COS 206-3 - Conservation efforts based in vulnerability status are not effective to protect the phylogenetic diversity of fishes globally

Abstract: Overfishing plays a significant role in fish population decline, and despite global management efforts, it has increased in the last decade. The threat of overfishing is particularly high for long-lived and large-sized species with high size at first maturity, and aggregated spawning. Closely related species are expected to be more ecologically similar to each other than to distant ones because of shared evolutionary history and/or niche conservatism. The conservation of the global phylogenetic diversity (PD) is critical because it preserves material for future evolutionary processes and the variation in ecological traits necessary to adapt to environmental change. Hence, we investigate how the non-random loss of the most vulnerable fish species to fisheries would affect the amount of evolutionary history of fish globally. For doing that, we generated a phylogenetic hypothesis for all fishes in the world by taking the Fish Tree of Life as a backbone in which species with unknown phylogenetic positions were systematically grafted based on their taxonomic identity. We calculated the PD simulating the loss of up to 10% of the most vulnerable species to fisheries and compared this value to a null PD generated by the simulation of a random loss of up to 10% of fishes (3,343 species; 1,000 runs). Vulnerability for fisheries was retrieved from Fishbase. Finally, we calculated the phylogenetic signal of the vulnerability to fisheries and the tree symmetry to explain observed patterns. On average, losing the top-50 most vulnerable species led to a decline of 9% more PD than losing 50 species randomly. If more than 50 species are lost, losing the vulnerable species first maintained a significantly higher PD than losing species randomly. These patterns are related to the asymmetry of the fish tree of life (Colless I = 0.62) with a moderate to high phylogenetic signal in vulnerability (Pagel’s λ = 0.761). Since vulnerability is conserved in the phylogeny of rich clades, the loss of vulnerable species is the same as the loss of species with shared evolutionary history, then conserving other branches of the fish tree of life. While conserving the most vulnerable fish species to fisheries may not be the best strategy to conserve phylogenetic diversity, vulnerable fish species still provide essential ecosystem services (e.g., food provisioning). Therefore, effective conservation strategies should combine phylogenetic conservation approaches with other measures like fish vulnerability.