Image: Philip Bentz, a former graduate student in the Leebens-Mack lab, was recognized by the Department of Plant Biology with the 2024 Paper of the Year Award for his graduate work on Asparagus (published in September 2024). Philip is now a researcher at the HudsonAlpha Institute for Biotechnology. Out of Africa: rapid diversification, dispersal, and two origins of dioecy punctuate the evolutionary history of Asparagus The ancestors of Asparagus plants were hermaphrodites, which means they had both male and female reproductive organs. These plants began diversifying in southern Africa approximately 5 million years ago (Ma) into the different Asparagus species we see today, including species with now separate male and female plants. In their paper published in Genome Biology and Evolution, Bentz and coworkers describe how dioecy (i.e., separate male and female plants) evolved independently in two distinct clades (closely related species) of Asparagus, 2-3 million years after the earliest ancestral diversification events in Southern Africa. Each of these two shifts from hermaphroditism to dioecy was found to be associated with long-distance dispersals out-of-Southern-Africa. One of these two clades dispersed and established itself in Asia, where it further diversified, while the other clade dispersed to the Mediterranean Basin. It has been hypothesized that the evolution of dioecy was a mechanism for avoiding inbreeding by plants, and this new work suggests that dispersal of a few plants (founder events) may also have played an important role in the evolution of dioecy. The study also documents bursts of speciation among hermaphroditic Southern African lineages that may be driven by habitat specialization. Read the original paper here
