Appendix S1: Detailed diet information for benthic, subtidal mollusc species
Native herbivorous molluscs are ubiquitous in shallow, subtidal habitats in this
region. The snail Calliostoma ligatum is an herbivore that feeds on a variety of algae
(Vadas 1968, Morris et al. 1980). The chiton Cryptochiton stelleri is a specialist on
understory red algae (Yates 1989) and commonly ingests the entire thallus of individual
red algae (personal observation). Other chiton species, including Lepidochitona dentiens,
Mopalia spp., and Lepidozona spp. feed on a variety of algae including diatoms and noncoralline crusts (Fulton 1975, Smith 1975, O’Clair and O’Clair 1998). Finally, the limpet
Acmea mitra and the chiton Tonicella spp. specialize on crustose coralline algae
(Demopulos 1975, Morris et al. 1980, O’Clair and O’Clair 1998) and Acmea is known to
scrape these crusts down to bare rock (Padilla 1984). Collectively, these species are a
source of frequent, small-scale disturbances, creating microsites that can be used by
newly arriving species including Sargassum muticum.
Online Appendix A Literature Cited
Demopulos, P. A. 1975. Diet, activity and feeding in Tonicella lineata (Wood, 1815).
Veliger (Suppl) 18:42-46.
Fulton, F. T. 1975. The diet of the chiton Mopalia lignosa (Gould, 1846). Veliger
18(Suppl.):38-41.
Morris, R. H., D. P. Abbott, and E. C. Haderlie. 1980. Intertidal invertebrates of
California. Stanford University Press, Stanford, CA.
O’Clair, R. M., and C. E. O’Clair. 1998. Southeast Alaska’s rocky shores: Animals. Plant
Press, Auke Bay, AK.
Padilla, D. K. 1984. The importance of form differences in competitive ability, resistance
to consumers, and environmental stress in an assemblage of coralline algae. Journal
of Experimental Marine Biology and Ecology 79:105-128.
Smith, S. Y. 1975. Temporal and spatial activity patterns of the intertidal chiton Mopalia
muscosa. Veliger 18(Suppl.):57-62.
Vadas, R. L. 1968. The ecology of Agarum and the kelp bed community. Ph.D.
dissertation. University of Washington.
Yates, K. R. 1989. The feeding ecology of the gumboot chiton, Cryptochiton stelleri
(Middendorff, 1846). Ph.D. Thesis, Oregon State University.