Limits...
The geographic mosaic of herbicide resistance evolution in the common morning glory, Ipomoea purpurea: Evidence for resistance hotspots and low genetic differentiation across the landscape.

Kuester A, Chang SM, Baucom RS - Evol Appl (2015)

Bottom Line: We uncovered a mosaic pattern of resistance across the landscape, with some populations exhibiting high-survival postherbicide and other populations showing high death.SSR genotyping revealed little evidence of isolation by distance and very little neutral genetic structure associated with geography.An approximate Bayesian computation (ABC) analysis uncovered evidence for migration and admixture among populations before the widespread use of glyphosate rather than the very recent contemporary gene flow.

View Article: PubMed Central - PubMed

Affiliation: Department of Ecology and Evolutionary Biology, 830 North University, University of Michigan Ann Arbor, MI, USA.

ABSTRACT
Strong human-mediated selection via herbicide application in agroecosystems has repeatedly led to the evolution of resistance in weedy plants. Although resistance can occur among separate populations of a species across the landscape, the spatial scale of resistance in many weeds is often left unexamined. We assessed the potential that resistance to the herbicide glyphosate in the agricultural weed Ipomoea purpurea has evolved independently multiple times across its North American range. We examined both adaptive and neutral genetic variations in 44 populations of I. purpurea by pairing a replicated dose-response greenhouse experiment with SSR genotyping of experimental individuals. We uncovered a mosaic pattern of resistance across the landscape, with some populations exhibiting high-survival postherbicide and other populations showing high death. SSR genotyping revealed little evidence of isolation by distance and very little neutral genetic structure associated with geography. An approximate Bayesian computation (ABC) analysis uncovered evidence for migration and admixture among populations before the widespread use of glyphosate rather than the very recent contemporary gene flow. The pattern of adaptive and neutral genetic variations indicates that resistance in this mixed-mating weed species appears to have evolved in independent hotspots rather than through transmission of resistance alleles across the landscape.

No MeSH data available.


Related in: MedlinePlus

Principle coordinate analysis of pairwise Nei's genetic distance. Populations are assigned to state (shape) and resistance level by color (red-blue gradient). The proportion of genetic variance explained by coordinates 1 and 2 were 8.9 and 6.3%, respectively. The dashed open circle represents the coordinate space representing all of the Midwestern US populations.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4561571&req=5

fig06: Principle coordinate analysis of pairwise Nei's genetic distance. Populations are assigned to state (shape) and resistance level by color (red-blue gradient). The proportion of genetic variance explained by coordinates 1 and 2 were 8.9 and 6.3%, respectively. The dashed open circle represents the coordinate space representing all of the Midwestern US populations.

Mentions: Our PCoA of neutral genetic variation revealed a slight clustering of Midwestern US populations, which had similarly been found in the amova result for regional genetic differentiation (FRT = 0.043, P = 0.001). However, these populations were contained within the range of variation across the Southeastern US populations (Fig. 6), and the first two axes of the PCoA explained only 8.9% and 6.3% of the variation. Thus, geography explains only a small portion of the neutral genetic diversity of this species, and the majority of neutral genetic variation across this species' range in the USA is present within the southern populations. Wilcoxon tests on the first 2 axes of the principle coordinates found no difference, across either axis, for the populations when assigned either ‘resistant’ (<50% death, N = 11) or ‘susceptible’ (>50% death, N = 22) in PC1 or PC2 mean scores (Axis 1: W = 157, P = 0.175; Axis 2: W = 106, P = 0.585). Hence, there was no indication that the neutral genetic variation of this species clustered according to resistance status rather than geography, as would be expected if propagules from, for example, resistant TN populations had migrated to the resistant Carolina populations and established and/or admixed. We did not uncover evidence of isolation by distance using linearized FST over geographic distance (R2 = 0.012, P = 0.142), nor did we uncover significant isolation by distance measured as the Cavalli-Sforza Edwards chord distance (R2 = 0.010, P = 0.192). Pairwise estimates of Nei's genetic distance similarly did not correlate with geographical distance (R = −0.065, P = 0.11), reinforcing our finding of either widespread gene flow across populations or colonization following a recent bottleneck.


