This is the first revision of Philodendron subg. Philodendron since that of K. Krause in Das Pflanzenreich in 1913. Philodendron subg. Philodendron, the largest of the three subgenera, includes 103 taxa (95 species and 8 subspecies or varieties) for Central America. Sixty-eight taxa are new to science. These include 62 species: P. albisuccus Croat, P. alticola Croat & Grayum, P. augustilobum Croat & Grayum, P. annulatum Croat & Grayum, P. antonioanum Croat, P. aromaticum Croat & Grayum. P. baheri Croat & Grayum, P. breedlovei Croat, P. brewsterense Croat, P. brunneicaule Croat & Grayum, P. chiriquense Croat, P. chirripoense Croat & Grayum, P. clewellii Croat, P. coloradense Croat, I! copense Croat, P. correae Croat, P. cotobrusense Croat & Grayum, P. cetonense Croat & Grayum, P. crassispathum Croat & Grayum, P. cretosum Croat & Grayum, P. dodsonii Croat & Grayum, P. dolichophyllum Croat, P. dominicalense Croat & Grayum, P. dwyeri Croat, P. edenudatum Croat, P. ferrugineum Croat, P. findens Croat 8; Grayum, P. folsomii Croat, P. fortunense Croat, P. gigas Croat. P. granulare Croat, P. grayumii Croat, P. hammelii Croat, P. hebetatum Croat, I? heleniae Croat, P. immixtum Croat, P. jefense Croat, P. knappiae Croat, P. lazorii Croat, P. lentii Croat & Grayum, P. llanense Croat, P. madronense Croat. P. malesevichiae Croat. P. morii Croat, P. niqueanum Croat, P. pirrense Croat, P. pseudauriculatum Croat, P. purulhense Croat, P. roseospathum Croat, P. scalarinerve Croat & Grayum, P. sousae Croat, P. squamicaule Croat & Grayum, P. squamipetiolatum Croat, P. straminicaule Croat, P. sulcicaule Croat & Grayum, P. thalassicum Croat & Grayum, P. tysonii Croat, P. ubigantupense Croat, P. utleyanum Croat, P. verapazense Croat, Fl wilburii Croat & Grayum, P. zhuanum; 6 infraspecific taxa: P. davidsonii Croat subsp. bocatoranum Croat, P. hederaceum (Jacq.) Schott var. kirkbridei Croat, P. ligulatum Schott var. heraclioanum Croat, P. ligulatum Schott var. ovatum Croat, P. roseospathum Croat var. angustilaminatum Croat, P. wilburii var. longipedunculatum Croat & Grayum; and 2 new combinations: P. hederaceum (Jacq.) Schott var. oxycardium (Schott) Croat, P. radiatum Schott var. pseudoradiatum (Matuda) Croat. Species diversity of P. subg. Philodendron in Central America shows a general diminution from Mexico to Middle America, followed by a marked increase closer to South America. Mexico has 21 taxa, Guatemala 15, Belize 9, El Salvador 5, Honduras 13 Nicaragua 18, Costa Rica 49, and Panama 80, respectively. Endemism is high, especially for Panama where 39 taxa are currently considered endemic. Mexico and Costa Rica each have 7 endemic species. With the exception of Belize, which has 1 endemic, no other country in Middle America has any endemic species. Only 26 species (28 taxa), a total of 20% of all Central American species, range into South America, 8 species (7% of the total) only to Colombia.
