Allelic sequence divergence in the apomictic Boechera holboellii complex

Abstract

It has been suggested that the absence of meiosis in asexual lineages should lead to higher interallelic divergence at any given locus within an individual (i.e., allelic sequence divergence - ASD) compared to sexual populations (i.e., Meselson effect; Mark Welch and Meselson 2000). In the present study, ASD was investigated in 2 diploid sexual, 3 diploid apomictic and 3 triploid apomictic Boechera (Brassicaceae) using 8 microsatellite loci considering both repeat and flanking region polymorphism. A trend of higher ASD in apomictic versus sexual individuals, both in DNA sequence and repeat motif polymorphisms, was identified, although the pattern of polymorphism is complex and has likely resulted from a combination of mutation accumulation, gene duplication and hybridization. These data demonstrate that caution must be taken when using population genetic models to compare microsatellite variation between sexual and asexual taxa.