Geographic patterns of microsatellite variation in Boechera stricta, a close relative of Arabidopsis

• Published in: Molecular ecology Vol. 15; no. 2; pp. 357 - 369
• Main Authors: Song, Bao-Hua, Clauss, Maria J, Pepper, Alan, Mitchell-Olds, Thomas
• Format: Journal Article
• Language: English
• Published: Oxford, UK Oxford, UK : Blackwell Science Ltd 01.02.2006; Blackwell Science Ltd; Blackwell Publishing Ltd
• Subjects: admixture; Arabis drummondii; Boechera stricta; Brassicaceae; Brassicaceae - genetics; Diploidy; Flowers & plants; Genetic diversity; genetic markers; Genetic Variation; Genetics, Population; geographical variation; glacial refugium; heterozygosity; inbreeding; inbreeding coefficient; introgression; loci; Microsatellite Repeats; Midwestern United States; Northwestern United States; Plant ecology; Population genetics; population structure; Rocky Mountain region; Midwestern United States; Northwestern United States; Rocky Mountains
• ISSN: 0962-1083; 1365-294X
• DOI: 10.1111/j.1365-294X.2005.02817.x

The genus Boechera is a widespread North American group with great potential for studies of ecology and evolution: Boechera is closely related to Arabidopsis and exhibits different ecological and reproductive strategies. Boechera stricta (previously Arabis drummondii) is a morphologically and genetically well-defined, perennial crucifer species. Fifteen natural populations of diploid individuals from the Rocky Mountains were analysed using 21 microsatellite loci. In accordance with our expectation for this predominately inbreeding species, a high F[subscript IS] value (0.89) was observed. Furthermore, populations of B. stricta were highly differentiated, as indicated by F[subscript ST] = 0.56. Three clusters were identified using structure-- the majority of populations belonged to either the Northern or Southern cluster. Together, the north-south partitioning and evenness of genetic variation across the two clusters suggested multiple refugia for this perennial herb in the Rocky Mountains. Pleistocene glaciation, together with the topographically and climatologically heterogeneous cordillera, has profoundly influenced the genetic architecture of B. stricta. Genetic population structure was also influenced by relatively recent genome admixture at two levels: within species (involving individuals from the Northern and Southern clusters) and between species (with the hybridization of B. stricta and Boechera holboellii). This complexity of population structure at presumably neutral microsatellite loci located throughout the genome in B. stricta provides a baseline against which to test whether functional genetic variation is undergoing local adaptive evolution throughout the natural species range.