Timeline of evolution of some modern ice-associated marine mammal species
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Box 1. The long history of ice-associated marine mammals Seals and walruses are, for the most part, confined to polar and sub-polar regions [27]. Fossil evidence shows that most of the current ice-associated whales and seals in the Arctic were common throughout the Pleistocene, roughly over the past three million years [28]. The polar bear evolved as a species much more recently [29, 30], as did modern humans [31].
Figure 2. Timeline of evolution of some modern ice-associated marine mammal species
Conservation of Arctic Flora and Fauna (CAFF) The data can be downloaded freely. Users are requested to reference the source. Eamer, J., Donaldson, G.M., Gaston, A.J., Kosobokova, K.N., Lárusson, K.F., Melnikov, I.A., Reist, J.D., Richardson, E., Staples, L., von Quillfeldt, C.H. 2013. Life Linked to Ice: A guide to sea-ice-associated biodiversity in this time of rapid change. CAFF Assessment Series No. 10. Conservation of Arctic Flora and Fauna, Iceland. ISBN: 978-9935-431-25-7.
27. Cairns, D.K., Gaston, A.J., and Huettmann, F. 2008. Endothermy, ectothermy and the global structure of marine vertebrate communities. Marine Ecology Progress Series 356: 239-250. doi:10.3354/meps07286. 28. Harington, C.R. 2008. The evolution of Arctic marine mammals. Ecological Applications 18(2): S23-S40. doi:10.1890/06-0624.1. 29. Lindqvist, C., Schuster, S.C., Sun, Y.Z., Talbot, S.L., Qi, J., Ratan, A., Tomsho, L.P., Kasson, L., Zeyl, E., Aars, J., Miller, W., Ingolfsson, O., Bachmann, L., and Wiig, O. 2010. Complete mitochondrial genome of a Pleistocene jawbone unveils the origin of polar bear. Proceedings of the National Academy of Sciences of the United States of America 107(13): 6118-6118. 30. Hailer, F., Kutschera, V.E., Hallstroem, B.M., Klassert, D., Fain, S.R., Leonard, J.A., Arnason, U., and Janke, A. 2012. Nuclear genomic sequences reveal that polar bears are an old and distinct bear lineage. Science 336(6079): 344-347. 31. McEvoy, B.P., Powell, J.E., Goddard, M.E., and Visscher, P.M. 2011. Human population dispersal “Out of Africa’’ estimated from linkage disequilibrium and allele frequencies of SNPs. Genome Research 21(6): 821-829. doi:10.1101/gr.119636.110. 32. Arnason, U., Gullberg, A., Janke, A., Kullberg, M., Lehman, N., Petrov, E.A., and Vainola, R. 2006. Pinniped phylogeny and a new hypothesis for their origin and dispersal. Molecular Phylogenetics and Evolution 41(2): 345-354. doi:10.1016/j. ympev.2006.05.022. 33. Xiong, Y., Brandley, M.C., Xu, S.X., Zhou, K.Y., and Yang, G. 2009. Seven new dolphin mitochondrial genomes and a timecalibrated phylogeny of whales. Bmc Evolutionary Biology 9. doi:10.1186/1471-2148-9-20. 34. Sasaki, T., Nikaido, M., Hamilton, H., Goto, M., Kato, H., Kanda, N., Pastene, L.A., Cao, Y., Fordyce, R.E., Hasegawa, M., and Okada, N. 2005. Mitochondrial phylogenetics and evolution of mysticete whales. Systematic Biology 54(1): 77-90. doi:10.1080/10635150590905939.
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