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Phylogeography of a cryptic speciation continuum in Eurasian spadefoot toads ( Pelobates )
Author(s) -
Dufresnes Christophe,
Strachinis Ilias,
Suriadtaliia,
Mykytynets Galyna,
Cogălniceanu Dan,
Székely Paul,
Vukov Tanja,
Arntzen Jan W.,
Wielstra Ben,
Lymberakis Petros,
Geffen Eli,
Gafny Sarig,
Kumlutaş Yusuf,
Ilgaz Çetin,
Candan Kamil,
Mizsei Edvárd,
Szabolcs Márton,
Kolenda Krzysztof,
Smirnov Nazar,
Géniez Philippe,
Lukanov Simeon,
Crochet PierreAndré,
Dubey Sylvain,
Perrin Nicolas,
Litvinchuk Spartak N.,
Denoël Mathieu
Publication year - 2019
Publication title -
molecular ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.619
H-Index - 225
eISSN - 1365-294X
pISSN - 0962-1083
DOI - 10.1111/mec.15133
Subject(s) - biology , parapatric speciation , reproductive isolation , phylogeography , species complex , allopatric speciation , sympatry , evolutionary biology , ecology , phylogenetic tree , gene flow , sympatric speciation , population , genetics , genetic variation , demography , sociology , gene
Cryptic phylogeographic diversifications provide unique models to examine the role of phylogenetic divergence on the evolution of reproductive isolation, without extrinsic factors such as ecological and behavioural differentiation. Yet, to date very few comparative studies have been attempted within such radiations. Here, we characterize a new speciation continuum in a group of widespread Eurasian amphibians, the Pelobates spadefoot toads, by conducting multilocus (restriction site associated DNA sequencing and mitochondrial DNA) phylogenetic, phylogeographic and hybrid zone analyses. Within the P. syriacus complex, we discovered species‐level cryptic divergences (>5 million years ago [My]) between populations distributed in the Near‐East (hereafter P. syriacus sensu stricto [ s.s .]) and southeastern Europe (hereafter P. balcanicus ), each featuring deep intraspecific lineages. Altogether, we could scale hybridizability to divergence time along six different stages, spanning from sympatry without gene flow ( P. fuscus and P. balcanicus , >10 My), parapatry with highly restricted hybridization ( P. balcanicus and P. syriacus s.s ., >5 My), narrow hybrid zones (~15 km) consistent with partial reproductive isolation ( P. fuscus and P. vespertinus , ~3 My), to extensive admixture between Pleistocene and refugial lineages (≤2 My). This full spectrum empirically supports a gradual build up of reproductive barriers through time, reversible up until a threshold that we estimate at ~3 My. Hence, cryptic phylogeographic lineages may fade away or become reproductively isolated species simply depending on the time they persist in allopatry, and without definite ecomorphological divergence.