Arabidopsis lyrata subspecies petraea (A. petraea) is a model plant used to address how changes in population size can impact the level of genetic diversity in populations. Natural populations of A. petraea have different glacial histories, resulting in differences in population size over the last few thousand years. The haplotype (genetically related) networks pictured represent the distribution of different alleles (unique copies of a particular gene) across six populations of A. petraea. There are four networks (for four genes) pictured – showing how different genes have diverse network topologies. These networks are used to visualize how alleles are shared between populations. Each circle represents a unique allele and each color represents the population in which those alleles are found. Significance in these networks is in the variation in patterns, especially in how the A. petraea populations connect to ecotypes of the sister species A. thaliana. A. thaliana was the first plant species to have its entire genome sequenced in 2000 (represented in black). The flower pictured is of an A. petraea plant grown in a growth chamber used in our study.