Two major evolutionary lineages revealed by molecular phylogeny in the parthenogenetic collembola species Folsomia candida

In order to measure the genetic variability and determine the evolutionary relationships among strains of the parthenogenetic "standard" springtail Folsomia candida, we used Random Amplified Polymorphic DNA (RAPD-PCR) markers and determined the nucleotide sequence of the 18S and 28S rDNA genes. Both types of molecular characters were found to be polymorphic. We obtained phylogenetic trees using Direct Optimization in the dynamic homology paradigm. The trees were polarized with Isotoma viridis as an outgroup. All the trees based on one or the other type of molecular characters or based on all characters pooled together, support the hypothesis of an early divergence of two distinct lineages among the 11 strains of F. candida under study. Our results also suggest that these lineages differ in their rate of evolution and mode of diversification. The geographical origin of the studied strains was examined but we found no clear relation between the phylogenetic relationships and probable geographical origins. The early divergence of several lineages in this species should be taken into account when comparing studies on genetically different strains of this model organism. RAPD-PCR typing is an easy and efficient tool for doing such a task.