Systematics and Biogeography of Hard Ticks, a Total Evidence Approach.

Area of Science:

• Zoology
• Evolutionary Biology
• Genomics

Background:

• The evolutionary relationships of basal Ixodidae (ticks) remain incompletely understood.
• Previous studies have yielded conflicting phylogenetic hypotheses for this important family of ectoparasites.

Purpose of the Study:

• To resolve the systematic relationships among basal Ixodidae using a multi-dataset approach.
• To investigate the impact of data partitioning and missing data on phylogenetic inference.
• To infer the biogeographic origins of Ixodidae, particularly endemic Australian taxa.

Main Methods:

• Phylogenetic analyses were conducted using one morphological and three molecular data sets (18S and 28S nuclear rDNA, 16S mitochondrial rDNA).
• Partition homogeneity tests were performed to assess data set compatibility.
• Analyses explored the effects of including/excluding taxa with missing data and different gap treatments in the 28S rDNA data set.

Main Results:

• Combined analyses provided strong support for the Metastriata and a distinct lineage of remaining Ixodes, but not for the Prostriata.
• Inclusion or exclusion of taxa with missing data minimally impacted overall tree topology and support levels.
• Gap treatment in the 28S rDNA data set significantly altered a basal node's arrangement and support.

Conclusions:

• The phylogenetic framework supports recent origins for endemic Australian Ixodidae lineages, aligning with Australia's late Cretaceous isolation.
• Ixodidae, and its major lineages, likely originated after Australia's isolation, contradicting older hypotheses.
• Integrated phylogenetic analyses, despite data set incompatibilities, offer robust insights into tick evolution and biogeography.