Competitive co-existence of the dorid nudibranchs Doridella steinbergae and Corambe pacifica

Abstract

The roles of resource partitioning and environmental variability in the competitive coexistence of the dorid nudibranchs Doridella steinbergae and Corambe pacifica are examined in this study. These species CO-occur episodically in southern California Macrocystis kelp beds during periods of high abundances of their bryozoan prey, Membranipora membranacea. Veligers of both species settle prior to peak prey densities because of the higher age-specific prey requirements of older nudibranchs. C. pacdica settles before D. steinbergae during periods of nuhbranch occurrence because of longer development times. Coupled w t h age-specific feeding rates, this difference In appearance increases the potential for competltlon by maximizing the concurrent demand for prey by both species, and therefore contradicts the expectations of resource partitioning theory. Spahal and temporal variations in the relative abundance of prey can account for the coexistence of the nudibranchs. Prey abundances span the range from insufficient (no nudibranch reproduction poss~ble), to limilng (some reproduction possible), to overabundant (maximum reproduction poss~ble). These variat~ons allow the relative advantages of both D steinbergae (reproductive efficiency) and C. pacifica (fecundity) to be expressed.