Population structure of Apis cerana in Thailand reflects biogeography and current gene flow rather than Varroa mite association

Abstract

Concordance between the mitochondrial haplotypes of the Eastern honey bee, Apis cerana, and its ectoparasitic Varroa mites across the Isthmus of Kra in Thailand has suggested that local host-pathogen co-evolution may be responsible for the geographic distribution of particular genotypes. To investigate nuclear microsatellites population structure in A. cerana, single workers of A. cerana colonies from Thailand were genotyped at 18 microsatellite loci. The loci showed intermediate to high levels of heterozygosity and a range of allele numbers. The analyses confirmed a fundamental subdivision of the Thai A. cerana population into the "Asia Mainland" and "Sundaland" regions at the Isthmus of Kra. However, the nuclear microsatellite differentiation was less distinct than mtDNA haplotype differences, suggesting male-biased dispersal and population admixture. Overall, samples showed a weak isolation-by-distance effect. The isolated population on Samui island was most differentiated from the other samples. The results do not support our initial hypothesis of local host-pathogen co-evolution, which predicts a strict correspondence between the nuclear genome and the lineage of parasitic Varroa mite of the A. cerana samples, because the gene flow indicated by our nuclear microsatellite markers should also mix potential Varroa resistance alleles among subpopulations. Instead, our study suggests that the coincidental distribution of Varroa lineages and A. cerana population structure in Thailand are the result of biogeographic history and current migration patterns Keywords: biogeography | co-evolution | local adaptation | microsatellites | population structure | apis cerana | honey bees | Thailand | Varroa mite association | social insects | biology Article:

Geographic variation in polyandry of the Eastern Honey Bee, Apis cerana, in Thailand

“…In addition, we sampled colonies near Phatthalung (7.6°N, 100.1°E) in the tropical Phatthalung province mostly in rubber tree plantations. The third population was collected from Ko Samui (9.5°N, 100.0°E), a tropical island of mixed use and vegetation, which is approximately 16 km from the mainland and genetically isolated (Rueppell et al, 2011). The variance and range of monthly average minimum and maximum temperatures for Chiang Mai exceed the respective values of the other two populations by 75% or more.…”

“…The only reliable study of polyandry in A.cerana has reported an average estimate of 18.8 matings per queen, based on four colonies from separate populations (Oldroyd et al, 1998; Tarpy et al, 2004). Following several studies that demonstrate a distinct population structure of A. cerana in Thailand (Rueppell et al, 2011; Warrit et al, 2006), we investigated the geographic variation in queen mating behavior in this species. We selected six colonies from each of three populations.…”

No evidence that habitat disturbance affects mating frequency in the giant honey bee Apis dorsata

“…The program was asked to place individuals from all six aggregations into one, two, three, four, five, and six groups. We used a burn-in period and iteration number of 10,000 each and assumed correlated allele frequencies, with program defaults for all other parameters and options (Pritchard et al 2000;Rueppell et al 2011). The best estimate of number of populations (K) was determined by looking at the Table I. values of the probability of the Bayesian model [Ln P (X/K), abbreviated as Ln(P) in the following] and the value of α.…”

“…The program STRUCTURE was used to estimate the most likely number of sub populations in our overall population (Delaney et al 2009;Pritchard et al 2000;Rueppell et al 2011). This program uses a Bayesian model to probabilistically allocate individuals into one of K sub-populations assuming that subpopulations have different allele frequencies (Pritchard et al 2000).…”

Phylogeography of Apis cerana populations on Hainan island and southern mainland China revealed by microsatellite polymorphism and mitochondrial DNA

“…In virtue of these genomic and genetic characteristics, it is widely used to interpret within-species variability of a variety of organisms (Paetkau et al 1995;Van Hooft et al 2000;Juan et al 2008;Serrano et al 2009;Boykin et al 2010;Tashima et al 2010). However, to the best of our knowledge, relatively few population genetic analyses have been performed on A. cerana using SSR (Sittipraneed et al 2001;Ji et al 2011;Rueppell et al 2011).…”