Does size really matter in biogeography? Patterns and drivers of global distribution of marine micro‐ and meiofauna

Abstract

Aim:This study aims to evaluate the role of various factors in structuring biogeographical distribution of small-sized organisms. More specifically, we analysed the distribution of three groups of marine benthic organisms differing in body size, both unicellular and metazoans, to assess the relevance of geographical and environmental factors on their taxonomic composition. Location: Global.Taxon: Heterotrophic flagellates, Ciliophora, Harpacticoida (Copepoda). Methods:The set of predictors included species richness (a proxy for sampling effort), geographical distance, isolation by geographical or hydrological barriers and three environmental variables (sea surface temperature, its annual variation and salinity). Multiple regression on the distance matrices and null modelling were used to quantify the relative effects of these variables in taxonomic similarity among 21 regions of the Ocean.Results: Each group showed a unique biogeographical pattern. The smallest-sized organisms, the flagellates, had high regional but low global diversity and low endemicity and demonstrated worldwide, environmentally driven distribution without any dispersal limitation (only the effects of climatic variables, but neither distance nor isolation effects, were significant). Thus, flagellates basically meet the 'ubiquity model' of global distribution. The ciliates showed a moderate level of endemicity, and their distribution depended on both spatial distance and the climatic variables, in accord with the 'moderate endemicity model'. In contrast, harpacticoids demonstrated high endemicity level, and their distribution was mostly geographically driven, indicating the considerable role of dispersal limitation-the pattern typical of other multicellular taxa with 'classical biogeography'. Species richness significantly influenced the interregional similarity of each group and explained 26%-65% of the total variance, indicating the strong impact of undersampling on faunistic similarity estimations. Main conclusions:Our results support the hypothesis that body size is the 'master trait' that shapes global biogeographical patterns towards higher predictability and increasing role of dispersal limitation for larger organisms. | 1181 AZOVSKY et Al.

Heterotrophic flagellates and centrohelid heliozoans from marine waters of Curacao, the Netherlands Antilles

“…It is made available under a preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in The copyright holder for this this version posted August 10, 2020. ; https://doi.org/10.1101/2020.08.10.243865 doi: bioRxiv preprint similarly turned out to be a new, high-ranking phylogenetic lineage of eukaryotes (Lax et al 2018). Predatory protists with Colponemid-like morphology and behavior are also very intriguing and evolutionarily important, as they are falling in severaldifferent parts of the tree, and contribute to the understanding of the origin of photosynthesis, parasitism, and evolution of mitochondrial genome (Gawryluk et al 2019;Janouškovec et al 2013Janouškovec et al , 2017Tikhonenkov et al 2020).…”

“…CC-BY-ND 4.0 International license perpetuity. It is made available under a preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in The copyright holder for this this version posted August 10, 2020. ; https://doi.org/10.1101/2020.08.10.243865 doi: bioRxiv preprint previously published database (Azovsky et al, 2016(Azovsky et al, , 2020 and available literature sources. Only morphology-based (or morphology-confirmed) data were considered.…”

Heterotrophic flagellates and centrohelid heliozoans from marine waters of Curacao, the Netherlands Antilles

“…The under-studied and puzzling Hemimastix similarly turned out to be a new, high-ranking phylogenetic lineage of eukaryotes (Lax et al 2018). Predatory protists with Colponemid-like morphology and behavior are also very intriguing and evolutionarily important, as they are falling in severaldifferent parts of the tree, and contribute to the understanding of the origin of photosynthesis, parasitism, and evolution of mitochondrial genome (Gawryluk et al 2019;Janouškovec et al 2013Janouškovec et al , 2017Tikhonenkov et al 2020).…”

“…Many regions of the world remain insufficiently studied for flagellates and even more so for heliozoans. Indeed, under-sampling is currently the key factor affecting our understanding of protists diversity and distribution (Azovsky et al 2020). To illustrate this, the species accumulation curve for studied Curacao samples (Fig.…”

“…The analysis of geographic distribution of heterotrophic flagellates was based on "morphospecies" concept (Fenchel and Finlay 2006;Finlay et al 1996) and carried out using the previously published database (Azovsky et al, 2016(Azovsky et al, , 2020 and available literature sources. Only morphology-based (or morphology-confirmed) data were considered.…”