Macroinvertebrate biodiversity and metacommunity dynamics in temporary rivers: fundamental aspects and insights for conservation planning
[eng] Temporary rivers (RTs) are dynamic ecosystems characterized by flow phases, disconnected ponds and dry riverbeds that alternate, creating a mosaic of habitats that change in space and time. These rivers are found all over the world and make up more than half of the global river network, with a...
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| Tipo de documento: | tese |
| Estado: | Versão publicada |
| Data de publicação: | 2026 |
| País: | España |
| Recursos: | Universidad de Barcelona |
| Repositório: | Dipòsit Digital de la UB |
| OAI Identifier: | oai:diposit.ub.edu:2445/226843 |
| Acesso em linha: | https://hdl.handle.net/2445/226843 http://hdl.handle.net/10803/696691 |
| Access Level: | Acceso aberto |
| Palavra-chave: | Ecologia fluvial Limnologia Invertebrats d'aigua dolça Stream ecology Limnology Freshwater invertebrates |
| Resumo: | [eng] Temporary rivers (RTs) are dynamic ecosystems characterized by flow phases, disconnected ponds and dry riverbeds that alternate, creating a mosaic of habitats that change in space and time. These rivers are found all over the world and make up more than half of the global river network, with a particularly prominent presence in arid and Mediterranean climate regions. Due to their unique dynamics and fragmentation caused by drying up, the metacommunities of RTs appear to differ from the general patterns observed in permanent river networks. This divergence is attributed to the effects of drying, which alters spatial and temporal connectivity. This thesis integrates innovative methodologies, empirical studies and conservation tools to advance the understanding of spatio-temporal dynamics, the assembly of metacommunities and the conservation of biodiversity in Mediterranean RTs. Using macroinvertebrates as model organisms, this study highlights the complex interaction between hydrological connectivity, environmental variables and habitat heterogeneity. Together with various dispersal strategies, these factors shape biodiversity patterns at local and regional scales. The objective of this thesis is to deepen the understanding of the dynamics of metacommunities within a small-scale region, taking advantage of this knowledge to inform and improve the conservation and management strategies of these ecosystems. In Chapter 1, an innovative methodological framework is developed to jointly quantify the effects of drying on spatial and temporal connectivity, using data on the presence and absence of water. The resulting connectivity metrics describe hydrological dynamics over time and river networks, revealing that spatiotemporally connected sites exhibit greater richness of macroinvertebrates and less dissimilarity of communities. These metrics have a high potential to be applicable beyond RTs, offering a valuable tool for studying dynamic ecosystems in scenarios of global change. Chapter 2 explores the general patterns of macroinvertebrate diversity in the RTs studied and identifies the main factors influencing the assembly of metacommunities on a small regional scale in Mediterranean RTs. Using null models and generalized additive models (GAMs), the study finds that alpha diversity is primarily influenced by habitat heterogeneity and spatiotemporal connectivity, especially for aquatic passive dispersers. In contrast, beta diversity is configured by environmental gradients and factors related to dispersion. Active aerial dispersers are mainly structured by local environmental conditions (i.e., species sorting), while space-time connectivity is a key factor for passive aquatic dispersers (i.e., dispersal limitation). In Chapter 3, the thesis considers metapopulations and metacommunities in RTs, and investigates the effects of fragmentation on genetic and community variability. Using bulk sample metabarding, the study evaluates the intraspecific genetic diversity of the entire community and analyzes the genetic structure patterns of two species with opposite dispersal capacities (Anax imperator and Physella acuta). In addition, metacommunity patterns in alpha and beta diversity are analyzed using morphological and molecular data separately. The results show that spatio-temporal isolation can promote intraspecific variability in highly permanent and isolated sites. Both morphological and metabarcoding data reveal similar patterns in alpha and beta diversity, suggesting that drying and spatiotemporal connectivity influence the structure of metacommunities when different identification approaches are used. Chapter 4 employs mesocosm experiments and isotopic enrichment techniques to track the aerial dispersal of macroinvertebrates from disconnected ponds during the dry phase. The study finds that spatial proximity to disconnected ponds significantly influenced community structure, with dispersion gradually decreasing with distance. Airborne dispersal is detected, not only in aquatic taxa with aerial adults, but also in strictly aquatic taxa, demonstrating the role of disconnected ponds as refuges in maintaining biodiversity during the dry phase and contributing to community recovery during flow restoration. The results highlight the critical importance of maintaining disconnected ponds in RTs under future drying scenarios to preserve both local and regional biodiversity. Using seasonal data from diatoms and macroinvertebrates, the study combines beta diversity metrics (LCBD and SCBD) and prioritization tools (Marxan) to identify key conservation sites. It is shown that spatio-temporal connectivity and habitat heterogeneity are critical factors for biodiversity patterns and site prioritization. Specific recommendations are provided to promote the conservation of RTs, including monitoring along hydrological phases and stations, the combination of complementary conservation tools and the incorporation of spatio-temporal dynamics in management strategies. In addition, in relation to biodiversity conservation, this thesis documents new records of distribution of aquatic macroinvertebrates inhabiting RTs, including the first record of a plecopter specializing in ephemeral rivers (Leuctridae: Tyrrhenoleuctra) for the northeast of the Iberian Peninsula, the first record of a species of diptera (Dixidae: Dixella graeca) for continental Europe, and numerous new records for the natural park where the research was carried out. Overall, this thesis highlights the complex ecological processes that shape biodiversity in Mediterranean RTs and provides innovative methodologies and practical recommendations for their conservation. Integrating spatio-temporal perspectives, metacommunity frameworks and advanced molecular tools, this work contributes to a more comprehensive understanding of RT ecosystems, increasingly threatened by global change. |
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