β-fibrinogen intron 7 variation in Discoglossus (Anura: Discoglossidae): implications for the taxonomic assessment of morphologically cryptic species

Abstract

Abstract. The generalized use of nuclear introns in combination with mitochondrial DNA data in molecular systematic and intraspecific phylogeographical studies is providing new insights into the complex evolutionary histories of taxa surviving the Quaternary glaciations. Previous studies have highlighted the suitability of the beta-fibrinogen intron 7 (β-fibint7) for phylogenetic and phylogeographic studies in a wide variety of taxa, including amphibians. Here we use sequences of this marker to assess inter-and intraspecific variation in Discoglossus (Discoglossidae), with special emphasis on geographic patterns of genetic structure in the Iberian Peninsula, where recent studies have questioned the taxonomic status of D. jeanneae. We obtained 81 sequences of β-fibint7 from samples including all currently recognized species except D. montalentii and 37 populations in the Iberian Peninsula and compared levels of genetic variation with those observed in a fragment of similar length of the mtDNA gene cytochrome b. The sequence of β-fibint7 in Discoglossus is the shortest described for amphibians so far, 378 base pairs. In general, we found low levels of variability (only 26 parsimony-informative sites in the dataset), with no alternatively fixed haplotypes in samples attributed to D. galganoi or D. jeanneae based on their mtDNA. Values of pairwise sequence divergence between non-Iberian species ranged from 1.1% to 4.5% (13.3% to 20.9% in mtDNA). The patterns observed in samples from the Iberian Peninsula are consistent with either incomplete lineage sorting or ongoing gene flow between D. galganoi and D. jeanneae. We conclude by reviewing the genetic evidence available to address the taxonomic status of Iberian species of Discoglossus.

Genes on the edge: A framework to detect genetic diversity imperiled by climate change

“…This fact can be explained by the varied spatial structuring of genetic diversity within the different species analyzed and by their climatic affinities. Indeed, the physiographic heterogeneity of the Iberian Peninsula, together with climatic fluctuations occurred herein, were the main drivers responsible for structuring the spatial genetic diversity of different species: (a) the barrier effect of fluvial systems or river valleys (e.g., C. lusitanica ; Sequeira, Alexandrino, Rocha, Arntzen, & Ferrand, ; Vipera latastei ; Velo‐Antón et al, ); (b) the mountains along the Central System as barriers to gene flow ( P. waltl ; Gutierrez‐Rodriguez, Barbosa, & Martinez‐Solano, ); and (c) climatic oscillations during the Pleistocene that induced range contractions and allopatric isolation processes (e.g., D. galganoi ; García‐París, Martínez‐Solano, & Velo‐Antón, ; T. Lepidus ; Miraldo, Hewitt, Paulo, & Emerson, ; C. girondica ; Santos, Roca, Pleguezuelos, Donaire, & Carranza, ; A. cisternasii ; Gonçalves et al, ; L. boscai ; Teixeira et al, ; P. hispanica complex; Caeiro‐Dias et al, ). Furthermore, the intraspecific structure observed in H. meridionalis is likely the result of a Moroccan lineage introduced in NW Iberia (Recuero, Iraola, Rubio, Machordom, & Garcia‐Paris, ), while I. alpestris in Central Iberia was introduced from northern Iberian populations (Recuero et al, ).…”

New insights on phylogeography and distribution of painted frogs (Discoglossus) in northern Africa and the Iberian Peninsula

“…The third example is the contact zone between two main Iberian lineages, which are considered distinct species by some (e.g., Busack, 1986;García-París and Jockusch, 1999;Martinez-Solano, 2004;Real et al, 2005) and subspecies by others (Lanza et al, 1986;Vences and Glaw, 1996;Zangari, Cimmaruta and Nascetti, 2006;Speybroeck, Beukema and Crochet, 2010;Pabijan et al, 2012;Sillero et al, 2014). These two mitochondrial lineages clearly are sister to each other (Pabijan et al, 2012); they show no consistent divergence in the nuclear markers investigated so far, and only comparatively weak divergence in mtDNA (e.g., Zangari, Cimmaruta and Nascetti, 2006;Velo-Antón, Martínez-Solano and García-Paris, 2008;Pabijan et al, 2012;data herein). Their uncorrected pairwise divergence in the 16S rRNA gene (as sequenced for instance by Fromhage et al, 2004) is only about 2%, and thus below the minimum threshold of 3% that characterizes many well-differentiated species of amphibians from their closest relatives (e.g., Fouquet et al, 2007).…”

“…The phylogeny and phylogeography of Discoglossus has been subject of numerous studies (Lanza et al, 1984(Lanza et al, , 1986García-Paris and Jockusch, 1999;Martínez-Solano, 2004;Real et al, 2005;Zangari, Cimmaruta and Nascetti, 2006;Velo-Antón et al, 2008;Pabijan et al, 2012;Biton et al, 2013). The available evidence strongly suggests D. montalentii being the sister taxon of all other species of Discoglossus, and a sister group relationship of D. g. galganoi and D. g. jeanneae.…”