| Neolucanus sinicus species group consists of seven taxa in Neolucanus Thomson of Lucanidae(Coleoptera).All of them distribute in South China,with relatively weak migration ability and high dependence on the habitats in tropical,subtropical forest.This species group thus could be an ideal model for the study of speciation,species delimitation and phylogeny of stag beetles.The multi-genes including three mitochondrial genes(COI,16 S r DNA and Cytb)and two nuclear genes(28S r DNA,Wingless)applied to reconstruct the phylogeny of Neolucanus sinicus species group.In addition,we discuss the species differentiation and the existing geographical pattern underlying the integrated effect of the important geological events,climatic oscillation and ecological environment factors change during the evolutionary history of these seven taxa.The main results are as follows:(1)A total of 2747 bp of five gene fragments were obtained for this study,including 102 COI sequences(589 bp),105 16 S r DNA sequences(526 bp),101 Cytb sequences(384 bp),104 28 S r DNA sequences(801 bp)and 86 Wingless sequences(447 bp).(2)Phylogenetic analysis based on the Maximum Likelihood method and Bayesian Inference method obtained the consistent topology.Neolucanus sinicus species group should be monophyletic composed of three main clades in its distribution area: Southwest clade,Central China clade and Southeast clade.The genetic distance between each clade is 0.019-0.056,which is much smaller than the average of 0.199.Three species delimitation methods(ABGD,PTP and GMYC)all cluster this species group into the same species.(3)Divergent time estimation result shows that in the late Miocene(circa 5.89Ma)there was a divergence between the Southwest-Southeast clade and Central China clade;the internal divergence of Central China clade was about 5.78 Ma;the internal divergence of the Southwest-Southeast occurred in the Middle Pleistocene(circa 1.17Ma).(4)The high haplotype diversity(Haplotype diversity,Hd>0.90)and low nucleotide diversity(Nucleotide diversity,Pi<0.05)of the three branches of Southwest,Central China and Southeast China clades indicate that all the three clades once had refuges during the glacial period.Haplotype network and population history dynamics analysis showed that there were no shared haplotypes among different geographic populations.Molecular variation analysis also shows that the variation within the species group was mainly inter-population variation.The results of mismatch distribution and neutral test indicate that all three phylogenetic clades of Neolucanus sinicus species group had experienced the pressure of gene selection and might also have experienced the process of heterotropical species differentiation.(5)Niche modeling analysis showed that precipitation in the hottest season(bio18)was the main environmental factor affecting the distribution of the species group,with a contribution rate of 67.8%.The contribution rate of temperature seasonality(bio 04)was 17.7%,ranking the second.Humidity and temperature not only determine the geographical distribution of the species,but also may cause the different body size and color patterns in different distribution regions.Our analyses supported merely the taxa of N.sinicus Saunders,1854 was valid,and other six taxa in this species group should propose as the synonyms of N.sinicus according to the law of priority.The studied samples in this work represented the variously geographical populations from the different part in South China.Their divergences occurred mainly from the Late Miocene to the Middle Pleistocene.The present lineages and their geographic pattern could be potentially responsible for the East Asian monsoon,the arid and cold environment in the inland region of South China during the geologic time scale.Two environmental climatic factors,temperature and humidity have highly affected differences in body color and body shape among different populations.Our results suggested that the complex topography and historical climate could play an important role in shaping speciation and geographical distribution of stag beetles in South China.Moreover,our study could facilitate the understanding in differentiation of those problematic species groups under global climate change scenarios. |
