Palaeo-ecophysiological perspectives on plant responses to global change.

Taxonomic classifications of plant species, based on morphological characteristics, provide a stable and robust approach for inferring taxonomic and phylogenetic relationships between extant and extinct species. This implies that, although evolution is a continuous process for a species, there is no whole-scale change in those suites of morphological characteristics that define higher order (genus and greater) relationships. Recent research suggests that a higher order characteristic - stomatal density - may reflect not only the atmospheric C0(2) concentration during initial evolution, but may also strongly constrain the responses of higher order plant groups to future C0(2)-enrichment.