LACK OF NUCLEOTIDE VARIABILITY IN A BEETLE PEST WITH EXTREME INBREEDING

The coffee berry borer beetle Hypothenemus hampei (Ferrari) (Curculion idae: Scolytinae) is the major insect pest of coffee and has spread to most of the coffee-growing countries of the world. This beetle also d isplays an unusual rife cycle, with regular sibling mating. This regul ar inbreeding and the population bottlenecks occurring on colonization of new regions should lead to low levels of genetic diversity. We wer e therefore interested in determining the level of nucleotide variatio n in nuclear and mitochondrial genomes of this beetle worldwide. Here we show that two nuclear loci (Resistance to dieldrin and ITS2) are co mpletely invariant, whereas some variability is maintained at a mitoch ondrial locus (COI), probably corresponding to a higher mutation rate in the mitochondrial genome. Phylogenetic analysis of the mitochondria l data shows only two clades of beetle haplotypes outside of Kenya, th e proposed origin of the species. These data confirm that inbreeding g reatly reduces nucleotide variation and suggest the recent global spre ad of only two inbreeding lines of this bark beetle.