Edinburgh, Scotland, United Kingdom - TAIR

Local-scale population structure and outcrossing
in Arabidopsis thaliana
Arabidopsis thaliana is increasingly employed to investigate questions in
evolution and ecology. It is thus critical to understand population structure and
dynamics of wild populations at a scale relevant to individuals. We collected
seeds from >1000 individuals in 78 populations within 25 km of Tuebingen,
Germany. We genotyped all plants at 436 single nucleotide polymorphism (SNP)
markers distributed across all chromosomes. We found pronounced variation
among sites in genetic diversity and heterozygosity. About 70% of sites contain
at least two distinct genotypes. Sites were strongly isolated and genetic identities
of individuals spaced more than a few dozen meters apart were very rare.
Distinct genotypes within populations tended to be more closely related than
those from different populations. Pairwise genetic distance comparisons among
genotypes in neighboring populations were often lower than comparisons among
more distant populations and nonparametric clustering often groups individuals
from nearby populations together. Some populations had surprisingly high
estimated outcrossing rates – up to 20% - while others were completely
homozygous with no evidence of past or ongoing outcrossing. We observed
striking differences between sites in rural and urban settings. Rural sites have
more distinct genotypes, higher genetic diversity, higher heterozygosity, and
evidence of past recombination. The picture emerging from our work, together
with other studies, is that A. thaliana exists in the wild in isolated populations
that differ greatly in structure, stability and natural history. Outcrossing is
sufficiently high in some populations to maintain overall genetic variation and
generate novel haplotypes with a regional stamp. These patterns have
implications for sampling for natural variation and ecological adaptation studies.
57
C06
Wednesday 15:15 - 15:30
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Kirsten Bomblies1,2
Levi Yant1 Roosa
Laitinen1
Sang-Tae Kim1
Detlef Weigel1
1Max Planck Institute for
Developmental Biology
Tuebingen
Germany
2Present Address:
Harvard University
Cambridge
MA
USA