Temperature and multiple parasites combine to alter host community structure

Abstract

Predicting the effects of climate change requires understanding complex interactions among multiple abiotic and biotic factors. By influencing key interactions among host species, parasites can affect community and ecosystem structuring. Yet, our understanding of how multiple parasites and abiotic factors interact to alter ecosystem structure remains limited. To empirically test the role of temperature variation and parasites in shaping communities, we used a multigenerational mesocosm experiment composed of four sympatric freshwater crustacean species (isopods and amphipods) that share up to four parasite species. Mesocosms were assigned to one of four different treatments with contrasting seasonal temperatures (normal and elevated) and parasite exposure levels (continuous and arrested (presence or absence of parasite larvae in mesocosm)). We found that parasite exposure and water temperature had interactive effects on the host community. Continuous exposure to parasites altered the community structure and differences in water temperature altered species abundance. The abundance of the amphipod Paracalliope fluviatilis decreased substantially when experiencing continuous parasite exposure and elevated water temperatures. Elevated temperatures also led to parasite-induced mortality in another amphipod host, Paracorophium excavatum. Contrastingly, isopod hosts were affected much less, suggesting increasing temperatures in conjunction with higher parasite exposure might increase their relative abundance in the community. Changes in invertebrate host populations have implications for other species such as fish and birds that consume crustaceans as well as having impacts on ecosystem processes, such as aquatic primary production and nutrient cycling. In light of climate change predictions, parasite exposure and rise in average temperatures may have substantial impacts on communities and ecosystems, altering ecosystem structure and dynamics.

Major drivers of biodiversity loss and their impacts on helminth parasite populations and communities

“…Another freshwater mesocosm experiment tested interactive effects of infection by two species of parasite larvae and temperature on four species of crustacean hosts (Friesen et al , 2021). Hosts included two amphipods ( Paracalliope fluviatilis and Paracorophium excavatum ) and two isopods ( Austridotea annectens and Austridotea lacustris ).…”

Combined effects of salinity and trematode infections on the filtration capacity, growth and condition of mussels

“…Reisser & Forward (1991) found no significant effect of parasite and salinity on the osmoregulation and mortality of the crab host. At the community level, Friesen et al (2021) detected a decline in amphipod population abundance when exposed to parasitic infection and elevated water temperature, whereas the isopod population was not affected. Few studies have focused on the effects of trematode infections in non-optimal environmental conditions on bivalve hosts and their function.…”

Disease decreases variation in host community structure in an old-field grassland

“…The role of disease in structuring host communities may also depend on the structure of the parasite community. Hosts are commonly infected with a diverse community of parasite species that vary in their effects on host fitness and growth (Friesen et al 2017), so variation in parasite community structure can drive disease impacts on host individuals (Mordecai et al 2015) and communities (Cappelli et al 2020, Friesen et al 2021). Moreover, parasite abundance and diversity both vary temporally.…”

“…Specifically, infections are often seasonal, which will generate differences in disease burdens over time and contribute to variation in parasite community structure (Sapp and Esch 1994, Grunberg and Sukhdeo 2017). Previous field experiments have found that parasite impacts on the host community can depend on parasite community composition (Cappelli et al 2020, Friesen et al 2021) and that parasite community composition can shift seasonally (Sapp and Esch 1994, Grunberg and Sukhdeo 2017, Halliday et al 2017). But, the effect of seasonal variation in parasite community composition on plant community structure remains untested.…”

“…The copyright holder for this preprint this version posted August 16, 2022. ; https://doi.org/10.1101/2022.08.15.503989 doi: bioRxiv preprint community composition (Cappelli et al 2020, Friesen et al 2021 and that parasite community composition can shift seasonally (Sapp and Esch 1994, Grunberg and Sukhdeo 2017. But, the effect of seasonal variation in parasite community composition on plant community structure remains untested.…”