Separating Developmental and Environmental Effects on Fluctuating Asymmetry in Lythrum salicaria and Penthorum sedoides

Abstract

Etivirotimental stress can disrupt developmental processes on biological, physiological, and chemical levels and thereby affect the symmetry of a trait. For this reason, fluctuating asymmetry is often proposed as a measure of stress encountered by an individual. One problem is that asymmetry may bave multiple causes, including developmental noise and genetic background, and genetic differences may interact with any physiological stress imposed by the environment. The main objective of tbis research was to determine whether developmental noise and genetic stress can be separated from environmental effects on leaf asymmetry. Tbe experiments were conducted on two wetland plants, Lytbrum salicaria (purple loosestrife) and Pentborum sedoides (ditch stonecrop). Replicates of different genotypes were measured wben young and after tbey matured, with the latter group grown under two nutrient treatments. Tbe largest and healthiest leaf of each plant was measured for lengtb, widtb, and differences in widtb between the left and right sides (measuring from the central vein at the widest point). Nutrient enrichment increased leaf asymmetry, wbile age reduced asymmetry in L. salicaria. However, leaf asymmetry cbanged only as a consequence of development in P. sedoides and decreased. Genotype didnot affect asymmetry in either species.

Leaf morphology of progenies in Q. suber, Q. ilex, and their hybrids using multivariate and geometric morphometric analysis

“…However, the frequency of fluctuating and developmental asymmetry was variable between cohorts, species and families, supporting the hypothesis of factors of different nature operating on each type of asymmetry (Milligan et al 2008).…”

“…One possible explanation is that the modification of the epigenetic systems involved in the development of the foliar primordia produced by hybridization induces a higher degree of malformation in younger than in older plants. The few studies that have investigated the relationship between age and leaf anomalies suggest that leaf asymmetry decreased with age in leaves (Milligan et al 2008). Alternatively, extremely asymmetric leaves may fall from the seedlings earlier, showing apparently shorter life-spans than normal leaves.…”

Edge effect and phenology in Erythroxylum tortuosum (Erythroxylaceae), a typical plant of the Brazilian Cerrado

“…Leaf size and leaf asymmetry are quite variable physical traits within populations and even within individual plants (overall, hereafter leaf asymmetry was considered a leaf trait), and measurement of these traits has been used to predict changes in environmental conditions (Brown and Lawton, 1991;Burns and Dawson, 2006;Roslin et al, 2006;Milligan et al, 2008;Shi and Cai, 2009). Fluctuating asymmetry (FA) describes the small but random variations in bilaterally symmetrical characters (Polak, 2003) and represents a potential measure of developmental instability (DI) in plants (Milligan et al, 2008;Puerta-Piñero et al, 2008).…”

“…Fluctuating asymmetry (FA) describes the small but random variations in bilaterally symmetrical characters (Polak, 2003) and represents a potential measure of developmental instability (DI) in plants (Milligan et al, 2008;Puerta-Piñero et al, 2008). Because small deviations from perfect symmetry usually represent DI, FA has been used as an indicator of stress (Parsons, 1990;Martel et al, 1999;Alados et al, 2001;Cornelissen et al, 2003;Cornelissen and Stiling, 2005).…”

“…Because small deviations from perfect symmetry usually represent DI, FA has been used as an indicator of stress (Parsons, 1990;Martel et al, 1999;Alados et al, 2001;Cornelissen et al, 2003;Cornelissen and Stiling, 2005). Stress may not only modify physical traits directly but may also alter the concentrations of chemical compounds in plants that are responsible for changes in physical traits (White, 1984;Black-Samuelsson and Andersson, 2003;Milligan et al, 2008).…”