The genus Philodendron can be divided into three subgenera which are very distinct in vegetative and floral morphology, floral anatomy and distribution. Phylogenetic and phenetic analysis of floral characters indicate that subgenus Meconostigma, which unlike subgenera Philodendron and Pteromischum has a predominantly southeastern range in South America, is highly apomorphic but cladistically primitive in the genus. Phenetic analyses show that the genus can be viewed as distinct, although no definitive diagnostic character is known to exist. These analyses also show that Philodendron is phenetically closer to certain west African genera (Culcasia, Cercestis, Rhektophyllum) than to the mainly Asiatic genera with it has been traditionally associated. Gynoecial morphology in subgen. Meconostigma varies considerably, with simpler forms predominating in southeastern Brazil, and the most elaborate in Amazonia. Outgroup comparison suggests that the simpler types are more primitive and indicates that the rupicolous species P. adamantinum Schott and P. leal-costae Mayo & G.M.Barroso possess the most primitive gynoecial type. Based on gynoecial morphology it is suggested that the subgenus evolved initially in eastern Brazil as a group adapted to open habitats, arriving only later in the Amazon basin. The other two subgenera, Philodendron aud Pteromischum, arose later, as epiphytes of humid forestes and today are most diverse in the northeast of South America
Philodendron; Araceae; biogeography; phylogenetic systematics