Implications of self/non-self discrimination for spatial patterning of clonal plants

Many clonal plants are characterised by tussock growth forms, but the mechanisms that account for their formation and maintenance are still vague. Here we examine the possible effects of the recently identified phenomenon of self/non-self discrimination on the spatial distribution and patterning of ramets, tussocks and clones in stands of clonal plants. Spatially explicit ramet-based simulation modeling of growth and competition have shown that compact tussocks can be generated as a transient phenomenon that typically disappears at equilibrium. We introduced self/non-self discrimination into a spatial model by decreasing competition between neighbouring ramets on the same clonal fragment. The results demonstrate that self/non-self discrimination can have significant effects on clonal growth and architecture with a clear tendency to generate long-lasting and self-sustaining clumps. Interestingly, this effect was qualitatively independent of other architectural and growth attributes of the plants, making it a candidate mechanism of stable clumped growth forms observed in many clonal plants and communities. Furthermore, the introduction of self/non-self discrimination shifted competition from the level of ramets to that of clonal fragments, which in turns strongly increased genet extinction rates. Our results stress the need for greater attention to the rather neglected scaling up of physiological and morphogenetical controls to the population and community levels.