Population Genetic Structure of the Bumblebee, Bombus ignitus (Hymenoptera: Apidae), Based on Mitochondrial COI Gene and Nuclear Ribosomal ITS2 Sequences

Abstract

The bumblebee, Bombus ignitus (Hymenoptera: Apidae), is a valuable natural resource that is widely utilized for greenhouse pollination in South Korea. Understanding the magnitude of genetic diversity and geographic relationships is of fundamental importance for long term preservation and utilization. As a first step, we sequenced a partial COI gene of mitochondrial DNA (mtDNA) corresponding to the "DNA barcode" region and the complete internal transcribed spacer 2 (ITS2) of nuclear ribosomal DNA from 88 individuals collected in nine South Korean localities. The complete ITS2 sequences were longest among known insects, ranging in size from 2,034 bp ~ 2,052 bp, harboring two duplicated 112-bp long repeats. The 658-bp long mtDNA sequences provided only six haplotypes with a maximum sequence divergence of 0.61% (4 bp), whereas the ITS sequences provided 84 sequence types with a maximum sequence divergence of 1.02% (21 sites). The combination of the current COI data with those of published data suggest that the B. ignitus in South Korea and China are genetically a large group, but those in Japan can be roughly separated into another group.Overall, a very high per generation migration ratio, a very low level of genetic fixation, and no discernable hierarchical population were found to exist among the South Korean populations of B. ignitus, which suggests panmixia. This finding is consistent with our understanding of the dispersal capability of the species.

Genetic structure of Korean populations of bumblebees Bombus ignitus (Hymenoptera: Apidae) as revealed by microsatellite markers

“…Although Oh et al . () examined four local populations (CC, JS, TB and MJ) that overlapped with the present study, the results are inconsistent with our findings that the five populations examined here (CC, JS, SB, TB and MJ) are significantly genetically divergent based on nine microsatellite loci. This disagreement most likely results from the fact that microsatellites evolve faster and have more polymorphisms than nuclear non‐coding regions of the ITS2 , thereby accumulating enhanced levels of mutations (i.e.…”

“…The nuclear ITS2 data obtained from the nine local populations in South Korea revealed that these populations are all genetically indistinguishable, suggesting high levels of gene flow among them, regardless of geographic distance among those populations (Oh et al . ). Although Oh et al .…”

“…: mtDNA COI ; Oh et al . : mtDNA COI and nuclear ITS2 ). Interestingly, the data inferred from mtDNA in these studies showed the identical pattern that the mainland populations of Korea and China are genetically homogeneous, but significantly different from the island populations of Japan.…”

“…The Korean populations, including 88 individuals collected from nine localities, showed no genetic differentiation among populations, suggesting that they should constitute a single panmictic population with extensive gene flow, probably from the large dispersal ability of B. ignitus (Oh et al . ).…”

“…More recently, Oh et al . () reported that two geographical populations occurring in Korea and China formed a genetically similar large group, whereas those in Japan were well separated as another distinct group from the analyses of mitochondrial COI and nuclear internal transcribed spacer 2 ( ITS2 ). The Korean populations, including 88 individuals collected from nine localities, showed no genetic differentiation among populations, suggesting that they should constitute a single panmictic population with extensive gene flow, probably from the large dispersal ability of B. ignitus (Oh et al .…”