Leaf mottling/variegation and shape in the Ledebouria revoluta complex ? Development, stability and putative function

Abstract

The aims of this paper are three-fold: 1. To analyse the development and stability in vegetative traits such as leaf shape, growth and pigmentation patterns in three different morphotypes (defined by leaf shape and pigmentation) of the Ledebouria revoluta complex. 2. To discuss the putative function of leaf mottling/variegation. 3. To discuss plasticity in these traits in relation to taxonomy and species delimitation within the complex. Clones were analysed in a cultivation experiment with two nitrogen levels (N1 and N2), three morphotypes (A, B & C) and two light levels (L1 and L2). Anthocyanins were found in hypodermal cells, particularly in the proximal (i.e. young) parts of the leaf. The red pigmentation faded out in distal (i.e. more mature) parts of the leaf. Furthermore, older, outer leaves had more pigmentation than younger, inner leaves. Increased nitrogen availability had no effect on leaf pigmentation. Some plants developed significantly more red pigmentation adaxially at high light intensities, whereas abaxial pigmentation was unaffected by light intensity. The pigmentation of the two sides of a leaf therefore seems to be regulated independently and may accordingly serve different functions for the plants. Adaxial pigmentation (mainly in the form of mottling, pigmentation mainly in spots) may serve as photoprotection, whereas abaxial pigmentation (mainly in the form of variegation, pigmentation mainly in bands) may possibly be aposematic. In the field a high degree of intrapopulational variation in pigmentation patterns was observed. This might be due to local habitat heterogeneity and gene flow or frequency dependent selection. Characters relevant to taxonomy (leaf shape, pigmentation pattern) only changed to a limited extent, suggesting that the vegetative traits are genetically based. The three different morphotypes were easily recognized unrelated to the different treatments. Whether a formal taxonomic status is justified for the different morphotypes will need more plant material and genetic data and cannot be decided based on this study.