How do functional traits syndromes covary with growth and reproductive performance in a water-stressed population of Fagus sylvatica?

A central issue in plant evolutionary ecology is to understand how several coordinated suites of traits (i.e. traits syndrome) may be jointly selected within a single species. This study aims to describe patterns of variation and co-variation of functional traits in a water-stressed tree population and test their relationships with performance traits. Within a Mediterranean population of Fagus sylvatica experiencing recurrent summer droughts, we investigated the phenotypic variation of leaf unfolding phenology, Leaf Area (LA), Leaf Mass per Area (LMA), Leaf Water Content (LWC), water use efficiency (WUE) estimated by carbon isotopic discrimination (d13C), twig Huber-value (HV: the stem cross-section divided by the leaf area distal to the stem), wood density (WDens), and leaf nitrogen content (Nmass). First, a Principal Component Analysis revealed that two main axes structured the phenotypic variability: the first axis opposed leaf unfolding earliness and LWC to LMA and WUE; the second a...