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Proc Biol Sci. 2015 Jun 22;282(1809):20150425. doi: 10.1098/rspb.2015.0425.

Hybridization masks speciation in the evolutionary history of the Galápagos marine iguana.

Author information

1
Zoological Institute, Technische Universität Braunschweig, Mendelssohnstrasse 4, Braunschweig 38106, Germany Department of Animal Behavior, University of Bielefeld, Bielefeld 33501, Germany.
2
Zoological Institute, Technische Universität Braunschweig, Mendelssohnstrasse 4, Braunschweig 38106, Germany.
3
Biomedical Science Department, Cardiff University, Museum Avenue, Cardiff CF10 3AX, UK.
4
Charles Darwin Foundation, Puerto Ayora, Santa Cruz Island, Galápagos, Ecuador.
5
Department of Animal Behavior, University of Bielefeld, Bielefeld 33501, Germany.
6
Laboratory of Experimental Ecology and Aquaculture, Department of Biology, University of Rome, Tor Vergata, Rome 0033, Italy.
7
Department of Ecology and Evolutionary Biology, Yale University, PO Box 208106, New Haven, CT 06520-8106, USA.
8
Galápagos National Park Authority, Central Office, Puerto Ayora, Santa Cruz Island, Galápagos, Ecuador.
9
Zoological Institute, Technische Universität Braunschweig, Mendelssohnstrasse 4, Braunschweig 38106, Germany s.steinfartz@tu-bs.de.

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.

KEYWORDS:

El Niño; introgressive hybridization; morphometrics; restriction site-associated DNA (RAD) sequencing; single-nucleotide polymorphisms; volcanism

PMID:
26041359
PMCID:
PMC4590447
DOI:
10.1098/rspb.2015.0425
[Indexed for MEDLINE]
Free PMC Article

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