Environmental heterogeneity leads to higher plasticity in dry‐edge populations of a semi‐arid Chilean shrub: insights into climate change responses

Abstract

Summary 1.Interannual variability in climatic conditions should be taken into account in climate change studies in semiarid ecosystems. It may determine differentiation in phenotypic plasticity among populations, with populations experiencing higher environmental heterogeneity showing higher levels of plasticity.2. The ability of populations to evolve key functional traits and plasticity may determine the survival of plant populations under the drier and more variable climate expected for semi-arid ecosystems.3. Working with populations of the semi-arid Chilean shrub Senna candolleana along its entire distribution range, we assessed inter-and intra-population variation in functional traits as well as in their plasticity in response to water availability. We measured morphological and physiological traits related to drought resistance in both field conditions and in a greenhouse experiment, where drought response was evaluated under two water availability treatments.4. All populations responded plastically, but higher precipitation heterogeneity in dry-edge populations seemed to have selected for more plastic genotypes compared to populations growing at mesic sites and with more homogeneous environmental conditions. 5. Synthesis. Our results suggest adaptive plasticity since higher levels of phenotypic plasticity were positively associated with plant performance. However, we did not find evidence for genetic variation for plasticity within populations. To the extent that phenotypic plasticity may play a key role in future persistence, populations at mesic sites may be more vulnerable to climate change due to their lower plasticity and their current limitations to evolve novel norms of reaction. Conversely, although Senna candolleana populations at the dry edge are exposed to higher levels of stress, they may be less susceptible to climate change in view of their greater plasticity. We highlight the need to consider population differentiation in both mean traits and their plasticity to model realistic scenarios of species distribution under climate change.

Dryland Vegetation Functional Response to Altered Rainfall Amounts and Variability Derived from Satellite Time Series Data

“…Moreover, SWA shows a stronger difference between dry and wet periods, has clearer unimodal shapes along the MAP gradient and possesses higher variability along the MAP gradient. This agrees with the hypothesized higher β dynamics in regions with higher interannual variability of annual rainfall [36,37], such as SWA (Figure 3a). In addition, this suggests that a higher rain use efficiency, which has been observed during dry periods [18], might be particularly favoured by greater rainfall variability.…”

“…Both can be expected from the overall higher β in SWA (Figure 4a). It thus further supports the hypothesis that greater rainfall variability (CVP, Figure 3a) may lead to a temporally more dynamic vegetation response to rainfall [37,67]. MAP β-max values (the positions of β max on the rainfall gradients) are significantly lower in SWA compared to WA (Figure 4c).…”

“…Savanna and grass type vegetation are both found at considerably higher MAP values than shrubs in both regions ( Figure 6). This might lead to the assumption that the vegetation adaptability to dry periods is most strongly pronounced in arid regions [37]. Secondly, how strongly β increases from wet to dry periods in arid regions depends on the respective variability of annual rainfall with greater interannual variability promoting relatively higher β during dry periods.…”

“…Additionally, there is evidence that greater environmental heterogeneity (such as rainfall variability) affects the way ecosystems react with changing resource availability [35,36]. Lázaro-Nogal et al [37] found greater phenotypic plasticity…”

Dryland vegetation functional response to altered rainfall amounts and variability derived from satellite time series data

“…Lázaro-Nogal et al (2015) found greater phenotypic plasticity being associated with higher rainfall variability in dryland plant communities which is considered an important feature for dryland ecosystems in face of future changes in rainfall. Thus, it may be hypothesized that higher rainfall variability promotes a more dynamic vegetation functional response to rainfall.…”