Exploring adaptive radiation through a phylogenetic revision of Hawaii’s remarkable endemic Trupanea (Diptera: Tephritidae)

There are an estimated forty species (half of which are undescribed) of endemic Hawaiian Trupanea (Diptera: Tephritidae) feeding in the flowerheads, shoot-tips, or stems of endemic Hawaiian Asteraceae. All but one of the known host plants are vulnerable to critically endangered, with most host plants being in the unique “Silversword Alliance”. The biology of the group provides an excellent window into the evolution of stem-galling behaviors in flies, with previous work indicating at least three independent evolutions of this behavior. In addition, there is evidence of sympatric/ecological speciation with host plant-switching, host plant-partitioning, and even an example of an endemic species (Trupanea crassipes) shifting to an introduced weed species (Bidens pilosa).

The last taxonomic revision of the group was conducted in the 1980’s prior to modern molecular techniques; the most recent phylogenetic work only used two mitochondrial genes, and did not resolve the relationships between Trupanea species. Here, we discuss the production of a reference-quality genome for Hawaiian Trupanea (T. dubautiae of Oʻahu) by combining PacBio high molecular weight HiFi sequencing, RNAseq, and Hi-C techniques. In addition, we perform shotgun genome sequencing of all other extant Hawaiian Trupanea species, which is mapped onto this reference genome. From this, a full phylogenomic analysis examining gene location, host plant, and feeding mode in light of their evolution will be performed to understand herbivore evolution more broadly.