In this present work, we have investigated morphological characteristics and microsatellite DNA polymorphisms of Anhui Apis mellifera, Nigeria African honey bee and their Hybrid generationⅡ. The results showed that the average tongue length of Apis mellifera, African honey bee and their hybrid generationⅡ, respectively, is 6.09mm, 5.23mm and 5.53mm, and a highly significant difference existed among them(P < 0.01); the average width of right forewing, respectively, is 3.35mm, 8.42mm and 8.65mm; the average area of the anterior wing, respectively, is 15.18mm², 13.23mm² and 13.95mm²; the average length of right forewing cubital vein a, respectively, is 0.59mm, 0.49mm and 0.55mm; the average length of tergum 3+4, respectively, is 4.38mm, 3.80mm and 4.04mm; the average length of right forewing, respectively, is 9.06mm, 3.12mm and 3.22mm, and a significant difference existed among them(P < 0.05); the average length of right forewing cubital vein b, respectively, is 0.18mm, 0.17mm and 0.17mm, but no significant difference existed among them(P > 0.05); and the average index number of cubital vein Ci, respectively, is 3.31mm, 3.07mm and 3.17mm.
We further detected the microsatellite polymorphisms of Anhui Apis mellifera, Nigeria African honey bee and their Hybrid generationⅡ, and found 121 alleles. The mean number of effective alleles was 8.067, and the number of alleles per locus varied from 3 to 13, indicating that the three populations all have rich genetic diversities. The expected heterozygosity(He) of the three populations ranged from 0.5801 to 0.8526, and the average value of expected heterozygosity was 0.7591±0.0762. The polymorphism information content (PIC) ranged from 0.5158 to 0.8363, and the average value of the PIC was 0.7283±0.0879. The average expected heterozygosity of Anhui Apis mellifera, Nigeria African honey bee and their hybrid generation Ⅱ, respectively, was 0.6208, 0.5780 and 0.7451. Statistical analysis indicated that highly significant difference in average expected heterozygosity existed between Nigeria African honey bee and hybrid generation Ⅱ, as well as between Anhui Apis mellifera and hybrid generation Ⅱ, but no significant difference existed between Anhui Apis mellifera and Nigeria African honey bee. The above results displayed that all three populations have high heterozygosity and rich polymorphism, and the hybrid generationⅡis highest in all three populations. The value of average genetic differentiation coefficient (FST) between Anhui Apis mellifera and Nigeria African honey bee was 4.36%, indicating that the differentiation level between the two populations was extremely high, and 8 loci were found to contribute significantly to this differentiation. In addition, the value of inbreeding coefficient (FIS) in each population was also very low(0.070), and all 15 loci were found to contribute significantly to this differentiation, indicating less inbreeding between Anhui Apis mellifera and Nigeria African honey bee. The Reynold's distance values of Nigeria African honey bee and Anhui Apis mellifera was 0.725, and the Nm value was 0.213. These results showed that there are further Reynold's distance and less gene flow between the two populations.
These remarkable differences in morphological parameters might be caused by geographic isolation between Nigeria African honey bee and Anhui Apis mellifera in long term. Moreover, our findings indicated that morphological parameter values of the hybrid generationⅡwere lower than those of Anhui Apis mellifera, but were higher than Nigeria African honey bee, indicating that hybrid vigor in morphological characters is very significant. The genetic diversity index such as allele number, gene heterozygosity and polymorphism information content of the hybrid generationⅡ has also been significantly improved.