Data and code from: Departures from Mendelian inheritance of EPSPS gene copies in a herbicide-resistant weed

Here we report on inheritance and intra-individual variation in gene copy
number associated with rapid evolution of herbicide resistance in the
dioecious, agricultural weed Amaranthus palmeri. Copy number variation for
glyphosate resistance gene EPSPS was quantified using digital droplet PCR
within individuals, and for parents and offspring of controlled crosses
with copy number ranging from 1 to ~160. The non-linear pattern of gene
copy number inheritance from parent to offspring exhibits shifting
directionality. Below the threshold of ~33 copies, the slope of the
parent-offspring relation is high (1.60) because parents with fewer gene
copies yield similar or increased mean offspring copy numbers, relative to
parents. In contrast, above the threshold, the slope is low (0.21), and
offspring of high copy number parents carry increasingly fewer EPSPS
copies than parents. Intra-individual variance in copy number increases
with mean individual copy number, likely contributing to variation in
offspring copy number, but not sufficient to explain extreme transgressive
copy number variants, nor the loss of high copy number. In short, copy
number is less stable and transmitted to offspring at a lower rate in
parents with more copies. This suggests a constraint on the evolution of
herbicide resistance through increased EPSPS copy number.