Genetic evidence of closed life-cycles for some coral reef fishes within Taiaro Lagoon (Tuamotu Archipelago, French Polynesia)

Abstract

Taiaro Lagoon has no permanent or regular connection with the ocean (ingress is restricted to episodes of high sea-level and/or strong wave action) raising the question of how fish populations with normally dispersive larvae are maintained inside this lagoon. We compared the genetic population structures of two coral reef fishes, Acanthurus triostegus and Chaetodon ulietensis, present on both sides of the atoll rim to determine whether there is evidence of reproductive isolation. Genetic surveys showed that the lagoonal and oceanic populations were statistically different at five loci (AAT * -3, GDA *, HPD *, MDH * and SDH *) in A. triostegus and three loci (PGI-2*, IDH * and PGD *) in C. ulietensis, producing high F st values of 0.055 and 0.021, respectively. Our genetic and demographic data on these species suggest that both may be completing their life-cycles inside the lagoon, which leads us to question the common assumption that coral reef fishes require oceanic conditions for larval development.