Systematics and biogeography of the Pandanaceae family

The Kew team is inferring the phylogeny and biogeography of the Pandanaceae family based on plastid DNA sequences.

The Pandanaceae family includes arborescent or lianoid dioecious plants, traditionally comprising four genera confined to the Paleotropics: Pandanus, Freycinetia, Martellidendron and Sararanga (in decreasing order of species diversity). The genus Pandanus has the broadest geographical distribution, occurring in the tropics from Hawaii to West Africa, and includes approximately 600 species of trees and shrubs. Freycinetia, with a more limited range (Southeast Asia, Pacific Islands and Oceania), comprises nearly 300 species of lianas. Martellidendron is confined to Madagascar and the granitic Seychelles (Mahé and Praslin) and comprises seven species of shrubs or trees. Finally Sararanga, which is restricted to the Philippines, New Guinea, and the Solomon Islands, has only two species of large trees. The current distribution range of Pandanaceae would suggest a putative Gondwanan origin of the family. This hypothesis is also supported by additional evidence. Recent phylogenetic analyses of the angiosperms showed that Pandanaceae are among the earliest-diverging lineages within the monocotyledons. Furthermore, based on the fossil record, the family is estimated to be at least from the Late to Early Cretaceous (an estimation that is corroborated by large-scale angiosperms dating analyses).
Although several botanists (e.g. B. Stone, M.W. Callmander) have greatly contributed to the current taxonomic knowledge of Pandanaceae, the family still lacks a strong phylogenetic framework. As part of this project, Kew researchers, jointly with researchers at the Missouri Botanical Garden (USA), are currently working towards a phylogeny of Pandanaceae based on plastid DNA sequences and a dataset comprising more than 250 taxa representing the whole spectrum of morphological diversity and distribution range of the family. This phylogenetic framework will be first used to evaluate the former classification based on morphological features and propose new subgeneric arrangements for the genus. Secondly, the spatio-temporal history of this early-diverging lineage of monocotyledons will be inferred using the newly-established phylogenetic framework combined with molecular date estimates based on fossil evidence and state-of-the-art methods in biogeographical reconstruction (constrained according to paleogeography).