old-World branch of the livebearers: the viviparous halfbeaks (Zenarchopteridae) of South-East Asia — Dermogenys, Nomorhamphus and Hemirhamphodon — across the Malay Peninsula, Borneo, Sumatra and the ancient lakes of Sulawesi. Surface-dwelling ambush feeders of forest streams, peat swamps and rocky upland creeks.

Widespread & introduced

1 species

Species whose documented ranges cross several regions, and the great travellers of the group — Gambusia affinis and G. holbrooki, Poecilia reticulata and Xiphophorus hellerii — now feral on every warm continent after a century of mosquito-control releases and aquarium escapes. Also gathers species whose distributional data remains incomplete.

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