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Apparent plasticity in functional traits determining competitive ability and spatial distribution: a case from desert.

Xie JB, Xu GQ, Jenerette GD, Bai YF, Wang ZY, Li Y - Sci Rep (2015)

Bottom Line: We found that (1) the biomass allocation patterns of both Haloxylon species in responses to environmental conditions were apparent rather than true plasticity and (2) the allometric allocation patterns affected the plants' competition for soil nutrient supply.A key implication of our results is that the apparent plasticity in functional traits of plants determines their response to environmental change.Without identifying the apparent and true plasticity, we would substantially overestimate the magnitude, duration and even the direction of plant responses in functional traits to climate change.

View Article: PubMed Central - PubMed

Affiliation: 1] State Key Lab of Desert and Oasis Ecology, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, 40-3 South Beijing Road, Urumqi, Xinjiang 830011, P. R. China [2] University of Chinese Academy of Sciences, 19A, Yu-Quan Road, Beijing 100039, P. R. China.

ABSTRACT
Species competitive abilities and their distributions are closely related to functional traits such as biomass allocation patterns. When we consider how nutrient supply affects competitive abilities, quantifying the apparent and true plasticity in functional traits is important because the allometric relationships among traits are universal in plants. We propose to integrate the notion of allometry and the classical reaction norm into a composite theoretical framework that quantifies the apparent and true plasticity. Combining the framework with a meta-analysis, a series of field surveys and a competition experiment, we aimed to determine the causes of the dune/interdune distribution patterns of two Haloxylon species in the Gurbantonggut Desert. We found that (1) the biomass allocation patterns of both Haloxylon species in responses to environmental conditions were apparent rather than true plasticity and (2) the allometric allocation patterns affected the plants' competition for soil nutrient supply. A key implication of our results is that the apparent plasticity in functional traits of plants determines their response to environmental change. Without identifying the apparent and true plasticity, we would substantially overestimate the magnitude, duration and even the direction of plant responses in functional traits to climate change.

No MeSH data available.


Scenarios for re-evaluating the levels of phenotypic plasticity.(A) Lines overlap (no phenotypic plasticity); (B) lines share a common slope and also share a common elevation, but shift in location along the common slope (apparent plasticity); (C) lines share a common slope but difference in elevations (apparent plasticity + true plasticity); and (D) the slopes are not equal (apparent plasticity + true plasticity). In an allometric view, different slopes and/or different elevations show that the biomass allocation is affected by varying environment factors (true plasticity). However, the allometric relationships among traits are universal in plants, thereby the phenotypic plasticity in C and D also include the apparent plasticity. The blue (or red) dots in (E) represent the trait at sample start time, ts and sample end time, te under a low-resource environment, e1 (or high-resource environment, e2), respectively. The blue (or red) squares represent the phenotypes in sample time, t. The empty blue (or empty red) squares represent the phenotypes in sample of the same plant size. The right curves represent the normal distribution of trait value in a low-resource (blue) and a high-resource (red) environment, respectively. The representation is the same for (F–H).
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f2: Scenarios for re-evaluating the levels of phenotypic plasticity.(A) Lines overlap (no phenotypic plasticity); (B) lines share a common slope and also share a common elevation, but shift in location along the common slope (apparent plasticity); (C) lines share a common slope but difference in elevations (apparent plasticity + true plasticity); and (D) the slopes are not equal (apparent plasticity + true plasticity). In an allometric view, different slopes and/or different elevations show that the biomass allocation is affected by varying environment factors (true plasticity). However, the allometric relationships among traits are universal in plants, thereby the phenotypic plasticity in C and D also include the apparent plasticity. The blue (or red) dots in (E) represent the trait at sample start time, ts and sample end time, te under a low-resource environment, e1 (or high-resource environment, e2), respectively. The blue (or red) squares represent the phenotypes in sample time, t. The empty blue (or empty red) squares represent the phenotypes in sample of the same plant size. The right curves represent the normal distribution of trait value in a low-resource (blue) and a high-resource (red) environment, respectively. The representation is the same for (F–H).

