Alien Invasion in Wallace’s Dreamponds: Records of the Hybridogenic “Flowerhorn” Cichlid in Lake Matano, with an Annotated Checklist of Fish Species Introduced to the Malili Lakes System in Sulawesi

Invasive fish species can have major impacts on freshwater faunas, particularly in isolated systems harbouring adaptive animal radiations. Here, we report on the occurrence and recent rapid expansion of the hybridogenic “flowerhorn” cichlid in ancient Lake Matano, the hydrological head of the Malili Lakes system in Central Sulawesi, Indonesia. We show that flowerhorns rapidly dispersed along the lake’s shoreline, inhabited most of the southern inshore habitats in 2010, and were present all around the lake in mid-2012. In addition, we present stomach content and observational data supporting the hypothesis that this cichlid threatens the local fauna through both predation and competition. We discuss 13 additional alien fish species recorded in the Malili Lakes drainage since 2000, including the recent, first record of the invasive sailfin catfish Pterygoplichthys pardalis for Sulawesi, highlighting the multitude of artificial introductions of foreign fish species into these unique and highly isolated freshwater systems. We conclude that alien fish species pose both serious and diverse threats to the fauna of the Malili Lakes system – an ecosystem of high socio-economic importance and an exceptional natural laboratory for study of evolution, referred to as “Wallace’s Dreamponds”. Finally, we provide recommendations for minimizing future alien species introductions. Aquatic Invasions, Vol. 7, No. 4. Hal. 521-535