Multiple common garden experiments suggest lack of local adaptation in an invasive ornamental plant

Adaptive evolution along geographic gradients of climatic conditions is suggested to facilitate the spread of invasive plant species,leading to clinal variation among populations in the introduced range.We investigated whether adaptation to climate is also involved in the invasive spread of an ornamental shrub,Buddleja davidii,across western and central Europe.Methods We combined a common garden experiment,replicated in three climatically different central European regions,with reciprocal transplantation to quantify genetic differentiation in growth and reproductive traits of 20 invasive B.davidii populations.Additionally,we compared compensatory regrowth among populations after clipping of stems to simulate mechanical damage.Important Findings Our results do not provide evidence for clinal variation among invasive B.davidii populations:populations responded similarly to the different environments,and trait values were not correlated to climatic conditions or geographic coordinates of their home sites.Moreover,we did not detect differences in the compensatory ability of populations.We suppose that the invasive spread of B.davidii has been facilitated by phenotypic plasticity rather than by adaptation to climate and that continent-wide shuffling of cultivars due to horticultural trade may have limited local adaptation so far.

Regulation of the water status in three co-occurring phreatophytes at the southern fringe of the Taklamakan Desert

Aims We investigated the regulation of the water status in three predominant perennial C3 phreatophytes(Alhagi sparsifolia,Populus euphratica,Tamarix ramosissima)at typical sites of their occurrence at the southern fringe of the hyperarid Taklamakan Desert(north-west China).Methods In the foreland of the river oasis of Qira(Cele),we determined meteorological variables,plant biomass production,plant water potentials(WL)and the water flux through the plants.We calculated the hydraulic conductance on the flow path from the soil to the leaves(kSL)and tested the effects of kSL,WL and the leaf-to-air difference in the partial pressure of water vapour(Dw)on stomatal regulation using regression analyses.Important Findings Despite high values of plant water potential at the point of turgor loss,all plants sustained WL at levels that were high enough to maintain transpiration throughout the growing season.In A.sparsifolia,stomatal resistance(rs;related to leaf area or leaf mass)was most closely correlated with kSL;whereas in P.euphratica,~70%of the variation in rs was explained by Dw.In T.ramosissima,leaf area-related rs was significantly correlated with WL and kSL.The regulation mechanisms are in accordance with the growth patterns and the occurrence of the species in relation to their distance to the ground water.