Orestias

Orestias is a genus of freshwater fishes in the order Cyprinodontiformes, commonly known as pupfishes. They are endemic to the high-altitude basins of the Andes in South America, particularly the Lake Titicaca region in Peru and Bolivia, with additional species described from nearby lakes and rivers.

The genus comprises numerous species that have diversified across isolated aquatic systems. Members are generally small to medium-sized fishes with laterally compressed bodies and varied coloration. They occupy a range of microhabitats from shoreline shallows to deeper water, often in cool, seasonal freshwater environments.

Distribution and habitat: Orestias is primarily associated with the Titicaca basin and surrounding Andean basins at elevations around 3,000 meters and higher. They inhabit freshwater lakes and streams in these regions, where environmental conditions can be variable in temperature and flow.

Ecology and biology: They are omnivorous, feeding on algae, invertebrates, and detritus. Reproduction is typically oviparous, with eggs laid on substrate or among vegetation; many species exhibit specific spawning behaviors and limited dispersal, contributing to their diversification in isolated habitats.

Conservation: The genus faces significant threats from introduced predators such as non-native trout, habitat modification, water extraction, pollution, and climate change. Some species are listed as threatened or extinct in the wild, and conservation efforts emphasize habitat protection and management of invasive species.

Evolution and significance: Orestias is noted for rapid speciation and adaptive radiation in isolated high-altitude freshwater systems, making it important for studies of evolutionary processes in the Andes.

See also: Pupfish; Lake Titicaca; Andes.