Abteilung Aquatische Ökologie

Mountain building reorganizes drainage networks, influencing riverine biodiversity. Northern Italy offers a natural experiment in the impact of tectonic and geomorphic processes on aquatic species distribution. We combined geomorphic analysis with environmental DNA from rivers to assess the influence of tectonically driven drainage reorganization on genetic diversity, targeting an endemic fish species, Telestes muticellus (Risso et al., 1826, https://www.biodiversitylibrary.org/bibliography/58984). In the Northern Apennines, horizontal shortening and topographic advection in an orogenic wedge have been hypothesized as leading to river capture and drainage divide migration. In addition, slab rollback has produced a spatial transition from contraction to extension that is more pronounced from north to south, with normal faulting producing range-parallel drainage only in the southern regions. In contrast, the adjacent Ligurian Alps are a remnant of the Alpine orogen with little modern deformation. We found distinct zones of geomorphic characteristics from north to south, including divide asymmetry and frequency of range-parallel drainage. Analysis of DNA sequences shows cross-divide assemblage characteristics that correlate with the geomorphic zonation. In terms of directional measures of assemblage change, the Northern Apennines show higher values of overlap, gain, loss, turnover, and nestedness than those in the Ligurian Alps. Main drainage divide asymmetry correlates positively with genetic distance and gain, loss, and turnover of DNA sequences from Adriatic to Ligurian sites and negatively with overlap and nestedness. Since the species is confined to freshwater environments, tectonically driven drainage reorganization can explain its spatial genetic differentiation.

Genetic diversity is a fundamental aspect of biodiversity, yet it is rarely assessed and monitored in conservation practice. Unionid freshwater mussels exemplify the dramatic loss of biodiversity in freshwater ecosystems, yet genomic data for these ecologically important species remain scarce. Here, we conducted a high-resolution population genomics study of all Anodonta species in Switzerland, with a focus on two species with contrasting reproductive strategies. After generating draft genomes of the hermaphroditic Anodonta cygnea and the gonochoric Anodonta anatina, we performed whole-genome resequencing of 421 individuals collected in 31 localities. While A. anatina populations followed a metapopulation structure shaped by catchment areas, genetic diversity correlated positively with waterbody size, suggesting greater vulnerability in small ponds compared with large lakes. Inbreeding levels were low; however, effective population sizes were consistently below 100, indicating serious extinction risks. Strong divergence between A. anatina populations north and south of the Alps suggests a putative undescribed Anodonta species in the Ticino area. Furthermore, we detected hybridisation between A. cygnea and A. exulcerata, indicating genomic permeability between these species. In addition, genomic data suggested facultative selfing in A. cygnea, leading to a marked reduction in genetic diversity, increased population structure and inbreeding and a decline in effective population size compared to the outcrossing A. anatina. Our study underscores that reproductive strategy fundamentally shapes genetic indicators of biodiversity and influences extinction risk; conservation targets should therefore be adapted to the biology of the species of interest. To conclude, we advocate for integrating reproductive mode and genomic data into conservation planning to more accurately assess vulnerability and guide effective action.