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By assuming a power law curve instead to the often assumed logarithmic curve Nee and May 1997 the relationship between observed species richness and the observed phylogenetic diversity in each site suggests that species extinctions translate to higher PD loss than random extinction because of tree imbalance That is to say several sites host at the same time old clades with long terminal branches and young taxonomic groups whose extinction in the given site could be a key indicator of potential large PD loss and particularly applies to lowland sites hosting few rare and evolutionary distinct species but also to several other sites where indeed threatened species richness is quite low less than 10 taxa Whilst the search for environmental correlates revealed that threatened species Expected PDloss EDGE and EDR can be weakly explained by the climatic variables used in our analyses the positive effects of temperature and precipitation seasonality represent a tentative indication of higher accumulation of threatened plant evolutionary history in southern Italy Nevertheless the overall weak effects and especially the absence of significances for EDR suggest that threats evolutionary distinctiveness and endemicity seem to be independent from climatic factors at least at the geographical scale used in our study
