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Tuesday - March 13, 2012

From: Kerrville, TX
Region: Southwest
Topic: General Botany
Title: Are Cuscuta spp. (dodders) in Cuscutaceae or Convolvulaceae?
Answered by: Nan Hampton

QUESTION:

USDA plant database has the species Cuscuta in the CUSCUTACEAE FAMILY; you have it in the CONVOLVULACEAE FAMILY. Which is correct? Thank you.

ANSWER:

Our Native Plant Database shows all but one of the 13 species in the Genus Cuscuta (dodders) included in our Native Plant Database as being in the Family Cuscutaceae. There is one, however, Cuscuta cuspidata (Angel hair), that is, at present, mistakenly shown in our database as being in the Family Convolvulaceae.

There is some controversy about which family the Genus Cuscuta belongs in. Some botanists have it in the Family Cuscutaceae and some would put it in the Family Convolvulaceae. Our Native Plant Database follows the nomenclature used by the USDA Plants Database that has all the Cuscuta in the Family Cuscutaceae. The Integrated Taxonomic Information System (ITIS), however, lists all Cuscuta spp. under the Family Convolvulaceae. I found this statement under the entry for Cuscutaceae in Shinners and Mahler's Illustrated Flora of North Central Texas, page 572:

"Related to the Convolvulaceae and sometimes treated as a monogeneric tribe in that family; however, Cuscutaceae can be readily distinguished by their parasitic habit, absence of chlorophyll and lack of contact with the soil after parasitizing a host..."

You can read more about the choice of Cuscutaceae or Convolvulaceae in a 1999 lecture by James L. Reveal from the Norton-Brown Herbarium, University of Maryland.