Ecological consequences of plant clonality.

Abstract

Clonal plants are those that reproduce asexually by means of vegetative offspring that remain attached to the parent, at least until they establish. Clonal plant species are widespread, dominate a variety of habitats and probably play key roles in the maintenance of biodiversity, ecosystem function and biological invasion. For example, many of the most invasive introduced plants in the world are clonal. This makes it important to deepen our understanding of the ecology of clonal plants, including effects of clonality on ecosystem function, species abundance, plant performance in different habitats, capacity for evolution and invasiveness. The six papers in this Highlight explore these effects. The effects of clonality on ecosystem function have been under-studied. In a conceptual review, Cornelissen et al. (2014) discuss likely potential effects based on a response – effect trait framework, and call for research that links clonal traits to traits that affect carbon, nutrient and water cycling. In order to promote understanding of how clonality shapes species abundance, Herben et al. (2014) examine the relationships between plant traits and species abundance in 836 perennial, herbaceous species in Central Europe. Their results show that clonal growth traits explain a substantial proportion of variation in abundance, and that capacity for clonal growth and lateral expansion are positively correlated with abundance at both regional and local scales. Patterns of resource sharing between connected ramets vary between and within clonal species and may reflect selection for performance in different habitats. Using a spatially explicit, dynamic model, Oborny and Hubai (2014) test how the proportion of resource-rich patches in a heterogeneous environment determine the relative foraging efficiencies of clones in which parental ramets do or do not subsidize the growth of offspring in resource-poor patches. Not sharing is more efficient than sharing when more than half of patches are rich, but a mixed strategy is most efficient over a wide range of environments. While clonal integration is well known to increase growth in patchy habitats, the underlying physiological mechanisms remain elusive. Roiloa et al. (2014) test the effects of integration on photochemical efficiency, leaf spectral reflectance, photosynthesis and discrimination between isotopes of carbon and nitrogen in the wild strawberry Fragaria vesca. Their results provide novel evidence that clonal plants may preferentially transport specific forms of nitrogen between connected ramets. Potential for the evolution and local adaptation of clonal plant species might be limited if reproduction is mainly asexual. James and McDougall (2014) use microsatellite analysis and chromosome counts to document genetic diversity in all known populations of the clonal shrub Grevillea renwickiana. They find that triploidy has probably rendered the species exclusively asexual, but somatic mutation has generated diversity within clones. Introduced, invasive, clonal plants often spread both via seed dispersal and vegetative growth. Qi et al. (2014) document inhibition of seedling establishment under existing clones in the clonal, invasive plant Wedelia trilobata. Removal of adult plants fosters seedling establishment: important information for controlling the spread of this species. These six papers illuminate different aspects of the ecology of clonal plants and tackle current questions about the ecological consequences of clonality. We hope that this Highlight will stimulate further ecological research on clonal plants.