Modeling variation in interaction strength between barnacles and fucoids |
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Authors: | Rebecca L Kordas Steve Dudgeon |
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Institution: | (1) Department of Biology, California State University, Northridge, CA 91330-8303, USA;(2) Department of Zoology, University of British Columbia, 6270 University Boulevard, Vancouver, BC, V61Z4, Canada |
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Abstract: | The strength by which species interact can vary throughout their ontogeny, as environments vary in space and time, and with
the density of their populations. Characterizing strengths of interaction in situ for even a small number of species is logistically
difficult and may apply only to those conditions under which the estimates were derived. We sought to combine data from field
experiments estimating interaction strength of life stages of the barnacle, Semibalanus balanoides, on germlings of Ascophyllum nodosum, with a model that explored the consequences of variability at per capita and per population levels to the abundance of year-old
algal recruits. We further simulated how this interaction affected fucoid germling abundance as the timing of their respective
settlements varied relative to one another, as occurs regionally across the Gulf of Maine, USA. Juvenile S. balanoides have a weak estimated per capita effect on germlings. Germling populations are sensitive to variation in per capita effects
of juvenile barnacles because of the typically large population sizes of the latter. However, high mortality of juvenile barnacles
weakens the population interaction strength over time. Adult barnacles probably weakly facilitate fucoid germlings, but greater
survival of adults sustains the strength of that interaction at the population level. Germling abundance is positively associated
with densities of adult barnacles and negatively associated with that of juvenile barnacles. Metamorphosing cyprid larvae
have the strongest per capita effect on germling abundance, but the interaction between the two stages is so short-lived that
germling abundance is altered little. Variation in the timing of barnacle and A. nodosum settlement relative to one another had very little influence on the abundance of yearling germlings. Interactions between
barnacles and germlings may influence the demographic structure of A. nodosum populations and the persistence of fucoid-dominated communities on sheltered rocky shores in New England.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. |
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Keywords: | Per capita interaction strength Population dynamics Semibalanus balanoides Ascophyllum nodosum Gulf of Maine |
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