DISTRIBUTION PATTERN AND RICHNESS OF ENDEMIC PLANT SPECIES IN MARITIME AND LIGURIAN ALPS.

Abstract

In recent years we made an overview of endemic plants (sunsu lato) of the Maritime Alps (115 taxa representing 3.2 % of the flora). Ecological preferences and plant life strategies were detected, showing a particular ability of endemics to colonize habitats with low competition and disturbance characteristics. The comparison with other areas of the Mediterranean basin appears to show that the Maritime Alps are really a ‘hot spot’ owing to the high total number of vascular plants and the high number of endemic plants. Subsequently, looking for any focus, centre and area of endemism, analyses were performed on a presence/absence matrix of 36 vascular plant taxa endemic to the study area. For each operational geographic unit the number of endemic taxa present was counted. Additionally, the weighted endemism value was calculated. Areas of endemism were distinguished using cluster analysis and parsimony analysis of endemicity (PAE). The influence of ecological characteristics and historical factors was evaluated using Multi-Response Permutation Procedure and Non-Parametric Multiplicative Regression. The Indicator Species Analysis (INDVAL) was also used to identify the species characterizing the areas of endemism. Our results point out the importance and location of four main area of endemism within the Maritime and Ligurian Alps explaining the distribution pattern of endemic plants. These areas are easily interpreted by historical and ecological factors: the NPMR model indicated that the variation in number of endemic taxa is correlated with the thermoclimatic belts and the extent of Würm glaciations. No significant relationship was found between the number of endemism and the soil type. The comparison between the distribution of richness of species and the extension of glaciations, the OGU harbouring the higher number of endemics were in marginal position from the Quaternary glacial sheets. NPMR didn’t find models environmental patterns comparing the weighted endemism values The main focus and centre of endemism of the study area were evidenced inside the Roya Valley areas of endemism. This territory may be considered as a “hotspot within a hotspot”, and its statistically well supported identification appears to be very useful for future conservation purposes. Finally, the identification of a “hotspots within a hotspot” as a sum of the previous elements appears to be very useful for future conservation purposes.