Genetic structure and gene flow in wild beet populations: the potential influence of habitat on transgene spread and risk assessment

Abstract

Summary1. The consequences of the movement of transgenes from genetically modified (GM) crops into wild populations of plants continues to be of concern to ecologists and conservationists because of the possible threat posed to those populations in terms of their continued survival and because of the further knock-on effects that might occur to habitats in which they occur. 2. We examined five UK sea beet Beta vulgari s ssp. maritima populations from each of two major habitat types, cliff top and drift line. We assessed population genetic parameters, genetic diversity, gene flow, population differentiation and isolation by distance, to enable determination of the likelihood and consequences of spread to wild populations of genes from cultivated sugar beet group Beta vulgaris ssp. vulgaris , which could in the future be transgenic. 3. Drift line populations were more diverse than cliff top populations and also showed greater levels of gene flow. 4. Isolation by distance was identified in both habitats, but the relationship between genetic and geographical distance was detectable over longer distances for drift line populations. However, clear indications of vicariance (the subdivision of a population into distinct taxa by the appearance of a geological barrier) between cliff and drift line populations were also evident, because of the restriction of gene flow between the two habitats occurring more in one direction than the other. 5. Synthesis and applications. The likelihood of transgene spread from crop to wild populations is habitat dependent and conservation management decisions could therefore vary from one population to another, for example water courses were found to facilitate seed dispersal. This should be taken into account when estimating isolation distances for GM beet, and when predicting transgene frequencies (exposure estimates) for environmental risk assessments of GM beet.

Genomic distances reveal relationships of wild and cultivated beets

“…The separation of sea beet accessions originating from Atlantic or Mediterranean coasts seems to be triggered by a genetic barrier coinciding with the Strait of Gibraltar. Since the propagation of sea beets relies on seed dispersal through water 30 , 31 there may be a physical barrier due to ocean currents. Oceanographic barriers have been described as a reason for gene flow reduction between species, and the Strait of Gibraltar was identified as one of them 32 .…”

Spatial Genetic Structure in Natural Populations of Phragmites australis in a Mosaic of Saline Habitats in the Yellow River Delta, China

“…Diverse patches of habitat created by natural disturbances have profound influences on ecological and evolutionary processes across scales [2] , [4] , [5] , [6] , [7] , [8] , [9] . The population structure and dynamics of species in patchy environments depend on the spatial arrangement and heterogeneity of habitats [2] , [8] , [9] , [10] , [11] , [12] , [13] , [14] , [15] .…”

Landscape genetics: where are we now?

“…2007), but may actually facilitate gene flow in amphibians (Spear et al. 2005) and transgenic crops (Cureton et al. 2006).…”