The impact of study design and life history traits on genetic variation of plants determined with AFLPs

In this study, we analysed the impact of study design and life history traits on genetic variation of plants determined with amplified fragment length polymorphisms (AFLPs), a technique widely applied in all fields of molecular plant ecology. For the proper interpretation and comparison of genetic variation based upon AFLPs, a meta-analysis based upon a large number of studies of the relationship between study design and plant life history traits on the one hand and of AFLP variation on the other hand is needed but is lacking. To bridge this gap, we extracted data on study design and genetic variation from 115 AFLP studies comprising a total of 152 species. Subsequently, we ascribed the life history traits taxonomic status, life span, frequency, mating system and pollination vector to each of the species. Then, we used linear models to analyse the impact of study design and life history traits on genetic variation. In our data set genetic variation within and among populations depended neither on the number of analysed populations nor the number of analysed individuals per population. However, maximum geographic distance between populations strongly affected genetic variation. Variation within populations decreased while variation among populations increased with maximum geographic distance. Concerning the impact of life history traits, both genetic variation within and among populations depended with increasing strength on the life span, the frequency and the mating system of the species. Following the results of this study, the number of analysed populations or individuals per population is not necessarily a problem when comparing results of different studies, at least when not very low sample sizes are used. However, corresponding study ranges would be highly recommendable, since the maximum geographic distance between populations strongly affects genetic variation.