title: Hybridization masks speciation in the evolutionary history of the Galápagos marine iguana.
abstract: The effects of the direct interaction between hybridization and speciation-two major contrasting evolutionary processes--are poorly understood. We present here the evolutionary history of the Galápagos marine iguana (Amblyrhynchus cristatus) and reveal a case of incipient within--island speciation, which is paralleled by between-island hybridization. In-depth genome-wide analyses suggest that Amblyrhynchus diverged from its sister group, the Galápagos land iguanas, around 4.5 million years ago (Ma), but divergence among extant populations is exceedingly young (less than 50,000 years). Despite Amblyrhynchus appearing as a single long-branch species phylogenetically, we find strong population structure between islands, and one case of incipient speciation of sister lineages within the same island--ostensibly initiated by volcanic events. Hybridization between both lineages is exceedingly rare, yet frequent hybridization with migrants from nearby islands is evident. The contemporary snapshot provided by highly variable markers indicates that speciation events may have occurred throughout the evolutionary history of marine iguanas, though these events are not visible in the deeper phylogenetic trees. We hypothesize that the observed interplay of speciation and hybridization might be a mechanism by which local adaptations, generated by incipient speciation, can be absorbed into a common gene pool, thereby enhancing the evolutionary potential of the species as a whole.
authors.affiliation: Zoological Institute, Technische Universität Braunschweig, Mendelssohnstrasse 4, Braunschweig 38106, Germany Department of Animal Behavior, University of Bielefeld, Bielefeld 33501, Germany.
authors.forename: Amy
authors.initials: A
authors.lastname: MacLeod
authors.affiliation: Zoological Institute, Technische Universität Braunschweig, Mendelssohnstrasse 4, Braunschweig 38106, Germany.
authors.forename: Ariel
authors.initials: A
authors.lastname: Rodríguez
authors.affiliation: Zoological Institute, Technische Universität Braunschweig, Mendelssohnstrasse 4, Braunschweig 38106, Germany.
authors.forename: Miguel
authors.initials: M
authors.lastname: Vences
authors.affiliation: Biomedical Science Department, Cardiff University, Museum Avenue, Cardiff CF10 3AX, UK.
authors.forename: Pablo
authors.initials: P
authors.lastname: Orozco-terWengel
authors.affiliation: Charles Darwin Foundation, Puerto Ayora, Santa Cruz Island, Galápagos, Ecuador.
authors.forename: Carolina
authors.initials: C
authors.lastname: García
authors.affiliation: Department of Animal Behavior, University of Bielefeld, Bielefeld 33501, Germany.
authors.forename: Fritz
authors.initials: F
authors.lastname: Trillmich
authors.affiliation: Laboratory of Experimental Ecology and Aquaculture, Department of Biology, University of Rome, Tor Vergata, Rome 0033, Italy.
authors.forename: Gabriele
authors.initials: G
authors.lastname: Gentile
authors.affiliation: Department of Ecology and Evolutionary Biology, Yale University, PO Box 208106, New Haven, CT 06520-8106, USA.
authors.forename: Adalgisa
authors.initials: A
authors.lastname: Caccone
authors.affiliation: Galápagos National Park Authority, Central Office, Puerto Ayora, Santa Cruz Island, Galápagos, Ecuador.
authors.forename: Galo
authors.initials: G
authors.lastname: Quezada
authors.affiliation: Zoological Institute, Technische Universität Braunschweig, Mendelssohnstrasse 4, Braunschweig 38106, Germany s.steinfartz@tu-bs.de.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Steinfartz
mesh_terms: D000818:Animals; D004484:Ecuador; D049810:Genetic Speciation; D006824:Hybridization, Genetic; D007076:Iguanas / Q000235:genetics*; D008969:Molecular Sequence Data; D010802:Phylogeny; D017422:Sequence Analysis, DNA
keywords: El Niño; introgressive hybridization; morphometrics; restriction site-associated DNA (RAD) sequencing; single-nucleotide polymorphisms; volcanism