| Apis cerana Fabricius,as an importantly economic and pollinating insect,plays significant roles in maintaining species diversity and agricultural security of Asia.Despite this,relatively little work has been devoted to the study of geographic variation in Chinese A.cerana.This is particularly true of studies of genetic variation.Here geometric morphometrics method and genome-wide resequencing were used for the first time in this study to conduct a comprehensive research of A.cerana within China,and it will provide a theoretical basis for the development and protection of the species germplasm resources.The main results of our study were as following:1.Geographical patterns of morphological variation help to elucidate the natural evolution of phenotypic variation.The geometric morphometrics method was used to characterize a total of 1,660 worker-bee forewings of A.cerana belonging to 170 colonies collected from 31 geographic populations in all climatic zones of China.We selected 20 landmark to describe wing shape and size,and 21 environmental variables to describe local environmental conditions.Our results showed that A.cerana wing size but not shape varies geographically.The difference in wing shape was detected between 8 ecotypes from China,of which there was an obvious difference between the Hainan ecotype and ecotypes from the Chinese mainland.We conclude that the variation of wing size and body size follows Bergmann's rule,with temperature playing a vital role in the phenotypic variation of A.cerana.Wing shape was driven by genetic developmental and evolutionary factors more than environmental factors.Geometric morphometries is a more effective approach to discriminate between different ecotypes in A.cerana.These results can be used as a starting point for the use of geometric morphometries in the discrimination of honeybee populations in China.2.Based on genome-wide resequencing,90 worker-bee of A.cerana collected from 18 geographic populations in all climatic zones of China were sequenced.The results showed as following:Resecquencing of ninety A.cerana generated a total of 2197.3 million paired-end reads of 150 bp read length(219.73 Gb).Genome alignment of A.cerana sequences indicated an average depth of 9.0-fold and coverage of 98.98%relative to the A.cerana reference genome.After stringent quality filtering,we identified a total of 2,988,481 high-quality population single nucleotide polymorphisms(SNPs)and 1,167,851 small indels(insertion-deletion).Population structure analysis showed that Hainan group and Xizang group were significantly different with the mainland groups,which may result from the barrier of Qiongzhou Strait and Hengduan Mountains.The results of phylogenetic tree based on Neighbor-Joining method supported the 9 types of A.cerana within China.Within the mainland groups,differentiation was found between temperate populations located on the north of Qinling Moutains in China and subtropics populations located on the south of Qinling Moutains.The genetic difference among populations in the north of Qinling Moutains was larger than those in the south of Qinling Moutains,which may be related to the segregation effects caused by fragmented habitats in the north of Qinling Moutain regions.The dynamic of demographic history analysis suggested that effective population size change with the periodic changes of temperature.The most recent population expansion appeared during the interglacial period of 80,000 to 130,000 years ago.The results of our study support the hypothesis that the populations of A.cerana in post-Pleistocene experienced rapid expansion.3,Morphological data and genetic data of A.cerana were constructed by NJ.The results showed that the analysis results of the Forewing from were consisten with the genetic data.We observed that the results of Fst data combined with Mahalanobis distances consistency exhibited this differentiation between mainland and Hainan island populations. |
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