Do the New Zealand divaricates defy Corner’s rules? (2020)
AuthorsMaurin, Kévin J. L., Lusk, Christopher H.show all
Divaricate plants are a collection of New Zealand shrubs and tree juvenile forms with interlaced branches bearing leptophylls to nanophylls. Although the divaricate form has attracted much attention from ecologist and botanists, it is not clear to what extent divaricate plants depart from usual patterns of plant allometry. Here, we explore the relationship between twig and leaf size in a set of 11 divaricate species and 13 non-divaricate congeners, as a test of one of Corner’s rules: the axial conformity rule. This rule states that stouter branches should bear larger and more complex leaves, a pattern that has been widely observed throughout the world. The non-divaricate species we examined conformed to the expected positive relationship between twig diameter and leaf area. In contrast, there was no correlation between these two variables among divaricate species: there was no significant trend in leaf size across a three-fold range of twig diameter. These results support qualitative field observations, and conducting this work suggested that testing Corner’s second rule (the greater the ramification, the smaller the branches and appendages) might be compromised by the difficulty of finding a suitable protocol for accurately measuring the degree of ramification in divaricate and non-divaricate species.