www.nature.com/scientificreports OPEN The evolutionary history of manatees told by their mitogenomes Érica Martinha Silva de Souza1,9*, Lucas Freitas1,9, Elisa Karen da Silva Ramos1,9, Giovanna Selleghin‑Veiga1,9, Michelle Carneiro Rachid‑Ribeiro1,9, Felipe André Silva1, Miriam Marmontel2, Fabrício Rodrigues dos Santos3, Anne Laudisoit4, Erik Verheyen5,6, Daryl P. Domning7,8 & Mariana Freitas Nery1,9* The manatee family encompasses three extant congeneric species: Trichechus senegalensis (African manatee), T. inunguis (Amazonian manatee), and T. manatus (West Indian manatee). The fossil record for manatees is scant, and few phylogenetic studies have focused on their evolutionary history. We use full mitogenomes of all extant manatee species to infer the divergence dates and biogeographical histories of these species and the efect of natural selection on their mitogenomes. The complete mitochondrial genomes of T. inunguis (16,851 bp), T. senegalensis (16,882 bp), and T. manatus (16,882 bp), comprise 13 protein‑coding genes, 2 ribosomal RNA genes (rRNA ‑ 12S and 16S), and 22 transfer RNA genes (tRNA), and (D‑loop/CR). Our analyses show that the frst split within Trichechus occurred during the Late Miocene (posterior mean 6.56 Ma and 95% HPD 3.81–10.66 Ma), followed by a diversifcation event in the Plio‑Pleistocene (posterior mean 1.34 Ma, 95% HPD 0.1–4.23) in the clade composed by T. inunguis and T. manatus; T. senegalensis is the sister group of this clade with higher support values (pp > 0.90). The branch‑site test identifed positive selection on T. inunguis in the 181st position of the ND4 amino acid gene (LRT = 6.06, p = 0.0069, BEB posterior probability = 0.96). The ND4 gene encodes one subunit of the NADH dehydrogenase complex, part of the oxidative phosphorylation machinery. In conclusion, our results provide novel insight into the evolutionary history of the Trichechidae during the Late Miocene, which was infuenced by geological events, such as Amazon Basin formation. Te Order Sirenia comprises a group of Afrotherian aquatic mammals that arose by the Early Paleocene1 and are currently distributed throughout the Indo-Pacifc region and from the southeastern part of the United States of America to part of the Brazilian coast, Amazon region, and African coast 2,3. Sirenians are classifed into two extant families: Trichechidae and Dugongidae. Te Family Dugongidae has only one living species (Dugong dugon MÜLLER, 1776), because the Steller’s sea cow (Hydrodamalis gigas ZIMMERMANN, 1780) was driven to extinction in the eighteenth century due to overhunting 4. Dugongidae is considered the older of these two families and it was cosmopolitan until its diversity decreased during the Pliocene 5,6. Te modern dugong is restricted to the Indian Ocean and West Pacifc region, specifcally in regions of high concentration of seagrass7. Te Family Trichechidae is composed of two subfamilies, Miosireninae (extinct species), and Trichechinae, which includes all modern species8. Te Subfamily Trichechinae has only one extant genus (Trichechus) and three spe- cies: Trichechus senegalensis LINK, 1795 (African manatee) living along the coasts and rivers of western Africa, T. inunguis NATTERER, 1883 (Amazonian manatee) which is endemic to the Amazon Basin, and T. manatus 1Departamento de Genética, Evolução, Microbiologia e Imunologia, Instituto de Biologia, Universidade Estadual de Campinas, Campinas, Brazil. 2Instituto de Desenvolvimento Sustentável Mamirauá, Tefé, Brazil. 3Departamento de Biologia Geral, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil. 4EcoHealth Alliance, New York, USA. 5Royal Belgian Institute of Natural Sciences, Brussels, Belgium. 6Biology Department, Evolutionary Ecology Group, University of Antwerp, Antwerp, Belgium. 7Laboratory of Evolutionary Biology, Department of Anatomy, Howard University, Washington, D.C. 20059, USA. 8Research Associate, Department of Paleobiology, National Museum of Natural History, Smithsonian Institution, Washington, D.C. 20560, USA. 9These authors contributed equally: Érica Martinha Silva de Souza, Lucas Freitas, Elisa Karen da Silva Ramos, Giovanna Selleghin-Veiga, Michelle Carneiro Rachid Ribeiro and Mariana Freitas Nery. *email: [email protected]; mariananery@ gmail.com Scientifc Reports | (2021) 11:3564 | https://doi.org/10.1038/s41598-021-82390-2 1 Vol.:(0123456789) www.nature.com/scientificreports/ Figure 1. Distribution of Trichechus species in the world, map made by EMSS with Rstudio v.1.3 using distribution shapefle from IUCN database, script available at author’s Github webpage (https ://githu b.com/ souza ems/scrip ts/blob/maste r/map_on_R.r). LINNAEUS, 1758 (West Indian manatee) ranging from the southeastern USA and the Caribbean region to the Brazilian northeastern