How reproducible are the measurements of leaf fluctuating asymmetry?

A comparison of two methods for estimating measurement repeatability in morphometric studies

Measurement repeatability is often reported in morphometric studies as an index of the contribution of measurement error to trait measurements. However, the common method of remeasuring a mounted specimen fails to capture some components of measurement error and could therefore yield inflated repeatability estimates. Remounting specimens between successive measurements is likely to provide more realistic estimates of repeatability, particularly for structures that are difficult to measure.Using measurements of 22 somatic and genitalic traits of the neriid fly Telostylinus angusticollis, we compared repeatability estimates obtained via remeasurement of a specimen that is mounted once (single-mounted method) versus remeasurement of a specimen that is remounted between measurements (remounted method). We also asked whether the difference in repeatability estimates obtained via the two methods depends on trait size, trait type (somatic vs. genitalic), sclerotization, or sex.Repeatability estimates obtained via the remounted method were lower than estimates obtained via the single-mounted method for each of the 22 traits, and the difference between estimates obtained via the two methods was generally greater for small structures (such as genitalic traits) than for large structures (such as legs and wings). However, the difference between estimates obtained via the two methods did not depend on trait type (genitalic or somatic), tissue type (soft or sclerotized) or sex.Remounting specimens between successive measurements can provide more accurate estimates of measurement repeatability than remeasuring from a single mount, especially for small structures that are difficult to measure.

High leaf fluctuating asymmetry in two native plants growing in heavy metal-contaminated soil: the case of Metlaoui phosphate mining basin (Gafsa, Tunisia)

In order to estimate pollution impact in soil and plants by phosphates mining activities, three mining sites and one control site were selected around Metlaoui (phosphates basin of Gafsa, southern Tunisia) in March 2019. Heavy metal concentrations in soil and in two native plants (Moricandia arvensis and Diplotaxis harra: Brassicaceae) were measured using atomic absorption spectrometry. Development instability was estimated using leaf fluctuating asymmetry of the two plant species. The results showed that the soils of the Metlaoui sites contain higher levels of Cd, Ni, Zn, and Cr compared with control site (maximum of 33.225 ± 2.588; 100.86 ± 0.314; 180.267 ± 16.103; and 16.554 ± 0.313 ppm, respectively). These levels are higher than the maximal contents tolerated in soils. Heavy metals also occurred at high concentrations in plant organs in Metlaoui sites especially in leaves. Cadmium and Zn concentrations in these plants exceed the phytotoxic level (with maximum of 20.498 ± 0.627 ppm and maximum of 337.901 ± 16.686 ppm, respectively). Statistical analysis showed that fluctuating asymmetries (FA) of leaves of the two sampled plants are higher in mining sites compared with control. Pearson correlation and PCA analysis showed that FA is related to Cd, Ni, and Zn concentrations in soil. The results indicate that phosphate extraction and laundries in the mining sites caused heavy metal pollution in soil that accumulates in plant organs and caused also development instability. Our study showed that Moricandia arvensis may have the potential for phytoremediation.

Effects of ploidy level and haplotype on variation of photosynthetic traits: Novel evidence from two Fragaria species

To reveal the effects of ploidy level and haplotype on photosynthetic traits, we chose 175 genotypes of wild strawberries belonging to two haplotypes at two types of ploidy levels (diploidy and tetraploidy) and measured photosynthetic traits. Our results revealed that ploidy significantly affected the characteristics of light-response curves, CO2-response curves, and leaf gas exchange parameters, except intercellular CO2 concentration (Ci). Tetraploid species had a lower light saturation point (LSP) and CO2 saturation point (CSP), higher light compensation point (LCP), dark respiration (Rd), and CO2 compensation point (CCP) than diploid species. Furthermore, tetraploid species have lower photosynthetic capacity than diploid species, including net photosynthetic rate (Pn), stomatal conductivity (Gs), and transpiration rate (Tr). In addition, haplotype had a significant effect on LSP, CSP, Tr, and Ci as well as a significant interactive effect between ploidy and haplotype on the maximal photosynethic rate of the light-response curve and Rd. Most of the variance existed within haplotypes among individuals. These results suggest that polyploidization was the main driver for the evolution of photosynthesis with increasing ploidy level (i.e. from diploidy to tetraploidy in Fragaria species), while the origin of a chromosome could also affect the photosynthetic traits and the polyploidization effect on photosynthetic traits.