Influence of voltine ecotype divergence on genetic and haplotype
variation in the Asian corn borer
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 Ostrinia furnacalis
influences adult mating generation number (voltinism) across different
local environments. The degree of mating period overlap between
sympatric voltine ecotypes influence hybridization level, but impacts 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.
Mitochondrial haplotypes were significantly different between
historically allopatric univoltine and bivoltine locations. Haplotypes
from sympatric locations were clustered more-closely to bivoltine
locations, but influenced by local demographics. Additionally, analyses
of single nucleotide polymorphism (SNP) genotypes implicate voltinism,
as opposed to geographic distance, as contributing to low, but
significant levels of variation among voltine ecotypes. 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
maintenance of observed haplotype divergence remains unresolved.