Comparative taxonomic structure of the floras of two Mediterranean-climate regions: Iberia and California

• Published in: Diversity & distributions Vol. 11; no. 5; pp. 399 - 408
• Main Authors: Lozano, Felipe Domínguez, Schwartz, Mark W.
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Science Ltd 01-09-2005; Blackwell Science
• Subjects: Biodiversity Research; Biological taxonomies; California; conservation; Flora; Habitat conservation; Habitats; Iberia; Mediterranean floras; Plant ecology; Plant taxonomy; Plants; rarity; Species diversity; Species extinction; species richness; Taxa
• ISSN: 1366-9516; 1472-4642
• DOI: 10.1111/j.1366-9516.2005.00168.x

Two major events were invoked to understand recent biodiversity patterns in Mediterranean floras: northern hemisphere glaciations and historical human impacts. These two events were considered in this work, where we investigated general patterns in plant species richness and rarity attributes in two different Mediterranean regions: California and Iberia. Our goal was to assess whether comparisons of this sort provided evidence of different extinctions rates, making an effort to decouple anthropogenic from ice age-related effects in both regions. We employed a taxonomically revised database for eight Mediterranean floras containing information on species richness for 298 families and rarity attributes for 11,834 taxa. We used summary statistics (Gini coefficient) and randomly generated models to test for general patterns of the distribution of diversity within and among taxonomic groups. We then used this general pattern among Mediterranean floras to provide a context in which to evaluate our two focal areas. Results indicated that floras of California and Iberia share the closest taxonomic structure among Mediterranean regions. Differences emerged in rarity attributes and the taxonomic identities of rarity rich groups. These findings were interpreted in the light of Pleistocene changes. In addition, a closer focus on rarity attributes allowed us to pinpoint some segments of these floras where anthropogenic activities may drive variation from general patterns, specifically for rare species in ecologically sensitive habitats.