Variable effects on growth and defense traits for plant ecotypic differentiation and phenotypic plasticity along elevation gradients.

Moe Bakhtiari,Gaëtan Glauser,Veronica Caggìa,Ludovico Formenti,Sergio Rasmann

doi:10.1002/ece3.4999

Moe Bakhtiari, Gaëtan Glauser + Show 3 more

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https://doi.org/10.1002/ece3.4999

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Abstract

Along ecological gradients, phenotypic differentiation can arise through natural selection on trait diversity and magnitude, and environment‐driven plastic changes. The magnitude of ecotypic differentiation versus phenotypic plasticity can vary depending on the traits under study. Using reciprocal transplant‐common gardens along steep elevation gradients, we evaluated patterns of ecotypic differentiation and phenotypic plasticity of several growth and defense‐related traits for two coexisting but unrelated plant species, Cardamine pratensis and Plantago major. For both species, we observed ecotypic differentiation accompanied by plasticity in growth‐related traits. Plants grew faster and produced more biomass when placed at low elevation. In contrast, we observed fixed ecotypic differentiation for defense and resistance traits. Generally, low‐elevation ecotypes produced higher chemical defenses regardless of the growing elevation. Yet, some plasticity was observed for specific compounds, such as indole glucosinolates. The results of this study may suggest that ecotypic differentiation in defense traits is maintained by costs of chemical defense production, while plasticity in growth traits is regulated by temperature‐driven growth response maximization.

Highlights

Species with wide distributions tend to exhibit large intraspecific variation in most functional and phenotypic traits
In C. pratensis, we observed phenotypic plasticity in total in‐ dole GLS, where the total indole GLS concentration of high‐elevation ecotypes signifi‐ cantly increased at the low elevation by 28% (SMD = 0.77), while indole GLS of low‐elevation ecotypes does not vary (Figures 2a, 3; Table 1)
The major aim of this study was to elucidate on the variable re‐ sponses of growth versus defense related traits using common gardens of plant ecotypes growing at different elevations

Summary

| INTRODUCTION

Species with wide distributions tend to exhibit large intraspecific variation in most functional and phenotypic traits. High and low‐elevation Plantago lanceolata ecotypes growing at two tempera‐ ture regimes (12 and 20°C to simulate cold and warm environment of different elevation gradients) showed strong plasticity in growth (i.e. both genotypes grew within each environment), while their resistance to generalist herbivores reflected genetically‐fixed patterns; high‐elevation ecotypes were always less resistant, inde‐ pendently of the temperature regimes (Pellissier et al, 2014) Such differences would suggest that ecotypes growing at high elevation were selected to produce lower amounts of constitutive defenses because of lower amount of herbivory, while retaining a high de‐ gree of plasticity of growth‐related responses to temperature. This study builds toward a better understanding of the ecological and evolu‐ tionary drivers of pathways mediating plant adaptation along eco‐ logical clines

| MATERIAL AND METHODS

| DISCUSSION

Findings

| CONCLUSIONS