ABSTRACT: As one component of invasion resistance, native predators may consume non-indigenous species in the invaded habitat. I studied the contribution of predation to mortality in populations of a potentially dominant, habitat-modifying mussel (Musculista senhousia) which has been introduced from Asia to California. In short-term (2 to 4 wk) experiments performed in San Diego Bay, a muricid snail (Pteropurpura festiva) decimated transplanted mussel populations by up to 65% within 2 wk. Crustacean predators were responsible for mortality rates of <4%. The experimental removal of byssal cocoons in M. senhousia did not increase the susceptibility of the mussel to predation compared to unmanipulated individuals. In all experiments, predation was more intense inside an eelgrass (Zostera marina) bed compared to either unvegetated clearings or to sand flats adjacent to the eelgrass bed. In a 4 mo predator exclusion experiment, mussel numbers were reduced by 95% in the eelgrass compared to a decimation of only 36 and 50% on the unvegetated sand flat above and below the Z. marina bed, respectively. An aquarium experiment revealed that P. festiva favored M. senhousia over an abundant native clam in San Diego Bay, Chione undatella. In southern California, predation contributes significantly to the resistance of the recipient community to invasion and may locally prevent M. senhousia from establishing dense, habitat-modifying beds with potential effects on native infauna and eelgrass.

KEY WORDS: Biological invasion · Community ecology · Ecological resistance · Non-indigenous species · Musculista senhousia · Predation · Pteropurpura festiva · Zostera marina

Published in MEPS Vol. 170 (1998) on September 3
ISSN: 0171-8630. Copyright © Inter-Research, Oldendorf/Luhe, 1998