title: How complex is the Bufo bufo species group?
abstract: Species delineation remains one of the most challenging tasks in the study of biodiversity, mostly owing to the application of different species concepts, which results in contrasting taxonomic arrangements. This has important practical consequences, since species are basic units in fields like ecology and conservation biology. We here review molecular genetic evidence relevant to the systematics of toads in the Bufo bufo species group (Anura, Bufonidae). Two studies recently published in this journal (Recuero et al., MPE 62: 71-86 and García-Porta et al., MPE 63: 113-130) addressed this issue but reached opposing conclusions on the taxonomy of the group (four versus two species). In particular, allozyme data in the latter paper were interpreted as evidence for hybridization across species (between B. bufo-B. spinosus and B. bufo-B. verrucosissimus). We tested claims for hybridization through re-analysis of allozyme data for individuals instead of populations, to be able to distinguish between sympatry with and without admixture, and found no evidence of hybridization across taxa. We propose alternative explanations for the observed patterns that García-Porta et al. (2012) failed to consider. In the absence of unequivocal evidence for hybridization and introgression, we reject the proposal to downgrade Bufo spinosus and Bufo verrucosissimus to the subspecies level.
authors.affiliation: Naturalis Biodiversity Center, P.O. Box 9517, 2300 RA Leiden, The Netherlands.
authors.forename: Jan W
authors.initials: JW
authors.lastname: Arntzen
authors.forename: Ernesto
authors.initials: E
authors.lastname: Recuero
authors.forename: Daniele
authors.initials: D
authors.lastname: Canestrelli
authors.forename: Iñigo
authors.initials: I
authors.lastname: Martínez-Solano
mesh_terms: D000818:Animals; D001499:Bayes Theorem; D002025:Bufonidae / Q000145:classification* / Q000235:genetics; D005060:Europe; D019143:Evolution, Molecular; D049810:Genetic Speciation; D005828:Genetics, Population; D006824:Hybridization, Genetic; D007527:Isoenzymes / Q000235:genetics; D010802:Phylogeny; D017422:Sequence Analysis, DNA; D061350:Sympatry
chemical_list: D007527:Isoenzymes
keywords: Allozymes; Bufo bufo; Bufo spinosus; Bufo verrucosissimus; Molecular systematics; Phylogeny