The Colorado potato beetle is one of the most challenging agricultural pests to manage. It has shown a spectacular ability to adapt to a variety of solanaceaeous plants and variable climates during its global invasion, and, notably, to rapidly evolve insecticide resistance. To examine evidence of rapid evolutionary change, and to understand the genetic basis of herbivory and insecticide resistance, we tested for structural and functional genomic changes relative to other arthropod species using genome sequencing, transcriptomics, and community annotation. Two factors that might facilitate rapid evolutionary change include transposable elements, which comprise at least 17% of the genome and are rapidly evolving compared to other Coleoptera, and high levels of nucleotide diversity in rapidly growing pest populations. Adaptations to plant feeding are evident in gene expansions and differential expression of digestive enzymes in gut tissues, as well as expansions of gustatory receptors for bitter tasting. Surprisingly, the suite of genes involved in insecticide resistance is similar to other beetles. Finally, duplications in the RNAi pathway might explain why Leptinotarsa decemlineata has high sensitivity to dsRNA. The L. decemlineata genome provides opportunities to investigate a broad range of phenotypes and to develop sustainable methods to control this widely successful pest.

The paradox of successful invading species is that they are likely to be genetically depauperate compared to their source population. This study on Colorado potato beetles is one of the few studies of the genetic consequences of continent-scale invasion in an insect pest. Understanding gene flow, population structure and the potential for rapid evolution in native and invasive populations offers insights both into the dynamics of small populations that become successful invaders and for their management as pests. We used this approach to investigate the invasion of the Colorado potato beetle (Leptinotarsa decemlineata) from North America to Europe. The beetles invaded Europe at the beginning of the 20th century and expanded almost throughout the continent in about 30 years. From the analysis of mitochondrial DNA (mtDNA) and amplified fragment length polymorphism (AFLP) markers, we found the highest genetic diversity in beetle populations from the central United States. The European populations clearly contained only a fraction of the genetic variability observed in North American populations. European populations show a significant reduction at nuclear markers (AFLPs) and are fixed for one mitochondrial haplotype, suggesting a single successful founder event. Despite the high vagility of the species and the reduction of genetic diversity in Europe, we found a similar, high level of population structure and low gene flow among populations on both continents. Founder events during range expansion, agricultural management with crop rotation, and selection due to insecticide applications are most likely the causes partitioning genetic diversity in this species.

Despite numerous indices proposed to predict the evolution of mating systems, a unified measure of sexual selection has remained elusive. Three previous studies have compared indices of sexual selection under laboratory conditions. Here, we use a genetic study to compare the most widely used measures of sexual selection in natural populations. We explored the mating and reproductive successes of male and female bank voles, Clethrionomys glareolus, across manipulated operational sex ratios (OSRs) by genotyping all adult and pup bank voles on 13 islands using six microsatellite loci. We used Bateman's principles (Is and I and Bateman gradients) and selection coefficients (s' and beta') to evaluate, for the first time, the genetic mating system of bank voles and compared these measures with alternative indices of sexual selection (index of monopolization and Morisita's index) across the OSRs. We found that all the sexual selection indices show significant positive intercorrelations for both males and females, suggesting that Bateman's principles are an accurate and a valid measure of the mating system. The Bateman gradient, in particular, provides information over and above that of other sexual selection indices. Male bank voles show a greater potential for sexual selection than females, and Bateman gradients indicate a polygynandrous mating system. Selection coefficients reveal strong selection gradients on male bank vole plasma testosterone level rather than body size.

We analysed the relationship between three life history characteristics (mobility, length of flight period and body size) and niche breadth (larval host plant specificity and adult habitat breadth), resource availability (distribution and abundance of host plants) and range position (distance between the northernmost distribution record and southernmost point of Finland) of the butterfly fauna of Finland. The data is based on literature and questionnaires. Often in across species studies phylogeny may create spurious relationships between life-history and ecological variables. We took the phylogenetic relatedness of butterfly species into account by analysing the data with phylogenetically independent contrasts (CAIC method). Butterfly mobility was positively related to the niche breadth, resource availability and range position. The length of the flight period was negatively related to the range position, indicating that the species at the northern edge of their distribution range have shorter flight period than species which are further way from the range edge. After controlling for the phylogenetic relatedness we found no significant correlations between body size and niche breadth, resource availability or range position. We suggest that the relationship between the length of the flight period and range position may arise as a consequence of lower hatching asynchrony in edge species as a result of lower environmental variance in larval growth conditions. Our results on the mobility suggest that there is selection pressure towards lower migration rate in species that have restricted niche breadth, low resource availability and in species that are on the northern edge of their geographical distribution range. In such species, selection against mobile individuals is likely to result from the decreased probability of finding another habitat patch suitable for egg laying