Organisms exposed to major environmental change face atypical and stressful conditions across multiple environmental variables, yet studies of phenotypically plastic responses historically focus on one environmental variable at a time. Evaluating multivariate plasticity of traits across different, simultaneously varying environmental variables provides new insights into the fate of populations amidst environmental changes. We aimed to investigate plasticity in multivariate environments by 1) examining the individual and joint effects of two environmental variables and 2) calculating genotype-by-environment interactions and genetic correlations of character states to investigate potential evolutionary constraints.

We performed a lab controlled-environment experiment under a full factorial design of low and high temperatures and salinities with multiple maternal lineages of a parthenogenetic freshwater snail, Potamopyrgus antipodarum. Our results revealed that predictions of plastic trait responses among multivariate environments may be unexpected due to non-additive effects of environmental variables and varying magnitudes and orientations of genetic correlations among fitness-related traits. Considering multivariate environments provides deeper insight and advancement of understanding trait evolution by revealing trait patterns that would otherwise be missed in univariate studies.