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Abstract. Four contrasting ecotones were sampled to address three questions: (1) Are there ‘ecotonal’ species, (2) Do ecotones possess higher (or lower) species richness than the adjacent communities? and (3) Are exotic species more likely to occur in ecotones? One ecotone was edaphic, one was apparently caused by a positive‐feedback switch, one was environmental/anthropogenic and one was entirely anthropogenic. The exact position of each ecotone was established from the spatial change in ordination scores. Ecotonal species, in the sense of species mainly restricted to the ecotone at the site, were present in all four ecotones. All but one of the ecotonal species were native. The switch ecotone and the purely anthropogenic ecotone also contained native species that were significantly more frequent in the ecotone than in either adjacent community. Species richness was intermediate between that of the two adjacent communities in three of the ecotones. In the environmental/anthropogenic ecotone, species richness was higher than in adjacent communities, but not significantly so. There were appreciable numbers of exotic species in the two ecotones with anthropogenic influence, one of which had a proportion of exotic species intermediate between the two adjacent communities. Contrary to theory, the proportion of exotic species in the second ecotone was significantly lower than in either adjacent community. We conclude that all three features we examined depend on the particular ecological conditions and the ecology of the species present; they are not intrinsic properties of ecotones.

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It is commonly suggested that rare plant species are poor competitors. However, the study of rarity and competitive ability has, like much of the research on rare species, been hindered by insufficient sample size, scarce use of experimental methods, and lack of comparison with common species. We used a within‐taxon comparative approach to test for differences in competitive ability between rare and common species in two genera, Acaena ( Rosaceae: six rare and four common species) and Chionochloa ( Poaceae: four rare and five common species). We grew plants in replicated experiments at two levels of soil fertility and with two levels of competition, in monoculture or mixed with the introduced grass Agrostis capillaris. Competitive response was measured as relative yield, relative tiller increase, and change in live‐leaf fraction. Rarity was measured by geographic range size, defined as the number of 10‐km grid squares occupied by each species in New Zealand. The relationship between competitive ability and geographic range size was tested with correlations. Within Acaena, four of the rare species had high competitive ability, but there was no general relationship between competitive ability and rarity at either high or low levels of fertility. Differences in competitive ability appeared related to differences in ecological distribution rather than to rarity or commonness in a geographic sense. Within Chionochloa, common species tended to be stronger competitors than rare species, with the relationship being significant at the low level of fertility. Several of the common Chionochloa species have expanded their geographic ranges relatively recently, consistent with their greater competitive ability. Conversely, rare Chionochloa species occupy specialized habitats that may be interpreted as refuges from competition. Disparate results from Acaena and Chionochloa do not support the notion that rare species are generally poor competitors. Although rare species may have low competitive ability in some cases, it should not be assumed to be a cause of rarity for all rare species.