Delimiting genetic units in Neotropical toads under incomplete lineage sorting and hybridization

BMC Evolutionary Biology

Research Article

Célio F B Haddad¹  Maria Tereza C Thomé¹  João Alexandrino²  Kelly R Zamudio³ 

[1] Departamento de Zoologia, Instituto de Biociências, UNESP - Univ Estadual Paulista, Campus Rio Claro, Caixa Postal, 19913506-900, Rio Claro, SP, Brazil;Departamento de Zoologia, Instituto de Biociências, UNESP - Univ Estadual Paulista, Campus Rio Claro, Caixa Postal, 19913506-900, Rio Claro, SP, Brazil;Departamento de Ciências Biológicas, UNIFESP - Univ Federal de São Paulo, Campus Diadema, Rua Professor Artur Riedel 275, 09972-270, Diadema, SP, Brazil;Department of Ecology and Evolutionary Biology, Cornell University, E209 Corson Hall, 14853-2701, Ithaca, NY, USA;

关键词: Rhinella crucifer;    Species complex;    Bufonidae;    Taxonomy;   

DOI  :  10.1186/1471-2148-12-242

 received in 2012-07-13, accepted in 2012-12-04,  发布年份 2012

来源: Springer

【 摘 要 】

BackgroundDelimiting genetic units is useful to enhance taxonomic discovery and is often the first step toward understanding evolutionary mechanisms generating diversification. The six species within the Rhinella crucifer group of toads were defined under morphological criteria alone. Previous data suggest limited correspondence of these species to mitochondrial lineages, and morphological intergradation at transitions between forms suggests hybridization. Here we extensively sampled populations throughout the geographic distribution of the group and analyzed mitochondrial and nuclear sequence data to delimit genetic units using tree–based and allele frequency–based approaches.ResultsThese approaches yielded complementary results, with allele frequency-based methods performing unexpectedly well given the limited number of loci examined. Both mitochondrial and nuclear markers supported a genetic structure of five units within the group, with three of the inferred units distributed within its main range, while two other units occur in separate isolates. The inferred units are mostly discordant with currently described forms: unequivocal association exists for only two of the six species in the group. Genetic evidence for hybridization exists for two pairs of units, with clear cyto–nuclear allele mixing observed in one case.ConclusionsOur results confirmed that current taxonomy does not represent evolutionary units in the Rhinella crucifer group. Correspondence between genetically distinguishable units and the currently recognized species is only possible for Rhinella henseli and R. inopina. The recognition of other species relies on the reassessment of the geographic range of R. crucifer, the examination of the type series of R. ornata for hybrids, and on the use of additional markers to verify the genetic distinctiveness of R. abei. We state that R. pombali should not remain a valid species since its description appears to be based on hybrids, and that the name R. pombali should be considered a synonym of both R. crucifer and R. ornata. The fifth inferred but undescribed genetic unit may represent a new species. Our results underscore the potential of the R. crucifer species group to contribute to a better understanding of diversification processes and hybridization patterns in the Neotropics, and provide the basis for future evolutionary and taxonomic studies.

【 授权许可】

CC BY   
© Thomé et al.; licensee BioMed Central Ltd. 2012