Ixodidae (Hard Ticks) [chapter]

Dongyou Liu, Chong Yin
2012 Molecular Detection of Human Parasitic Pathogens  
Hard ticks are widely distributed across temperate regions, show strong variation in host associations, and are potential vectors of a diversity of medically important zoonoses, such as Lyme disease. to address unresolved issues with respect to the evolutionary relationships among certain species or genera, we produced novel RNA-Seq data sets for nine different Ixodes species. We combined this new data with 18 data sets obtained from public databases, both for Ixodes and non-Ixodes hard tick
more » ... Ixodes hard tick species, using soft ticks as an outgroup. We assembled transcriptomes (for 27 species in total), predicted coding sequences and identified single copy orthologues (SCO). Using Maximum-likelihood and Bayesian frameworks, we reconstructed a hard tick phylogeny for the nuclear genome. We also obtained a mitochondrial DnA-based phylogeny using published genome sequences and mitochondrial sequences derived from the new transcriptomes. Our results confirm previous studies showing that the Ixodes genus is monophyletic and clarify the relationships among Ixodes sub-genera. this work provides a baseline for studying the evolutionary history of ticks: we indeed found an unexpected acceleration of substitutions for mitochondrial sequences of prostriata, and for nuclear and mitochondrial genes of two species of Rhipicephalus, which we relate with patterns of genome architecture and changes of lifecycle, respectively. www.nature.com/scientificreports www.nature.com/scientificreports/ comparing rates of substitution. To test for a possible difference in evolutionary rates among species, we used Tajima's relative rate test 75 . This test uses counts of substitutions unique to each of two focus species (A and B), using a third species as an as an outgroup. These comparisons were performed after observing particular long branches in the phylogenetic analyses, and concerned (i) a comparison between Prostriata and Metastriata ticks, using a soft tick species as an outgroup (ii) a comparison between species of the Rhipicephalus genus -comparing the Boophilus subgenus to other species -using another species of Metastriata as the outgroup. Data Availability Reads from newly sequenced transcriptomes were deposited into the SRA section of the NCBI under BioProject accessions PRJNA528282 and PRJNA550328. DNA alignments of the SCO50 matrix (nuclear genes) are available at https://doi.org/10.5281/zenodo.3382009.
doi:10.1201/b12264-81 fatcat:3ovkw4wtjrazdocrrg4db4g4mu