Latitudinal diversity gradient and cetaceans from the perspective of MHC genes
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Latitudinal diversity gradient and cetaceans from the perspective of MHC genes Maria Luiza Andreani 1
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Lucas Freitas 1
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Elisa K. S. Ramos 1
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Mariana F. Nery 1
Received: 17 December 2019 / Accepted: 5 June 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Pathogen diversity is a key source of selective pressure on immune system genes, shaping molecular evolution mainly on widely distributed or migratory organisms such as cetaceans. Here, we investigated the effects of latitudinal span migration, different biomes occupation, and pathogen-mediated selection on MHC DQB locus divergence on cetaceans. We applied some evolutionary genetics methods using a dataset of 15 species and 121 sequences, and we found a trend on greater MHC divergence on tropical species when compared with either temperate or migratory species. In addition, oceanic cetaceans exhibit greater MHC divergence. Here, we show that, despite there was a correlation between the diversity of MHC DQB alleles with the distribution of organisms, the pattern of diversity found is not completely explained by pathogenic pressure, suggesting that other factors must be investigated for a better understanding of the processes related to the diversity of MHC in cetaceans. Keywords evolution . MHC . cetaceans . migration . latitudinal gradient
Species diversity tends to diminish as latitude rises (Gaston 2000) and this pattern has been suggested to apply also to pathogens as previous studies described latitudinal gradients on diseases and parasites, both in continental and marine habitats (Rohde 2002; Guernier et al. 2004; Stearns and Koella 2008). This raises questions about the molecular dynamics of immune genes and the evolutionary processes behind ecological processes, more specifically, whether and how genetic variability of immune genes is related to the species’ habitat. Among immune genes, major histocompatibility complex (MHC) molecules act as a bridge between adaptive and innate immune responses, and they are subdivided into classes I and II. MHC molecules are extremely polymorphic and they are reported to be evolving under balancing selection, reflecting a diverse repertoire, which is necessary to fight incoming Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00251-020-01171-9) contains supplementary material, which is available to authorized users. * Mariana F. Nery [email protected] 1
Laboratório de Genômica Evolutiva, Departamento de Genética, Evolução, Microbiologia e Imunologia, Instituto de Biologia, Universidade Estadual de Campinas – UNICAMP, Rua Monteiro Lobato, 255, Cidade Universitária, IB, Bloco H, Campinas, SP CEP 13083-862, Brazil
pathogens (Edwards and Hedrick 1998). Recently, variability patterns have been investigated in migratory and widely distributed birds, showing more variability in residents of tropical regions (O’Connor et al. 2018). Cetaceans are widely distributed aquatic mammals, with representatives ranging from very loca
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