Evolutionary potential in the Alpine: trait heritabilities and performance variation of the dwarf willow Salix herbacea from different elevations and microhabitats.

Janosch Sedlacek,Christian Rixen,Guenter Hoch,Mark Van Kleunen,Jaroslav Klápště,Julia Wheeler,Andrés J Cortés,Christian Lexer,Sophie Karrenberg,Sonja Wipf,Oliver Bossdorf

doi:10.1002/ece3.2171

Abstract

Alpine ecosystems are seriously threatened by climate change. One of the key mechanisms by which plants can adapt to changing environmental conditions is through evolutionary change. However, we still know little about the evolutionary potential in wild populations of long‐lived alpine plants. Here, we investigated heritabilities of phenological traits, leaf size, and performance traits in natural populations of the long‐lived alpine dwarf shrub Salix herbacea using relatedness estimates inferred from SSR (Simple Sequence Repeat) markers. Salix herbacea occurs in early‐ and late‐snowmelt microhabitats (ridges and snowbeds), and we assessed how performance consequences of phenological traits and leaf size differ between these microhabitats in order to infer potential for evolutionary responses. Salix herbacea showed low, but significant, heritabilities of leaf size, clonal and sexual reproduction, and moderate heritabilities of phenological traits. In both microhabitats, we found that larger leaves, longer intervals between snowmelt and leaf expansion, and longer GDD (growing‐degree days) until leaf expansion resulted in a stronger increase in the number of stems (clonal reproduction). In snowbeds, clonal reproduction increased with a shorter GDD until flowering, while the opposite was found on ridges. Furthermore, the proportion of flowering stems increased with GDD until flowering in both microhabitats. Our results suggest that the presence of significant heritable variation in morphology and phenology might help S. herbacea to adapt to changing environmental conditions. However, it remains to be seen if the rate of such an evolutionary response can keep pace with the rapid rate of climate change.

Highlights

Snowmelt patterns in alpine ecosystems are considerably impacted by current changes in temperature and precipitation
Salix herbacea occurs in early- and late-snowmelt microhabitats, and we assessed how performance consequences of phenological traits and leaf size differ between these microhabitats in order to infer potential for evolutionary responses
We found that larger leaves, longer intervals between snowmelt and leaf expansion, and longer Growing-degree days (GDD) until leaf expansion resulted in a stronger increase in the number of stems

Summary

Introduction

Snowmelt patterns in alpine ecosystems are considerably impacted by current changes in temperature and precipitation. Earlier snowmelt may extend the growing season above altitudes of 2000 m by up to 60 days (Beniston et al 2003) This is likely to have strong impacts on plants by altering the developmental timing, increasing exposure to frost, changing moisture availability in the soil and affecting interactions with other plants, pollinators, herbivores, and pathogens (Beniston et al 2003; Inouye 2008; Wipf et al 2009; Little 2014; Wheeler et al 2014). Most research on responses of alpine plant species to changing snowmelt and temperature conditions has focused on species migration toward higher altitudes, as this may allow plants to track their climatic requirements (Conradin and Walther 2005; Lenoir et al 2008; Eskelinen et al 2009; Matteodo et al 2013; Wipf et al 2013). Plasticity may be constrained or even maladaptive, if species or populations are exposed to novel environmental conditions outside the range of conditions they encountered in their evolutionary history (Ghalambor et al 2007; Visser 2008; Scheepens and Sto€cklin 2013)

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Conclusion