Are there habitats that contribute best to plant species diversity in coastal dunes ?

This paper describes patterns of diversity across major habitat typesin a relatively well preserved coastal dune system in central Italy. The research addressesthe following questions: (a) whether different habitats defined on the base of a land covermap support similar levels of biodiversity in terms of vascular flora richness and number ofrare and endangered species, and (b) how each habitat contributes to the total speciesdiversity of the coastal environment. A random stratified sampling approach based on adetailed land cover map was applied to construct rarefaction curves for each habitat typeand to estimate total species richness. In addition, the number of exclusive, rare andendangered species was calculated for each habitat type. Results highlight the importanceof the coastal dune zonation (embryo-dune, main dune, transition and stabilized dune) inspecies conservation because they harbour progressively higher species richness. However,differences among these habitats were not significant, so no particular species rich ‘‘hotspots’’could be evidenced. On the contrary, rarefaction curves show that the upper beach(strand) habitat sustains significantly smaller number of species, but surprisingly, it showsthe highest rarity values and highest proportion of endangered species. Therefore, for theestablishment of successful biodiversity conservation programs in these coastal environments,it is imperative not only to conserve biologically rich hotspots but also to includespecies poor habitats containing endangered or unique elements. Thus, the completecoastal vegetation mosaic including all coastal habitats is important to adequately characterizethe plant species diversity of coastal dune ecosystems.