The Gobiidae family occupy one of the most diverse habitat ranges of all fishes. One key reason for their successful colonization of different habitats is their ability to adapt to different energy demands. This energy requirement is related to the ability of mitochondria in cells to generate energy via oxidative phosphorylation (OXPHOS). Here, we assembled three complete mitochondrial genomes of Rhinogobius shennongensis, Rhinogobius wuyanlingensis, and Chaenogobius annularis. These mitogenomes are circular and include 13 protein-coding genes (PCGs), two rRNAs, 22 tRNAs, and one non-coding control region (CR). We used comparative mitochondrial DNA (mtDNA) genome and selection pressure analyses to explore the structure and evolutionary rates of Gobiidae mitogenomics in different environments. The CmC model showed that the ω ratios of all mtDNA PCGs were <1, and that the evolutionary rate of adenosine triphosphate 8 (atp8) was faster in Gobiidae than in other mitochondrial DNA PCGs. We also found evidence of positive selection for several sites of NADH dehydrogenase (nd) 6 and atp8 genes. Thus, divergent mechanisms appear to underlie the evolution of mtDNA PCGs, which might explain the ability of Gobiidae to adapt to diverse environments. Our study provides new insights on the adaptive evolution of Gobiidae mtDNA genome and molecular mechanisms of OXPHOS.

The species living in the Qinghai-Tibet Plateau provide an excellent model system for studying the relationship between molecular convergent evolution and adaptation. Distant species experiencing the same selection pressure (i.e., hypoxia, low temperature and strong ultraviolet radiation) are likely to evolve similar genetic adaptations independently. Here, we performed comparative genomics studies on six independently evolved high-altitude species. The results also showed that the convergent evolution of the six species was mainly reflected at the level of rapidly evolving genes, and the functions of these rapidly evolving genes were mainly related to hypoxia response and DNA damage repair. In addition, we found that high-altitude species had more gene family changes than their low-altitude relatives, except for the order Lagomorpha. The results also show that the convergence of the gene family contraction of high-altitude species is much greater than that of expansion, revealing a possible pattern of species in adapting to high-altitude. Furthermore, we detected a positive selection signature in four genes related to hypoxia response and ultraviolet radiation damage in these six species (FYCO1, ERBIN, SCAMP1 and CXCL10). Our study reveals that hypoxia response might play an important role in the adaptation of independently evolved species to a high-altitude environment, providing a basic perspective for further exploring the high-altitude adaptation mechanism of different related species in the future.

P. brasiliensis and L. canadensis are two otter species, which successfully occupied semi-aquatic habitats and diverged from other Mustelidae. Herein, the full-length mitochondrial genome sequences were constructed for these two otter species for the first time. Comparative mitochondrial genome, selection pressure, and phylogenetic independent contrasts (PICs) analyses were conducted to determine the structure and evolutionary characteristics of their mitochondrial genomes. Phylogenetic analyses were also conducted to confirm these two otter species’ phylogenetic position. The results demonstrated that the mitochondrial genome structure of P. brasiliensis and L. canadensis were consistent across Mustelidae. However, selection pressure analyses demonstrated that the evolutionary rates of mitochondrial genome protein-coding genes (PCGs) ND1, ND4, and ND4L were higher in otters than in terrestrial Mustelidae, whereas the evolutionary rates of ND2, ND6, and COX1 were lower in otters. Additionally, PIC analysis demonstrated that the evolutionary rates of ND2, ND4, and ND4L markedly correlated with a niche type. Phylogenetic analysis showed that P. brasiliensis is situated at the base of the evolutionary tree of otters, and then L. canadensis diverged from it. This study suggests a divergent evolutionary pattern of Mustelidae mitochondrial genome PCGs, prompting the otters’ adaptation to semi-aquatic habitats.

Host phylogeny can imprint the gut microbiota, but it is often masked by diet and environment. Leveraging the standardized husbandry of a zoological collection, we profiled fecal microbiota from 55 captive artiodactyls representing 12 species in Bovidae, Cervidae, and Camelidae using 16S rRNA amplicon sequencing targeting the V3–V4 region on the Illumina MiSeq platform. Community composition differed significantly among host families (Bray–Curtis PERMANOVA, R² = 0.1075, p = 0.001). A host–microbiota tanglegram, which juxtaposes the host phylogeny with a dendrogram of microbiota similarity, recovered a topology congruent with the host phylogeny, with camelids forming a distinct branch separate from true ruminants in both trees. The linear discriminant analysis effect size (LEfSe; LDA ≥ 3.5) identified family-specific biomarkers, including enrichment of Acinetobacter/Moraxellaceae in Bovidae, Rikenellaceae (the Rikenellaceae_RC9_gut_group) in Cervidae, and Rummeliibacillus together with the Christensenellaceae_R-7_group in Camelidae. Functional inference with PICRUSt2 revealed significant differences in KEGG level-2 pathways (e.g., carbohydrate metabolism and xenobiotics biodegradation), consistent with taxonomic shifts. Altogether, these findings show that—even under uniform captive conditions—host evolutionary history remains a primary determinant of both the structure and the predicted functions of the artiodactyl gut microbiota, refining the scope of phylosymbiosis and providing actionable baselines for veterinary monitoring and conservation management in zoo settings.

The Eyebrowed Thrush (Turdus obscurus) is a highly migratory bird, which breeds in northeastern Asia and overwinters in southeastern Asia. We obtained the mitochondrial genome of T. obscurus by Sanger sequencing. The mitogenome was 16,739 bp in length, which contains 13 protein-coding genes, 22 tRNA genes, two rRNA genes, and one control region. Its composition is consistent with the species in genus Turdus. Phylogenetic analysis based on the whole mitochondrial genome showed that the relationship between T. obscurus and Turdus kessleri was relatively close. This study improves the understanding of phylogeny and genetics of Turdidae and Muscicapoidea.

Although the American mink is extremely dependent on water and has evolved a range of aquatic characteristics, its structural adaptation to water is still less obvious than that of other typical semi-aquatic mammals, such as otters. Therefore, many scholars consider it not to be a semi-aquatic mammal. In order to make the point that minks are semi-aquatic mammals more convincing, we provide evidence at the micro (genome)-level. In particular, we used the genomes of the American mink and 13 mammalian species to reconstruct their evolutionary history, identified genes that affect aquatic adaptation, and examined the evolution of aquatic adaptation. By analyzing unique gene families, the expansion and contraction of gene families, and positive selection genes, we found that the American mink genome has evolved specifically for aquatic adaptation. In particular, we found that the main adaptive characteristics of the American mink include the external structural characteristics of bone and hair development, as well as the internal physiological characteristics of immunity, olfaction, coagulation, lipid metabolism, energy metabolism, and nitrogen metabolism. We also observed that the genomic characteristics of the American mink are similar to those of other aquatic and semi-aquatic mammals. This not only provides solid genomic evidence for the idea that minks are semi-aquatic mammals, but also leads to a clearer understanding of semi-aquatic species. At the same time, this study also provides a reference for the protection and utilization of the American mink.