AUTHOR=Pacheco-Sierra Gualberto , Vázquez-Domínguez Ella , Pérez-Alquicira Jessica , Suárez-Atilano Marco , Domínguez-Laso Jerónimo 

TITLE=Ancestral Hybridization Yields Evolutionary Distinct Hybrids Lineages and Species Boundaries in Crocodiles, Posing Unique Conservation Conundrums

JOURNAL=Frontiers in Ecology and Evolution

VOLUME=6

YEAR=2018

URL=https://www.frontiersin.org/journals/ecology-and-evolution/articles/10.3389/fevo.2018.00138

DOI=10.3389/fevo.2018.00138

ISSN=2296-701X

ABSTRACT=<p>Interspecific hybridization can lead to adaptation and speciation, especially in the context of recent radiations. The emblematic Crocodylus (true crocodiles) is the most broadly distributed, ecologically diverse, and species-rich crocodylian genus. Nonetheless, their within-species evolutionary processes are poorly resolved mainly due to their potential for hybridization. Notably, the evolutionary outcomes when hybridization is ancient and involves long-lived species, like crocodiles, remain largely unexplored. Here, we evaluate the genomic admixture between the American (<italic>Crocodylus acutus</italic>) and the Morelet's (<italic>Crocodylus moreletii</italic>) species, and demonstrate that this hybridization system challenges the definition of species boundaries and poses a triple conservation conundrum: what has been recognized as <italic>C. acutus</italic> is actually two distinct species, therefore its taxonomic reassessment is needed; we identified two evolutionary distinct hybrids lineages, which are genetically discernible from the parental species; the remaining <italic>C. moreletii</italic> populations evidence its likely extinction as a species and/or evolution via hybridization. Hence, the crocodiles' distinct species and hybrids lineages warrant recognition and need urgent conservation efforts.</p>