title: Impacts associated with the recent range shift of the aeolid nudibranchPhidiana hiltoni(Mollusca, Opisthobranchia) in California.
abstract: In 1977,Phidiana hiltoni(O'Donoghue in J. Entomol Zool (Pomona College, Claremont, California) 19:77-119, 1927) began spreading northward from Monterey, California. By 1992, it had reached Duxbury Reef (37° 53' 23″ N, 122° 41' 59″ W), 100 km to the north, where other nudibranchs subsequently appeared to decline. The role ofP.hiltoniin this decline was investigated through diet analysis, feeding trials, and comparison of historical and recent abundance data. In the wild,P.hiltonipreyed largely on hydroids, but also showed evidence of predation on nudibranchs. In the laboratory,P.hiltoniattacked most of the dendronotid and aeolid nudibranchs presented to it, ingesting small individuals whole. The pooled abundance of nudibranchs vulnerable to attack byP.hiltonideclined an average of two-thirds at Duxbury Reef since its arrival, compared to (1) no change in the non-vulnerable species and (2) no change in either group at two other sites whereP.hiltoniwas one to two orders of magnitude less abundant.Phidianahiltonitherefore appears to have caused this decline, likely through a combination of direct predation and competition for prey. A brief larval period, combined with cyclonic re-circulation in the lee of Point Reyes, may be driving self-recruitment ofP.hiltoniat Duxbury Reef, as well as hindering further northward spread.
authors.affiliation: Marine Science Institute, University of California, Santa Barbara, CA 93106-6150 USA.
authors.forename: Jeffrey H R
authors.initials: JH
authors.lastname: Goddard
authors.affiliation: Department of Invertebrate Zoology and Geology, California Academy of Sciences, San Francisco, CA 94103 USA.
authors.forename: Terrence M
authors.initials: TM
authors.lastname: Gosliner
authors.affiliation: Department of Invertebrate Zoology and Geology, California Academy of Sciences, San Francisco, CA 94103 USA ; Long Marine Laboratory, University of California, Santa Cruz, CA 95060 USA.
authors.forename: John S
authors.initials: JS
authors.lastname: Pearse