Different responses but complementary views: patterns of cross-taxa diversity under contrasting coastal dynamics in secondary sand dunes

Coastal sand dunes are dynamic ecosystems, with vegetation and biota responding to continuous changes in its typical environmental severity. Understanding vegetation patterns is relevant to early detect shifts in prevailing coastal dynamics and to refine monitoring strategies, especially in secondary sand dunes, which are under legal protection in Europe. We assessed the diversity patterns and cross-taxa congruence among lichens, bryophytes and vascular plants in secondary sand dunes under contrasting coastal dynamics (i.e. stable versus erosion sites), along a major biogeographic transition (i.e. Eurosiberian versus Mediterranean regions) in Western Europe. Our results show that the diversity patterns of bryophytes, lichens and vascular plants differ between contrasting coastal dynamics, regardless of the biogeographic context. Also, we found the absence of an explicit cross-taxa congruence among the diversity patterns of the three taxonomic groups. These results highlight the importance of taking into account the diversity of vascular plants, lichens and bryophytes, and the inclusion of other factors besides coastal dynamics, such as anthropogenic pressures. By doing so, a complementary view on the diversity patterns in secondary sand dunes can be provided to better guide conservation actions and monitoring strategies.