| Accurate taxonomic status and phylogenetic relationships among species are important foundations for studying their environmental adaptation mechanisms,which have become the core content of evolutionary biology since Darwinian times.Grylloblattodea is not only a very small monophyletic branch of insecta with low species diversity,but also the only extant ancient remnant group of insecta known as a “living fossil” of contemporary insect.As the only modern family in the Grylloblattodea,Grylloblattidae has extremely low species diversity and abundance,and is recognized as a rare group in the academic community.Grylloblattidae mainly distributes in the Americas and Asia,with a narrow distribution range.They have a high preference for their habitat environment,often travel at night,and do not like clustering.In this paper,a new genus and new species of Grylloblattodea,Grylloprimevala jilina Zhou et Ren,was collected to analyze the molecular basis of species formation and environmental adaptation of G.jilina from four aspects: external morphological characteristics and taxonomic status,types and distribution of sensilla,identification and expression characteristics of environmental adaptation genes,and local adaptation and driving factors.The results of this study will be helpful to facilitate the understanding of the important factors that influence the species formation and evolution of Grylloblattodea.A systematic morphological study of G.jilina samples collected from Ji’an district,Jilin Province,China,revealed that,it has typical morphological characteristics of troglobites.A new key for Grylloblattidae was integrated and Grylloprimevala Zhou et Ren was established.Combining with traditional markers in different genes(18S r RNA、28S r RNA、histone 3、12S r RNA、16S r RNA、cytochrome oxidase Ⅱ),it could be revealed that Grylloprimevala and Galloisiana are sister taxa to each other,.and verified that Grylloblattodea and Mantophasmatodea are sister taxa to each other.Scanning electron microscopy(sigma300,ZEISS)was used to investigate the type,distribution and abundance of sensilla of the developed appendages such as antennae and cerci of G.jilina.The results showed that G.jilina with well-developed appendages such as antennae and cerci having olfactory sensors(Sensilla coeloconica,Sensilla auricillica,Sensilla trichodea,Sensilla basiconica),mechanical sensors(B?hm bristles,Sensilla chaetica,Sensilla filiform,Sensilla campaniformia),temperature and humidity sensors(Apertures,Sensilla capitulum).Meanwhile,an unknown functional sensor(Spines)was found.Based on the Illumina Nova Seq high-throughput sequencing platform,the transcriptome of six different tissue samples(antennae,head,thorax,leg,abdomen and cerci)of G.jilina was sequenced.A total of 45.16 Gb Clean Reads were obtained,which were assembled.Besides,a total of 48,071 Unigene were acquired for functional annotation,and a total of20,517 annotations of Unigene were obtained.Furthermore,46 chemosensory-related genes were identified,1 visual system homeobox,26 reproduction-related genes,107 temperatureadapted genes,22 wing-type differentiation-related genes.FPKM was used to assess the expression levels of environmental adaptation genes in six different tissues of G.jilina.Among the chemosensory-related genes,the vast majorities were highly expressed in appendages such as antennae,cerci,and legs,and some OR,IR,OBP,and CSP were expressed in other parts.Only one vision-related gene was expressed merely in the head.Among the reproduction-related genes,most of them were expressed throughout the body of G.jilina,and some Vg,SPF,Tudor and SOX were locally expressed.Among the temperature adaptation-related genes,most Trets and HSP genes were expressed throughout the body of G.jilina,and most DNAj and TRP genes were locally expressed.Among the genes related to wing type differentiation,most of them were expressed throughout the body of G.jilina,and some wnt,Ec R,and JH genes were locally expressed.In this study,the distribution pattern of Grylloblattidae in Asia and its correlation with geographical environmental factors,as well as the molecular basis of environmental adaptation in Grylloblattidae were investigated based on information on genetic markers and gene expression.The correlation among geographical distance,environmental distance,and genetic divergence in Grylloblattidae were also evaluated.The results indicate that the distribution of Grylloblattidae in Asia is closely related to nine geographical environmental factors,including soil potential of hydrogen,annual mean minimum temperature,soil available water content,top layer is exchangeable for sodium salt,top layer organic carbon content,annual mean maximum temperature,top layer carbonate or lime content,annual average temperature,and top layer USDA soil texture classification.The regulation of the top five key environmental adaptation genes,"sno","Q1A7B1","Tf IIFalpha","ATPsyn B",and "CNOT10",is crucial for Grylloblattidae to adapt to soil conditions.Our findings also reveal that both geographical and environmental distances are significantly correlated with genetic divergence in Grylloblattidae,with the most significant factors being exchangeable sodium,carbonate or lime content,and percent of gravel in soil.Importantly,environmental factors have a greater contribution than geographical factors in driving genetic divergence in Grylloblattidae.In summary,the results of this paper not only provide an important basis to add new genus to Grylloblattodea,and determine the phylogenetic status of Grylloblattodea,but also provide important theoretical support for the study of the evolution of Grylloblattodea.Moreover,the results are of great importance for exploring the origin,evolution,and geographic spread of the insect class as well as its relationship with the evolution of geological history,studying the causes of insect endangerment,and formulating conservation measures. |
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