Currently, plant ecological research is aimed at analysing the co-variation patterns in functional plant traits at an intraspecific level (i.e., within species). So far, these studies were analyzed only at the interspecific level, identifying a global pattern of trait variation along wide environmental gradients. Nevertheless, a growing number of experimental evidences highlighted that intraspecific variability is a component not at all negligible. To identify the source of functional trait variation, there is need of a better understanding, eventually leading to re-define the identified global pattern. Plant performance in an ecological context depends on plant capacity to acquire and use resources over the time. A direct expression of investment strategies resulting from different selective pressures is given by the relative amount of biomass present in the various organs i.e. biomass allocation. Biomass allocation, measured for each individual by biomass fractions or ratios, reflects plant capacity to uptake resources, especially water and nutrients, assuming therefore an important functional meaning. In this general context, this proposal aims at investigating the intraspecific variability in biomass allocation traits under water and nutrient stress to evaluate their ecological implication on plant capacity to counteract environmental stressors. Specifically, the proposal focuses on Mediterranean plant species that are a good model to study the population level of the intraspecific variability, as they experience different selective pressures due to remarkable environmental heterogeneity that promotes variability and can be a driver for species to promote a high phenotypic plasticity degree, mirrored in the different populations. Overall, the expected results of this project will allow to make more realistic previsions on the capacity of the Mediterranean species to persist under new climatic conditions.
The achievement of the project objectives will get information to further understanding on two important and topical aspects of plant ecology. First, the role of the intraspecific variability in plant traits to conferring the ability of a species to adapt to a chancing environment. Second, the functional meaning of the biomass allocation patterns. Starting from the beginning of the 21th century, the theoretical and experimental development of the plant functional traits has given a valuable opportunity to explain the functional mechanisms underlying the ecological observations. As previous said, comparative ecology has been focused so far on interspecific trait differences overlooking the intraspecific variation. As for interspecific variability the progresses have been surprising so that now it extensively recognized that a global pattern of trait variations has been identified along wide environmental gradients [1]. Nevertheless, ignoring intraspecific trait variation hides a grave risk, that is not completely understanding the extent at what a given genotype is able to adjust to changing environmental conditions by acclimation process. In fact, those traits that mostly vary at interspecific level and that may, therefore, mediate the acclimation response, could not vary at intraspecific level due to other factors involved. Among these plant size and ontogenetic plant development, organ size and biotic interactions [2]. Thus, especially under the current global climate change context, it is important to stress plant ecological research toward this topic that is still largely unexplored despite the growing number of studies produced in the last years. These studies assume even a greater importance in Mediterranean-type ecosystems, where the high environmental heterogeneity allows the affirmation of an elevated degree of the intraspecific variability.
Another novel aspect of this research concerns the choice to focus on biomass allocation traits (BAT). In particular, their use will contribute to disentangle the intricate question about the functional and the allometric meaning of the biomass allocation [3]. The first implies the changes in biomass allocation is a plastic response to environmental change factors. The second, considers biomass allocation from an allometric perspective namely as a size-dependent process [3]. Distinguish between the allocation and the allometric perspective is very important because a change in biomass allocation traits, for example under stress conditions, could be interpreted as part of the acclimation process, whereas it could be an apparent plastic response due to plant growth process. The methodological approach of this proposal will allow to clarify this aspect because the collected data could be used to test the possible effect of the water and nutrient shortage on the allometric trajectory between plant size (i.e. plant biomass) and biomass allocation traits (i.e. biomass fractions). A change in allometric trajectory will mean a real plastic response, while not changes will mean an apparent plastic response [3].
References
[1] Kattge et al. Global Change Biol 26: 119-188
[2] Poorter et al. 2018 New Phytol 219: 109-121
[3] Weiner 2004 Perspect Plant Ecol Evol Syst 6/4: 207-215