Localised versus Regional Adaptation in Limpet Shell Morphology across the Iberian Peninsula.

Abstract

The climate envelope approach to predicting climate-induced species range shift is limited. There are many possible reasons for this, but one novel explanation is that species adapt to changes in temperature at the expense of adaptation to other stressors. Here we test this hypothesis using the limpet, Patella depressa (Mollusca, Patellidae), over a large geographical area covering most of the Atlantic coast of Iberian Peninsula, known to consist of a genetically inter-connected population. We examine limpet shell morphology on four shores in each of three regions, from northern Spain to southern Portugal. Within each region, shell morphology (measured as maximum shell profile to length ratio) varied between shore types differing in their insolation, wave action, microhabitat availability and biological factors. However, this ratio, which is known to be an adaptive response to heat stress, was found to be consistently higher in more southern latitudes, despite differences between shore types being found in all regions. This implies that localised adaptation to shore type (most likely through phenotypic plasticity) is compromised by factors which change over latitudinal or regional scales, or which could occur in response to climate change. Even though such climate-induced changes may initially be localized, compromised adaptation (through plasticity or genetic) may result in altered community interactions and potentially large shifts in community structure.