Apocynaceae (, from Apocynum, Greek for "dog-away") is a family of flowering plants that includes trees, shrubs, herbs, stem succulents, and vines, commonly known as the dogbane family, because some taxa were used as dog poison. Members of the family are native to the European, Asian, African, Australian, and American tropics or subtropics, with some temperate members. The former family Asclepiadaceae (now known as Asclepiadoideae) is considered a subfamily of Apocynaceae and contains 348 genera. A list of Apocynaceae genera may be found here.
Many species are tall trees found in tropical forests, but some grow in tropical dry (xeric) environments. Also perennial herbs from temperate zones occur. Many of these plants have milky latex, and many species are poisonous if ingested, the family being rich in genera containing alkaloids and cardiac glycosides, those containing the latter often finding use as arrow poisons. Some genera of Apocynaceae, such as Adenium, bleed clear sap without latex when damaged, and others, such as Pachypodium, have milky latex apart from their sap.
Taxonomy
As of 2012, the family was described as comprising some 5,100 species, in five subfamilies: Apocynoideae Burnett, 1835 Asclepiadoideae Burnett, 1835 (incorporating the Asclepiadaceae) Periplocoideae Endl., 1838 Rauvolfioideae Kostel., 1834 Secamonoideae Endl., 1838
The former family Asclepiadaceae is included in Apocynaceae according to the Angiosperm Phylogeny Group III (APG III) modern, largely molecular-based system of flowering plant taxonomy. An updated classification, including 366 genera, 25 tribes and 49 subtribes, was published in 2014.
376 genera are currently accepted.
Distribution and habitat
Species in this family are distributed mainly in tropical regions: In the tropical forests and swamps of Indomalaya: small to very tall evergreen trees up to tall, often with buttress roots, such as Alstonia and Dyera In northern Australia: small evergreen trees such as Alstonia, Alyxia, Cerbera and Ochrosia In deciduous forests of Africa, India and Indo-China: smaller trees such as Carissa, Wrightia and Holarrhena In tropical America, India, Myanmar and Malaya: evergreen trees and shrubs, such as Rauvolfia, Tabernaemontana and Acokanthera In Central America: Plumeria, or the frangipani, with its waxy white or pink flowers and a sweet scent In South America, Africa and Madagascar: many lianas, such as Landolphia In the Mediterranean region: Nerium, with the well-known oleander or be-still tree (Nerium oleander) and Apple of Sodom (Calotropis procera), with other (Calotropis) species extending into South Asia. The only genera found in temperate Europe away from the Mediterranean are Vinca (Rauvolfioideae) and Vincetoxicum (Asclepiadoideae). Also Asclepias syriaca is an invasive weed (e. g., in many areas of Ukraine). In North America: Apocynum, dogbane or Indian hemp, including Apocynum cannabinum, a traditional source of fiber. Also the bluestars, Amsonia, herbaceous perennials of upright habit, grown as ornamental plants for their attractive flowers. In continental southern Africa (Angola, Botswana, Eswatini, Mozambique, South Africa, and Zimbabwe) and Madagascar, except for the humid evergreen forest of the eastern side of Madagascar, and never above for the entire island: Pachypodium and Fockea
Description
Growth pattern
The dogbane/milkweed family includes annual plants, perennial herbs, stem succulents, woody shrubs, trees, or vines. Most exude a milky latex when cut.
Leaves and stems
Leaves are simple. They may appear one at a time (singly) with each occurrence on alternating sides of the stem (alternate), but usually occur in pairs (and rarely in whorls). When paired, they occur on opposite sides of the stem (opposite), with each pair occurring at an angle rotated 90° to the pair below it (decussate).
There is no stipule (a small leaf-like structure at the base of the leaf stem), or stipules are small and sometimes fingerlike.