Leaf fluctuating asymmetry in tree-line mountain birches, Betula pubescens ssp. tortuosa: genetic or environmentally influenced?

摘要

Fluctuating asymmetry (FA), or random nondirectional deviations from anticipated symmetry, is increasingly being discussed as a potential indicator of environmental stress. However, the factors underlying FA, especially in plants, remain poorly understood. We measured leaf FA by comparing the difference in width between the right and left halves of leaves in mountain birch (Betula pubescens ssp. tortuosa) from half-sib families growing in the field at its northern/altitudinal distributional limit to determine if genetic variance existed in this trait. We also tested for a correlation between leaf fluctuating asymmetry and tree-wide shoot growth to determine if leaf FA was associated with a decline in plant performance. There was no relationship between leaf FA and shoot growth. There was also no among-family variation in leaf FA, which suggests that there is little or no genetic variance in this trait in mountain birch.