Ecological dynamics and ciliate dispersal in temporary aquatic environments: an experimental analysis.

Abstract

Temporary aquatic ecosystems play a crucial role in maintaining biodiversity and ecological functioning, harboring highly dynamic microbial communities. Among these organisms, cili-ates stand out for their taxonomic and functional diversity, as well as their ability to disperse through various mechanisms, including endozoochory mediated by waterbirds. This process enables the transport of resistant cysts and potentially active cells, facilitating colonization of new habitats and promoting connectivity among isolated environments. In this context, we in-vestigated the structure and dynamics of ciliate communities in temporary aquatic habitats of Doñana National Park (Spain), focusing on beta diversity (β-diversity) and dispersal via endo-zoochory. The central hypothesis proposed that ciliate community structure and dynamics are shaped by environmental factors, seasonality, and waterbird-mediated dispersal, influencing patterns of β-diversity and ecological functioning. We analyzed how seasonal (spring and sum-mer) and environmental factors (salinity, nutrients, pH, among others) affect taxonomic β-di-versity and functional trait patterns of ciliates in temporary ponds and marshes. Specific hy-potheses predicted that hydrological connectivity in spring would reduce β-diversity through biotic homogenization, that species with high SCBD values would also show high IndVal scores, and that functional traits such as body size and trophic guild would relate to species contributions to β-diversity. The results confirmed that β-diversity was seasonally modulated, with higher homogenization in spring due to increased connectivity, and greater differentiation in summer associated with environmental stress and ecological filtering. Functional traits ac-counted for part of the variation, highlighting the spatial importance of small filter-feeding cil-iates. We assessed ciliate dispersal via waterbirds using a microcosm experiment, investigating the potential of endozoochory to trigger emergence and temporal succession of communities. Specific hypotheses predicted increasing richness and abundance over time, community com-position shifts toward more complex trophic structures, and that traits such as encystment ca-pacity, small body size, and trophic guild would influence dispersal success and establishment. The experiment supported these predictions, revealing progressive increases in richness and abundance, compositional changes indicative of ecological succession, and the emergence of characteristic species with traits linked to resistance and rapid colonization. This study provides the first evidence that ciliates can be dispersed via endozoochory by waterbirds, remaining vi-able and functionally active after excretion. By integrating functional traits and beta diversity in an innovative feces-based experiment, this research advances microbial ecology and offers direct implications for the conservation of Mediterranean wetlands under climate change.