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

Over a large-scale domain (e.g., a basin-scale), the role of temperature or other environ- mental correlates as biogeographic predictors for copepods is still unclear for the South Pacific region. The remaining questions are: do copepod species exhibit significant clustering or dis- tinctive spatial assemblies? and, what are the most plausible environmental correlates to pre- dict the diversity distribution of copepods at a basin scale? Lastly, is temperature alone the best predictor of such spatial structures, and whether such structures and biogeographic patterns replicate those observed in the North Pacific or Atlantic Ocean? In this study, we addressed these questions using a long-term (1983–2019) data base on occurrence of copepod species, extracted from the OBIS Portal, allowing us to further evaluate the robustness of these com- piled data on species records of epipelagic copepods. For this, we assessed the diversity patterns of planktonic Copepoda and their relationship with oceanographic conditions in the upper 200 m of the western and eastern sides of the SPO to identify biogeographic regions and the presence of hot and cold spots of diversity. We aimed at testing the hypothesis that water tem- perature is the best predictor explaining spatial diversity patterns of planktonic copepods at basin scale in the SPO. Ultimately, our study will provide a first assessment of copepods diver- sity for the entire basin, helping us to gain insights into how such patterns may vary under

ongoing ocean warming and, also allowing us to evaluate the robustness of current data bases for plankton organisms in this large ocean basin. Materials and methods Study area The SPO possesses the greatest surface and seabed area, as well as the greatest volume, with a mean depth of 3993 m [42]. The ocean stretches from the Equator—including the islands of the Gilbert and Gala´pagos Groups, which lie to the northward thereof—until the parallel of 60˚S, and between South America and the northeastern limit of the East Indian Archipelago (from New Guinea to the Equator), along the southern, eastern and northern limits of the Bis- marck and Solomon Seas; the southeastern and northeastern limits of the Coral Sea; and the southern, eastern and northern limits of the Tasman Sea, going down the meridian of 146˚ 55’E starting at the South East Cape, the southern point of Tasmania, up to the parallel of 60˚S [43, 44] (Fig 1). The general circulation in the SPO and major current systems are illustrated in Fig 1. Data sources—Copepoda species and quality control procedures Species occurrence records were obtained from the Ocean Biodiversity Information System, OBIS [22] (http://www.iobis.org) data base, using the robis [45] and devtools [46] packages implemented in the R Core Team (2021). The data were obtained for all occurrences between 0–200 m of the SPO, from 1993 to 2019. Following the retrieval of the data, we eliminated rec- ords without information on the geographic coordinates, coordinates equal to zero, or records

located inside continents. We selected only records at level of species and excluded duplicate records. This procedure allowed us to compile data to estimate species diversity, but also resulted in a drastic reduction of information since many records are reported for genera or higher taxonomic levels (e.g. families), and in some cases without clear or wrong georeference. Taxonomy was revised and updated using the WoRMS portal (http://www.marinespecies.org) through the match_taxa function of robis package [45] implemented in R software (R Core Team, 2021). After we had cleaned and curated the data, a total of 22345 records of Copepoda were selected. The data on occurrences of Copepoda species are available in a Zenodo reposi- tory: https://doi.org/10.5281/zenodo.8257222 (version 1). Finally, diversity indexes (see below) were generated based on biogeographic information of copepod biodiversity patterns, PLOS ONE Biodiversity of copepods in the South Pacific PLOS ONE | https://doi.org/10.1371/journal.pone.0306440 July 11, 2024 3 / 28