Comparative Ecology of Clonal Plants

Somatic embryogenesis is a phylogenetically ancient trait that allows sessile plants to grow in a modular fashion and to respond plastically to different environmental cues. It facilitates damage repair and permits clonal growth, the capacity to produce potentially independent but genetically identical offspring. Clonal growth is observed to originate from both the shoot or the root part of the plant body and it has been assigned various ecological functions such as reproduction, exploitation and persistence. These functions are rooted in two basic morphological characteristics of clonal growth: the longevity and the length of the connection between clonal parts. Clonality, although an ancient trait, shows a polyphyletic distribution among plant taxa with a strong representation especially among monocots. Phylogenetically controlled comparisons show that clonality is more common among species that occur in cold or nutrient-poor habitats and under poor light conditions. The frequent occurrence of clonals among aquatic species is confounded by the fact that many aquatics are monocots. This however does not necessarily preclude a functional ecological explanation. It is further shown that longevity and length of connection covary negatively, yielding two distinct clonal growth strategies (fragmenting versus compact, persistent clones) with a preference for the more common habitat trait combinations: nutrient-rich, shaded and/or wet versus nutrient-poor, open and/or dry, respectively.