Biodiversity patterns of epipelagic copepods in the South Pacific Ocean: Strengths and limitations of current data bases

The expected number of species, as a function of sampling units for different defined regions can illustrate the actual level of sampling coverage (Fig 5). As shown by species rarefac- tion curves, the sampling effort (samples per sampling units) varied extensively within and between regions, and no saturated curves were found in any of the regions, indicating a rather low coverage to assess the whole copepod community (Fig 5A). The distribution of the defined regions or current systems are illustrated in Fig 5B. The spatial variability in diversity among potential distinct assemblies can be reflected in beta diversity, which may also indicate the degree to which such communities differ from each other. Beta diversity of copepods in the eastern SPO was higher in its equatorial-tropical area, with another area showing higher values at is temperate zone (Fig 6A); whereas the western side of the SPO had higher values of beta diversity expanding from tropical to subpolar areas (Fig 6A). This beta diversity (Fig 6A; mean beta = 0.579) was better explained by mean turn- over (Fig 6B; mean turnover = 0.295) rather than mean nestedness (Fig 6C; mean nested- ness = 0.284). The turnover rate at the eastern side of the SPO was higher in its equatorial- tropical area, with another area showing higher values at is temperate zone (Fig 6B); whereas the western side of the SPO had higher values of turnover expanding form tropical to subpolar areas (Fig 6B). Nestedness was found to be higher at the open ocean in the eastern side, with a

higher values patch associated to the coastal area in the temperate zone (Fig 6C); whereas at the western side, it showed higher values in more oceanic areas at the temperate and subpolar zones (Fig 6C). When applying the GDM-based spatial analysis to assess species composition, we found that salinity was the strongest predictor of the observed dissimilarities, followed by oxygen concentration, mean temperature and chlorophyll-a concentration. In contrast, mixed layer depth, temperature stability and standard deviation of temperature were the least important predictors, (S2 Fig). The spatial layers were generated and plotted with the best predictors and showed three clear latitudinal bands of similar color that kept almost the same distribution interpolation for family richness. Transparent squares are the 1˚ sampled cells used for interpolation, whereas the grey dotted line delimits the South Pacific Ocean. Map projection is WGS 84/PDC Mercator (EPSG 3832). https://doi.org/10.1371/journal.pone.0306440.g002 Fig 3. Shannon-Wiener index of Copepoda in the western and eastern sides of the South Pacific Ocean. Transparent squares are the 1˚ sampled cells used for Kriging interpolation, whereas the grey dotted line delimits the South Pacific Ocean. *Estimates based on available data at species level. Map projection is WGS 84/PDC Mercator (EPSG 3832). https://doi.org/10.1371/journal.pone.0306440.g003 PLOS ONE Biodiversity of copepods in the South Pacific PLOS ONE | https://doi.org/10.1371/journal.pone.0306440 July 11, 2024 10 / 28