Variation in phenology and overall performance traits can help to explain the plant invasion process amongst Mediterranean ecosystems

Plant traits such as phenological development, growth rate, stress tolerance and seeds production may play an important role in the process of acclimatisation to new environments for introduced plants. Experiments that distinguish phenotypic plasticity from ecotypic differentiation would allow an understanding of the role of plant traits in the invasion process. We quantified the variation in phenological and overall performance traits associated with the invasion process for three herbaceous species native to Spain and invasive to Chile (Trifolium glomeratum, Hypochaeris glabra and Leontodon saxatilis). We grew plants from native and exotic populations along rainfall gradients in outdoor common gardens, located in the native and the introduced ranges and measured plant survival, phenology (days to flowering), biomass and seed output. Days to flowering was positively correlated with precipitation of the origin population for T. glomeratum and the native populations of H. glabra, but this pattern was not adaptive, as it was not associated with an increase in performance traits of these species. Phenology may instead reflect ecotypic differentiation to the environmental conditions of the original populations. Comparison between ranges (i.e. performance in both common gardens) was only possible for L. saxatilis. This species showed little variation in phenology and both native and exotic populations had higher fitness in the introduced range. This suggests that plasticity enhances invasiveness through increased propagule pressure in the novel environment. Our findings highlight the utility of common garden experiments in examining patterns of phenological and performance traits that relate to species invasiveness.We thank the Spanish Ministry of Science and Innovation for the financial support received to carry out this study (CGL2009-08718) and the grants REMEDINAL (S2013/MAE-2719 REMEDINAL3-Comunidad de Madrid) and SPONFOREST (BiodivERsA3-2015-58, PCIN-2016-055) and the Spanish Ministry of Education, Culture and Sport, because of the pre-doctoral FPU scholarship of the main author (AP2009-0518). We thank the State Meteorological Agency for providing meteorological data (AEMET, http://www.aemet.es/es/portada). We are especially grateful for the advice and suggestions provided by Greg Guerin. We would like to acknowledge Teresa Aravena, María Elena Díaz, Teresa Moreno Vicente, Marta Avilés, Devayana Valero and Ricardo Prentice for their support in phenological observations and Laura Sánchez-Jardón and Carlos Ovalle for field support. Likewise, we would like to acknowledge the whole INIA-Cauquenes Institution, in central Chile and the team from the Faculty of Agronomy of the Polytechnic University of Madrid, especially Daniel de la Torre Llorente.Peer reviewe