Study On Diversity Of Seed Insects And Their Relationship With The Host Plants Of Quercus In IB-CAS

Through the research and analysis of seeds and seed-feeding insects of the genus Quercus in Beijing Botanical Garden,Institute of Botany,Chinese Academy of Sciences(BBG,IB-CAS)IB-CAS,we have a preliminary understanding on the diversity of the Quercus species and their seed insects,made a comparison of the differences in the seed insect diversity between the native and non-native species groups of Quercus plants,and a further exploration of the reasons for the differences The main results are as follows;1)There are 9 species of Quercus plants involved in this study,the local species group are including 4 species belonging to the native group,i.e.Q.aliena,Q.aliena var.acutiserrata,Q.liaotungensis and Q.variabilis and 5 species belonging to the non-native species group,i.e.Q.rubra,Q.stellata var.acutiserrata,Q.palustris,Q.robur and Q.acutissima.2)Investigation on the diversity of seed insects showed that it is very effective to identify seed insects by DNA barcode technology.There are many species of seed insects,most of the sampled individuals are the larvae.Therefor,it is difficult to complete the task of species identification using the traditional morphological classification method.Combining the DNA barcoding technique with morphological method,we randomly selected 293 specimens of the seed insects,obtained partial fragments of the nuclear 28S gene(D2.domain)and mitochondrial COI gene sequences of the samples,and then constructed the NJ tree and computed the genetic distances,compared the sequences with those in the NCBI and BOLD databases,and finally made a further inference in combination with the morphological evidences.The results showed that the seed-feeding insects can be distinguished well using DNA barcoding technique,a total of 17 species belonging to 9 families were identified and the main parasitic insect species are Cyllorhynchites ursulus;Curculio dentipes,Cu.robustus,Cu.hardio and Cydia glandicolana and C.kurokio.3)The seed characters had an effect on the selection of parasitic feeding of the seed insects.The fresh weight,seed size and shell thickness of different host seeds were significantly different(p<0.05).One-Way ANOVA analysis showed that the parasitic rate of Q.palustris was significantly lower than the other 8 species,and the rate of other 8 kinds was not significant.Correlation analysis showed that the seed characteristics were correlated with the rate of insect parasitism,fresh weight and seed size were negatively correlated with parasitism rate,and the thickness of seed shell is also negatively correlated with parasitism rate.These indicates the seed characters are very important factors that affect the success of insects.4)To compare the rate of insect parasitism between native and non-native species of the genus,the result of the comparison is that the genetic distances between the native and non-native groups are significantly different(sig<0.05).The average seed insect parasitic on the non-native species was 2.702±1.208,and the local group had 3.209 ± 1.555 species of insects on average.The T test analysis means that there is no significant difference between the two groups in the number of parasitic species(sig=0.216),but the parasitic rate of native species was significantly higher than that of non-native species.