Abstract
The Mediterranean region with its islands is among the top biodiversity hotspots. It houses numerous freshwater taxa with a high rate of endemism, but is heavily impacted by anthropogenic pressures and global climate change. To conserve biodiversity, reliable data on species and genetic diversity are needed especially for the scarcely known insular freshwater ecosystems. Environmental DNA (eDNA) metabarcoding provides a straight-forward opportunity to assess aquatic biodiversity. Therefore, we conducted the first eDNA metabarcoding study in one stream catchment on Sicily. Specifically, we aimed to (i) investigate spatial diversity patterns of macroinvertebrate communities, (ii) assess seasonal changes (autumn and winter), and (iii) check if dispersal barriers can be identified. Water samples were taken at 27 different sites in two seasons and eDNA metabarcoding was performed using a fragment of the mitochondrial cytochrome c oxidase subunit I gene as a marker. In total, we detected 98 macroinvertebrate species, including 28 taxa potentially new to Sicily. Exact sequence variant and species composition data showed that diversity differed between seasons with less taxa detected in winter. We also detected a dispersal barrier, which had a stronger effect in autumn. Our findings show that eDNA metabarcoding provides valuable information on Sicilian freshwater biodiversity. We therefore encourage its application for understudied regions to better understand the state and dynamics of freshwater biodiversity.
Highlights
Freshwater ecosystems are hotspots of biodiversity (Strayer & Dudgeon, 2010)
Taxonomic filtering for freshwater macroinvertebrates resulted in a read table consisting of 14,868,364 reads, assigned to 466 exact sequence variants (ESVs) (‘benthic macroinvertebrates (BMI) ESVs’ dataset; Table S4)
Our results indicate that Sicilian freshwater macroinvertebrates seem to be relatively underrepresented with only 35% of our dataset being assigned to species level, compared to the European average of approximately 64.5% freshwater macroinvertebrate species having at least a single barcode publicly available (Weigand et al, 2019)
Summary
Freshwater ecosystems are hotspots of biodiversity (Strayer & Dudgeon, 2010). Even though they only comprise roughly 1% of global land surface area (Dudgeon et al, 2006; Strayer & Dudgeon, 2010), freshwater ecosystems host nearly 9.5% of Earth’s described animal species (Balian et al, 2007). Freshwater faunal biodiversity is declining, making rivers and lakes the most endangered ecosystems in the world (Dudgeon et al, 2006; Reid et al, 2019; Almond et al, 2020). This holds true in particular for the Mediterranean region (De Figueroa et al, 2013), which is considered as one of the top biodiversity hotspots in the world (Medail & Quezel, 1999; Myers et al, 2000). Islands are among the most threatened ecosystems within the region, with a predominance of non-perennial rivers and streams vulnerable to anthropogenic impacts (Hopkins, 2002; Skoulikidis et al, 2017)
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