Consistent Pattern of Local Adaptation during an Experimental Heat Wave in a Pipefish-Trematode Host-Parasite System

Abstract

Extreme climate events such as heat waves are expected to increase in frequency under global change. As one indirect effect, they can alter magnitude and direction of species interactions, for example those between hosts and parasites. We simulated a summer heat wave to investigate how a changing environment affects the interaction between the broad-nosed pipefish (Syngnathus typhle) as a host and its digenean trematode parasite (Cryptocotyle lingua). In a fully reciprocal laboratory infection experiment, pipefish from three different coastal locations were exposed to sympatric and allopatric trematode cercariae. In order to examine whether an extreme climatic event disrupts patterns of locally adapted host-parasite combinations we measured the parasite's transmission success as well as the host's adaptive and innate immune defence under control and heat wave conditions. Independent of temperature, sympatric cercariae were always more successful than allopatric ones, indicating that parasites are locally adapted to their hosts. Hosts suffered from heat stress as suggested by fewer cells of the adaptive immune system (lymphocytes) compared to the same groups that were kept at 18°C. However, the proportion of the innate immune cells (monocytes) was higher in the 18°C water. Contrary to our expectations, no interaction between host immune defence, parasite infectivity and temperature stress were found, nor did the pattern of local adaptation change due to increased water temperature. Thus, in this host-parasite interaction, the sympatric parasite keeps ahead of the coevolutionary dynamics across sites, even under increasing temperatures as expected under marine global warming.

Are heat waves susceptible to mitigate the expansion of a species progressing with global warming?

“…; Landis et al. ; Sentis et al. ) is the simulation of heat wave conditions in laboratory, with different severity levels.…”

“…Regarding the complexity of insect response to climatic anomalies but also the stochasticity and unpredictability of such anomalies, and their localized occurrence in time and space, a wide range of experiments can be conducted (Jentsch et al 2007). The approach that has been used here but also in other recent studies (e.g., Sorte et al 2010;Gillespie et al 2012;Landis et al 2012;Sentis et al 2013) is the simulation of heat wave conditions in laboratory, with different severity levels. Although this method does not allow reproducing exactly what happens outdoors, it allows exploring some mechanisms.…”

Heat and immunity: an experimental heat wave alters immune functions in three‐spined sticklebacks (Gasterosteus aculeatus)

“…In ectothermic animals, such as fish, the activity and efficiency of their immune systems is strongly temperature dependent (Ellis 2001). At the same time, metabolic rates and virulence traits of parasites are influenced and temperature is thought to be a strong modifier of host-parasite interactions (Lazzaro & Little 2009;Studer, Thieltges & Poulin 2010;Landis et al 2012).…”

Isolation over 35 years in a heated biotest basin causes selection on MHC class IIß genes in the European perch (Perca fluviatilis L.)

“…In an experimental test, Landis et al. (2012) showed that an increase in water temperature decreased the proportion of innate immune cells in infected host pipefish ( Syngnathus typhle ). The results of this experiment indicates that there is a strong host × parasite × environment interaction that may affect the genes that play major roles in parasite defense such as MHC genes.…”