1d: The mutualism-parasitism continuum in ecology

1d:     The mutualism-parasitism continuum in ecology

Conveners:     Antoine Grenier-Journe (Netherlands Institute of Ecology)

                       Aileen Berasategui (Vrije Universiteit Amsterdam)

                       Ana Born-Torrijos (Royal Netherlands Institute for Sea Research)

                       Cyril Hammoud (Royal Netherlands Institute for Sea Research)

                       Antoine Guiguet (Naturalis Biodiversity Centre)

1. Host-symbiont relationships in a changing world

Emilia Hannula Aileen Berasategui, Cyril Hammoud, Leiden University Vrije Universiteit Amsterdam, Royal Netherlands Institute for Sea Research

2. Mycoviruses in soil saprotrophic fungi

Ruiqi Wang, Hazal Kandermir, Peter van Bodegom, Martijn Bezemer, Emilia Hannula, Leiden University

Saprotrophic fungi play a fundamental role in soil ecosystems as primary decomposers driving nutrient and carbon turnover on a global scale. Mycoviruses are known to be widespread in fungi and can affect hosts by altering their properties such as growth rate, virulence, drug resistance, and metabolite production, thereby potentially influencing broader soil ecosystem functions. To advance understanding of prevalence and diversity of mycoviruses of soil saprotrophic fungi, we conducted RNA mycoviruses screenings of both saprotrophic fungi isolated from soil and explored soil metatranscriptome data. De novo assembly of RNA-seq data uncovered two viral sequences from 28 fungal isolates, one of which, a ssRNA virus from Mucor plumbeus, appears to represent a putative new species with 52.4% sequence identity to known viruses. Analysis of eukaryotic RNA viruses in soil metatranscriptomes indicated that viruses have a wide host range, with fungi and oomycetes accounting for 39.6% of classified eukaryotic viruses, yet no sequences were definitively linked to saprotrophic fungi. The parallel findings from fungal cultures and complex soil viral communities point to a low prevalence of mycoviruses in soil saprotrophic fungal hosts. Thus, we propose that further culture-based identifications are essential for a comprehensive understanding of mycovirus distribution and to guide future studies into mycovirus transmission and ecological functions.

3. Ecological stoichiometry of phytoplankton disease

Dedmer Van de Waal, Angela Peace, Esmee Clijsen, Kevin Kammers, Eric Seabloom, Thijs Frenken, Silke van den Wyngaert, Elizabeth Borer, Netherlands Institute of Ecology

Primary producer hosts rely on nutrients for growth and defense against parasites. At the same time, parasites require host nutrients for their growth. Relationships between primary producer hosts and their parasites may be predicted by stoichiometric mismatches, similar to herbivores, with decreased parasite performance under nitrogen (N) or phosphorus (P) limitation (i.e., low P:C or N:C ratios). At the same time, host defense also may be nutrient dependent, particularly on N, restricting the ability of cells to invest in their immunity under N limitation (i.e., low N:C ratios). We tested the effects of shifting host elemental ratios on interactions between host and parasite growth and host defense. To this end, we performed a literature survey, developed a stoichiometric disease model, and tested outcomes using laboratory experiments. Overall, our findings demonstrate that nutrients can modulate primary producer host-parasite interactions via shifting host investment in growth and defense, providing a mechanistic base for understanding disease dynamics in changing nutrient conditions.

4. Warming-driven changes in invasive parasite populations and their impact on mussel hosts

Rosa Jolma, Hans Heesterbeek, David Thieltges, Mathias Wegner, Anieke van Leeuwen, Mick Roberts, Royal Netherlands Institute for Sea Research

Climate change may influence the spread and ecosystem impact of emerging infectious diseases. We investigated how warming affects the impact of two invasive intestinal parasitic copepods, Mytilicola intestinalis and M. orientalis, on blue mussel (Mytilus edulis) populations in the Dutch Wadden Sea through laboratory experiments across temperatures (10°C–26°C) and population modelling. In the experiments, we found that the parasite M. intestinalis reduces host condition, and M. orientalis decreases host growth, while higher temperatures accelerate the life cycles of both parasites. In our model, the projected temperature increased by 2100 led to the basic reproduction number (R0) of M. intestinalis falling below one, while the R0 of M. orientalis increased, the latter resulting in a negative effect on mussel population. Our results indicate that invasive parasites can shape and increase the impact of climate change on native species populations even in the absence of lethal effects at the individual level.

5. Seasonal Dynamics of Gut Microbiota in Feral Pigeons: Influence of Diet and Environmental Variation

Kangqing Zhang, Maurine Dietz, Henri Zomer, Gerrit Potkamp, Joana Falcao Salles, Irene Tieleman, Royal Netherlands Institute for Sea Research Institute for Evolutionary Life Science

Gut microbiota significantly impacts host physiology and life-history traits, including seasonal phenotypic variations. This study investigated the role of seasonal diet and environmental factors in shaping gut microbiota composition in feral pigeons (Columba livia). Cloacal and fecal samples were collected from three locations in Groningen across winter and summer. 16S rRNA results showed distinct seasonal shifts in microbial diversity and composition, with elevated levels of Firmicutes and Fusobacteria, particularly Lactobacillus and Enterococcus, in summer. Microbial variation correlated with environmental factors, such as precipitation and day length. Dietary changes were also observed through metabarcoding, with higher consumption of Helianthus sp. and Poa sp. during summer months. Partial Least Squares Path Modeling (PLS-PM) analysis highlighted that environmental and dietary shifts are key drivers of gut microbiota seasonality in feral pigeons. These findings underscore the dynamic relationship between host ecology and gut microbiota in response to seasonal environmental changes.