Selection's Role in Maintaining a Color Polymorphism in the Sulawesi Fish Telmatherina antoniae

Abstract

Explaining the extraordinary genetic variation present in natural populations is a central and longstanding problem of evolutionary biology. Color polymorphisms have proven to be powerful models for studying how genetic variation, associated with distinct color patterns, persists and the processes responsible. We analyzed data collected from underwater focal male video recordings (n=310), taken over eight years, to elucidate the possible contributions of sexual and natural selection to the persistence of the blue and yellow polymorphism in males of Telmatherina antoniae. T. antoniae is a species of sailfin silverside fish endemic to Lake Matano, which belongs to the Malili Lake system of Sulawesi, Indonesia. The specific goals of the study were to test the hypotheses that (i) elevated antagonistic interactions between individuals of the same morph facilitate morph persistence, and (ii) trade-offs between fitness components, possibly associated with distinct behavioral strategies, contribute to morph persistence. We found that same-morph male interactions had a significant negative effect on the spawning rates of T. antoniae and that blue males exhibited elevated same-morph agonistic interactions, which could result in negative frequency-dependent selection for this morph. Yellow males tended to have higher spawning rates compared to blue males but also showed a non-significant tendency to experience more frequent egg predation. These processes may contribute to the maintenance of the blue-yellow color polymorphism in T. antoniae, but still larger samples will be needed to definitively evaluate the possibility of trade-offs in spawning success versus susceptibility to egg predation.