Steve Wagstaff is a plant systematist affiliated with the Allan Herbarium. His research focuses on the evolution and diversification of island floras. He has travelled widely in the south pacific with research projects on Lord Howe Island, New Caledonia, New Zealand, and Tasmania.

Steve studies small errors or mutations in DNA molecules, and reconstructs past evolutionary events by examining the distribution and frequency of DNA mutations, and incorporating information from fossil records to calibrate molecular clocks. Steve uses a dated phylogeny as a framework to trace plant origins, dispersal and diversification.