Sexual and Asexual Reproduction in Kalanchoe (Crassulaceae): A Review of Known and Newly Recorded Strategies

Abstract: Apart from reproducing sexually through the production of seed that follows self- or cross-pollination and fertilisation, representatives of Kalanchoe (Crassulaceae subfam. Kalanchooideae) have evolved a range of different asexual reproductive strategies. Especially several species indigenous to Madagascar show pronounced asexual reproduction that enables them to successfully colonise, and sometimes become weedy in, suitable habitats well beyond their natural geographical ranges. The environmental conditions and ancestral genetic set up which in combination triggered the evolution of asexual reproduction in the genus, particularly in phyllo-bulbiliferous species, are not yet entirely known. The current model suggests that asexual reproduction has evolved as a result of the recruitment of both organogenesis and embryogenesis processes to the leaf margin. We illustrate and present an overview of aspects of sexual reproduction and asexual reproductive strategies in Kalanchoe and discuss to what extent the proposed model explains the diversity of reproductive strategies observed in phyllo-bulbiliferous Kalanchoe species.