title: Global diversification at the harsh sea-land interface: mitochondrial phylogeny of the supralittoral isopod genus Tylos (Tylidae, Oniscidea).
abstract: The supralittoral environment, at the transition between sea and land, is characterized by harsh conditions for life. Nonetheless, evolution of terrestrial isopods (Oniscidea), the only group of Crustacea fully adapted to live on land, appears to have involved a transitional step within the supralittoral. The two most basal oniscidean lineages (Ligiidae and Tylidae) have representatives that successfully colonized the supralittoral. One of them is the genus Tylos, which is found exclusively in supralittoral sandy beaches from tropical and subtropical coasts around the world. Comprehensive phylogenetic hypotheses for this genus are lacking, which are necessary for understanding the evolution and biogeography of a lineage that successfully diversified in the harsh sea-land interface. Herein, we studied the phylogenetic relationships among 17 of the 21 currently recognized species of the genus Tylos, based on sequences from four mitochondrial genes (Cytochrome Oxidase I, Cytochrome b, 16S rDNA, and 12S rDNA). Maximum Likelihood and Bayesian phylogenetic analyses identified several lineages with deep divergences and discrete geographic distributions. Phylogenetic and distributional patterns of Tylos provide important clues on the biogeography and evolution of this group. Large divergences among the most basal clades are consistent with ancient splits. Due to the biological characteristics of Tylos, which likely prevent dispersal of these isopods across vast oceanic scales, we argue that tectonic events rather than trans-oceanic dispersal explain the distribution of Tylos in different continents. Overwater dispersal, however, likely enabled range expansions within some basins, and explains the colonization of volcanic oceanic islands. Present-day distributions were also likely influenced by sea level and climate changes. High levels of allopatric cryptic genetic differentiation are observed in different regions of the world, implying that the dispersal abilities of Tylos isopods are more limited than previously thought. Our results indicate that a taxonomic revision of this group is necessary.
authors.affiliation: Department of Wildlife and Fisheries Sciences, Texas A&M University, College Station, Texas, United States of America.
authors.forename: Luis A
authors.initials: LA
authors.lastname: Hurtado
authors.affiliation: Department of Wildlife and Fisheries Sciences, Texas A&M University, College Station, Texas, United States of America.
authors.forename: Eun J
authors.initials: EJ
authors.lastname: Lee
authors.affiliation: Department of Wildlife and Fisheries Sciences, Texas A&M University, College Station, Texas, United States of America.
authors.forename: Mariana
authors.initials: M
authors.lastname: Mateos
authors.affiliation: Istituto per lo Studio degli Ecosistemi, CNR, Florence, Italy.
authors.forename: Stefano
authors.initials: S
authors.lastname: Taiti
mesh_terms: D000818:Animals; D044822:Biodiversity; D004272:DNA, Mitochondrial; D004777:Environment; D005843:Geography; D033321:Isopoda / Q000145:classification* / Q000235:genetics*; D008969:Molecular Sequence Data; D010802:Phylogeny; D058974:Phylogeography
chemical_list: D004272:DNA, Mitochondrial
references.citation: Mol Biol Evol. 2000 Apr;17(4):540-52
references.pmid: 10742046
references.citation: Mol Biol Evol. 2012 Jan;29(1):325-35
references.pmid: 21890479
references.citation: Syst Biol. 2005 Jun;54(3):455-70
references.pmid: 16012111
references.citation: PLoS One. 2010 Jul 21;5(7):e11633
references.pmid: 20657776
references.citation: Syst Biol. 2012 Oct;61(5):779-84
references.pmid: 22328570
references.citation: Bioinformatics. 2001 Aug;17(8):754-5
references.pmid: 11524383
references.citation: Trends Ecol Evol. 2009 Jun;24(6):332-40
references.pmid: 19307040
references.citation: Syst Biol. 2012 May;61(3):539-42
references.pmid: 22357727
references.citation: Bioinformatics. 2008 Feb 15;24(4):581-3
references.pmid: 17766271
references.citation: Bioinformatics. 2003 Aug 12;19(12):1572-4
references.pmid: 12912839
references.citation: Mol Biol Evol. 2012 Jun;29(6):1695-701
references.pmid: 22319168
references.citation: PLoS One. 2013 Dec 30;8(12):e85199
references.pmid: 24386463
references.citation: Bioinformatics. 2010 Jun 15;26(12):1569-71
references.pmid: 20421198
references.citation: Syst Biol. 2005 Apr;54(2):241-53
references.pmid: 16012095
references.citation: Bioinformatics. 2014 May 1;30(9):1312-3
references.pmid: 24451623
references.citation: Mol Biol Evol. 2008 Jul;25(7):1253-6
references.pmid: 18397919
references.citation: BMC Bioinformatics. 2008 Apr 25;9:212
references.pmid: 18439255
references.citation: Trends Ecol Evol. 2008 Apr;23(4):229-36
references.pmid: 18276035
references.citation: Syst Biol. 2010 May;59(3):307-21
references.pmid: 20525638
references.citation: PLoS One. 2013 Jul 02;8(7):e67827
references.pmid: 23844103
references.citation: Nature. 2009 Dec 10;462(7274):778-81
references.pmid: 20010684
references.citation: Proc Natl Acad Sci U S A. 2002 Dec 10;99(25):16138-43
references.pmid: 12451182