DOI: 10.5061/dryad.547d7wmgk
title: Leaf fluctuating asymmetry is not a reliable indicator of stress

description: Stress experienced during development in organisms with bilateral
 structures could result in developmental instability, which is expressed
 as subtle non-directional deviations from perfect symmetry, known as
 fluctuating asymmetry (FA). As such, FA has been proposed, and extensively
 used, as a trait indicating stress for many organisms with bilateral
 structures and many types of stress. However, while this concept may apply
 to animals, the evidence for plants' main vegetative structures,
 i.e., leaves, remains equivocal, and a comprehensive synthesis on this
 topic is still missing. We designed observational field and controlled
 greenhouse studies, combining different growth and leaf forms across
 multiple stress gradients, comprising 21 species and 80 populations. We
 measured FA as the difference between the left and right area of the leaf,
 an approach that accommodates diverse leaf forms. We used high-precision,
 blind, single-person measurements and tested for other forms of symmetry
 and the effect of leaf size. We further complemented our study with a
 systematic literature review of FA in plant leaves, compiling 51 studies
 comprising 72 species, 23 stress types, and 131 unique entries (species ×
 stress type).  We consistently found no effect of stress on leaf
 FA in any of the studied species in both our field and experimental
 gradients. In the systematic literature review, only 39% of the unique
 entries showed the expected increase in FA with stress, 53% showed no
 effect, 9% showed an opposite trend of a decrease in FA with stress, and
 1% showed an unimodal relationship. Importantly, only 40% of all entries
 fulfilled the crucial step of controlling for a high-precision
 measurement, and of these 49% reported the expected increase of FA with
 stress.  Both the results of our observational and experimental
 approaches and the systematic literature review failed to support a clear
 relationship between stress and FA in plant leaves. These results clearly
 show that FA in plant leaves cannot be used as a reliable trait indicating
 stress during development.
description: We designed observational field and controlled greenhouse
 studies, combining different growth and leaf forms across multiple stress
 gradients, comprising 21 species and 80 populations. We measured FA as the
 difference between the left and right area of the leaf, an approach that
 accommodates diverse leaf forms. We used high-precision, blind,
 single-person measurements and tested for other forms of symmetry and the
 effect of leaf size. We further complemented our study with a systematic
 literature review of FA in plant leaves, compiling 51 studies comprising
 72 species, 23 stress types, and 131 unique entries (species × stress
 type).
description: # Leaf fluctuating asymmetry is not a reliable indicator of stress
 [https://doi.org/10.5061/dryad.547d7wmgk](https://doi.org/10.5061/dryad.547d7wmgk) These data are linked to the manuscript Majekova et al. 2024 Functional Ecology. Data correspond to the observational and experimental studies reported in the manuscript. Data for the systematic literature review are saved as Appendix A Table A1 of the manuscript. ## Description of the data and file structure The dataset contains three files ordered as separate spreadsheets: (1) "*Greenhouse experiment*" "with columns for: * "*Species*" (Hedypnoides rhagadioloides, Hymenocarpos circinatus) * "*Watering\_ treatments*" (30, 50, 90 ml) * "*Locality*" of origin of species seeds (Mediterranean, Semi-arid) * "*Individual*" per Species x Treatment x Locality * "*FA_index*" - fluctuating asymmetry index used (|log (Right leaf side/ Left leaf side)| (2) "*Productivity_Gradient_Germany*" with columns for: * "*Species*" (perennial temperate grasslands species) * "*Indicator_Value_Nitrogen*" - Represents the gradient of productivity that was estimated based on nitrogen indicator values (IVN; Ellenberg et al., 1991) calculated as mean value of all species present in the given plant community (on average 15 species per site) weighted by the relative abundance of each species (relative abundance was estimate as visual cover in %) * "*Individual*" per Species x Indicator_Value_Nitrogen * "*FA_index*" - fluctuating asymmetry index used (|log (Right leaf side/ Left leaf side)|) (3) "*Aridity_Gradient_Israel*" with columns for: * "*Species*" (winter annual species) * "*MAP*" - Represents the gradient of aridity estimated as mean annual precipitation in mm * "*Individual*" per Species x MAP * "*FA_index*" - fluctuating asymmetry index used (|log (Right leaf side/ Left leaf side)|) Missing data are depicted as "NA".