Character Evolution Of The Larvae Of Scarabaeoidea Based On Mitogenome(Insecta:Coleoptera)

Scarabaeoidea belongs to the Coleoptera,containing more than 30,000 species with a confusing taxonomic system.White grubs,the common name of larval Scarabaeoidea,are usually considered serious pests,for some of them attack plant roots and cause great losses to agriculture and forestry.Larval identification is inevitably to be an important prerequisite for pest management.However,larval morphological identification facing great challenges,without an auxiliary method such as using COI.Previously,less than 1500 COI sequences and 85 whole mitochondrial genome were uploaded to Gene Bank in the Scarabaeoidea,most of which are distributed in neocearctic and paleo tropical regions,unable to meet the requiement of pest identification in China.In this study,we described the mitochondrial genomes of 29 species of Scarabaeoidea,enirching the mitochondrial genome database of Scarabaeoidae.We also analyze the phylogeny of Scarabaeoidae containing 29 new sequenced and 85 previous mitogenome using ML and BI methods focused on four datasets(PCG 123,PCG 12,PCG 123 + 2 r RNA,AA).We also analyzed the divergence time and the larval character evolution of Scarabaeoidea.Elucidate the evolution process of palidia and stridulatory area of the Scarabaeoidea lavra.In this study:(1)The mitochondrial genomes of the 29 species of Scarabaeoidea ranging in length from 14 to 20 kb,all contained 37 coding gene fragments.Included 13 PCGs,22 t RNAs,2 r RNAs and 1 control region of variable length.Except for the rearrangement of t RNA-Gln and t RNA-Ile in the Pentodon quadridens and Eophileurus chinensis,the order of the gene fragments in all species was the same as that of their ancestors.The start codons of PCGs of some species were TTG and GTG,and the stop codons of some species were incomplete TA and T.Most of the t RNAs could be folded into a trilobal structure except for the missing DHU arm of t RNA-Ser(AGN).(2)Although the phylogenetic analysis using ML and BI methods result in different tree topology,the results strongly support the monophyly of Rutelinae,Cetoniinae,Dynastinae,Aphodiinae,Scarabaeinae and Lucanidae.Moreover,all of Rutelinae form a sister group with the Dynastinae and then with the Cetoniinae.The Aphodiinae and Scarabaeinae are sister groups.The Geotrupidae and the Trogidae form a sister group.The Lucanidae are at the base of the Scarabaeoidea.However,the ML topology of the AA dataset partially had the Melolonthinae forming a paraphyletic group with the Scarabaeinae.Aphodiinae forms a paraphyletic group with the Oehodaeidae and Geotrupidae.(3)Analyzed the evolution of the larval morphological character among the 38 species of Scarabaeoidea.The synapomorphy of the larval raster was considered to be the absence palidia,which later evolved into the absence of palidia instead of hamate seta and finally evolved into palidia;The synapomorphy of the sound producing organs was the meta trochanter and mesocoxa,which later evolved into the vallate instead of smooth.(4)Estimated the divergence time of 38 species of Scarabaeoidea.It is demonstrated that the earliest appearances of Scarabaeoidea are dung-feeding and carrion-feeding insects,with the Lucanidae appearing at about 150 million years ago.Oehodaeidae and Trogidae originated about 140 million years ago.The phytophagous ancestor of Scarabaeidae appeared about 87 million years ago.The dung-feeding Scarabaeinae and Aphodiinae appeared 56 and 53 million years ago.Finaly,the phytophagous Cetoniinae,Dynastinae,and Rutelinae is originated at 47,38,and 15 million years ago.Suggesting that the Cetoniinae appear after the emergence of flowering plants.