Genetic differentiation and estimated gene flow
A
female gamete contributes both nuclear and cytoplasmic material, whereas
a male gamete does not carry cytoplasmic material contrubuting to the
formation of a zygote. When hybridization occurs between species, the
nuclear genes of the offspring are a combined product of the different
parental species, whereas the cytoplasmic genes of the offspring are
contributed by their mother and are not recombinant
(Greiner et al. 2015;
Hagstrom et al. 2014). Thus,
interspecies hybridization may lead to asymmetric genetic
differentiation between nuclear and cytoplasmic material. There will be
high genetic differentiation of nuclear genes but low genetic
differentiation of cytoplasmic genes.
Thus,
we calculated the genetic differentiation of the termite species at the
mitochondrial gene (COII) and nuclear gene (SSR) levels.F ST, a standardized measure of the genetic
variance among populations, was calculated using
GenAIEx
v. 6.5, DnaSP v5 and FSTAT v.
2.9.3.2.
Gene flow was indirectly measured using genetic frequency data.
To determine whether there was species-related genetic clustering of the
populations of R. flaviceps, R. chinensis and their hybrid
populations, we employed a Bayesian approach for inferring population
structure using STRUCTURE 2.3. We ran the admixture model with
correlated frequencies, with 10 independent runs for each K (from 1 to
10) performed with 10,000 MCMC repetitions and a burn-in of 10,000. We
used the mean maximum estimated logarithm of the posterior probability
of the data for each K (LnP(D)) to identify the most likely number of
clusters, and we used DK values combined with species identification to
obtain the optimal K.