Cover Picture and Issue Information

This month's cover image shows the inflorescences of the exotic plant Senecio pterophorus being consumed by a geometrid Lepidoptera at Montseny Natural Park (Catalonia, Spain). S. pterophorus is a South African species introduced to Europe more than 30 years ago, which co‐occurs with another exotic species, S. inaequidens , and two native congeners ( S. vulgaris and S. lividus ). This system was used to test the Enemy release hypothesis, which predicts that exotic plants will experience a decrease in their natural enemies thus acquiring a competitive advantage over the native vegetation. When the authors aimed to compare the number of herbivores on the exotic versus the native species they faced a statistical challenge: due to the nature of the hypothesis, data was expected to be zero inflated (a large number of exotic plants were expected to be undamaged). This case study was the starting point of “ What does a zero mean? Understanding false, random and structural zeros in ecology” where the authors explore the modelling options for count data in relation to overdispersion and zero inflation, and describe a protocol to assist with the statistical analyses of count data. Photo credit: © Jaume Danés Garolera