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

Abstract

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. K E Y W O R D S colour pattern variation, expert evaluation, Lepidoptera, mobility, Noctuidae, trait 1 | INTRODUC TI ON The ability to disperse and move through the landscape is an important feature of species' ecology. Virtually, all species are confronted with challenges associated with spatial and temporal environmental heterogeneity, and a high capacity for long-distance dispersal is a key to success in finding new areas, suitable for survival and reproduction. Knowledge of dispersal capacity and movements is required to better understand, model and S U PP O RTI N G I N FO R M ATI O N Additional supporting information may be found online in the Supporting Information section at the end of the article. How to cite this article: Betzholtz P-E, Forsman A, Franzén M. Inter-individual variation in colour patterns in noctuid moths characterizes long-distance dispersers and agricultural pests. J Appl Entomol. 2019;143:992-999. https ://doi.

Variable colour patterns indicate multidimensional, intraspecific trait variation and ecological generalization in moths

“…We studied all noctuid species known to occur in Sweden (Aarvik et al ). The taxonomy, distribution, life history and ecology of noctuid moths in the Nordic countries is well known (Svensson , Huldén et al , Aarvik et al ), variation in the colour patterns of adults have been quantified (Betzholtz et al ), and larvae have been illustrated and described (Ahola and Silvonen , , ).…”

“…Variation in colour pattern among adult moths previously was assessed by 12 independent Swedish lepidopterologists as non‐variable (0), variable (1) or highly variable (2) (for details see Supporting information I–II in Betzholtz et al ). The 12 lepidopterologists, all with extensive experience and expertise of the moth fauna in Sweden and adjacent countries, were provided with a list of 489 moth species in the families Noctuidae and Erebidae, and asked to classify variability in forewing colour pattern among individuals of each species on the basis of their personal experience with individuals observed or captured in Sweden.…”

“…Previous comparisons among moth species indicated that species with relatively high levels of individual variation in adult colour patterns also have an increased capacity for long‐distance dispersal (Betzholtz et al ), faster poleward range expansions (Forsman et al ), increased colonization success on islands (Franzén et al ), more stable population dynamics (Forsman et al ), decreased extinction risk (Betzholtz et al ) and larger geographic ranges (Franzén et al ). Species of moths with more‐variable colour patterns are also overrepresented in depauperate moth communities that inhabit novel, variable, fragmented and hotter urban environments (Franzén et al unpubl.…”

“…Species of moths with more‐variable colour patterns are also overrepresented in depauperate moth communities that inhabit novel, variable, fragmented and hotter urban environments (Franzén et al unpubl. ), and moth species that are considered to be agricultural pests have more variable colour patterns than other species (Betzholtz et al ). Here, we address whether and how variation in colour pattern is associated with the level of variation in morphological, behavioural and life‐history traits among individuals.…”

“…Second, if variable coloration is a reliable proxy for multidimensional trait variation and ecological generalization, coloration can inform management and conservation. For example, previous research suggested that information on colour pattern variation may assist with identifying and prioritizing species for protection (Krüger and Radford , Pizzatto and Dubey , Delhey et al , Forsman , Betzholtz et al ) and identifying species with a high capacity for population growth and expansion that are more likely to become agricultural pests (Forsman , Betzholtz et al ).…”