Secondary spread largely determines the distribution and success of invasive species and depends ultimately on the capacity of the invader to disperse and colonise over multiple scales. Spread of the invasive seaweed Codium fragile ssp. fragile (Codium) can occur through the dispersal of vegetative fragments, which can be buoyant or non-buoyant depending on environmental conditions. This study examined the factors influencing the dispersal, settlement, and establishment of these two types of propagules in eelgrass (Zosteramarina) meadows of îles de la Madeleine, Canada, where Codium lives epiphytically on eelgrass rhizomes. To measure dispersal, ~1,400 Codium fragments were marked, released, and tracked under different hydrodynamic conditions in areas of high and low eelgrass density. Under all conditions, buoyant fragments dispersed one to two orders of magnitude further than non-buoyant fragments. Dispersal distance was positively correlated with wind speed (a proxy for surface currents in this system) for buoyant fragments and with current speed for non-buoyant fragments. For the latter, dispersal distance was also negatively correlated with eelgrass height and density. Natural deposition of drifting fragments in experimentally-manipulated eelgrass meadows was variable in space and time, but was not affected by eelgrass shoot density. Experimental disturbance of eelgrass meadows enhanced the density, biomass, and percent cover of Codium, suggesting that the exposure of eelgrass rhizomes by natural or anthropogenic disturbance promotes invasion by Codium. Our results highlight the importance of small-scale field experiments in determining the local factors affecting the spread of invasive species.
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This study was funded by the Canadian Aquatic Invasive Species Network (CAISN) of the Natural Sciences and Engineering Research Council (NSERC) of Canada, Québec-Océan, the Fondation Communautaire Gaspésie-les-Îles, and an NSERC Discovery Grant (LEJ). We greatly appreciate the logistical support of the Ministère de l’Agriculture, des Pêcheries et de l’Alimentation du Québec (MAPAQ) in Îles-de-la-Madeleine, especially M. Nadeau, B. Myrand, and F. Gallien. Finally we thank C. Chevrier-Turbide and O.Rhoades for assistance in the field, and V. Jormalainen for advice on statistical methods. We are also grateful for the comments of J. Ruesink and two anonymous reviewers which greatly improved the quality of this manuscript.
Bégin C, Scheibling RE (2003) Growth and survival of the invasive green alga Codium fragile ssp. tomentosoides in tide pools on a rocky shore in Nova Scotia. Bot Mar 46:404–412. doi:10.1515/BOT.2003.040CrossRefGoogle Scholar
Blakeslee AMH, McKenzie CH, Darling JA, Byers JE, Pringle JM, Roman J (2010) A hitchhiker’s guide to the Maritimes: anthropogenic transport facilitates long-distance dispersal of an invasive marine crab to Newfoundland. Divers Distrib 16:879–891. doi:10.1111/j.1472-4642.2010.00703.xCrossRefGoogle Scholar
Bushing WW (1994) Biogeographic and ecological implications of kelp rafting as a dispersal vector for marine invertebrates. In: Halvorson WL, Maender GJ (eds) The fourth California islands symposium: update on the status of resources. Santa Barbara Museum of Natural History, Santa Barbara, pp 103–110Google Scholar
Carlton JT, Scanlon JA (1985) Progression and dispersal of an introduced alga: Codium fragile ssp. tomentosoides (Chlorophyta) on the Atlantic coast of North America. Bot Mar 28:155–1665. doi:10.1515/botm.19188.8.131.52CrossRefGoogle Scholar
D’Amours O, Scheibling RE (2007) Effect of wave exposure on morphology, attachment strength and survival of the invasive green alga Codium fragile ssp. tomentosoides. J Exp Mar Biol Ecol 351:129–142. doi:10.1016/j.jembe.2007.06.018CrossRefGoogle Scholar
Drouin A (2013) Établissement et impacts de la macroalgue non indigène Codium fragile ssp. fragile dans les herbiers marins aux îles de la Madeleine. PhD Thesis, Université LavalGoogle Scholar
Drouin A, McKindsey CW, Johnson LE (2011) Detecting the impacts of notorious invaders: experiments versus observations in the invasion of eelgrass meadows by the green seaweed Codium fragile. Oecologia 168:491–502. doi:10.1007/s00442-011-2086-xCrossRefPubMedGoogle Scholar
Gaylord B, Reed DC, Raimondi PT, Washburn L, McLean SR (2002) A physically based model of macroalgal spore dispersal in the wave and current-dominated nearshore. Ecology 83:1239–1251. doi:10.1890/0012-9658(2002)083[1239:APBMOM]2.0.CO;2CrossRefGoogle Scholar
Helmuth B, Veit RR, Holberton R (1994) Long-distance dispersal of a subantarctic brooding bivalve (Gaimardia trapesina) by kelp-rafting. Mar Biol 120:421–426. doi:10.1007/BF00680216CrossRefGoogle Scholar
Irestedt M, Fabre P-H, Batalha-Filho H et al (2013) The spatio-temporal colonization and diversification across the Indo-Pacific by a “great speciator” (Aves, Erythropitta erythrogaster). Proc R Soc B 280:20130309. doi:10.1098/rspb.2013.0309
Johnson LE, Ricciardi A, Carlton JT (2001) Overland dispersal of aquatic invasive species: a risk assessment of transient recreational boating. Ecol Appl 11:1789–1799. doi:10.2307/3061096CrossRefGoogle Scholar
Johnson LE, Brawley SH, Adey WH (2012) Secondary spread of invasive species: historic patterns and underlying mechanisms of the continuing invasion of the European rockweed Fucus serratus in eastern North America. Biol Invasions 14:79–97. doi:10.1007/s10530-011-9976-zCrossRefGoogle Scholar
Kirk H, Paul J, Straka J, Freeland JR (2011) Long-distance dispersal and high genetic diversity are implicated in the invasive spread of the common reed, Phragmites australis (Poaceae), in northeastern North America. Am J Bot. doi:10.3732/ajb.1000278PubMedGoogle Scholar
Reed DC, Raimondi PT, Carr MH, Goldwasser L (2000) The role of dispersal and disturbance in determining spatial heterogeneity in sedentary organisms. Ecology 81:2011–2026. doi:10.2307/177289CrossRefGoogle Scholar
Scheibling RE, Melady RA (2008) Effect of water movement and substratum type on vegetative recruitment of the invasive green alga Codium fragile ssp. tomentosoides. Bot Mar 51:341–349. doi:10.1515/BOT.2008.046CrossRefGoogle Scholar
Shanks AL, Grantham BA, Carr MH (2003) Propagule dispersal distance and the size and spacing of marine reserves. Ecol Appl 13:159–169. doi:10.1890/1051-0761(2003)013[0159:PDDATS]2.0.CO%3B2CrossRefGoogle Scholar
Simard N, Paille N, McKindsey CW (2007) Codium fragile ssp. tomentosoides: revue de littérature et situation aux Îles-de-la-Madeleine. Can Manuscr Rep Fish Aquat Sci 2786, vii + 39 pGoogle Scholar
Vander Zanden MJ, Olden JD (2008) A management framework for preventing the secondary spread of aquatic invasive species. Can J Fish Aquat Sci 65:1512–1522. doi:10.1139/F08-099CrossRefGoogle Scholar
Vogel P, Cosson J-F, López Jurado LF (2003) Taxonomic status and origin of the shrews (Soricidae) from the Canary islands inferred from a mtDNA comparison with the European Crocidura species. Mol Phylogenet Evol 27:271–282. doi:10.1016/S1055-7903(02)00403-7