Recruitment -- In the first year of funding (2024) I successfully recruited 1 postdoc (providing bioinformatics support), and two very talented Ph.D students whose thesis research projects correspond roughly to work packages 1 & 2 in the project proposal.
Genomic data -- (WP1 & 2) In the first year of the project, my team generated draft genomes based on long-read DNA sequence data for one male and female of each of four species for which we had greenhouse specimens, along with short-read sequence data for all greenhouse individuals. In 2025, one Ph.D. student conducted field work in Hawai'i, and collected short read genomic data for over 30 populations of 5 different species across the islands of O'ahu and Hawai'i. The draft genomes were given preliminary annotations based on lift-over from closely related Stellera chamaejasme and gene prediction with BRAKER using several plant protein dbs, until we can supplement/replace with our own gene expression data (expected 2026).
(WP1) Using the preliminary genomic data described above, the bioinformatics postdoc and one PhD student focused on identifying sex-linked genome regions and candidate sex-determining genes. Using a combination of kmer based mapping, GWAS, and synteny analyses, we successfully identified two unique sex-linked genomic regions, each associated with one of the two forms of dioecy located on different chromosomes, and each associated with a chromosomal inversion present only on the male haplotype. This major achievement confirms the putative origin of two different sex determining systems in the Hawaiian Wikstroemia, and lays the foundation for the remaining goals in this WP, including identification of sex-determining genes, and study of the expansion of the non-recombining region associated with one of the dioecy forms.
Greenhouse crosses aimed at generating F1 individuals for gene expression and segregation analyses have been ongoing through 2025, and we are currently waiting for the offspring to mature to flowering.
(WP2) For the goals of WP2, we sampled Wikstroemia specimens extensively from herbaria across Europe and Hawaii. We successfully sampled more than half of the species covering the entire geographic range of the genus (from continental Asia, through Australasia, the pacific islands, to Hawaii), and generated short-read DNA sequence data for over 200 specimens with which to construct a genus-level phylogeny. Preliminary phylogenomic analyses based on the herbarium specimens combined with greenhouse and field collected samples indicate a genus origin in mainland China, and colonization route to Hawaii through Australasia and the south Pacific, and confirm that the Hawaiian clade is monophyletic (originated from a single colonization event). Species relationship within the Hawaiian radiation appear to follow a linear 'stepping-stone' colonization pattern that corresponds to the relative ages of the high Hawaiian islands. The genomic dataset we have compiled represents a second major achievement that far exceeded the original goals for WP2, and provides the macroevolutionary context needed for the broader project as well as a variety of new insights into the systematics of the genus.
