Macroecological and Biogeographic Patterns of Kinorhyncha in the Iberian Peninsula

ABSTRACT Aim Biogeography and macroecology aim to understand the processes that determine patterns in nature. In the marine environment, most of what we know has been documented for fish and macrobenthic organisms. As a result, this knowledge is negatively biased towards smaller benthic organisms, including meiofauna. In this study, we analysed the occurrence of species from the phylum Kinorhyncha, a meiobenthic group with presumably low dispersal potential. Location Around the Iberian Peninsula. Our goal was to explore the biogeographic and macroecological patterns across the Lusitanian and Mediterranean Sea biogeographic provinces. Time Period 1990–2021. Major Taxa Studied Kinorhyncha Reinhard 1885. Methods Species occurrence data were examined in relation to marine biogeographical classifications, considering multiple spatial scales across the Iberian Peninsula and key environmental variables. We applied generalised linear models (GLMs), generalised additive models (GAMs), and permutational multivariate analysis of variance (PERMANOVA) to evaluate the influence of province, ecoregion, area, sediment type, depth, latitude, and longitude on Kinorhyncha species richness and composition. Results Species richness was primarily influenced by depth and biogeographic province, while species composition was better explained by area (geographic location) and sediment type. These results indicate that geographic location is a significant factor influencing the composition and distribution of Kinorhyncha. Despite their low dispersal capacity and limited mobility, we found that both provinces shared species. The Mediterranean Sea contained more exclusive species, despite being less thoroughly sampled. Main Conclusions We found a biogeographic affinity between Atlantic and Mediterranean kinorhynchs, suggesting their coexistence across both marine provinces. However, species associations were weak at this broader spatial scale, underscoring the need to investigate finer‐scale patterns, such as areas within specific regions, to more accurately characterise meiofaunal distribution. While this study focused exclusively on Kinorhyncha, we anticipate that similar spatial patterns may be present in other meiofaunal taxa lacking planktonic larvae, given their inherently limited dispersal capabilities.