Functional convergence of different communities in similar environments would be expected as an outcome of the operation of 'assembly rules'. At an ecological level, competitive exclusion would restrict the co-occurrence of species with similar niches. Repetition of competitive sorting on an evolutionary time scale might lead to character displacement.
In New Zealand, there are treelines of two main forms: abrupt southern beech treelines and gradual conifer–broadleaved treelines. At similar latitudes, abrupt treelines form at higher elevation than gradual treelines, but it is unclear whether this difference is also reflected in the climatic conditions experienced at the contrasting treeline ecotones. In this study, we measured soil and air temperatures across four gradual and two abrupt treelines ecotones in New Zealand for 2 years, and compared the climatic conditions between the treeline forms.