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

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, wh...

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Published in:Proceedings of the Royal Society. B, Biological sciences Biological sciences, 2015-06, Vol.282 (1809), p.20150425-20150425
Main Authors: MacLeod, Amy, Rodríguez, Ariel, Vences, Miguel, Orozco-terWengel, Pablo, García, Carolina, Trillmich, Fritz, Gentile, Gabriele, Caccone, Adalgisa, Quezada, Galo, Steinfartz, Sebastian
Format: Article
Language:English
Subjects:
Amblyrhynchus cristatus
Animals
Ecuador
El Niño
Genetic Speciation
Hybridization, Genetic
Iguana
Iguanas - genetics
Introgressive Hybridization
Molecular Sequence Data
Morphometrics
Phylogeny
Restriction Site-Associated Dna (rad) Sequencing
Sequence Analysis, DNA
Single-Nucleotide Polymorphisms
Volcanism
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Summary: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.
ISSN:0962-8452
1471-2954
DOI:10.1098/rspb.2015.0425