Genotypic and Phenotypic Diversity Does Not Affect Productivity and Drought Response in Competitive Stands of Trifolium repens.

Heidrun Huber,Heinjo J During,Fabienne Bruine De Bruin,Peter J Vermeulen,Niels P R Anten

doi:10.3389/fpls.2016.00364

Heidrun Huber, Heinjo J During + Show 3 more

Open Access

https://doi.org/10.3389/fpls.2016.00364

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Abstract

Clonal plants can form dense canopies in which plants of different genetic origin are competing for the uptake of essential resources. The competitive relationships among these clones are likely to be affected by extreme environmental conditions, such as prolonged drought spells, which are predicted to occur more frequently due to global climate change. This, in turn, may alter characteristics of the ecological system and its associated functioning. We hypothesized that the relative success of individual clones will depend on the size of the ramets as ramets with larger leaves and longer petioles (large ramets) were predicted to have a competitive advantage in terms of increased light interception over smaller-sized ramets. Under drier conditions the relative performances of genotypes were expected to change leading to a change in genotype ranking. We also hypothesized that increased genotypic and phenotypic diversity will increase stand performance and resistance to drought. These hypotheses and the mechanisms responsible for shifts in competitive relationships were investigated by subjecting genotypes of the important pasture legume Trifolium repens to competition with either genetically identical clones, genetically different but similarly sized clones, or genetically as well as morphologically different clones under well-watered and dry conditions. Competitive relationships were affected by ramet size with large genotypes outperforming small genotypes in diverse stands in terms of biomass production. However, large genotypes also produced relatively fewer ramets than small genotypes and could not benefit in terms of clonal reproduction from competing with smaller genotypes, indicating that evolutionary shifts in genotype composition will depend on whether ramet size or ramet number is under selection. In contrast to our hypotheses, diversity did not increase stand performance under different selection regimes and genotype ranking was hardly affected by soil moisture, indicating that increasing fluctuations in water availability result in few short-term effects on genotypic diversity in this stoloniferous grassland species. Communities dominated by stoloniferous herbs such as T. repens may be relatively resilient to environmental change and to low levels of genetic diversity.

Highlights

Ecosystem productivity and resilience to environmental fluctuations are generally believed to increase with increasing diversity (Cardinale et al, 2013; de Mazancourt et al, 2013; Gross et al, 2014)
The biomass of large and small plants responded differently to competition treatments (Table 2). This was mainly due to the positive response of the large sized genotypes B15 and B4 to increased diversity, and a negative response for most of the small genotypes in the phenotypically diverse treatment (Figure 2)
Our results clearly show that the relative performance of phenotypically different genotypes was neither affected by the competitive environment nor by the prevalent environmental conditions, resulting in an almost constant ranking among genotypes

Summary

Introduction

Ecosystem productivity and resilience to environmental fluctuations are generally believed to increase with increasing diversity (Cardinale et al, 2013; de Mazancourt et al, 2013; Gross et al, 2014). As different species can occupy different ecological niches, complex interactions of different trophic levels exist and negative feedback loops driven by, e.g., soil pathogens are less likely to affect species performance in diverse ecosystems as large species- or genotype-specific pathogen populations rarely build up (Hendriks et al, 2013; van der Putten et al, 2013; Bardgett and van der Putten, 2014; Brotherton and Joyce, 2015) While these concepts have long been applied to species diversity, increasing evidence exists that within-species genetic diversity can be important (Reusch et al, 2005; Hughes et al, 2008; Ellers et al, 2011; Grettenberger and Tooker, 2015). The interactions between genotypic and functional diversity and environmental fluctuations are largely unresolved to date

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