Global trends in cetacean biodiversity and biomass

<p dir="ltr">Cetaceans (the baleen and toothed whales) include some of the most threatened large mammal species on the planet. Despite this, our understanding of cetacean communities and diversity remains relatively fragmentary. This project aimed to provide a better understanding of the composition of cetacean communities, as well as spatial patterns in their diversity and biomass, by analysing a global dataset of visual surveys between 1986 and 2022. Data for 61 species were utilised to predict abundance and richness across 121 communities through abundance distribution modelling. Richness estimates were used to assess latitudinal diversity gradients, species-area relationships, and community trait variation. A decrease in diversity towards the northern hemisphere was detected, with mysticetes accounting for the greatest relative proportion of diversity in the southern hemisphere. A positive species-area relationship was detected based on richness estimates and survey area. Community biomass was found to peak at both Arctic and Antarctic latitudes, being significantly influenced by the density of mysticetes in these regions. Furthermore, community-wide population density and biomass were entirely decoupled from richness in cetacean communities, indicating a departure from species-energy theory and the more individuals hypothesis. This project provides results which strengthen our understanding of the global macroecology and biogeography of cetaceans.</p>