Genetic and haplotype divergence between voltine ecotypes of the Asian
corn borer (Ostrinia furnacalis)
Abstract
Diapause is an adaptive dormancy strategy by which arthropods endure
extended periods of adverse climatic conditions. Seasonal variation in
larval diapause initiation and duration in the Asian corn borer,
Ostrinia furnacalis, influences adult mating generation
number (voltinism) across local environmental conditions. Degree of
mating period overlap between sympatric voltine ecotypes influence
hybridization level, but impact on O. furnacalis population
genetic structure and evolution of divergent adaptive phenotypes remains
uncertain. Genetic differentiation was estimated between voltine
ecotypes collected from 8 locations in Jilin Province, China [3 single
generation (univoltine), 3 two generation (bivoltine), and 2 sympatric
locations] in 2014. Mitochondrial cytochrome c oxidase subunit
I (COI) haplotypes were partitioned into groups corresponding to
historically allopatric univoltine or bivoltine population origins using
Bayesian and phylogenetic clustering methods. Haplotypes from sympatric
locations were clustered more-closely to bivoltine locations, but
influenced by local demographics. Despite this COI haplotype divergence
between ecotypes, results were confounded by significant adherence to an
isolation-by-distance model. Additionally, analyses of single nucleotide
polymorphism (SNP) genotype data implicate voltinism, as opposed to
geographic distance, as contributing to low but significant levels of
variation among locations. Regardless, only 11 of 257 SNP loci were
predicted to be under selection, suggesting population genetic
homogenization except at loci proximal to factors putatively responsible
for locally adaptive or voltinism-specific traits. These findings
provide evidence that divergent voltine ecotypes may be maintained in
allopatric and sympatric areas despite relatively high rates of nuclear
gene flow, yet influence of voltinism on maintaining observed haplotype
divergence remains unresolved.