Within-plant variation of developmental instability in male and female Mercurialis perennis in contrasting light habitats

Abstract

Plants, as sessile organisms, are exposed to macro- and microenvironmental changes, the suboptimal stress conditions leading to developmental instability that can be quantified by assessing the fluctuating asymmetry (FA) of organs or their parts. The analysis of repeated plant organs (such as leaves of successive nodes) can be used to assess the intraindividual aspect of developmental instability patterns. In dioecious species, gender of plant can also be one of the factors affecting asymmetry levels. The aim of this study was to explore the inter- and intra-individual patterns of developmental instability in natural populations of a dioecious species in contrasting light habitats, with special focus on within-plant asymmetry patterns. Male and female individuals of dioecious understory forb Mercurialis perennis (Euphorbiaceae) were sampled from two contrasting light habitats, shaded (spruce forest) and open (sun-exposed field), located at mountain Kopaonik. Four leaf traits were measured: petiole length, midvein length, leaf blade width and leaf blade surface area. Leaf measurements were used to calculate univariate, as well as multivariate, size-scaled indices of fluctuating asymmetry for each node. Nested analysis of variance, with habitat, sex and node as fixed factors, and individual as random factor, was used to investigate the inter- and intra-individual variation in FA indices. Our results showed that the highest values of FA (i.e. developmental instability) have been found for the petiole length, while leaf blade width and midvein length had lower values of FA. We discussed the higher variability and developmental instability of petiole length in context of the role of this trait in leaf orientation. We found no significant effects of plant gender, light habitat and habitat x gender interaction on the analyzed FA indicators. On the other hand, between and within-plant variations in FA levels were significant, indicating the significant effects of small scale spatial and temporal variation of light conditions for plant development and emphasizing the importance of microenvironmental conditions.