Loss of thermal refugia near equatorial range limits

Abstract

This study examines the importance of thermal refugia along the majority of the geographical range of a key intertidal species (Patella vulgata Linnaeus, 1758) on the Atlantic coast of Europe. We asked whether differences between sun-exposed and shaded microhabitats were responsible for differences in physiological stress and ecological performance and examined the availability of refugia near equatorial range limits. Thermal differences between sun-exposed and shaded microhabitats are consistently associated with differences in physiological performance, and the frequency of occurrence of high temperatures is most probably limiting the maximum population densities supported at any given place. Topographical complexity provides thermal refugia throughout most of the distribution range, although towards the equatorial edges the magnitude of the amelioration provided by shaded microhabitats is largely reduced. Importantly, the limiting effects of temperature, rather than being related to latitude, seem to be tightly associated with microsite variability, which therefore is likely to have profound effects on the way local populations (and consequently species) respond to climatic changes.

Untangling the roles of microclimate, behaviour and physiological polymorphism in governing vulnerability of intertidal snails to heat stress

“…This small-scale variation in temperature provides a spectrum of thermal environments that can provide refugia to avoid lethal or sublethal heat stress [18]. The ability of an organism to benefit from those refugia depends on environmental factors [53], the rate at which it can move [54], its size relative to the microhabitat [21], and the frequency at which the organism can access shelter during unpredictable extreme conditions [55].…”

Equatorial range limits of an intertidal ectotherm are more linked to water than air temperature

“…Considering the results presented in this study, we suggest that this threshold is crossed when water temperature is equal or exceeds 23 °C. The existence of this threshold is in agreement with recent findings which revealed that P. vulgata is unable to acclimate to the conditions present at thermally stressful microhabitats (Chapperon et al ., ), and that the levels of thermal stress in P. vulgata are particularly high on shores close to its limit of distribution, even in shaded microhabitats (Lima et al ., ), as SST on these shores regularly approach the 23 °C threshold (shores G, I and N, Appendix S1).…”

Cool barnacles: Do common biogenic structures enhance or retard rates of deterioration of intertidal rocks and concrete?

“…The mediating role of epibiota on substrate thermal behaviours has, for example, particular bearing on the structuring of intertidal communities under altered climates given that many species have very specific physiological tolerances (Bertness et al, 1999;Denny and Harley, 2006;Miller et al, 2009). On developed coastlines, could the use certain materials in engineering offer more favourable thermal conditions for temperature-sensitive species under a warmer climate (sensu Lima et al, 2016)?…”