title: Rapid speciation with gene flow following the formation of Mt. Etna.
abstract: Environmental or geological changes can create new niches that drive ecological species divergence without the immediate cessation of gene flow. However, few such cases have been characterized. On a recently formed volcano, Mt. Etna, Senecio aethnensis and S. chrysanthemifolius inhabit contrasting environments of high and low altitude, respectively. They have very distinct phenotypes, despite hybridizing promiscuously, and thus may represent an important example of ecological speciation "in action," possibly as a response to the rapid geological changes that Mt. Etna has recently undergone. To elucidate the species' evolutionary history, and help establish the species as a study system for speciation genomics, we sequenced the transcriptomes of the two Etnean species, and the outgroup, S. vernalis, using Illumina sequencing. Despite the species' substantial phenotypic divergence, synonymous divergence between the high- and low-altitude species was low (dS = 0.016 ± 0.017 [SD]). A comparison of species divergence models with and without gene flow provided unequivocal support in favor of the former and demonstrated a recent time of species divergence (153,080 ya ± 11,470 [SE]) that coincides with the growth of Mt. Etna to the altitudes that separate the species today. Analysis of dN/dS revealed wide variation in selective constraint between genes, and evidence that highly expressed genes, more "multifunctional" genes, and those with more paralogs were under elevated purifying selection. Taken together, these results are consistent with a model of ecological speciation, potentially as a response to the emergence of a new, high-altitude niche as the volcano grew.
authors: Department of Plant Sciences, University of Oxford, Oxford, United Kingdom.
authors: Owen G
authors: OG
authors: Osborne
authors: Thomas E
authors: TE
authors: Batstone
authors: Simon J
authors: SJ
authors: Hiscock
authors: Dmitry A
authors: DA
authors: Filatov
mesh_terms: D000531:Altitude; D005075:Biological Evolution; D004463:Ecology; D004777:Environment; D051456:Gene Flow; D049810:Genetic Speciation; D014644:Genetic Variation; D010641:Phenotype
keywords: RNA-seq; altitude adaptation; ecological speciation; gene flow; hybrid zone; speciation genomics
references: Genetics. 1998 Mar;148(3):929-36
references: 9539414
references: Mol Ecol. 2009 Feb;18(3):375-402
references: 19143936
references: Evolution. 2001 Oct;55(10):1943-62
references: 11761056
references: Evolution. 2005 Dec;59(12):2533-47
references: 16526502
references: Mol Biol Evol. 2005 Apr;22(4):1107-18
references: 15689528
references: Bioinformatics. 2005 Sep 15;21(18):3674-6
references: 16081474
references: Mol Biol Evol. 1997 Apr;14(4):455-60
references: 9100375
references: Mol Biol Evol. 2005 Dec;22(12):2472-9
references: 16107592
references: Mol Phylogenet Evol. 2008 May;47(2):757-82
references: 18375151
references: Curr Opin Plant Biol. 2005 Apr;8(2):122-8
references: 15752990
references: Genetics. 2002 Dec;162(4):1811-23
references: 12524351
references: PLoS Comput Biol. 2011 Aug;7(8):e1002173
references: 21901087
references: Ann Bot. 2012 Nov;110(7):1439-47
references: 23071216
references: Mol Biol Evol. 2002 Jun;19(6):908-17
references: 12032247
references: Bioinformatics. 2009 Dec 1;25(23):3189-90
references: 19797407
references: BMC Evol Biol. 2004 Jul 06;4:22
references: 15238160
references: Genome Biol Evol. 2011;3:1210-9
references: 21926095
references: New Phytol. 2009 Aug;183(3):702-717
references: 19594693
references: Mol Biol Evol. 2007 Aug;24(8):1586-91
references: 17483113
references: Biol Lett. 2011 Oct 23;7(5):699-701
references: 21525055
references: Trends Ecol Evol. 2007 Nov;22(11):569-74
references: 17988759
references: Nucleic Acids Res. 2008 Jan;36(Database issue):D1009-14
references: 17986450
references: Proc Natl Acad Sci U S A. 2005 Oct 4;102(40):14338-43
references: 16176987
references: Mol Biol Evol. 2008 Nov;25(11):2445-55
references: 18728074
references: Mol Biol Evol. 2011 Aug;28(8):2359-69
references: 21389272
references: Mol Biol Evol. 2011 Oct;28(10):2731-9
references: 21546353
references: Trends Ecol Evol. 2009 Apr;24(4):192-200
references: 19201503
references: Proc Natl Acad Sci U S A. 1987 Dec;84(24):9054-8
references: 3480529
references: Genetics. 2000 May;155(1):431-49
references: 10790415
references: Am J Bot. 2012 Feb;99(2):397-406
references: 22301890
references: Mol Biol Evol. 2006 Apr;23(4):721-2
references: 16380406
references: Genome Biol Evol. 2010 Jul 12;2:200-11
references: 20624726
references: DNA Res. 2011 Apr;18(2):93-105
references: 21444340
references: Nat Methods. 2009 Apr;6(4):291-5
references: 19287394
references: PLoS Biol. 2004 Mar;2(3):E55
references: 15024414
references: Bioinformatics. 2009 Aug 15;25(16):2078-9
references: 19505943
references: Evolution. 2013 Oct;67(10):3032-42
references: 24094352
references: Nature. 2012 Apr 04;484(7392):55-61
references: 22481358
references: Curr Opin Biotechnol. 2006 Oct;17(5):481-7
references: 16962765
references: Trends Ecol Evol. 2004 Apr;19(4):198-207
references: 16701254
references: Am J Bot. 2005 Apr;92(4):730-5
references: 21652452
references: Nature. 2012 Jul 5;487(7405):94-8
references: 22722851
references: Genetics. 1993 Oct;135(2):599-607
references: 8244016
references: BMC Bioinformatics. 2009 Dec 15;10:421
references: 20003500
references: J Evol Biol. 2013 Feb;26(2):229-46
references: 23323997
references: Evolution. 2008 Aug;62(8):1936-50
references: 18462213
references: J Mol Biol. 1990 Oct 5;215(3):403-10
references: 2231712
references: Heredity (Edinb). 2011 Jul;107(1):1-15
references: 21139633
references: Genome Res. 2010 Oct;20(10):1432-40
references: 20693479