The spatiotemporal origin of Polynesian blueberries (Vaccinium)

We aimed to elucidate the spatiotemporal origins and biogeographic history of Polynesian blueberries within Vaccinium sect. Myrtillus, specifically those endemic to Hawai'i and the closely related V. cereum in southeastern Polynesia.

A HybSeq data set was constructed for Polynesian Vaccinium and added to a previously published data set for tribe Vaccinieae. Phylogenomic, ancestral area, fossil-calibrated divergence time, and phylogenetic network analyses were conducted to assess the origin and biogeographic history of the group.

Hawai'ian taxa plus a sample of Vaccinium cereum from Ua Pou Island formed a clade that was phylogenetically nested within continental Vaccinium sect. Myrtillus. The clade was inferred to have originated from temperate East Asia ca. 7.1-5.2 million years ago, dispersing to Kaua'i either directly or via one of the subsident or now-submerged Northwestern Islands of the archipelago. Nuclear-plastid genome discordance and network analysis corroborated the previously hypothesized hybrid origin of V. cereum and suggested a possible dispersal from Hawai'i to coastal North America followed by introgression into the mainland species V. ovalifolium.

Our study suggests that an ancestral exaptation to temperate climates and an evolutionary history of the Hawai'ian Vaccinium clade dating back at least to the origin of Kaua'i have likely contributed to the present-day diversity of the group. Our results support a temperate East Asian origin, rare among the native plants of Hawai'i, and highlight the ongoing potential for both short- and long-distance dispersal in this group of island plants without a reduction or loss of dispersibility.