Effect of light on the growth and photosynthesis of an invasive shrub in its native range.

Invasive species success may depend on ecophysiological attributes present in their native area or derived from changes that took place in the invaded environment. We studied the growth and photosynthetic capacity of Berberis darwinii shrubs growing under different light conditions (gap, forest edge and below the canopy) in their native area of Patagonia, Argentina. Leaf photosynthesis results determined in the native area were discussed in relation to information provided by studies carried out under the same light conditions in an invaded area in New Zealand. Shoot elongation, leaf production, stem and leaf biomass per shoot and specific leaf area (SLA, cm g) were determined in five adult plants, randomly selected in each of three light conditions in two forest sites. Net photosynthesis as a function of PPFD (Photosynthetic Photon Flux Density), stomatal conductance (gs), maximum light-saturated photosynthesis rate (Pmax), Pmass (on mass bases) and water-use efficiency (WUEi) were determined in plants of one site. We predicted that functional traits would differ between populations of native and invasive ranges. In their native area, plants growing under the canopy produced the longest shoots and had the lowest values for shoot emergence and foliar biomass per shoot, while their SLA was higher than gap and forest edge plants. Leaf number and stem biomass per shoot were independent of light differences. Leaves of gap plants showed higher Pmax, Pmass and gs but lower WUEi than plants growing at the forest edge. In its native range B. darwinii grows under different light conditions by adjusting shoot and leaf morphology and physiology. Plants of B. darwinii growing under the same light conditions show similar physiology in native and invasive ranges. This means that for B. darwinii, intra-specific variation of the functional traits studied here do not condition successful spread in new areas.