As of February 2010 there are at the last count 551* known Passiflora species. Most are climbing vines but there are some species that are trees. Passiflora colinvauxii from the Galapagos Islands shown above is very rare. Taxonomy or systematics is the classification of organisms based originally on their visible similarity. Its weakness is that organisms that look very similar may not be closely related. For example one non-poisonous species of snake may mimic another poisonous species. Cladistics, also known as phylogenetics, is a more modern way of analysing taxonomic relationships using objective quantitative analysis of data usually from DNA and RNA sequencing. Put simply a clade is a group that genetic analysis suggests has a single common ancestor and it and its descendants that have evolved from it are grouped in the same clade. The information gained from these studies can then be used to tweak the existing taxonomic classifications. Passiflora species are classified as part of the Passifloraceae family and are all in the genus Passiflora. Linnaeus (1753) named 24 species. Killip (1938) split Passiflora into 22 subgenera naming 355 species. Later Feuillet and MacDougal (2003) introduced a simplified infrageneric classification of only four subgenera, namely Astrophea, Deidamioides, Decaloba and Passiflora. * The Official List of Passiflora species 2010 (xls) (157 KB) by Yero R. Kuethe based on data from the MBG Tropicos site. It is a work in progress and updated versions will be added in due course. Many thanks to Yero for this. This list supercedes the C. Feuillet & J. M. MacDougal 2002 Checklist of recognized species names of Passion Flowers. Text only. PDF (86 KB) | 
