A Systematics On Heptageniidae From Mainland Of China(Insecta:Ephemeroptera)

Heptageniidae is known as the third largest family of Ephemeroptera,more than37 genera 600 species have been reported all over the world.However,only sporadic studies have been done in China and the simple original descriptions are usually based on nymphal or imaginal materials only.Compared to other countries,the knowledge of Chinese heptageniids is still very limited.Additionally,there are many unique and primitive species in China,and they are extremely important for the phylogeny reconstruction of this family.It is believed that careful study of them will provide new materials and ideas on this issue,which is still unclear.Moreover,the Heptageniidae has diverse species,large biomass,wide distribution and high opportunity to collect.Therefore,the taxonomy and systematics of the Heptageniidae in China not only has theoretical value,but also provides a practical basis for using large aquatic insects to monitor water quality.In this study,all specimens of Heptageniidae(except genera Epeorus,Paegniodes and Cinygmula)in our laboratory,including those collected by author in several recent years,are examined and classified comprehensively.A total of 57 species,which belongs to 11 genera in three subfamilies,are identified and described in detail.Therefore,currently 14 genera 84 valid heptageniid species are recorded in China.Among them,there are one new genus,three new record genera,one new record subgenus,22 new species and four new record species.In addition,nymphal and imaginal stages of 22 species are associated successfully.Those new data greatly improves classification level of Chinese Heptageniidae and Ephemeroptera as well.The specific information are as follows:The subfamily Ecdyonurinae contains eight genera 39 species,including one new genus,two new record genera,14 new species and three new record species.The new genus is Regulatneuria gen.nov.,these two new record genera are Asionurus Braasch&Soldán,1986 and Ecdyogymnurus Kluge,2004.One synonym is confirmed:Afronurus Lestage,1924(=Cinygmina Kimmins,1937).The nymphs of this subfamily can be identified by the unique scattered setae on the ventral surface of maxillae,and males by having medial depression of mesothoracic furcasternum parallel sided.The subfamily Heptageniinae includes two genera and five species:Heptagenia(four species)and Trichogenia(one species).Among them,there are one new record genus(Trichogenia),three new species and one new record species.Nymphs of Heptageniinae can be distinguished from others by the combination of having row of setae on the ventral surface of maxillae and forefemora without dorsal projection,the males are characterized by the presence of longitudinal and transverse ridges on prosternum and the medial depression of the mesothoracic furcasternum is convergent anteriorly.The subfamily Rhithrogeninae has one genus 13 species only,but includes one new record subgenus:Epeiron(Demoulin,1964)and five new species.Nymphs of this subfamily are differentiated by having row of setae on ventral surface of maxillae and apices of forefemora with projected dorsal process.The males are identified by having medial depression of mesothoracic furcasternum convergent anteriorly and without transverse and longitudinal ridge on prosternum.In order to explore the phylogenetic relationships of various genera and species in Heptageniidae,13 protein-coding genes from 25 heptageniid species(including 16 new sequenced mitogenomes and nine known ones)are used as dataset to construct phylogenetic trees by Bayesian inference(BI)and Maximum likelihood(ML)methods.The species Siphluriscus chinensis Ulmer,1920(Ephemeroptera,Siphluriscidae)is selected as outgroup.The phylogenetic analyses show that genera of Afronurus and Epeorus are monophyly and the genus of Notacanthurus is polyphyly,which is consistent with the morphological result.Based on the morphological characters and molecular evidence,the possible evolutionary trend of Heptageniidae is hypothesized here as:1)Paegniodes seems to be the earliest differentiated genus and the body size of heptageniid species has changed from large to small;2)Rhithrogena is likely to be a transitional genus in Rhithrogeninae;3)the possible evolutionary trend of Heptageniidae is from the genus Paegniodes to Rhithrogena,and then in to two directions:the first direction is from the former two genera and then to highly specialized genera such as Epeorus and Cinygmula in Rhithrogeninae,the other direction is from Paegniodes to Rhithrogena,and then to Heptageniinae and Ecdyonurinae.Molecularly,the duplicate t RNA^Metgene can be used as a molecular synapomorphy of the family Heptageniidae.