Inter-individual variation in colour patterns in noctuid moths characterizes long-distance dispersers and agricultural pests

A high capacity for long-distance dispersal is a key to success for species confronted with environmental heterogeneity, habitat modification, fragmentation and loss. However, dispersal capacity is difficult to quantify and therefore poorly known in most taxa. Here, we report on a test for an association of variation in dispersal capacity with variable colouration of noctuid moths. First, using data from 12 experienced lepidopterologists, we showed that despite variation among experts in average assessments, different species are consistently classified as having non-variable, variable or highly variable colour patterns when assessed by different experts. We then compared the incidence of non-resident species with high inter-individual variation in colour patterns recorded on the isolated island Utklippan (n = 47), with that in a species pool of potential long-distance dispersers from the nearest mainland (n = 295). Species with high inter-individual colour pattern variation were over-represented on the island compared with species having non-variable colouration. This finding constitutes rare evidence from the wild of long-distance dispersal, measured on a spatial scale relevant for moths when tracking habitats in fragmented and changing landscapes or when keeping pace with environmental challenges associated with climate change. Finally, we showed that Swedish noctuid moths classified as agricultural pests (n = 28) had more variable colour patterns compared with non-pests (n = 368). The majority of agricultural pests were also recorded on the isolated island, an outcome that is indicative of pest species having high dispersal capacity. Data on colour pattern variation may thus offer a simple and cost-effective proxy to estimate dispersal capacity and can also help identify potential pest species. Our findings are potentially useful when modelling and predicting population and range dynamics of species in spatiotemporally heterogeneous environments, with direct implications for conservation biology and pest management.