Discussion
Improving predictions for how species and communities will be affected
by climate change and extreme events is an urgent challenge. Here we
examined how populations of the functionally important seagrassPosidonia oceanica could be affected by heat stress, by
conducting a translocation experiment across its range. Cool-edge,
central and warm-edge populations displayed clear differences in thermal
performance when grown under common conditions, but patterns contrasted
with a priori expectations based on their thermal geography.
Cool-edge populations performed equally well to warm-edge populations
under common conditions and significantly better than central
populations in terms of growth rates and survivorship. The strong
performance of cool-edge populations was remarkable given they
experienced thermal anomalies of >5ºC above long term
summer maxima, compared to 1.5ºC for central populations and
<1ºC for warm-edge populations. Moreover, cool-edge
transplants suffered and subsequently recovered from severe overgrazing
at the warmest site that removed >75% of aboveground
biomass, highlighting remarkable resilience of cool-edge populations to
combined effects of thermal stress and herbivory – two pervasive
impacts of climate change in marine ecosystems.