| Summary: | The steady decline of the worldwide biodiversity is a significant global concern that stresses the need to explain, quantify and understand biodiversity in order to generate more suitable conservation strategies. The availability of high-quality species distribution data, especially at broad scales, is fundamental to assess and identify global patterns of richness and endemism, as well as, to prioritize conservation areas with confidence. Marine species inventories are important tools providing this fundamental information for marine biodiversity conservation management at different scales. Unfortunately, there is a lack in gamma-scale investigations to comprehend large-scale biodiversity processes in the marine realm. The objective of this research is to bring the first comparison between regional marine species inventories from major world regions to contribute with significant information for a better understanding of large-scale biodiversity patterns in the marine realm. The main data provider for this research is the World Register of Marine Species (WoRMS). The scope of this analysis comprises 56,376 species distributed in 14,915 genera, 3,076 families, 421 orders, and 98 classes distributed in 30 phyla belonging to the Kingdom Animalia. Study metrics in this research were regional richness and regional endemism in five taxonomic categories levels (class, order, family, genus, and species) across seven geographic regions (Europe, the Arctic, the Antarctic, New Zealand, the Gulf of Mexico, Canada, and China). Europe had the higher levels of richness and endemism whereas the Arctic registered the lowest levels across the taxonomic hierarchy. Arthropoda, Chordata, and Mollusca showed a consistent pattern across the five taxonomic categories comprising roughly half of the total regional richness and endemism count across the 7 regions. Results based on the Jaccard’s similarity index showed relatively low-inter regional similarity between the regions across the taxonomic hierarchy. There was a positive correlation between total regional richness and total regional endemism. However, correlations between richness and endemism for each taxon independently offered mixed support of the idea that richness and endemism are correlated. Richness and endemism were no correlated with sea volume, sea surface and maximum depth. These results as well as variations in the proportions of richness and the highest levels of endemism across the regions in the different taxonomic categories are certainly somehow biased by the geographic variation in sampling effort and the differences in taxonomic effort across the phyla that are still far from being homogeneous. Thus, there is a need to address gaps in marine biodiversity knowledge accelerating not only the species description and classification process but also the rate of discovery of marine species. This research provides substantial knowledge for a better understanding of marine biodiversity richness and endemism patterns at larger scales towards conservation purposes. Key words: regional marine species inventories, quantifying biodiversity, richness, endemism, taxonomic hierarchy, biodiversity conservation. Available to authenticated members of The University of Auckland.
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