Figure 2. a) Structural equation model representing the direct and indirect effects of trait values on individual performances, with all species included. We used the trait measurements of November 2020 for this analysis. Trait values were standardized separately for each species to get rid of variance due to species identity. The initial model is presented in Supporting information 6 and was reduced with lavaan package through variable selection based on AIC criteria. All variables were calculated at pond level. Single dark headed arrows indicate direct effects. Double headed blue arrows indicate correlation between two model variables. Standardized path coefficients are given in blue for correlations and in black for direct effects with their p-values: ***p < 0.001; **p < 0.01; ‘.’ 0.05 < p < 0.1; no asterisk p ≥ 0.1 not significant. The widths of the lines are proportional to the strength of relationships (values of path coefficients). Solid and dashed lines respectively indicated positive or negative direct effects. Grey paths and grey variables indicated paths and variables that did not have any significant direct or indirect effects on species performance. R² values were the variance proportion of response variables explained by their explanatory variables. b) Absolute direct and indirect effects of trait values on individual performance.
Among all tested traits, LDMC did not affect individual biomass, while we identified multiple direct or indirect effects of all other traits (Fig. 2). Traits related to resource acquisition (aerial, and root traits) did not have a stronger influence on individual performance than clonal traits. On the one hand, traits directly influencing individual biomass (i.e. height, and all clonal and root traits), also supported the biomass, with height (0.38***) and specific internode mass (0.43***) displaying the strongest effects. These direct effects on individual performances were additionally modulated i.e.amplified or decreased, by their correlations (Fig. 2). For example, internode length and specific root mass were correlated to height, indirectly supporting their total positive effect on individual performance, while specific internode mass indirectly and positively impacted individual performance via its correlation with internode length and specific root mass. On the other hand, SLA did not have any direct effects on individual performances, yet influencing it negatively through its relationship with specific internode mass (-0.20*). Finally, when considering total trait effects on plant performance (Fig. 2b), only SLA had a negative impact, while all other traits displayed overall positive effects.