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Simple Summary: Heptageniidae is the third most species-rich family within Ephemeroptera (mayflies). Although multiple studies have been conducted, the monophyly, phylogenetic relationships, and the divergence time of its subfamilies have always been controversial. The current study sequenced 17 new mitogenomes to reconstruct the phylogenetic relationships and calculate the divergence time within Heptageniidae. Therefore, based on comparing the composition of three mitogenomes bias, phylogenetic relationships, and divergence time of Epeorus montanus Brodsky, 1930, we suggest that cryptic species exist in E. montanus. Heptageniidae are known for their flat heads and bodies and are divided into three subfamilies. Despite the extensive diversity within this group and considerable efforts made to understand their evolutionary history, the internal classifications and origin time of Heptageniidae remains controversial. In this study, we newly sequenced 17 complete mitogenomes of Heptageniidae to reconstruct their phylogenetic positions within this family. Because of the ambiguous time of origin, our study also estimated the divergence time within Heptageniidae based on five fossil calibration points. The results of BI and ML trees all highly supported the monophyly of Heptageniidae and three subfamilies. The phylogenetic relationship of Rhithrogeninae + (Ecdyonurinae + Heptageniinae) was also recovered. The divergence time showed that Heptageniidae originated from 164.38 Mya (95% HPD, 150.23–181.53 Mya) in the mid-Jurassic, and Rhithrogeninae originated from 95.54 Mya (95% HPD, 73.86–120.19 Mya) in the mid-Cretaceous. Ecdyonurinae and Heptageniinae began to diverge at 90.08 Mya (95% HPD, 68.81–113.16 Mya) in the middle Cretaceous. After morphological identification, analysis of the mitogenome's composition, genetic distance calculation, phylogenetic analysis, and divergence time calculation, we suggest that two different populations of Epeorus montanus collected from Aksu, Xinjiang Uygur Autonomous Region (40°16′ N, 80°26′ E) and Xinyuan, Xinjiang Uygur Autonomous Region (43°20′ N, 83°43′ E) in China are cryptic species of E. montanus, but further detailed information on their morphological characteristics is needed to fully identify them. [ABSTRACT FROM AUTHOR]

Extreme weather poses huge challenges for animals that must adapt to wide variations in environmental temperature and, in many cases, it can lead to the local extirpation of populations or even the extinction of an entire species. Previous studies have found that one element of amphibian adaptation to environmental stress involves changes in mitochondrial gene expression at low temperatures. However, to date, comparative studies of gene expression in organisms living at extreme temperatures have focused mainly on nuclear genes. This study sequenced the complete mitochondrial genomes of five Asian hylid frog species: Dryophytes japonicus, D. immaculata, Hyla annectans, H. chinensis and H. zhaopingensis. It compared the phylogenetic relationships within the Hylidae family and explored the association between mitochondrial gene expression and evolutionary adaptations to cold stress. The present results showed that in D. immaculata, transcript levels of 12 out of 13 mitochondria genes were significantly reduced under cold exposure (p < 0.05); hence, we put forward the conjecture that D. immaculata adapts by entering a hibernation state at low temperature. In H. annectans, the transcripts of 10 genes (ND1, ND2, ND3, ND4, ND4L, ND5, ND6, COX1, COX2 and ATP8) were significantly reduced in response to cold exposure, and five mitochondrial genes in H. chinensis (ND1, ND2, ND3, ND4L and ATP6) also showed significantly reduced expression and transcript levels under cold conditions. By contrast, transcript levels of ND2 and ATP6 in H. zhaopingensis were significantly increased at low temperatures, possibly related to the narrow distribution of this species primarily at low latitudes. Indeed, H. zhaopingensis has little ability to adapt to low temperature (4 °C), or maybe to enter into hibernation, and it shows metabolic disorder in the cold. The present study demonstrates that the regulatory trend of mitochondrial gene expression in amphibians is correlated with their ability to adapt to variable climates in extreme environments. These results can predict which species are more likely to undergo extirpation or extinction with climate change and, thereby, provide new ideas for the study of species extinction in highly variable winter climates. [ABSTRACT FROM AUTHOR]

Simple Summary: Lamiinae is the largest subfamily among the Cerambycidae (longhorn beetles), and its members are distributed worldwide. The monophyly of Lamiinae is generally recognized, but there are still diverse ideas as to whether the tribes belonging to Lamiinae are monophylic. Ambiguous classification boundaries and the existence of synonyms are major issues leading to controversies over Lamiinae classification. It is not enough to conduct research solely on the morphological characteristics and simple molecular loci of longhorn beetles. Mitochondrial genomes have proven to be reliable markers and can shed more light on phylogenetic relationships among Lamiinae. The present study resolved infra-subfamilial relationships among Lamiinae and provides more mitochondrial data for further phylogenetic research on longhorn beetles. Lamiinae is the largest subfamily of the Cerambycidae (longhorn beetles), with approximately 21,863 described species. Previous phylogenetic studies of Lamiinae showed that this subfamily was monophyletic, but the relationship between the tribes of Lamiinae is still controversial. Partial molecular data and species morphological characteristics are not sufficient to resolve species phylogenetic studies perfectly. At the same time, the full mitochondrial genome contains more comprehensive genetic data. Benefiting from the development of next-generation sequencing (NGS), mitochondrial genomes can be easily acquired and used as reliable molecular markers to investigate phylogenetic relationships within Cerambycidae. Using NGS technology, we obtained 11 mitochondrial genome sequences of Lamiinae species. Based on this newly generated mitochondrial genome dataset matrix, we reconstructed the phylogeny of Lamiinae. The Bayesian Inference and Maximum Likelihood analyses strongly support the monophyly of four tribes (Lamiini, Batocerini, Mesosini, and Saperdini), whereas the tribe Acanthocinini was identified as paraphyletic. Other mitochondrial structural features were also observed: the start codon in the nad1 gene of all 11 mitochondrial genomes is TTG; 17–22 bp intergenic spacers (IGS) with a 'TACTA' motif were found between trnS2 and nad1. Moreover, two long IGS were found in Mesosa myops and Batocera sp. Tandem repeats were found in the IGS of Batocera sp. [ABSTRACT FROM AUTHOR]