Ancient Admixture in Freshwater Halfbeaks of the Genus in Southeast Sulawesi.

Freshwater halfbeaks of the genus (Zenarchopteridae) uniquely diversified on Sulawesi Island, where tectonic movements have been very active since the Pliocene. Most species of this genus have quite limited distributions, which indicates that geographic isolations have contributed to their diversification. In this study, we demonstrated that secondary contacts and resultant admixtures between long-isolated species/populations may have also been important.

Deeply divergent freshwater fish species within a single river system in central Sulawesi.

Sulawesi is a biodiversity hotspot for ricefishes (Adrianichthyidae), with many species endemic to the central part of this island in single ancient lakes or lake systems. Frequent vicariance by lake fragmentation since the Pliocene may be largely responsible for diversification in this family. In this study, we demonstrate that not only lacustrine species but also riverine species in this area are also deeply divergent even within a single river system.

Variation in Mating Behaviors Between a Tropical and a Temperate Species of Medaka Fishes.

In medaka fishes, the family Adrianichthyidae, tropical species are known to be sexually more dimorphic than temperate species. If this reflects that tropical species are exposed to stronger sexual-selection pressures than temperate species, mating behaviors may also differ between tropical and temperate species. Our mating experiments revealed that males of , a tropical species of the family, perform "chasing" another male more frequently than males of , a temperate congener, and that male-male "combats" of tended to be followed by chasing compared with combats of males, indicating that males are more aggressive in male-male interactions than males.

Convergent evolution of body color between sympatric freshwater fishes via different visual sensory evolution.

Although there are many examples of color evolution potentially driven by sensory drive, only few studies have examined whether distinct species inhabiting the same environments evolve similar body colors via shared sensory mechanisms. In this study, we tested whether two sympatric freshwater fish taxa, halfbeaks of the genus and ricefishes of the genus in Sulawesi Island, converge in both body color and visual sensitivity. After reconstructing the phylogeny separately for and using transcriptome-wide sequences, we demonstrated positive correlations of body redness between these two taxa across environments, even after phylogenetic corrections, which support convergent evolution.