Environmental factors influencing expression of bilateral symmetrical traits

Abstract

Fluctuating asymmetry (FA) is a kind of asymmetry used to assess the stability of development, as the body’s ability to regulate its development on the phylogenetic level. Phenotypic plasticity helps plants to overcome negative effects of temperature variability, and allow to adjusting traits to adverse conditions. The aim of the study is to evaluate the level of plasticity and fluctuating asymmetry in leaf blade under influence of environmental factors. The leaf blades from urban population linden, Tilia spp. located in Moscow region, Russia were used. Fluctuating asymmetry was measured as FA = L – R / (L + R) in absolute value (L and R – left and right value of bilaterally symmetrical metric trait. Plastic variability was measured as PL = 1 – x/X (x and X – smallest and largest value of trait size). When some traits of a leaf blade had a high plasticity, other ones exposed instability of development with an increased FA value. The correlation PL - FA was changeable. In one site correlation r was – 0.69 (p<0.05; 2014; high temperature in May, up to 60% higher norm). The cold and humid vegetative season in 2017 revealed an increase in the plastic dimensions of leaf blades of the broad-leaved linden (Tilia platyphyllos Scop.) with increasing plastic variability of bilateral traits. We attribute results to the phenotypic deviation caused by low temperatures. The predominance of one type of variability was compensating by the weakness of other type variability most likely due to genetic epistasis.