Species richness, species turnover and functional diversity in nematodes of the deep Mediterranean Sea: searching for drivers at different spatial scales

Abstract

AbstractAimUnderstanding how biodiversity varies at different spatial scales and the drivers behind these patterns is a crucial issue in ecology. This is evident for the deep sea, the largest biome of the biosphere, where there is little information available on the spatial and temporal variability of biodiversity. Here, we investigated the variability and potential drivers of species richness, turnover and functional biodiversity of deep‐sea nematodes at a depth of 3000 m across different spatial scales and in two periods of contrasting pelagic productivity.LocationThe Mediterranean Sea.MethodsWe used for the first time a hierarchical sampling strategy that includes different spatial scales, from tens of metres (small scale) to hundreds of kilometres (macroscale).ResultsWe show that the variability in biodiversity is greatest at the macroscale, although the rate of variability is about two‐ to three‐fold lower than observed for nematode abundance. Also, turnover diversity is highest at the macroscale (and uncoupled from species richness), and significantly decreases to the meso‐ and local scales. Functional diversity is positively related to species richness and its variability is associated with the change in richness of predators. The drivers of spatial variability of biodiversity are different at different spatial scales. Our data identify the pivotal role of food quantity in the control of variability in biodiversity attributes at the macroscale, while the quality and bioavailability of food sources have a key role in driving beta diversity and biodiversity attributes at small spatial scales. Also, the largest variations in biodiversity attributes at both macroscales and mesoscales are related to periods of high food input from the euphotic zone.Main conclusionsWe conclude that changes in food availability, which can also be expected as a consequence of climate change, have a significant impact in setting biodiversity attributes at different spatial scales in the deep sea.