Evidence of natural hybridization and introgression between Vasconcellea species (Caricaceae) from southern Ecuador revealed by chloroplast, mitochondrial and nuclear DNA markers.
OBJECTIVE
Vasconcellea x heilbornii is believed to be of natural hybrid origin between V. cundinamarcensis and V. stipulata, and is often difficult to discriminate from V. stipulata on morphological grounds. The aim of this paper is to examine individuals of these three taxa and of individuals from the closely related species V. parviflora and V. weberbaueri, which all inhabit a hybrid zone in southern Ecuador.


METHODS
Molecular data from mitochondrial, chloroplast and nuclear DNA from 61 individuals were analysed.


RESULTS
Molecular analysis confirmed occasional contemporary hybridization between V. stipulata, V. cundinamarcensis and V. x heilbornii and suggested the possible involvement of V. weberbaueri in the origin of V. x heilbornii. In addition, the molecular data indicated unidirectional introgression of the V. cundinamarcensis nuclear genome into that of V. stipulata. Several of the individuals examined with morphology similar to that of V. stipulata had genetic traces of hybridization with V. cundinamarcensis, which only seems to act as pollen donor in interspecific hybridization events. Molecular analyses also strongly suggested that most of the V. x heilbornii individuals are not F(1) hybrids but instead are progeny of repeated backcrosses with V. stipulata.


CONCLUSIONS
The results of the present study point to the need for re-evaluation of natural populations of V. stipulata and V. x heilbornii. In general, this analysis demonstrates the complex patterns of genetic and morphological diversity found in natural plant hybrid zones.
Van Droogenbroeck
B
B
Department of Molecular Biotechnology, Faculty of Bioscience Engineering, Ghent University (UGent), Coupure links 653, B-9000 Ghent, Belgium.
Kyndt
T
T
Romeijn-Peeters
E
E
Van Thuyne
W
W
Goetghebeur
P
P
Romero-motochi
J P
JP
Gheysen
G
G
D031241:Caricaceae / Q000235:genetics*; D016172:DNA Fingerprinting; D018742:DNA, Chloroplast; D004272:DNA, Mitochondrial; D018744:DNA, Plant; D004484:Ecuador; D005819:Genetic Markers; D006239:Haplotypes; D006824:Hybridization, Genetic; D012150:Polymorphism, Restriction Fragment Length
D018742:DNA, Chloroplast; D004272:DNA, Mitochondrial; D018744:DNA, Plant; D005819:Genetic Markers