Document: KEV-3-37-25

Factors in the control of parasite population that has abundant hosts: Cuscuta salina in the salt marsh.

CUMMINS, K.* and D.H.DEUTSCHMAN

San Diego State University, San Diego, CA 92182 USA ¹

Abstract:
Cuscuta salina is a parasitic plant found in the salt marshes of the northeastern Pacific. This species has been observed to parasitize most of the species found in our three San Diego County study sites. These hosts form large high density stands, although C. salina is not common these stands. We investigated factors controlling the abundance of C. salina. Quadrat and transect sampling was carried out to identify host and parasite patterns in relation to each other and to elevation. Although C. salina was found on all perennial salt marsh species, its abundance and frequency was highest within a 50cm middle elevation band. Beyond that band, presence was infrequent and absent at extremes. Greenhouse experiments were conducted to determine if inundation and salt stress could account for the distribution of C. salina. Inundation was found to significantly increase mortality in C. salina whereas increased salt stress did not illicit a significant change in mortality. We speculate that all individuals in the host population are suitable for parasite establishment and growth except at low elevations. Low densities of the parasite in higher elevations may be explained by dispersal limitation. Spatial distributions of C. salina and their hosts were mapped at multiple scales for up to three years. Cuscuta salina was significantly clustered in space and time. With field experiments we are currently testing the assumption that all individuals in high elevations are suitable hosts.

Keywords: Parasite Host interaction, Parasitic plant, Salt marsh, Cuscuta salina, Salicornia virginica, disperal limitation, spatial distribution, k-function analysis

This abstract is being presented at: 4:00 PM in session:
Oral Session #15: Parasitoids and Diseases.