[2] He specialises in plant taxonomy, biosystematics and applications of techniques from molecular biology, phytogeography and phylogenetics.
He has contributed to papers on the impacts of climate change on plant evolution[3][4][5] as well as reviews of data source quality[6] and computational approaches to large-scale niche modelling.
[7] His work on the evolutionary biology of plants of interest to horticulture includes relationships within Pelargonium[8][9][10] (a collaboration with Mary Gibby of the Royal Botanic Garden Edinburgh), evolutionary patterns within plant genera on islands, with emphasis on Echium, the phylogenetic history of Drosera and phylogenetic and taxonomic revision on Actaea[11] and Ranunculaceae tribe Actaeae[12] (in collaboration with James Compton), a phylogenetic evaluation of Plectranthus and Solenostemon (coleus) (in collaboration with Alan Paton from the Royal Botanic Gardens, Kew) and recently a review of Cyclamen phylogeny and classification[13] (in collaboration with James Compton and The Cyclamen Society).
Culham is also engaged in research on the use of molecular markers for the study of genetic diversity within plant populations for the conservation of endangered species.
[18] Along with Vernon Heywood, Richard Kenneth Brummitt and Ole Seberg, Culham is the author of the standard reference book, Flowering Plant Families of the World.