Abstract
The nature of species distribution boundaries is a key subject in ecology and evolution. Edge populations are potentially more exposed to climate-related environmental pressures. Despite research efforts, little is known about variability in fitness-related traits in leading (i.e., colder, high latitude) versus trailing (i.e., warmer, low latitude) edge populations. We tested whether the resilience, i.e. the resistance and recovery, of key traits differs between a distributional cold (Greenland) and warm (Portugal) range edge population of two foundation marine macrophytes, the intertidal macroalga Fucus vesiculosus and the subtidal seagrass Zostera marina. The resistance and recovery of edge populations to elevated seawater temperatures was compared under common experimental conditions using photosynthetic efficiency and expression of heat shock proteins (HSP). Cold and warm edge populations differed in their response, but this was species specific. The warm edge population of F. vesiculosus showed higher thermal resistance and recovery whereas the cold leading edge was less tolerant. The opposite was observed in Z. marina, with reduced recovery at the warm edge, while the cold edge was not markedly affected by warming. Our results confirm that differentiation of thermal stress responses can occur between leading and trailing edges, but such responses depend on local population traits and are thus not predictable just based on thermal pressures.
Highlights
In the current context of climate change, predictions of future species ranges often involve research on thermal responses of species
While the northern edge population showed a progressive decline from 18 ̊C onwards, Fv/Fm in the southern one remained unaffected by 3 h heat shock (HS) up to 28 ̊C and decreased significantly (14%) only at 32 ̊C
While statistical tests indicated that Fv/Fm failed to recover fully in either population, the reduction was minimal (4%) in the southern edge population and was significantly larger (26%) in the northern population (Fig 1; Table 2 and Table A in S1 File)
Summary
In the current context of climate change, predictions of future species ranges often involve research on thermal responses of species. Predictive approaches commonly assume that all individuals of a species have the same tolerance response to environmental stressors. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript
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