Research On Phylogeny And Acoustic Signal Evolution Of Ensifera Based On Complete Mitochondrial Genome

With more than 15000 species in approximately 2500 genera,Ensifera(crickets,katydids,wetas,and their relatives)is a diverse group in Orthoptera.Species in this suborder occupy every conceivable terrestrial habitat outside the polar regions and play important roles in ecosystems.Because most members of this group can produce songs by tegminal stridulation,Ensifera is considered a good model for studying acoustic communication,and some taxa have been widely studied for the phylogeny,and evolutionary aspects of their acoustic mating system.Due to a long history of conflicting classification schemes based on different interpretations of morphological characters,the phylogenetic relationships within Ensifera are not compeletely resolved yet.Acoustic signal and acoustic behavior were widely studied in Ensifera,but most study on evolution of acoustic communication were about tegminal stridulation.Research on evolutionary of acoustic signal was lack.In this study,the mitogenomes of Pseudophyllus titan(Pseudophyllinae),Sphagniana ussuriana(Tettigoniinae),Oecanthus sinensis(Oecanthinae)and Truljalia hibinonis(Podoscirtinae)were obtained by high-throughput sequencing.In addition,the phylogeny of Ensifera was reconstructed by maximum likelihood(ML)and Bayesian inference(BI)methods included 63 ingroup taxa,and the divergence time was further estimated for major ensiferan lineages based on corroborating fossil evidence.Lastly,the evolution of the frequency structure and dominant frequency of songs were evaluated based on an ancestral character state reconstruction(ACSR).The main results were as blow:(1)The phylogenetic relationships of P.titan(Pseudophyllinae),S.ussuriana(Tettigoniinae),O.sinensis(Oecanthinae)and T.hibinonis(Podoscirtinae)were clarified in this study based on mitochondrial genome.P.titan was in the subfamily Pseudophyllinae clade,and this clade had a distant relationship with other lineages in Phaneropteridae.The clade with S.ussuriana and Metrioptera bonneti was sister group to the clade formed by Uvarovites inflatus and Gampsocleis gratiosa.In family Gryllidae,O.sinensis and T.hibinonis formed one clade and remaining lineages in another clade.(2)All phylogenetic analyses indicated that Schizodactyloidea was the most basal lineage within non-grylloid clade.In this study,we expanded the taxon sampling of Gryllidea and obtained a stable position of Schizodactyloidea,all results were identical that Schizodactyloidea has a basal position within non-grylloid lineages.(3)The use of the site-heterogeneous CAT-GTR model significantly affected superfamilies' relationships of non-grylloid lineages.Recent studies suggested that the use of mitochondrial genomic data for resolving deep phylogenetic relationship requires an assessment of the potential impact of compositional biases by using site-heterogeneous models.The difference btween the two modle in our study was the superfamilies' relationships of non-grylloid lineages.(4)All phylogenetic analyses indicated that superfamily Tettigonioidea was divided into the families Phaneropteridae and Tettigoniidae.All our analyses strong supported(Bootstrap = 100,PP = 1.0)that elevated the subfamily group Phaneropteridae to the family level,and the two-family scheme that divided Tettigonioidea into the families Phaneropteridae and Tettigoniidae.(5)P.titan was found to using low frequency pure tone after the ancestors of katydids evolved high frequency broadband noise.This phenomenon is special in katydids.Living high on the tree crown with dense leaves,low frequency pure tone may advantageous to longdistance communication of P.titan.(6)The ancestor of Ensifera was more likely to produce pure tone signals,whereas the ancestor of katydids was more likely to produce broadband noise signals.The pathway of acoustic signal evolution is mainly from pure tones to broadband noise.Ancestor of Ensifera mostly live close to the ground like crickets,low frequency pure tone signals have been advantageous for long-distance communication close to the ground.As katydids move to the top of vegetation or closer to the top before calling or listening,high frequencies broadband signals are more effective.(7)Low frequency and ultrasonic songs occurs randomly in species across subfamilies of katydids,and is not particularly associated with broadband or pure tone calls.The various type of acoustic signals may contribute to katydids occupy different econiche and become an extremely diverse group.(8)The evolutionary of frequency of acoustic signal in Ensifera closely related to the change of Ecological environment,likely caused by adaptations to the changing habitat.The ACSR results show that when the acoustic signal changed in Ensifera,the conditions of climate change and plant evolution were occurred at the same time.To study the mitogenome phylogeny of Ensifera,representatives from the subfamilies Pseudophyllinae,Podoscirtina,and Oecanthinae were lacking in the past.In this study,phylogenetic analyses based on mitogenome data and 63 terminals provide a more robust phylogeny of Ensifera,and contribute to solve the remains queries in the Ensifera phylogeny.The ACSR results uncovered the evolutionary process of acoustic signal in Ensifera,and provided molecule evidence to the evolution of acoustic communication.