Evolution of feeding specialization in Tanganyikan scale-eating cichlids: a molecular phylogenetic approach.
BACKGROUND
Cichlid fishes in Lake Tanganyika exhibit remarkable diversity in their feeding habits. Among them, seven species in the genus Perissodus are known for their unique feeding habit of scale eating with specialized feeding morphology and behaviour. Although the origin of the scale-eating habit has long been questioned, its evolutionary process is still unknown. In the present study, we conducted interspecific phylogenetic analyses for all nine known species in the tribe Perissodini (seven Perissodus and two Haplotaxodon species) using amplified fragment length polymorphism (AFLP) analyses of the nuclear DNA. On the basis of the resultant phylogenetic frameworks, the evolution of their feeding habits was traced using data from analyses of stomach contents, habitat depths, and observations of oral jaw tooth morphology.


RESULTS
AFLP analyses resolved the phylogenetic relationships of the Perissodini, strongly supporting monophyly for each species. The character reconstruction of feeding ecology based on the AFLP tree suggested that scale eating evolved from general carnivorous feeding to highly specialized scale eating. Furthermore, scale eating is suggested to have evolved in deepwater habitats in the lake. Oral jaw tooth shape was also estimated to have diverged in step with specialization for scale eating.


CONCLUSIONS
The present evolutionary analyses of feeding ecology and morphology based on the obtained phylogenetic tree demonstrate for the first time the evolutionary process leading from generalised to highly specialized scale eating, with diversification in feeding morphology and behaviour among species.
Takahashi
Rieko
R
Department of Zoology, Division of Biological Science, Graduate school of Science, Kyoto University, Kitashirakawa-Oiwake, Sakyo, Kyoto 606-8502, Japan. takahashi@terra.zool.kyoto-u.ac.jp
Watanabe
Katsutoshi
K
Nishida
Mutsumi
M
Hori
Michio
M
D054458:Amplified Fragment Length Polymorphism Analysis; D000818:Animals; D023681:Cichlids / Q000145:classification / Q000235:genetics / Q000502:physiology*; D045303:Cytochromes b / Q000235:genetics; D004272:DNA, Mitochondrial / Q000235:genetics; D017753:Ecosystem; D005247:Feeding Behavior; D005618:Fresh Water; D005766:Gastrointestinal Contents; D010802:Phylogeny; D011235:Predatory Behavior; D013045:Species Specificity; D013636:Tanzania; D014070:Tooth / Q000033:anatomy & histology
D004272:DNA, Mitochondrial; D045303:Cytochromes b