Aims We aimed to test the hypothesis that plants that grow at lower latitudes will be better structurally defended than plants from higher latitudes.
Methods We collated binary spinescence data for 5145 species across Australia and New Zealand. Our dataset spanned 35° of latitude, and included over 1 million observations, making it the largest empirical study ever conducted for a single physical defence trait. A weighted logistic regression was applied first within Australia and New Zealand separately, and then across the combined dataset.
Important findings There was no significant latitudinal gradient in the proportion of species with spinescence in Australia or New Zealand, or in the overall dataset. That is, plant species are no more likely to be defended by spines at low latitudes than at high latitudes. This finding is counter to the idea that plant defences increase with latitude due to increased selective pressure from higher levels of herbivory. We suggest that future studies should investigate the relationship between herbivory and defence directly, without using latitude as a proxy.