Differences in performance between genotypes of Fragaria chiloensis with different degrees of resource sharing

Summary 1 The ability to transfer resources between separately rooted ramets through connecting stems or roots can increase the performance of clonal plants in heterogeneous environments. However, the degree to which connected ramets share resources differs between and within clonal species. This may be because a higher potential for resource sharing is selected for in more heterogeneous habitats. To test this, it was hypothesized that: (i) genotypes with a relatively high potential for resource sharing will accumulate more biomass in a highly heterogeneous environment than genotypes of the same species with a relatively low potential for resource sharing; (ii) disconnecting ramets to prevent sharing will eliminate this difference between genotypes; and (iii) there will be no relationship between potential for resource sharing and accumulation of biomass in a homogeneous environment. 2 Pairs of connected and disconnected ramets of three genotypes of the stoloniferous herb Fragaria chiloensis that had previously been shown to differ in potential for carbon sharing were grown in two environments in a glasshouse. In the heterogeneous environment, which was designed to mimic a natural pattern of resource heterogeneity encountered by F. chiloensis, one of the ramets in each pair was given lower light and higher nitrogen than the other. In the homogeneous environment, both ramets in each pair were given the same resource levels. 3 In the heterogeneous environment, the genotypes with the highest and the intermediate levels of resource sharing accumulated significantly more biomass than the genotype with the lowest level of sharing. Disconnecting ramets to prevent resource sharing eliminated these differences between genotypes, suggesting that the differences in biomass between the genotypes when grown in this environment were specifically due to differences in resource sharing. The net effect of ramet connection on biomass, measured as the difference between biomass of connected and disconnected ramets, was consistently higher in genotypes with a higher potential for resource sharing. In the homogeneous environment, the different genotypes performed similarly whether ramets were connected or not, and there was no net effect of connection on performance in any genotype. Although only three genotypes were tested in only two environments, these results were generally consistent with the hypotheses, and suggest that resource sharing in clonal plants may represent an adaptation to resource patchiness. 4 A second characteristic that is found in clonal but not in non-clonal plants is ‘division of labour’, the tendency for ramets to specialize to acquire resources that are locally abundant but scarce for ramets to which they are connected. Genotypes did not differ in their potential for division of labour between ramets, as measured by the effect of connection on allocation to roots in the heterogeneous environment. This suggests that potential for resource sharing may not be strongly associated with potential for division of labour in F. chiloensis.