Too Far From Relatives? Impact of the Genetic Distance on the Success of Exon Capture in Phylogenomics.

The exon capture approach allows for sequencing a large number of loci to reconstruct phylogenetic relationships at varying taxonomic levels. In order to efficiently recover the targeted loci, the probes designed to capture the exons need to be genetically sufficiently similar to bind to the DNA, with a proposed limit of 10% of divergence. However, this threshold has never been tested with a specific protocol. We have designed a set of probes to capture 1125 exons in the Neogastropoda (Mollusca, Gastropoda), processed with the same protocol from the field to the DNA sequencing to control for potential bias in DNA quantity and quality. We sequenced 30 different species, including 14 species of Neogastropoda and 16 species of Caenogastropoda non-Neogastropoda. Each species includes five specimens, for a total of 150 specimens, and for four specimens among the 150, DNA extracts were aliquoted in four samples, sequenced separately, to estimate the intraspecific and intraspecimen variability in capture success. Our results confirm the impact of genetic distance on the success of exon capture with a negative linear correlation between the genetic distance and the number of exons captured for each sample. Consequently, designing new capture probes would allow for capturing exons in genetically more distant groups without the need to redesign a new set of exons.