Phenotypic plasticity can increase the extent of the environmental gradient occupied by a species (niche breadth) and modify the portion of niche space shared among co-occurring species (niche overlap). Thus, phenotypic plasticity may play a role in community assembly processes. Given that plants deal with a multivariate environment, and that functional traits are often correlated, plastic responses to different environmental factors are likely correlated. However, the implications of correlations of plasticities for niche overlap remain unexplored. Here, we present and evaluate a conceptual framework that links correlations of plasticities and niche overlap patterns among co-occurring plant species. We specifically tested in an arid shrubland whether positive, negative, or null correlations between plasticity to light and water availability would be associated with patterns of high, low, or random niche overlap, respectively. Field data identified light and water availability as key factors shaping herbaceous plant community structure. We estimated species’ niche breadth and niche overlap using two-dimensional kernel-density estimations (NOK) and standardised effect sizes of Pianka’s niche overlap index (OSES). We measured phenotypic plasticity to light and water availability in the six most abundant species in a greenhouse experiment. We used the plasticity index (PI) to test i) the relationship between plasticity to light and water availability, and ii) the association between overall plasticity (average PI across traits) and niche breadth. We found a positive relationship between plasticity to light and water availability. Increased overall plasticity was associated with a broader niche breadth. Both NOK and OSES estimations indicated a significant niche overlap pattern. Results supported one of the predictions of our conceptual framework: that a positive correlation of plasticities would lead to increased niche overlap. The verified conceptual framework broadens our understanding of the role of phenotypic plasticity in plant community coexistence.

These data come from a greenhouse experiment carried out for a subset of six species from the ten most abundant annual herbaceous species in Las Cardas Experimental Station (5436 ha; Universidad de Chile), located at the southern edge of the Atacama Desert, northern-central Chile (30°15’S, 71°17’W).
 
On the one hand, the experiment was conducted at Universidad de La Serena (29°54’S, 71°14’W; 40 km N of Las Cardas). We collected 60–80 seedlings for each of the six species. Seedlings (≤ 3 cm in height) were unearthed randomly from the four types of microsites and transplanted immediately into 500-cm3 pots with their natural soil. Plants were watered to field capacity with tap water every other day. Seedlings were assigned to light conditions two weeks later and kept there for one week before watering treatments started. Each of the four experimental groups (sun/shade crossed by moist/drought) had 13–18 seedlings per species. Methodological details regarding trait measurements are provided in the paper’s main text.
Overall, these data provide results that support that plastic responses to light and water availability are positively correlated and that overall plasticity enhanced niche breadth.

On the other hand, all field data used in this study is available in a previous and permanent link on Dryad (https://doi.org/10.5061/dryad.0gb5mkm0z). This study correctly cited these accurate data (Escobedo et al. 2021b -  https://doi.org/10.1111/1365-2745.13650).

Therefore, here we have provided data on reproductive output (RO), reproductive allocation (RA), first flowering time (FFT), first reproductive output time (FRT), relative growth rate (RGR), final plant height (PH); basal stem diameter (BD); number of leaves (NL), number of branches (NB), leaf area (LA), leaf-dry matter content (LDMC), and specific leaf area (SLA). Missing values are represented by the symbol NA (not available).