• acropetal translocation;
  • clonal herbs;
  • Glechoma hederacea;
  • physiological integration;
  • sectoriality

Abstract The effects of physiological integration on clone behaviour are examined at various structural scales, using data from the stoloniferous herb Glechoma hederacea. The consequences for clone expansion of traumatic fragmentation of the connections between clonal ramets are also illustrated. These results, together with information from other species, are used to refute the commonly-quoted view that physiological integration between the ramets of clonal herbs evens out the effects of variation in environmental quality, and promotes equitable ramet performance. Instead, clonal species are responsive, at a variety of structural scales, to environmental quality. Therefore, in a heterogeneous habitat, within-clone variation in the performance of ramets and clonal sub-structures is to be expected. The seminal study which purports to demonstrate environmental averaging in clonal herbs is shown to be both inadequately designed and inappropriately analysed to accomplish its aim.

Physiological and architectural reasons for the local responses to environmental quality seen in the majority of clonal herbs are discussed.