AOBPreview originally published online on February 14, 2005
Annals of Botany 2005 95(5):799-806; doi:10.1093/aob/mci079
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Phylogeographic Inferences Concerning Evolution of Brazilian Passiflora actinia and P. elegans (Passifloraceae) Based on ITS (nrDNA) Variation
1 Departamento de Genética, Instituto de Biociências, Universidade Federal do Rio Grande do Sul, Caixa Postal 15053, 91501-970 Porto Alegre, RS, Brazil, 2 Centro de Biologia Genômica e Molecular, Faculdade de Biociências, Pontifícia Universidade Católica do Rio Grande do Sul, Ipiranga 6681, 90610-001 Porto Alegre, RS, Brazil and 3 Departamento de Botânica, Universidade Federal do Paraná, Caixa Postal 19031, 81531-970 Curitiba, PR, Brazil
* For correspondence. E-mail loreta.freitas{at}ufrgs.br
Received: 11 February 2004 Returned for revision: 28 September 2004 Accepted: 22 October 2004 Published electronically: 14 February 2005
• Background and Aims Passiflora actinia and P. elegans, two markedly parapatric species, have their southern and northern distribution limits, respectively, in the most southern part of the Brazilian Atlantic Rain Forest. Despite the fact that they are classified in different taxonomic series, previous phylogenetic studies of this genus revealed a high genetic similarity between them. The aim of the present work was to analyse in more detail their geographical range in this region of overlap, to investigate intraspecific genetic variability and phylogeographic structure, and to search for possible hybrids.
• Methods Eighty-two localities were searched for these species, and nuclear internal transcribed spacer (ITS) sequences were investigated for 32 individuals of P. actinia, 20 of P. elegans and one putative interspecific hybrid. Plastid trnL-trnF and psbA-trnH were examined for 12 plants of each species and the putative hybrid.
• Key Results Both species showed a high level of intraspecific and intra-individual ITS variability. Network analysis revealed a north–south geographic gradient in their intra and interspecific relationships. Mismatch analyses suggested a recent population expansion of P. elegans. The plastid markers showed restricted variability but, together with the nuclear data, they contributed to the identification of an interspecific hybrid of intermediate morphology at the border of the distribution of these two species. Both genetic and morphological data indicate the absence of an extensive hybridization zone between these species.
• Conclusions Gene flow between lineages is the possible cause for the presence of different ITS sequences within a given plant, the absence of homogenization being due to the high degree of vegetative reproduction in the two species. Differentiation of P. actinia into geographic groups and the origin of P. elegans may have been influenced by the Atlantic Forest migration towards southern Brazil. The genetic pattern of the interspecific hybrid indicates that plastid inheritance in these species is at least sometimes paternal.
Key words: Passiflora actinia, Passiflora elegans, Passifloraceae, ITS, trnL-trnF, psbA-trnH, phylogeography, hybridization, quaternary climatic changes, Atlantic Forest, migration
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