Genetic and sexual separation between insect resistant and susceptible Barbarea vulgaris plants in Denmark

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Co-evolution between herbivores and plants is believed to be one of the processes creating
Earth’s biodiversity. However, it is difficult to disentangle to what extent diversification is
really driven by herbivores or by other historical-geographical processes like allopatric
isolation. In the cruciferous plant Barbarea vulgaris, some Danish individuals are resistant
to herbivory by flea beetles (Phyllotreta nemorum), whereas others are not. The flea
beetles are, in parallel, either resistant or susceptible to the plants defenses. To understand
the historical-evolutionary framework of these interactions, we tested how genetically
divergent resistant and susceptible plants are, using microsatellite markers. To test
whether they are reproductively fully compatible, resistant and susceptible plants were
grown intermixed in an outdoor experiment, and the paternity of open-pollinated
offspring was determined by analysis of molecular markers. Resistant and susceptible
Danish plants were genetically strongly differentiated and produced significantly fewer
hybrids than expected from random mating or nearest neighbour mating. Our results
suggest that the two types belong to different evolutionary lineages that have been (partly)
isolated at some time, during which genetic and reproductive divergence evolved. A
parsimonious scenario could be that the two plant types were isolated in different refugia
during the previous ice age, from which they migrated into and met in Denmark and
possibly neighbouring regions. If so, resistance and susceptibility has for unknown
reasons become associated with the different evolutionary lineages.
TidsskriftMolecular Ecology
Udgave nummer16
Sider (fra-til)3456-3465
Antal sider10
StatusUdgivet - 2010


  • Det tidligere LIFE - evolutionary divergence, insect herbivory, paternity, resistance, sexual incompatibility

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