The geographic mosaic of herbicide resistance evolution in the common morning glory, Ipomoea purpurea: Evidence for resistance hotspots and low genetic differentiation across the landscape.

Kuester A, Chang SM, Baucom RS - Evol Appl (2015)

Principle coordinate analysis of pairwise Nei's genetic distance. Populations are assigned to state (shape) and resistance level by color (red-blue gradient). The proportion of genetic variance explained by coordinates 1 and 2 were 8.9 and 6.3%, respectively. The dashed open circle represents the coordinate space representing all of the Midwestern US populations.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4561571&req=5

fig06: Principle coordinate analysis of pairwise Nei's genetic distance. Populations are assigned to state (shape) and resistance level by color (red-blue gradient). The proportion of genetic variance explained by coordinates 1 and 2 were 8.9 and 6.3%, respectively. The dashed open circle represents the coordinate space representing all of the Midwestern US populations.
Mentions: Our PCoA of neutral genetic variation revealed a slight clustering of Midwestern US populations, which had similarly been found in the amova result for regional genetic differentiation (FRT = 0.043, P = 0.001). However, these populations were contained within the range of variation across the Southeastern US populations (Fig. 6), and the first two axes of the PCoA explained only 8.9% and 6.3% of the variation. Thus, geography explains only a small portion of the neutral genetic diversity of this species, and the majority of neutral genetic variation across this species' range in the USA is present within the southern populations. Wilcoxon tests on the first 2 axes of the principle coordinates found no difference, across either axis, for the populations when assigned either ‘resistant’ (<50% death, N = 11) or ‘susceptible’ (>50% death, N = 22) in PC1 or PC2 mean scores (Axis 1: W = 157, P = 0.175; Axis 2: W = 106, P = 0.585). Hence, there was no indication that the neutral genetic variation of this species clustered according to resistance status rather than geography, as would be expected if propagules from, for example, resistant TN populations had migrated to the resistant Carolina populations and established and/or admixed. We did not uncover evidence of isolation by distance using linearized FST over geographic distance (R2 = 0.012, P = 0.142), nor did we uncover significant isolation by distance measured as the Cavalli-Sforza Edwards chord distance (R2 = 0.010, P = 0.192). Pairwise estimates of Nei's genetic distance similarly did not correlate with geographical distance (R = −0.065, P = 0.11), reinforcing our finding of either widespread gene flow across populations or colonization following a recent bottleneck.

Bottom Line: We uncovered a mosaic pattern of resistance across the landscape, with some populations exhibiting high-survival postherbicide and other populations showing high death.SSR genotyping revealed little evidence of isolation by distance and very little neutral genetic structure associated with geography.An approximate Bayesian computation (ABC) analysis uncovered evidence for migration and admixture among populations before the widespread use of glyphosate rather than the very recent contemporary gene flow.

View Article: PubMed Central - PubMed

Affiliation: Department of Ecology and Evolutionary Biology, 830 North University, University of Michigan Ann Arbor, MI, USA.

ABSTRACT
Strong human-mediated selection via herbicide application in agroecosystems has repeatedly led to the evolution of resistance in weedy plants. Although resistance can occur among separate populations of a species across the landscape, the spatial scale of resistance in many weeds is often left unexamined. We assessed the potential that resistance to the herbicide glyphosate in the agricultural weed Ipomoea purpurea has evolved independently multiple times across its North American range. We examined both adaptive and neutral genetic variations in 44 populations of I. purpurea by pairing a replicated dose-response greenhouse experiment with SSR genotyping of experimental individuals. We uncovered a mosaic pattern of resistance across the landscape, with some populations exhibiting high-survival postherbicide and other populations showing high death. SSR genotyping revealed little evidence of isolation by distance and very little neutral genetic structure associated with geography. An approximate Bayesian computation (ABC) analysis uncovered evidence for migration and admixture among populations before the widespread use of glyphosate rather than the very recent contemporary gene flow. The pattern of adaptive and neutral genetic variations indicates that resistance in this mixed-mating weed species appears to have evolved in independent hotspots rather than through transmission of resistance alleles across the landscape.

No MeSH data available.


Related in: MedlinePlus