Hybridization and massive mtDNA unidirectional introgression between the closely related Neotropical toads Rhinella marina and R. schneideriinferred from mtDNA and nuclear markers

BMC Evolutionary Biology

Research Article

Fernando Sequeira¹  Nuno Ferrand²  Marcelo Vallinoto³  José AR Bernardi⁴  Horacio Schneider⁵  Davidson Sodré⁵  Iracilda Sampaio⁵ 

[1] CIBIO, Centro de Investigação em Biodiversidade e Recursos Genéticos, Campus Agrário de Vairão, Universidade do Porto, 4485-661, Vairão, Portugal;CIBIO, Centro de Investigação em Biodiversidade e Recursos Genéticos, Campus Agrário de Vairão, Universidade do Porto, 4485-661, Vairão, Portugal;Departamento de Biologia, Faculdade de Ciências da Universidade do Porto, Rua do Campo Alegre s/n, 4099-002, Porto, Portugal;CIBIO, Centro de Investigação em Biodiversidade e Recursos Genéticos, Campus Agrário de Vairão, Universidade do Porto, 4485-661, Vairão, Portugal;Universidade Federal do Pará, Campus de Bragança, Alameda Leandro Ribeiro s/n 68, 600-000, Bragança, Pará, Brazil;Instituto Federal de Educação, Ciência e Tecnologia, IFPA- Campus de Bragança, Travessa Santos Dumont, s/n 68, 600-000, Bragança, Pará, Brazil;Universidade Federal do Pará, Campus de Bragança, Alameda Leandro Ribeiro s/n 68, 600-000, Bragança, Pará, Brazil;

关键词: Last Glacial Maximum;    Incomplete Lineage Sorting;    Introgressive Hybridization;    Ancestral Polymorphism;    Marina Population;   

DOI  :  10.1186/1471-2148-11-264

 received in 2011-02-16, accepted in 2011-09-22,  发布年份 2011

来源: Springer

【 摘 要 】

BackgroundThe classical perspective that interspecific hybridization in animals is rare has been changing due to a growing list of empirical examples showing the occurrence of gene flow between closely related species. Using sequence data from cyt b mitochondrial gene and three intron nuclear genes (RPL9, c-myc, and RPL3) we investigated patterns of nucleotide polymorphism and divergence between two closely related toad species R. marina and R. schneideri. By comparing levels of differentiation at nuclear and mtDNA levels we were able to describe patterns of introgression and infer the history of hybridization between these species.ResultsAll nuclear loci are essentially concordant in revealing two well differentiated groups of haplotypes, corresponding to the morphologically-defined species R. marina and R. schneideri. Mitochondrial DNA analysis also revealed two well-differentiated groups of haplotypes but, in stark contrast with the nuclear genealogies, all R. schneideri sequences are clustered with sequences of R. marina from the right Amazon bank (RAB), while R. marina sequences from the left Amazon bank (LAB) are monophyletic. An Isolation-with-Migration (IM) analysis using nuclear data showed that R. marina and R. schneideri diverged at ≈ 1.69 Myr (early Pleistocene), while R. marina populations from LAB and RAB diverged at ≈ 0.33 Myr (middle Pleistocene). This time of divergence is not consistent with the split between LAB and RAB populations obtained with mtDNA data (≈ 1.59 Myr), which is notably similar to the estimate obtained with nuclear genes between R. marina and R. schneideri. Coalescent simulations of mtDNA phylogeny under the speciation history inferred from nuclear genes rejected the hypothesis of incomplete lineage sorting to explain the conflicting signal between mtDNA and nuclear-based phylogenies.ConclusionsThe cytonuclear discordance seems to reflect the occurrence of interspecific hybridization between these two closely related toad species. Overall, our results suggest a phenomenon of extensive mtDNA unidirectional introgression from the previously occurring R. schneideri into the invading R. marina. We hypothesize that climatic-induced range shifts during the Pleistocene/Holocene may have played an important role in the observed patterns of introgression.

【 授权许可】

CC BY   
© Sequeira et al; licensee BioMed Central Ltd. 2011