Although the structure and composition of plant communities is known to influence the functioning of ecosystems, there is as yet no agreement as to how these should be described from a functional perspective. We tested the biomass ratio hypothesis, which postulates that ecosystem properties should depend on species traits and on species contribution to the total biomass of the community, in a successional sere following vineyard abandonment in the Mediterranean region of France. Ecosystem-specific net primary productivity, litter decomposition rate, and total soil carbon and nitrogen varied significantly with field age, and correlated with community-aggregated (i.e., weighed according to the relative abundance of species) functional leaf traits. The three easily measurable traits tested, specific leaf area, leaf dry matter content, and nitrogen concentration, provide a simple means to scale up from organ to ecosystem functioning in complex plant communities. We propose that they be called ''functional markers,'' and be used to assess the impacts of community changes on ecosystem properties induced, in particular, by global change drivers.

Summary• Specific leaf area (leaf area to dry mass ratio), leaf dry matter content (leaf dry mass to saturated fresh mass ratio) and leaf nitrogen concentration (LNC) have been proposed as indicators of plant resource use in data bases of plant functional traits.• We tested whether species ranking based on these traits was repeatable by studying spatio-temporal variations in specific leaf area and leaf dry matter content of water-saturated leaves (SLA SAT and LDMC SAT ), as well as in LNC, for 57 herbaceous and woody species (or subsets thereof) growing under the Mediterranean climate of southern France.• Interseason and intersite variations were more pronounced than interannual variations, but species ranking for a given trait remained mostly consistent in space and time. Classifications based on LDMC SAT were generally more repeatable across years and sites, whereas those based on SLA SAT were more stable over seasons. LNC usually gave the least repeatable classifications.• Species rankings were not completely similar for the three traits. Discussion of reproducibility, ease of trait measurement, as well as trait-function relationships led us to propose that measurements of the leaf traits, SLA SAT and/or LDMC SAT , were the most suitable in large screening programmes.

The aim of this study was to detect suites of traits related to whole plant and seed morphology, phenology and resource use--including water--in species differing in successional status. Twenty traits were measured on 55 species representative of 5 successional stages in Mediterranean southern France, including eight pertaining to phenology and five to water economy. Suites of traits that changed along succession in agreement with the acquisition/conservation trade-off were completed by continuous changes in phenology. Early successional species had leaves with a high specific leaf area that were produced and lost continuously through the growing season. Late-successional species were taller with long-lived, high delta(13)C leaves produced during short periods, most of them persisting during summer, and produced large seeds requiring a long ripening period. Replacement of species occurred with change in strategies of drought survival: early successional species escaped drought by dying before summer; later herbaceous species maintained favourable water status in relation to leaf shedding during summer; late successional trees with a large body allowing access to a large pool of resources, produced dense leaves that could tolerate desiccation. These changes occurred concomitantly with a shift in CSR strategies, using traits related to resource use, plant size and flowering phenology: ruderal herbs were replaced by more stress-tolerant herbs and shrubs throughout the succession, with competitive trees dominating the latest successional stage. These results suggest that the breadth of functional variability found in natura is not predicted by the CSR framework, and calls for a more integrated view of whole plant functioning.

The dopamine receptor type 1 (DRD1) has been implicated in the development of hypertension in humans as well as in animal models of spontaneous hypertension. We screened the entire coding and promoter region of the human DRD1 receptor for polymorphisms to analyze their association with hypertension. The allele frequencies of two common single-nucleotide polymorphisms, A-48G and G-94A were determined in 493 hypertensive patients and 209 normotensive controls. Allele frequencies did not differ for both polymorphisms between the two groups (-48 G-allele in hypertension = 0.37; -48 G-allele in normotension = 0.36; -94 A-allele in hypertension = 0.14; -94 A-allele in normotension = 0.10). Our findings in these Caucasian patients are in contrast to a recent Japanese study that revealed a significant association of the -48 G-allele with hypertension. Thus, racial differences may play an important role concerning the association of variants in the dopamine receptor type 1 gene with essential hypertension.