Mentions: There are at least two different theoretical perspectives in estimating plasticity (Fig. 1). In the first, phenotypic plasticity is classically quantified as the slope of a reaction norm2021, b. There is a long tradition in ecology of investigating how different environments lead to plasticity in traits on the basis of the reaction norm. For example, a flat reaction norm indicates that the focal phenotype is insensitive to environmental variation or environmental canalization22. In contrast, a steep reaction norm represents plasticity22. These trait-based frameworks have been used to explain many ecological processes (e.g. species coexistence and interspecific competition1). Recent studies propose that many phenotypic expression and ecological processes are better understood as size-dependent and therefore are in fact allometry351617232425. Thus, size-dependent plasticity must be excluded when estimating true plasticity5262728. Unfortunately, the classical reaction norm totally ignores its relationship with plant size, thereby it is unable to distinguish between true and apparent plasticity and needs to be corrected. The second perspective is allometric analyses (Fig. 1B). To distinguish between true and apparent plasticity, some studies have proposed an allometric -model (by identifying whether or not the allometric trajectories change with varying environments) for studies in plasticity1729. Although allometric analyses have been quite successful in many cases5111625293031, we still lack a theoretical framework for clarifying the relationship between the classical reaction norm and allometric analyses. For example, what is the relationship between environmental canalization and apparent plasticity (as they both describe the focal phenotype insensitive to environmental variation)? How can apparent and true plasticity be quantified when the allometric trajectories change with environmental variation? Thus, we propose to integrate the notion of classical reaction norm and allometry into a composite theoretical framework (it is fully developed in Appendix A1) that: (1) corrects the classical reaction norm with plant size (Fig. 1 and Fig. S1 in Appendix A1; hereafter referred to as the size-correction reaction norm, b′, that excludes size-dependent plasticity and represents true plasticity); (2) illustrates the quantitative relationship between the classical reaction norm and allometric growth (Figs 1 and 2; including four scenarios to re-evaluate the levels of true plasticity); and (3) illustrates how to quantify the apparent and true plasticity.


Apparent plasticity in functional traits determining competitive ability and spatial distribution: a case from desert.

Xie JB, Xu GQ, Jenerette GD, Bai YF, Wang ZY, Li Y - Sci Rep (2015)

Scenarios for re-evaluating the levels of phenotypic plasticity.(A) Lines overlap (no phenotypic plasticity); (B) lines share a common slope and also share a common elevation, but shift in location along the common slope (apparent plasticity); (C) lines share a common slope but difference in elevations (apparent plasticity + true plasticity); and (D) the slopes are not equal (apparent plasticity + true plasticity). In an allometric view, different slopes and/or different elevations show that the biomass allocation is affected by varying environment factors (true plasticity). However, the allometric relationships among traits are universal in plants, thereby the phenotypic plasticity in C and D also include the apparent plasticity. The blue (or red) dots in (E) represent the trait at sample start time, ts and sample end time, te under a low-resource environment, e1 (or high-resource environment, e2), respectively. The blue (or red) squares represent the phenotypes in sample time, t. The empty blue (or empty red) squares represent the phenotypes in sample of the same plant size. The right curves represent the normal distribution of trait value in a low-resource (blue) and a high-resource (red) environment, respectively. The representation is the same for (F–H).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4507175&req=5

