The Effect of Clonal Integration on Plant Competition for Mosaic Habitat Space

Abstract

Physiological integration between ramets has been observed in several clonal plant species. But consequences of integration on the competitive ability and spatial development of genets have received little attention so far. This study is an attempt to examine the population-and community-level implications of integration in a spatially explicit model. We have simulated different resource patterns in a cellular automata, varying the proportion (p) and size (s) of resource-rich patches and the average resource level in the area (h). We compared the efficiency of integrator to splitter genets in exploring and utilizing the resource patches. In the integrator, ramets that belonged to the same genet were physiologically connected and shared the resource taken up by any part of the genet. In the splitter, all ramets were autonomous, i.e., survival and reproduction of each ramet only depended on the local resource conditions. Thus, the integrator sensed and responded to environmental heterogeneity on a larger spatial scale than the splitter. Integration can be interpreted as sharing the risk of genet mortality among interconnected ramets, while splitting represents risk spreading among autonomous ramets. In each simulated habitat type, we followed the course of competition between splitter and integrator genets for 500 generations. First, we examined the effect of environmental heterogeneity on the result of competition. We fixed the average resource level in the area and changed the spatial distribution of the resource by varying p and s. We found that the smaller the proportion of favorable sites, the better it is to integrate. But already a small deviation from random to clumped resource distribution (i.e., relatively small s) made the integrator competitively inferior to the splitter. In the next step, we varied the overall resource richness in the area. High productivity of the habitat promoted the dominance of integrators. The simulations demonstrated that there were habitat types in which one of the strategies (the integrator or the splitter) rapidly excluded its competitor. But at the medium range of environmental parameters, long-term coexistence of the strategies became possible. As integration proceeded simultaneously with horizontal growth and exploration of new patches, integrators remarkably differed from splitters in their pattern of space occupation. A spatial statistical analysis revealed that splitters maintained strong spatial association with the resource: splitting promoted habitat selection. Integration, on the other hand, led to gap-filling, fugitive spatial behavior. For a range of realistic habitat patterns, we need not expect the exclusion of any of the pure strategies-splitters and integrators can coexist.

Competition among plant species that interact with their environment at different spatial scales

“…However, those models and others (e.g. Oborny et al 2000Oborny et al , 2001 still include the potential for allocation to ramets in poorer patches to be one of the costs of integration. To the extent that ramets in richer patches do supplement ramets in poorer patches, and that doing so entails some cost, the mechanisms by which integration is detrimental in our model should still operate.…”

“…Most theoretical models exploring the implications of competition between clonal and nonclonal plants have not considered these effects, focusing instead on competition for a single, non-depletable resource and the implications of the spatial and temporal availability of sites (e.g. Oborny et al 2000;Oborny & Kun 2002;Magori et al 2003). Magyar et al (2007) model competition between clonal and non-clonal plants for two resources, but do not include feedback of plants on resource dynamics.…”

The prisoner’s dilemma on co-evolving networks under perfect rationality

“…The model is based on the prisoner's dilemma (PD) [5] -one of the most impressive ways of illustrating situations of human interactions where mutual trust is beneficial, but egotism leads to a breach of promise. The fundamental interest in the PD arises from its applicability in a variety of fields, ranging from physics and biology to economics and finance [6,7,8]. It is of particular interest in constitutional economics [9,10,11].…”

Morphometric structural analysis ofPhragmites australisstands in Lake Balaton

“…Although this is not a reed-specific feature (Stueffer et al, 1996;Schwinning and Weiner, 1998;Oborny et al, 2000), Phragmites is one of the few species that is able to efficiently exploit the capabilities of physiological integration and thus grow in monocultures. In the absence of high disturbance, this results in the uniform appearance of stands: great majority of the plants within the clone have the same size.…”

“…Due to its clonal nature, intraspecific competition of P. australis differs significantly from that of non-clonal plants (Makita, 1996;Oborny et al, 2000) and could result in significantly different morphological and physiological adaptation mechanisms that ought to be studied. This paper presents results of a morphometric field study of common reed (P. australis) performed in 2006 on stable and die-back reed stands of the northern shore of Lake Balaton and a stable stand of Lake Balaton's southern shore.…”