The Santalales are an order of flowering plants of eudicots. Well-known members of the Santalales include sandalwoods and the many species of mistletoes. The order has a cosmopolitan distribution, but is heavily concentrated in tropical and subtropical regions. It derives its name from its type genus, Santalum (sandalwood).
Overview Many of the members of the order are parasitic plants, mostly hemiparasites, able to produce sugars through photosynthesis, but tapping the stems or roots of other plants to obtain water and minerals; some (e.g. Arceuthobium) are obligate parasites, have low concentrations of chlorophyll within their shoots (1/5 to 1/10 of that found in their host's foliage), and derive the majority of their sustenance from their hosts' vascular tissues (water, micro- and macronutrients, and sucrose). Most have seeds without testae (seed coats), which is unusual for flowering plants.
Classification The APG IV system of 2016 includes seven families. As in the earlier APG III system, it was accepted that Olacaceae sensu lato was paraphyletic but new family limits were not proposed as relationships were considered uncertain. As of July 2021, this seven-family division of the Santalales was explicitly accepted by the World Flora Online, and implicitly by Plants of the World Online, in that it accepted none of the extra families recognized by other sources. The seven families are:
Balanophoraceae Loranthaceae Misodendraceae Olacaceae Opiliaceae Santalaceae Schoepfiaceae When only these families are recognized, one possible phylogenetic relationship among them is shown below. Support for some of the nodes is weak, and at least two families, Olacaceae s.l. and Balanophoraceae s.l., are not monophyletic:
A summary of the circumscription and phylogeny of the Santalales published in 2020 used 20 rather than seven families. Olacaceae s.l. was divided into seven families, Balanophoraceae s.l. was divided into two, and Santalaceae s.l. into seven. As of July 2021, the Angiosperm Phylogeny Website accepted the families resulting from the division of Olacaceae s.l. and Balanophoraceae s.l. but not those from the division of Santalaceae s.l.
Earlier systems In the classification system of Dahlgren, the Santalales were in the superorder Santaliflorae (also called Santalanae). The Cronquist system (1981) used this circumscription:
order Santalales family Medusandraceae – sole genus Medusandra now in family Peridiscaceae, order Saxifragales family Dipentodontaceae – now in order Huerteales in APG IV family Olacaceae family Opiliaceae family Santalaceae family Misodendraceae family Loranthaceae family Viscaceae - sunk into Santalaceae s.l. in the seven-family system family Eremolepidaceae - sunk into Santalaceae s.l. in the seven-family system family Balanophoraceae
Gallery of type genera
References
Hawksworth, FG (1996). Dwarf mistletoes : biology, pathology, and systematics. USDA For. Serv. Agric. Handb. p. 409. Soltis, Douglas E.; Soltis, Pamela S.; Endress, Peter K.; Chase, Mark W. (2005-06-15). Phylogeny & Evolution of Angiosperms. Sinauer Associates. p. 370. ISBN 978-0-87893-817-9. Santalales on the Parasitic Plant Connection web page NCBI Taxonomy Browser
