Disentangling effects of linked fitness QTL on local adaptation in Arabidopsis thaliana

• The genetic basis of local adaptation is of fundamental interest for understanding population differentiation and speciation. Here we used four near-isogenic lines (NILs) to test the effects of some previously identified and closely located quantitative trait loci (QTL) for fitness and putatively adaptive traits when reciprocally introgressed into the genetic backgrounds of two locally adapted ecotypes of Arabidopsis thaliana in Italy and Sweden. In three consecutive years, we reciprocally planted seeds and seedlings of the Italian and Swedish ecotypes and the NILs at the sites of the parental populations. There was strong selection against the non-local ecotype at both sites. Introgressions tended to increase the fitness of the non-local genotype and reduce the fitness of the local genotype. The magnitude of fitness effects of introgressions varied among years, and corresponded to 0-54% of the difference between parents in the seedling transplant experiment, and 17-36% in the seed transplant. The direction and magnitude of effects on fitness and flowering time were largely consistent with predictions based on QTL effects quantified in former transplants of recombinant inbred lines (RILs). The results provide additional evidence of epistatic interactions among fitness QTL and indicate that the direction of selection on fitness QTL may vary among years. Taken together, they demonstrate that genetic variation at the end of chromosome 5 contributes strongly to local adaptation between the two study populations, and more generally that NILs are a powerful tool for studies of the genetics of local adaptation.

Subject headings

NATURVETENSKAP  -- Biologi -- Evolutionsbiologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences -- Evolutionary Biology (hsv//eng)

Keyword

DOG1

field experiment

fitness

fitness QTL

flowering time

germination time

reciprocal transplant

seed transplant

seedling transplant

Biology with specialization in Evolutionary Genetics

Biologi med inriktning mot evolutionär genetik

Biology with specialization in Ecological Botany

Biologi med inriktning mot ekologisk botanik

Publication and Content Type

vet (subject category)

ovr (subject category)