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Marine Ecology Progress Series

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MEPS 604:163-171 (2018)  -  DOI:

Intraspecific trade-offs between facilitation and competition in the invasive mollusc Crepidula fornicata

Xavier de Montaudouin1,*, Chiara Accolla2

1University of Bordeaux-CNRS, UMR EPOC 5805, Station Marine d’Arcachon, 33120 Arcachon, France
2Department of Ecology, Evolution and Behavior, University of Minnesota, Minnesota 55108, USA
*Corresponding author:

ABSTRACT: We tested the hypothesis that high-density populations of the non-indigenous gastropod Crepidula fornicata increase settlement of conspecific recruits (facilitation process), and that this facilitation is balanced by competition processes. To verify our hypothesis, we sampled C. fornicata at 2 drastically different densities for 10 yr. We found that at high densities, the number of 1 yr old individuals per square meter colonizing the habitat and individual growth performances were higher in comparison with the low-density condition (Allee effect). In contrast, the production/biomass ratio (P/B), a good indicator of population fitness, was lower at higher densities. We relate this lower P/B ratio to the deficit of young individuals compared to adult biomass. We conclude that the net effect of high density on the conspecific colonization processes of the population is positive, thanks to the higher available hard substrate for larvae (facilitation). However, intraspecific competition also occurs and mitigates this positive effect. Therefore, we suggest that it is particularly important to take into account the ‘net’ balance between costs and benefits (i.e. what we observe) when analyzing population growth, in order to better understand its dynamics.

KEY WORDS: Crepidula fornicata · Facilitation · Competition · P/B ratio · Non-indigenous species · Population dynamics

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Cite this article as: de Montaudouin X, Accolla C (2018) Intraspecific trade-offs between facilitation and competition in the invasive mollusc Crepidula fornicata. Mar Ecol Prog Ser 604:163-171.

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