Evol Ecol Res 19: 561-574 (2018)     Full PDF if your library subscribes.

Alien attack:
trophic interactions of flowerhorn cichlids
with endemics of ancient Lake Matano (Sulawesi, Indonesia)

Leon Hilgers1, Fabian Herder1, Renny K. Hadiaty2 and Jobst Pfaender3

1Ichthyology, Zoological Research Museum Alexander Koenig, Bonn, Germany, 2Ichthyology Laboratory, Division of Zoology, Research Center for Biology, Indonesian Institute of Sciences (LIPI), Cibinong, Indonesia and 3Naturkundemuseum Potsdam, Potsdam. Germany

Correspondence: L. Hilgers, Ichthyology, Zoological Research Museum Alexander Koenig, Adenauerallee 160, 53113 Bonn, Germany. email: l.hilgers@leibniz-zfmk.de

ABSTRACT

Background: The ancient Malili Lakes (Sulawesi, Indonesia) harbour an exceptional diversity of freshwater animals, including several endemic species flocks. Lake Matano, the hydrological head of the lake system, has seen the successful invasion of a man-made hybrid fish, the flowerhorn cichlid. In less than one decade, flowerhorns colonized the entire shoreline of Lake Matano. However, little is known about the flowerhorn’s ecology in the wild, its potential impact on the ecosystems it invades, or the reasons for its invasive success.

Question: Do flowerhorn cichlids prey on endemic species and do they compete for dietary resources with endemic fish radiations?

Methods: We studied stomach contents of 136 flowerhorns from six locations around Lake Matano, investigated ontogenetic dietary niche shifts, and compared diets to available stomach-content data from two endemic fish radiations (Telmatherina).

Results: Flowerhorns undergo a pronounced ontogenetic dietary niche shift. While juveniles mostly prey on aquatic insects, adults have a generalized diet and prey on species of all major endemic radiations. Although flowerhorns consume most of the resources that dominate the diets of the Telmatherina radiations, dietary overlap between single endemic species and flowerhorns is limited. Minimal dietary overlap of juvenile flowerhorns with both adult conspecifics and endemic Telmatherina combined with omnivory and territoriality of adults potentially facilitated their invasive success.

Keywords: competition, flowerhorn cichlid, invasion, ontogenetic niche shift, predation, Telmatherina.

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