Hydrological alteration, critical swimming speed
and life history in inland fish
Summary: Fresh waters are among the most biodiverse ecosystems globally but, at the same time, also the most threatened. Serious menaces to freshwater ecosystems are, for instance, habitat alteration, invasive alien species, pollution, water abstraction and climate change. One of the most pervasive indicators of anthropogenic impacts on rivers is hydrological alteration caused by artificial barriers, which is known to reinforce the decline of local biodiversity and ecosystem services, and the species homogenisation of inland fish communities. Previous studies showed that the novel lentic habitats created by dams and habitat modifications occurring downstream of dams favour the establishment of alien fish, as many of them commonly prefer lentic habitats with warmer water temperatures compared with native fish. Thus, jointly studying species distribution patterns and species traits and their evolutionary history provides an essential link to better understand species’ responses to environmental change and biological invasions, and to design effective management tools and policies. For instance, swimming performance (often measured in the laboratory as critical swimming speed [Ucrit]) is a particularly important trait in aquatic organisms, mediating their fitness, habitat selection or survival. However, there are few studies that evaluated its evolutionary relationship with other traits, with fish distribution patterns or with invasion success in freshwater ecosystems. The Iberian Peninsula is a well-suited region to study the effects of climate, land use change and hydrological alteration on the distribution of native and alien fish species, due to its complex orography and diverse climate and ichthyofauna. In fact, the Iberian Peninsula is one of the most impacted regions by dams (over 1500 large dams fragment Iberian rivers) and invasive species (32 established alien fish species). Thus, this thesis aimed to evaluate the relationship of distribution patterns and traits of inland fishes, and to understand the ecological filtering with a special focus on hydrological alteration using the Iberian ichthyofauna as a study system. The research performed was structured in five chapters and included: (1) a compilation of Iberian inland fish trait data and corresponding reliability analysis of the different data sources; (2) the analysis of swimming capacity of native and alien Iberian inland fishes using random forests models, generalised linear mixed model and linear models; and (3) studies of the distribution patterns and niche characteristics of Iberian fish using species distribution models and the outlying mean index, as well as the analysis of relationships of these distribution patterns with fish traits using phylogenetic and non-phylogenetic approaches.
Awards:
XIV Limnology Research Award for the best doctoral thesis defended in 2022 (Asociación Ibérica de Limnología)
Premi extraordinari de doctorat en Ciència i Tecnologia de l’Aigua 2022 (Universitat de Girona)