TY - JOUR
T1 - Asymmetric gene introgression in two closely related Orchis species: evidence from morphometric and genetic analyses
AU - Hans, Jacquemyn
AU - Brys, Rein
AU - Honnay, Olivier
AU - Roldan-Ruiz, Isabel
PY - 2012
Y1 - 2012
N2 - Background: In food-deceptive orchids of the genera Anacamptis, Neotinea and Orchis floral isolation has been shown to be weak, whereas late-acting reproductive barriers are mostly strong, often restricting hybridization to the F1 generation. Only in a few species hybridization extends beyond the F1 generation, giving rise to hybrid swarms.However, little is known about the abundance of later-generation hybrids and what factors drive their occurrence in hybrid populations. In this study, molecular analyses were combined with detailed morphological measurements in a hybrid population of two closely related Orchis species (Orchis militaris and O. purpurea) to investigate the hypothesis that the abundance of later-generation hybrids is driven by changes in floral characters after hybridization that exert selective pressures that in turn affect hybridization.
Results: Both the molecular and morphological data point to extensive genetic and morphological homogenization and asymmetric introgression. Estimating genomic clines from the multi-locus genotype data and testing for deviation from neutrality revealed that 30 out of 113 (27%) AFLP markers significantly deviated from neutral expectations. Plants with large floral displays or plant with flowers that resembled more O. purpurea had higher female fitness than plants with small floral displays or plants with flowers resembling more O. militaris, suggesting that directional selection may have contributed to the observed patterns of introgression.
Conclusions: These results indicate that in closely related orchid species hybridization and gene introgression may be partly driven by selection for floral traits of one of the parental types. However, because some pure individuals
were still present in the studied population, the parental species appeared to be sufficiently isolated to survive the challenge of sympatry.
AB - Background: In food-deceptive orchids of the genera Anacamptis, Neotinea and Orchis floral isolation has been shown to be weak, whereas late-acting reproductive barriers are mostly strong, often restricting hybridization to the F1 generation. Only in a few species hybridization extends beyond the F1 generation, giving rise to hybrid swarms.However, little is known about the abundance of later-generation hybrids and what factors drive their occurrence in hybrid populations. In this study, molecular analyses were combined with detailed morphological measurements in a hybrid population of two closely related Orchis species (Orchis militaris and O. purpurea) to investigate the hypothesis that the abundance of later-generation hybrids is driven by changes in floral characters after hybridization that exert selective pressures that in turn affect hybridization.
Results: Both the molecular and morphological data point to extensive genetic and morphological homogenization and asymmetric introgression. Estimating genomic clines from the multi-locus genotype data and testing for deviation from neutrality revealed that 30 out of 113 (27%) AFLP markers significantly deviated from neutral expectations. Plants with large floral displays or plant with flowers that resembled more O. purpurea had higher female fitness than plants with small floral displays or plants with flowers resembling more O. militaris, suggesting that directional selection may have contributed to the observed patterns of introgression.
Conclusions: These results indicate that in closely related orchid species hybridization and gene introgression may be partly driven by selection for floral traits of one of the parental types. However, because some pure individuals
were still present in the studied population, the parental species appeared to be sufficiently isolated to survive the challenge of sympatry.
U2 - http://www.biomedcentral.com/1471-2148/12/178
DO - http://www.biomedcentral.com/1471-2148/12/178
M3 - A1: Web of Science-article
VL - 12
SP - 178
JO - BMC Evolutionary Biology
JF - BMC Evolutionary Biology
ER -