The role of non-native fish on littoral macroinvertebrates of Pyrenean high mountain lakes
[eng] High mountain freshwater ecosystems, such as Pyrenean lakes, are distinguished by their unique ecological characteristics, which encompass their near-pristine undisturbed state, unique biodiversity, and their role as refuges for a variety of organisms. High mountain lakes are naturally devoid...
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| Tipo de recurso: | tesis doctoral |
| Estado: | Versión publicada |
| Fecha de publicación: | 2024 |
| País: | España |
| Institución: | Universidad de Barcelona |
| Repositorio: | Dipòsit Digital de la UB |
| OAI Identifier: | oai:diposit.ub.edu:2445/209240 |
| Acceso en línea: | https://hdl.handle.net/2445/209240 http://hdl.handle.net/10803/690423 |
| Access Level: | acceso abierto |
| Palabra clave: | Limnologia Estanys Pirineus Invertebrats d'aigua dolça Peixos Limnology Ponds Pyrenees Freshwater invertebrates Fishes |
| Sumario: | [eng] High mountain freshwater ecosystems, such as Pyrenean lakes, are distinguished by their unique ecological characteristics, which encompass their near-pristine undisturbed state, unique biodiversity, and their role as refuges for a variety of organisms. High mountain lakes are naturally devoid of fish, yet many have experienced the introduction of non-native fish species, primarily trout, and more recently, minnows (Phoxinus sp.) introduced by anglers for use as live bait. The predation of native fauna by these introduced fish involves profound ecological changes, as fish occupy a higher trophic level that was formerly absent. While the effects of trout introduction have been the subject of many studies, the effects of minnows are poorly understood. This thesis aimed to investigate the effects of the introduction of non-native fish, and especially minnows, on the liHoral macroinvertebrate communities of Pyrenean high mountain lakes. By studying 54 high mountain lakes, we evaluated the impact of minnow and trout densities on macroinvertebrate community composition and abundance, relative to other biotic and abiotic factors. Minnow density emerged as the most significant factor influencing macroinvertebrate community composition in high mountain lakes, surpassing spatial factors, catchment features, and in-lake habitat characteristics. Aquatic macrophytes offered competitive and predatory refuges, enhancing the survival and abundance of taxa susceptible to fish predation. However, large and mobile macroinvertebrates, like Corixidae and Dytiscidae, were adversely affected by both minnows and trout, largely due to their vulnerability to visual predators. Notably, even at relatively low densities, minnows had a greater impact on macroinvertebrate communities than trout. In lakes inhabited by minnows, the macroinvertebrate community was typically limited to a small number of taxa, predominantly composed of small, semi-sessile burrower organisms. In a study across 27 Pyrenean lakes, we used DNA metabarcoding to explore the impact of trout and minnows on macroinvertebrate communities. Trout contributed to the homogenisation of these communities, resulting in lower beta diversity, increased Chironomidae species richness, and higher genetic relatedness among community species. This led to decreased phylogenetic and functional diversity in trout-inhabited lakes compared to fishless ones. On the other hand, minnows had a non-selective and extensive impact, causing a random removal of species from the phylogenetic tree and increased beta diversity. An examination of the gut contents of both trout and minnows did not reveal notable differences in their dietary preferences. However, it seemed that trout consumed species of larger size compared to minnows. Additionally, for nine years, we assessed the recovery of macroinvertebrate communities in eight lakes where trout and minnow populations were eradicated or controlled. The aim was to identify common recovery paHerns among the lakes and determine the time required for macroinvertebrate communities to achieve a composition similar to that of fishless lakes. A few years after the initiation of trout and minnow eradication, we observed clear signs of recovery, with communities gradually resembling those typical of fishless lakes. Biomass of many taxa increased and community-level parameters improved, yet full recovery appears to require more than 6-7 years from eradication onset. With the goal of promoting the use of DNA metabarcoding for monitoring freshwater biodiversity, we established a reference library for DNA-based identification of high mountain aquatic fauna. This effort was driven by the lack of comprehensive coverage in current public reference databases for the diversity of Pyrenean freshwater animals. In its initial stages, the library contains 322 mitochondrial sequences from 178 species, with a focus on aquatic insects and key vertebrates. A first phylogenetic analysis of the obtained sequences revealed two highly divergent mitochondrial lineages of the corixid Sigara distincta in Europe, highlighting the need for a comprehensive taxonomic revision integrating both molecular and morphological approaches. |
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