Syntaxa-area relationships, lessons from the vegetation of the Betic high mountain ranges (southern Spain)
Pérez-García, F. J.; Merlo, M. E.; Martínez-Hernández, F.; Medina-Cazorla, J. M.; Mendoza-Fernández, A. J.; Garrido-Becerra, J. A.; Salmerón-Sánchez, E.; Mota, J. F.
The species-area relationship is one of the most commonly studied issues in ecology and several explanatory models have been proposed for the question. Most papers on the relationships between taxa and area adopt the species-level approach. By contrast, our approach exports these concepts to other organizational levels of biodiversity and analyses the community-area relationships in the Betic mountain ranges at 4 levels of syntaxonomical hierarchy. Our approach also aims at studying the diversity of communities in the same way as taxonomical diversity is studied. To evaluate the matching of data to the different models, we used the regression coefficient (R2) and the corrected version of Akaike's information criterion (AICc). The highest altitude of a sierra was taken as a surrogate of habitat diversity. “Syntaxonomical diversity” was evaluated in a similar way to the taxonomical diversity of Clarke & Warwick. We have studied 94 associations (belonging to 42 alliances, 36 orders and 25 classes). The calculated indexes reveal higher regression coefficient between richness in syntaxa and the parameter under study (area and highest altitude) in a semi-log model than in a log-log model. Although the best correlation is obtained considering both variables, the patterns of richness exhibit a higher correspondence with altitude than with area. Results confirm very high regression coefficient between richness in syntaxa and in the quantity of the endemic flora present in each sierra. The higher the syntaxonomical level concerned, the higher the regression coefficient. The richness of the syntaxa exhibits patterns similar to those of the endemic flora: the most important sites are siliceous Sierra Nevada, Sierra de Las Nieves and Sierra de Gádor. There are important implications for conservation biology. These results show that approaches based on species and those based on communities are compatible for the preservation of biodiversity.