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Front. Ecol. Evol. | doi: 10.3389/fevo.2018.00144

Genomic evidence for cryptic speciation in tree frogs from the Apennine Peninsula, with description of Hyla perrini sp. nov.

 Christophe Dufresnes1, 2, 3*, Glib Mazepa2, 4, Nicolas Rodrigues2,  Alan Brelsford5,  Spartak N. Litvinchuk6, Roberto Sermier2, Caroline Betto-Colliard2, Olivier Blaser2,  Amaël Borzée7, Elisa Cavoto2, Guillaume Fabre2, Karim Ghali2,  Christine Grossen2, Agnes Horn2, Guillaume Lavanchy2, Julien Leuenberger2,  Barret C. Phillips2, Paul A. Saunders2, Romain Savary2, Tiziano Maddalena8,  Matthias Stöck9, Sylvain Dubey2, 3,  Daniele Canestrelli10 and Daniel L. Jeffries2
  • 1University of Sheffield, United Kingdom
  • 2Département d'écologie et évolution, Faculté de biologie et médecine, Université de Lausanne, Switzerland
  • 3Hintermann & Weber SA, Switzerland
  • 4Department of Ecology and Genetics, Uppsala University, Sweden
  • 5Department of Biology, University of California, Riverside, United States
  • 6Institute of Cytology (RAS), Russia
  • 7Division of EcoScience, Department of Life Science, Ewha Womans University, South Korea
  • 8Maddalena & associati sagl, Switzerland
  • 9Leibniz-Institut für Gewässerökologie und Binnenfischerei, Germany
  • 10Dipartimento di Scienze Ecologiche e Biologiche, Università degli Studi della Tuscia, Italy

Despite increasing appreciation of the “speciation continuum”, delimiting and describing new species is a major yet necessary challenge of modern phylogeography to help optimize conservation efforts. In amphibians, the lack of phenotypic differences between closely-related taxa, their complex, sometimes unresolved phylogenetic relationships, and their potential to hybridize all act to blur taxonomic boundaries. Here we implement a multi-disciplinary approach to evaluate the nature of two deeply-diverged mitochondrial lineages previously documented in Italian tree frogs (Hyla intermedia s. l.), distributed north and south of the Northern Apennine Mountains. Based on evidence from mitochondrial phylogenetics, nuclear phylogenomics, hybrid zone population genomics, niche modelling analyses, and biometric assessments, we propose that these lineages be considered distinct, cryptic species. Both mitochondrial and nuclear data affirm that they belong to two monophyletic clades of Pliocene divergence (~3.5 My), only admixing over a relatively narrow contact zone restricted to the southeast of the Po Plain (50-100km). These characteristics are comparable to similarly-studied parapatric amphibians bearing a specific status. Inferred from their current geographic distribution, the two Italian tree frogs feature distinct ecological niches (<15% of niche overlap), raising questions regarding potential adaptive components contributing to their incipient speciation. However, we found no diagnostic morphological and bioacoustic differences between them. This system illustrates the speciation continuum of Western-Palearctic tree frogs and identifies additional cryptic lineages of similar divergence to be treated as separate species (H. cf. meridionalis). We recommend combined approaches using genomic data as applied here for the future taxonomic assessment of cryptic diversity in alloparapatric radiations of terrestrial vertebrates, especially in controversial taxa. Finally, we formally described the northern Italian tree frogs as a new species, Hyla perrini, sp. nov.

Keywords: Amphibians, bioacoustics, hybrid zone, phylogenomics, RAD-seq, Taxonomy

Received: 12 Jun 2018; Accepted: 03 Sep 2018.

Edited by:

Mariana Mateos, Texas A&M University, United States

Reviewed by:

Alberto G. Sáez, Universität Zürich, Switzerland
Wieslaw Babik, Jagiellonian University, Poland  

Copyright: © 2018 Dufresnes, Mazepa, Rodrigues, Brelsford, Litvinchuk, Sermier, Betto-Colliard, Blaser, Borzée, Cavoto, Fabre, Ghali, Grossen, Horn, Lavanchy, Leuenberger, Phillips, Saunders, Savary, Maddalena, Stöck, Dubey, Canestrelli and Jeffries. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Dr. Christophe Dufresnes, University of Sheffield, Sheffield, United Kingdom, Christophe.Dufresnes@unil.ch