Essay Example on By assuming a power law curve Instead

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 

Whilst the use of phylogenetic methods to study extinction risk has been criticized because risk is not a phenotypic evolved trait Putland 2005 further studies could be oriented to sough to what extent threat is associated with endemicity and other ecological or plant traits and to evaluate whether they show phylogenetic signal because closely related taxa share many similarities including extinction proneness Purvis 2008 The negative association of threatened species richness and the degree of habitat transformation indicates that the majority of threatened species are located far from highly urbanised sites while they mostly occur in natural and semi natural environments However habitat degradation connected with agricultural urban and commercial development is among the most significant threat to plant diversity in Italy Rossi et al 2016 Orsenigo et al in prep but again the geographical scale used in our study is too coarse for detecting such modifications Overall regression analyses showed that the majority of species and the highest phylogenetic diversity scores are conserved into protected areas This seems also confirmed by the intersection of priority sites with protected areas However the gap analysis revealed that nearly half of Expected PDloss priority sites are not adequately protected and the percentage is reduced to around the half for the other metrics but still remain sufficiently high suggesting a moderate protection for the overall plant evolutionary history in Italy Forests and mountain sites are indeed currently included in protected areas while other sites such as the lowlands hilly areas and coastal plains are underrepresented Rosati et al 2008

Conservation resources should therefore allocated to protect species in those sites non adequately covered by protected areas and to better understand the overlap between EDGE or EDR species and protected areas Indeed the definition of protected areas and their management frequently does not take into account the needs of plant diversity Heywood 2017 Thus the inclusion of species of conservation concern within protected areas does not necessarily imply that they are actively conserved Species richness is well known to be positively correlated with cumulative scores of phylogenetic and other diversity metrics Schweiger et al 2008 Therefore without the application of randomisation test high cumulative scores would mostly reflect high species richness Investigating highly significant values of the biodiversity metrics however highlights areas where limited resources would be best spent to conserve the highest concentration of phylogenetic diversity irrespective of species richness This is the reason why the cells containing highly significant amount of Expected PDloss EDGE or EDR do not necessarily represent areas requiring protected areas but rather identify sites where priority species are concentrated much like the original definition of the biodiversity hotspots Myers et al 2000 Alternative approaches to conservation can be employed in these sites for such species ex situ Idée su altre opzioni non standard while protected areas should mostly be established to protect evolutionary history in sites also hosting high species richness together with ecosystems with higher complexity