Integrating ecological and genomic insights for monitoring conservation status and trends in seahorses

Seahorses (Hippocampus spp.) are flagship animals inspiring numerous conservation programs. They are the first marine genus to be fully listed on the Convention on International Trade in Endangered Species (CITES) Appendix II due to their substantial vulnerability to overexploitation and habitat loss. The peculiar life history of these fishes has been widely addressed through evolutionary and ecological analyses. Yet, no study has integrated current knowledge to approach species-based conservation status, including trends in abundance, diversity, and threats, hindering seahorses’ worldwide effective assessment and management. Here, we bridge these gaps by taking advantage of the available geographic, ecological and genomic (ultra-conserved elements and whole genomes) data in the Hippocampus species at a global scale, and present the most comprehensive study of the seahorses’ conservation status to date. Specifically, we explore species distributions and perform ecological niches modelling, phylogenomic mapping, comparative genomic applications, demographic inferences, and conservation gap analyses. We consider their evolutionary history, demographic changes and genomic erosion including genetic load, which have been largely disregarded by current conservation policies. We investigate the degree and type of protective measures currently granted to seahorses, and the biological and ecological factors that are contributing to their existing and future extinction risk. Our results raise questions on whether the current conservation indicators and practices are effective in preserving the present diversity and function of these iconic fishes, as well as their future evolutionary potential and ecological resilience. These insights provide a broad, more complete picture on the status and trends of seahorses and inform successful conservation initiatives. Finally, as more diverse datasets become available in the light of the “omics” and “open-access” era, we discuss the unprecedented opportunities to address interdisciplinary studies required for proper research-based conservation, assessment, and management of biodiversity.