coast9 (Fig. 1). Te fossil record is scant for the Family Trichechidae, which makes it difcult to infer their evolutionary history4. Te currently accepted evolutionary scenario for the genus Trichechus is that it originated in South American rivers from where it colonized the marine environment and reached the African continent9–11. How- ever, when and how the Trichechus species diverged are still mainly inferred from fossil age and morphological characteristics. Until recently, few genetic studies have attempted to shed light on their evolution, but these studies used single genetic markers or did not include all representatives of the genus9,12,13. One of these studies used a single mitochondrial gene to infer the divergence time between T. manatus and T. inunguis, which was estimated to have been 2–4 million years ago (Ma), in the Plio-Pleistocene3,9. Te mitochondrial genome encodes 13 proteins, which belong to a complex of oxidative phosphorylation pathways (OXPHOS) and have been extensively used to unravel phylogenetic relationships14–16. For a long time, the mitochondrial genome was considered to be under neutral or nearly neutral selection17. However, grow- ing evidence has revealed that these genes may be subject to positive directional selection16,18,19. Hence, more recently, attention has been given to the study of molecular adaptation of mitochondrial genes, and many studies have shown that amino acid substitutions on these proteins may improve aerobic capacity and may be related to adaptation to new environments 20,21. Te aquatic mammals, such as manatees, are textbook examples of line- ages that have undergone extreme adaptations related to the transition from land to aquatic environments3,22. Accordingly, positive selection in genes such as cytochrome b23 and ND2, ND4, and ND524 was already detected in killer whales (Orcinus orca, Linnaeus 1758) and dugongs, respectively, but such mitochondrial molecular evolution in manatees has been little studied. In this context, here we sequenced the complete mitogenomes of all extant species of manatees to infer their phylogenetic relationships, to estimate divergence times among the species and to evaluate the efect of natural selection on mitochondrial genes during their evolution. Material and methods Sampling and DNA extraction. We extracted DNA from one tissue sample of T. senegalensis (Democratic Republic of the Congo12), one tissue sample of Trichechus inunguis (female, Japurá River, Brazil) and one tissue sample from Trichechus manatus (male, Ceará, Brazil). All tissues were collected following the respective environ- mental regulations. Te DNA extraction of T. senegalensis was done following the Phenol:Chloroform:Isoamyl Alcohol 25:24:1 according to manufacturers. Te collecting permits were provided by Instituto Chico Mendes de Conservação da Biodiversidade (ICMBio, number 44628-2), and the re-importation tissue for T. senegalensis was provided by CITES number 19BR031212/DF. Te activity of access to the Genetic Heritage is registered under the Sistema Nacional De Gestão Do Patrimônio Genético E Do Conhecimento Tradicional Associado (SisGen) number A94D205. Tis study was carried out according to the Brazilian guidelines for animal care and authorized by the Committee on the Ethics of Animal Use and Care – CEUA of the State University of Campinas – UNICAMP. Te DNA quality and integrity were evaluated on 1% agarose gel. Te concentration and purity of samples were verifed using the NanoDrop 2000 Spectrophotometer (Termo Scientifc) and subsequently confrmed by fuorimetry on Qubit 2.0 (Invitrogen, Life Technologies). Te mitogenome of T. senegalensis was sequenced by an external company (BPI Biotecnologia Pesquisa e Inovação) using the MiSeq Illumina Platform. Scientifc Reports | (2021) 11:3564 | https://doi.org/10.1038/s41598-021-82390-2 2 Vol:.(1234567890) www.nature.com/scientificreports/ Node placement Specimen Age (Ma) Lognormal distribution parameters References Ofset = 9.0, Afrotheria (A) Ocepeia 59.2–61.6 Mean = 61.6, 67 SD = 0.25 Macroscelidae-Afrosoricida (B) Chambius 40.4–55.8 Ofset = 2.0, Mean = 55.8, SD = 0.25 68 Ofset = 2.0, Paenungulata (C) Phosphatherium 48.6–55.8 Mean = 55.8, 69 SD = 0.25 Sirenia (D) Prorastomus sirenoides 46.3–47.3 Ofset = 3.0, Mean = 47.3, SD = 0.15 70,71 Proboscidea (F) Eritreum melakeghebrekristosi 26.8–27.0 Ofset = 4.5, Mean = 27.0, SD = 0.25 72 Trichechus (G) Trichechus sp. 5.3–11.60 Ofset = 3.0, Mean = 11.6, SD = 0.7 73 Table 1. Parameters used to calibrate the divergence time analysis, using fossil data on BEAST2. mtDNA assembly and annotation. Te mitochondrial genomes (mtDNA) from T. inunguis and T. manatus were retrieved from the whole genome sequenced by the HiSeq 2500 platform. We frst created two cus-