Transcriptomics illuminate the phylogenetic backbone of tiger beetles

Phylogenomics is progressing rapidly, allowing large strides forward into our understanding of the tree of life. In

this study, we generated transcriptomes from ethanol-preserved specimens of 13 tiger beetle species (Coleoptera:

Cicindelinae) and one Scaritinae outgroup. From these 14 transcriptomes and seven publicly available transcriptomes,

we recovered an average of 2538 loci for phylogenetic analysis. We constructed an evolutionary tree of tiger beetles

to examine deep-level relationships and examined the extent to which the composition of the dataset, missing data,

gene tree inconsistency and codon position saturation impacted phylogenetic accuracy. Ethanol-preserved specimens

yielded similar numbers of loci to specimens originally preserved in costly reagents, showcasing more flexibility in

transcriptomics than anticipated. The number of loci and gene tree inconsistency had less impact on downstream

results than third codon position saturation and missing data. Our results recovered tiger beetles as sister to

Carabidae with strong support, confirming their taxonomic status as an independent family within Adephaga. Within

tiger beetles, phylogenetic relationships were robust across all nodes. This new phylogenomic backbone represents a

useful framework for future endeavours in tiger beetle systematics and serves as a starting point for the development

of less costly target capture toolkits to expand the taxonomic breadth of the future tiger beetle tree of life.

Methods
For complete information on collection, extraction and sequencing see (Gough et al. 2020).