A microbial mutualist within host individuals increases parasite transmission between host individuals: Evidence from a field mesocosm experiment

The interactions among host-associated microbes and parasites can have clear consequences for disease susceptibility and progression within host individuals. Yet, empirical evidence for how these interactions impact parasite transmission between host individuals remains scarce. We address this scarcity by using a field mesocosm experiment to investigate the interaction between a systemic fungal endophyte, Epichloe coenophiala, and a fungal parasite, Rhizoctonia solani, in leaves of a grass host, tall fescue. Specifically, we investigated how this interaction impacted parasite transmission under field conditions in replicated experimental host populations. Epichloe-inoculated populations tended to have greater disease prevalence over time, though this difference had weak statistical support. More clearly, Epichloe-inoculated populations experienced higher peak parasite prevalences than Epichloe-free populations. Epichloe conferred a benefit in growth; Epichloe-inoculated populations had greater aboveground biomass than Epichloe-free populations. Using biomass as a proxy, host density was correlated with peak parasite prevalence, but Epichloe still increased peak parasite prevalence after controlling for the effect of biomass. Together, these results suggest that within-host microbial interactions can impact disease at the population level. Further, while Epichloe is clearly a mutualist of tall fescue, it may not be a defensive mutualist in relation to R. solani.

ExMarine: An experimental field mesocosm system to study multiple-stressor impacts on rock pool biodiversity

Biodiversity loss due to increasing anthropogenic activities is one of the biggest threats to humanity. Understanding the impacts of multiple-stressors on ecosystems and biodiversity is therefore an urgent task. Shore ecosystems are especially valuable, as they harbour a high biodiversity and provide important ecosystems services. Until now, experimental approaches addressing multiple-stressor impacts on these ecosystems have been rare and mostly run with a limited number of replicates and under non-natural conditions. Here, an experimental field mesocosm system that allows studying multiple-stressor impacts on rock pool biodiversity is proposed. The ExMarine mesocosm system is composed of 64 experimental rock pool mesocosms in a fully randomised block design, which allows studying multiple-stressor impacts under highly standardised conditions. Water is taken directly from the sea, allowing biota to immigrate and emigrate freely. Water flow into the mesocosms can be regulated and it is possible to simulate disturbance through waves during high tide. The system can help to understand the impacts of multiple stressors on biodiversity, to monitor ecosystem health and to plan measures preventing the further loss of biodiversity.

ExMarine: An experimental field mesocosm system to study multiple-stressor impacts on rock pool biodiversity

Biodiversity loss due to increasing anthropogenic activities is one of the biggest threats to humanity. Understanding the impacts of multiple-stressors on ecosystems and biodiversity is therefore an urgent task. Shore ecosystems are especially valuable, as they harbour a high biodiversity and provide important ecosystems services. Until now, experimental approaches addressing multiple-stressor impacts on these ecosystems have been rare and mostly run with a limited number of replicates and under non-natural conditions. Here, an experimental field mesocosm system that allows studying multiple-stressor impacts on rock pool biodiversity is proposed. The ExMarine mesocosm system is composed of 64 experimental rock pool mesocosms in a fully randomised block design, which allows studying multiple-stressor impacts under highly standardised conditions. Water is taken directly from the sea, allowing biota to immigrate and emigrate freely. Water flow into the mesocosms can be regulated and it is possible to simulate disturbance through waves during high tide. The system can help to understand the impacts of multiple stressors on biodiversity, to monitor ecosystem health and to plan measures preventing the further loss of biodiversity.

ExMarine: An experimental field mesocosm system to study multiple-stressor impacts on rock pool biodiversity

Biodiversity loss due to increasing anthropogenic activities is one of the biggest threats to humanity. Understanding the impacts of multiple-stressors on ecosystems and biodiversity is therefore an urgent task. Shore ecosystems are especially valuable, as they harbour a high biodiversity and provide important ecosystems services. Until now, experimental approaches addressing multiple-stressor impacts on these ecosystems have been rare and mostly run with a limited number of replicates and under non-natural conditions. Here, an experimental field mesocosm system that allows studying multiple-stressor impacts on rock pool biodiversity is proposed. The ExMarine mesocosm system is composed of 64 experimental rock pool mesocosms in a fully randomised block design, which allows studying multiple-stressor impacts under highly standardised conditions. Water is taken directly from the sea, allowing biota to immigrate and emigrate freely. Water flow into the mesocosms can be regulated and it is possible to simulate disturbance through waves during high tide. The system can help to understand the impacts of multiple stressors on biodiversity, to monitor ecosystem health and to plan measures preventing the further loss of biodiversity.