Geographic Patterns of Intra‐ and Interspecific Diversity of Riverine Fish Species in the Italian Northern Apennines and Ligurian Alps

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Abstract
Understanding the intricate dynamics of biodiversity within and across riverine ecosystems, influenced by geological history and environmental factors, is crucial for effective conservation and management strategies. Italy, particularly the Ligurian region, harbors diverse freshwater fish communities and populations shaped by unique geological and hydrological conditions. Here, we investigated the suitability of environmental DNA (eDNA) metabarcoding to identify inter‐ and intraspecific diversity patterns of riverine fish populations in drainage basins on both sides of the main drainage divide (MDD) between the Adriatic and Ligurian river basins in Northern Italy. We collected 96 aquatic eDNA samples across 48 riverine sites, amplified them using a cytochrome b primer pair, and denoised the sequences to retrieve amplicon sequence variants (ASVs). We calculated communities' phylogenetic distance with betaMPD based on genetic distances derived from the ASVs, combined them with conductance‐based landscape metrics, and applied generalized dissimilarity models to assess spatial genetic structure. Our results reveal genetic differentiation among populations of several fish species, with some displaying clustering patterns across the main drainage divide and isolation by distance patterns. Overall, taxon richness was higher on the Adriatic side (12.82 ± 3.57; 26 unique taxa) than on the Ligurian side of the MDD (8.35 ± 3.66 SD, 25 unique taxa), but the other way around for ASV richness across all species (Ligurian side: 51.94 ± 25.79, 308 unique ASV, Adriatic side: 68.00 ± 32.97, 274 unique ASV). Our findings highlight the effectiveness of eDNA metabarcoding in uncovering various facets of diversity, shedding light on hidden genetic diversity among ASVs, and revealing significant spatial genetic structuring in freshwater fish populations across multiple species.
Funding Information
  • Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung (100744200)
  • National Science Foundation

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