Journal
<p>Freshwater species on tropical islands face localized extinction and the loss of genetic<br />
diversity. Their habitats can be ephemeral due to variability in freshwater run-off and<br />
erosion. Even worse, anthropogenic effects on these ecosystems are intense. Most of<br />
these species are amphidromous or catadromous (i.e. their life cycle includes a marine<br />
larval phase), which buffers them against many of these effects. A long pelagic larval<br />
duration (PLD) was thought to be critical to ensure the colonization and persistence in<br />
tropical islands, but recent findings indicated that several species with short PLDs are<br />
successful in those ecosystems. To test the potential of a short PLD in maintaining<br />
genetic connectivity and forestalling extirpation, we studied Kuhlia rupestris, a catadromous<br />
fish species with an extensive distribution in the western Pacific and Indian<br />
Oceans. Using a combination of molecular genetic markers (13 microsatellite loci and<br />
two gene regions from mtDNA) and modelling of larval dispersal, we show that<br />
a short PLD constrains genetic connectivity over a wide geographical range. Molecular<br />
markers showed that the short PLD did not prevent genetic divergence through evolutionary<br />
time and speciation has occurred or is occurring. Modelling of larvae dispersal<br />
suggested limited recent connectivity between genetically homogeneous populations<br />
across the Coral Sea. However, a short PLD can maintain connectivity on a subocean<br />
basin scale. Conservation and management of tropical diadromous species needs to<br />
take into account that population connectivity may be more limited than previously<br />
suspected in those species.<br />
Keywords: cryptic species, dispersion</p>