f2: Scenarios for re-evaluating the levels of phenotypic plasticity.(A) Lines overlap (no phenotypic plasticity); (B) lines share a common slope and also share a common elevation, but shift in location along the common slope (apparent plasticity); (C) lines share a common slope but difference in elevations (apparent plasticity + true plasticity); and (D) the slopes are not equal (apparent plasticity + true plasticity). In an allometric view, different slopes and/or different elevations show that the biomass allocation is affected by varying environment factors (true plasticity). However, the allometric relationships among traits are universal in plants, thereby the phenotypic plasticity in C and D also include the apparent plasticity. The blue (or red) dots in (E) represent the trait at sample start time, ts and sample end time, te under a low-resource environment, e1 (or high-resource environment, e2), respectively. The blue (or red) squares represent the phenotypes in sample time, t. The empty blue (or empty red) squares represent the phenotypes in sample of the same plant size. The right curves represent the normal distribution of trait value in a low-resource (blue) and a high-resource (red) environment, respectively. The representation is the same for (F–H).
Mentions: There are at least two different theoretical perspectives in estimating plasticity (Fig. 1). In the first, phenotypic plasticity is classically quantified as the slope of a reaction norm2021, b. There is a long tradition in ecology of investigating how different environments lead to plasticity in traits on the basis of the reaction norm. For example, a flat reaction norm indicates that the focal phenotype is insensitive to environmental variation or environmental canalization22. In contrast, a steep reaction norm represents plasticity22. These trait-based frameworks have been used to explain many ecological processes (e.g. species coexistence and interspecific competition1). Recent studies propose that many phenotypic expression and ecological processes are better understood as size-dependent and therefore are in fact allometry351617232425. Thus, size-dependent plasticity must be excluded when estimating true plasticity5262728. Unfortunately, the classical reaction norm totally ignores its relationship with plant size, thereby it is unable to distinguish between true and apparent plasticity and needs to be corrected. The second perspective is allometric analyses (Fig. 1B). To distinguish between true and apparent plasticity, some studies have proposed an allometric -model (by identifying whether or not the allometric trajectories change with varying environments) for studies in plasticity1729. Although allometric analyses have been quite successful in many cases5111625293031, we still lack a theoretical framework for clarifying the relationship between the classical reaction norm and allometric analyses. For example, what is the relationship between environmental canalization and apparent plasticity (as they both describe the focal phenotype insensitive to environmental variation)? How can apparent and true plasticity be quantified when the allometric trajectories change with environmental variation? Thus, we propose to integrate the notion of classical reaction norm and allometry into a composite theoretical framework (it is fully developed in Appendix A1) that: (1) corrects the classical reaction norm with plant size (Fig. 1 and Fig. S1 in Appendix A1; hereafter referred to as the size-correction reaction norm, b′, that excludes size-dependent plasticity and represents true plasticity); (2) illustrates the quantitative relationship between the classical reaction norm and allometric growth (Figs 1 and 2; including four scenarios to re-evaluate the levels of true plasticity); and (3) illustrates how to quantify the apparent and true plasticity.

Bottom Line: We found that (1) the biomass allocation patterns of both Haloxylon species in responses to environmental conditions were apparent rather than true plasticity and (2) the allometric allocation patterns affected the plants' competition for soil nutrient supply.A key implication of our results is that the apparent plasticity in functional traits of plants determines their response to environmental change.Without identifying the apparent and true plasticity, we would substantially overestimate the magnitude, duration and even the direction of plant responses in functional traits to climate change.

View Article: PubMed Central - PubMed

Affiliation: 1] State Key Lab of Desert and Oasis Ecology, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, 40-3 South Beijing Road, Urumqi, Xinjiang 830011, P. R. China [2] University of Chinese Academy of Sciences, 19A, Yu-Quan Road, Beijing 100039, P. R. China.

ABSTRACT
Species competitive abilities and their distributions are closely related to functional traits such as biomass allocation patterns. When we consider how nutrient supply affects competitive abilities, quantifying the apparent and true plasticity in functional traits is important because the allometric relationships among traits are universal in plants. We propose to integrate the notion of allometry and the classical reaction norm into a composite theoretical framework that quantifies the apparent and true plasticity. Combining the framework with a meta-analysis, a series of field surveys and a competition experiment, we aimed to determine the causes of the dune/interdune distribution patterns of two Haloxylon species in the Gurbantonggut Desert. We found that (1) the biomass allocation patterns of both Haloxylon species in responses to environmental conditions were apparent rather than true plasticity and (2) the allometric allocation patterns affected the plants' competition for soil nutrient supply. A key implication of our results is that the apparent plasticity in functional traits of plants determines their response to environmental change. Without identifying the apparent and true plasticity, we would substantially overestimate the magnitude, duration and even the direction of plant responses in functional traits to climate change.

No MeSH data available.