Abstract

Simple SummaryThe Himalayan marmot (Marmota himalayana) lives on the Qinghai-Tibet Plateau and may display plateau-adapted traits similar to other high-altitude species according to the principle of convergent evolution. We assessed 20 species (marmot group (n = 11), plateau group (n = 8), and Himalayan marmot), and analyzed their sequence of CYTB gene, CYTB protein, and ND3 protein. We found that the ND3 protein of Himalayan marmot plays an important role in adaptation to life on the plateau and would show a history of convergent evolution with other high-altitude animals at the molecular level.The Himalayan marmot (Marmota himalayana) mainly lives on the Qinghai-Tibet Plateau and it adopts multiple strategies to adapt to high-altitude environments. According to the principle of convergent evolution as expressed in genes and traits, the Himalayan marmot might display similar changes to other local species at the molecular level. In this study, we obtained high-quality sequences of the CYTB gene, CYTB protein, ND3 gene, and ND3 protein of representative species (n = 20) from NCBI, and divided them into the marmot group (n = 11), the plateau group (n = 8), and the Himalayan marmot (n = 1). To explore whether plateau species have convergent evolution on the microscale level, we built a phylogenetic tree, calculated genetic distance, and analyzed the conservation and space structure of Himalayan marmot ND3 protein. The marmot group and Himalayan marmots were in the same branch of the phylogenetic tree for the CYTB gene and CYTB protein, and mean genetic distance was 0.106 and 0.055, respectively, which was significantly lower than the plateau group. However, the plateau group and the Himalayan marmot were in the same branch of the phylogenetic tree, and the genetic distance was only 10% of the marmot group for the ND3 protein, except Marmota flaviventris. In addition, some sites of the ND3 amino acid sequence of Himalayan marmots were conserved from the plateau group, but not the marmot group. This could lead to different structures and functional diversifications. These findings indicate that Himalayan marmots have adapted to the plateau environment partly through convergent evolution of the ND3 protein with other plateau animals, however, this protein is not the only strategy to adapt to high altitudes, as there may have other methods to adapt to this environment.

Highlights

  • The geographic distribution and elevation of each species is shown in Figure 1A,C, and the twenty species under consideration were divided into the marmot group (n = 11) and the plateau group (n = 8), with the Himalayan marmot analyzed in a class by itself (Figure 1B)

  • Phylogenetic tree branch-site analysis revealed that the Himalayan marmot occurred on the same branch as the marmot group, compared against the plateau group (Figures 2A and 3A)

  • When the relationship was quantitatively analyzed using genetic distance, the results showed the CYTB gene and CYTB protein genetic distances of the marmot group were 0.064–0.136 and 0.045–0.072, respectively (Figures 2B and 3B, green bar), and for the plateau group the distances were 0.271–0.387 and 0.139–2.365 (Figures 2B and 3B, blue bar), 3–10 times greater

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Summary

Introduction

Himalayan marmots (Marmota himalayana) live between altitudes of 2900 and 5500 m above sea level on the Qinghai-Tibet Plateau. This region is perennially cold, with low atmospheric oxygen levels and constant exposure to strong ultraviolet radiation [5,6]. To explore whether plateau species have convergent evolution through the ND3 protein, the role of ND3 in energy metabolism and cellular respiration, and CYTB (cytochrome b), frequently used to resolve relationships between species [12,13], we constructed a phylogenetic tree for selected animal species based on those sequences and calculated genetic distances, paying particular attention to the ND3 protein in the Himalayan marmot. We hypothesized that the phylogenetic relationships of ND3 and CYTB would differ between the two groups in reference to Himalayan marmots, and that the ND3 protein of Himalayan marmots would show a history of convergent evolution at the molecular level

Species Geographic Distribution
Sequence Database
Phylogenetic Analyses
Consensus Sequence of ND3
Modelling ND3 Protein Tertiary Structure of Himalayan Marmot
Statistical Analysis
Relationship Analysis of CYTB Gene and CYTB Protein
Relationship Analysis of ND3 Proteins
ND3 Protein Sequence Analysis
Discussion
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