Phylogeography and Conservation Biogeography of the Humphead Wrasse, Cheilinus undulatus

Abstract

The Humphead wrasse (also known as the Napoleon fish), Cheilinus undulatus, is a highly prized coral reef fish, listed on CITES Appendix II and endangered on the IUCN Red List. It is widespread across much of the Indo-Pacific region. The fish has a 4-6 week pelagic egg and larval stage, suggesting the potential for high connectivity among populations. However, its range spans important biogeographic boundaries that are associated with barriers to gene flow and deep phylogeographic structure in some marine fishes and invertebrates, raising the possibility of significant population genetic structure. We describe preliminarily the genetic structure of the Humphead wrasse across much of its range and consider the implications for effective conservation. Using mitochondrial DNA sequencing (cytochrome b and control region) coupled with microsatellite analyses, we find primarily a signal of eurymixis-i.e., low, heterogeneous population genetic differentiation across much of the species' range (F ST analogs: <0.11 cytochrome b, <0.09 control region, <0.02 microsatellites) with the exception of modest differentiation primarily toward the peripheries (e.g., Pohnpei, Seychelles; F ST analogs: 0.03-0.24 cytochrome b, 0.05-0.24 control region, 0.03-0.22 microsatellites)-though isolation by distance is not excluded. The general dearth of structure is consistent with population expansion, following an historical bottleneck and with high contemporary gene flow. The implications are that Humphead wrasse is a metapopulation and that its conservation status depends on successful management of a sufficient but currently unknown number and distribution of populations across a multinational network.

Quantifying the rare: Baselines for the endangered Napoleon Wrasse, Cheilinus undulatus, and implications for conservation

“…The marine park was established in 1991 (van Beukering et al, 2007) Overall, the possible importance of both local and distant sources of recruits suggested by results and circumstances at the study locations is consistent with a recent study showing weak population structuring globally for Napoleon fish, which included samples from Indonesian fish. Napoleon fish can be considered a metapopulation, the conservation status of which depends on the successful management of a sufficient but currently unknown number and distribution of populations that could cross national boundaries (Ma, Colin, Sadovy de Mitcheson & Dawson, 2019).…”