Résumé
From a practical point of view, the determination of species in the wild
is based on their phenotypes. Consequently, many species remain unknown
because they are visually indistinguishable from described species.
Although molecular methods and advances in bioacoustical analysis have
been extensively used to uncover cryptic species, the combination of both
methodologies is still rare and concerns only some terrestrial taxa such
as insects, bats, frogs and birds. In this study, we aim to determine
whether the sounds produced by different populations of fish can also be a
tool to distinguish and identify cryptic species. The humbug damselfish
complex, Dascyllus aruanus, is widely distributed across the Indo-Pacific
Ocean and, since 2019, is thought to be composed of at least two species
with Dascyllus aruanus in the Pacific Ocean and Dascyllus abudafur in the
Indian Ocean. Recordings were made over a large geographical area with
populations from Madagascar (Indian Ocean), Taiwan (Pacific Ocean) and
French Polynesia (Society Islands). Two kinds of sounds were used for
analysis: sounds associated with conspecific chases, and sounds produced
during the “signal jump” of courtship behaviour. The sounds associated
with signal jumps differ geographically. Acoustic feature differences
between Taiwan and Madagascar align with the existence of genetic
differences confirming specific status and supporting for the first time
that sounds can help to discriminate cryptic species in Teleosts. However,
differences in both acoustic features and genetic data can also be found
between Taiwan and French Polynesia suggesting two clearly distinct
populations. Using the same reasoning, we propose to resurrect the epithet
“emamo” (Lesson 1830) for the Society Island humbug damselfish.
Interestingly, sounds associated to conspecific chases are more variable
than sounds related to signal jumps, suggesting that there are more
constraints on sounds related to courtship since they would serve as
indicators for species identity and contribute to premating isolation.