Diapause behaviour of the eight spined spruce bark beetle

Being in the right physiological and reproductive condition at the right time and place is an essential component for the fitness of an insect population. Insects use a genetically programmed period named diapause to synchronize their life histories. In this project, the genetic variation of diapause of the European spruce bark beetle, Ips typographus will be analyzed. Increases in temperature and progressively warmer springs permits more rapid rates of development in this spruce pest with the consequence of an increase in the number of generations per year in populations dominated normally by univoltine individuals. The method double digest restriction site associated DNA sequencing ddRADSeq will be applied in order to investigate 1) the genetic basis of the evolution of facultative diapause from an ancestral condition of obligate diapause and 2) the phylogeography of European I. typographus populations emphasizing functional genetic variation associated with the diapause phenotype. Ecopyhsiologically defined individuals reared in the laboratory will be genetically screened via ddRADSeq and information shall be obtained on the genetic basis of alternative diapause developmental pathways. As diapause is a complex developmental phenotype only the analysis of a large number of loci or single nucleotide polymorphisms covering the entire genome will distinguish genome-wide phylogeographic effects among loci from genetic divergence driven by selection on the diapause phenotype. Distinguishing between phylogeoraphic structure and local selection will allow the identification of genomic regions subject to adaptation. Consequently, ddRADSeq will be applied on European populations studying how populations from Europe are genetically structured. Besides demographic information this screening will bring insight how single populations are phenotypically structured i.e. an estimate how many obligate vs. facultative individuals are present in each population.

Population Genomics of Diapause Phenotypes in European Ips typographus Using High-Throughput RADSeq Being in the right physiological and reproductive condition at the right time and place is an essential component for the fitness of an insect population. Insects use a genetically programmed period named diapause to synchronize their life histories. Diapause, a strategy to endure unfavourable conditions (e.g. cold winters) is characterized by an arrest of development and reproduction, a reduction of metabolic rate, and an increased resistance to adversity. Diapause, significantly influences phenology, voltinism and ultimately population growth. The European spruce bark beetle Ips typographus is the most important forest pest of Norway spruce in Europe. Increases in temperature permit more rapid rates of development in this spruce pest in populations dominated normally by univoltine individuals. Ips typographus enters an adult reproductive diapause that might be either facultative or obligate. In a first step individuals from three populations were characterized applying a wide range of ecological and physiological methods. Consequently a genomic method, i.e. ddRADSeq was applied onto these individuals in order to investigate these individuals. As diapause is a complex developmental phenotype only the analysis of a large number of loci or single nucleotide polymorphisms covering the entire genome distinguished genome-wide phylogeographic effects among loci from genetic divergence driven by selection on the diapause phenotype. Distinguishing between phylogeographic structure and local selection allowed the identification of genomic regions subject to adaptation. The population structure of I. typographus largely follows a geographic pattern. Within this major geographic population structure, a genetic sub-division likely related to the diapause phenotype was found. Further data analyses will comprise in-depth population genetic analyses to unravel the genetic structure of I. typographus on a small scale in more detail.