Untangling the Systematics of Salt Marsh Dodders: Cuscuta pacifica a New Segregate Species from Cuscuta salina (Convolvulaceae)

Abstract

The salt marsh dodders, Cuscuta salina, have been historically delimited as a morphologically variable assemblage of inbreeding forms that parasitize hosts growing in alkaline or saline habitats from western North America. This morphological diversity has been tradi- tionally classified into three varieties: salina , major , and papillata . A morphometric analysis of floral characters and a molecular study using both plastid and nuclear DNA sequences strongly support the segregation of a new species, Cuscuta pacifica Costea and M. A. R. Wright, from C. salina . The new species corresponds to a lineage that includes varieties major and papillata , whereas C. salina is limited essentially to its type variety. Cuscuta pacifica and C. salina are sister species that have only a small area of parapatry in lower California, where they are ecologically and reproductively separated. Cuscuta salina occurs mostly in inland vernal pools and salt flats of Arizona, California, Nevada, Utah, Baja California, and Sonora, and grows primarily on Frankenia and Suaeda . Cuscuta pacifica can be found in salt marshes from the south- central Pacific coast of California north into British Columbia, parasitic especially on Salicornia and Jaumea carnosa . Cuscuta salina var. papillata (Yunck.) Costea and M. A. R. Wright, parasitic on hosts that grow in coastal interdunes, falls within the range of variation of C. pacifica , where it is transferred.