Genetics of the ambrosia beetle

Amounts and patterns of genetic variability in an extreme inbreeder

Are species which inbreed over many generations “clonal”? How often do such extreme inbreeders outbreed, and what effect does outbreeding have on local genetic variability?

The tiny Asian ambrosia beetle Xylosandrus morigerus is one of the most abundant and widespread scolytine beetles in Central America and northern South America. Like many ambrosia beetles, X. morigerus breeds in dozens of host plant families and can breed in a wide variety of host plant tissues. Xylosandrus belongs to a clade of at least 1500 species of haplodiploid beetles which all reproduce by regular brother-sister mating. In theory, such extreme inbreeding should produce quasi-clonal lineages which are homozygous at nearly all loci, though large populations can retain variation among family lineages. Since population geneticists and evolutionary biologists believe that genetic polymorphism and heterozygosity are generally advantageous, especially in biotically complex environments such as tropical forests, the ecological success of inbreeding ambrosia beetles seems paradoxical. Furthermore, the fact that any given tropical forest has dozens of host-generalist ambrosia beetle species challenges our thinking about those explanations for tropical arthropod hyperdiversity which link species richness to plant diversity. Thus, understanding the success of inbreeding generalist ambrosia beetles in tropical forests would help us understand the ecological consequences of gene diversity, both within species and within communities.

How much genetic variability does X. morigerus have in Costa Rica? This Masters project would undertake to quantify genetic variability within individuals and within local populations, and estimate the amount of outbreeding which is occuring in nature.

Mengder av og mønstre i genetisk variasjon hos en art med ekstrem innavl