title: Relationship between propagule pressure and colonization pressure in invasion ecology: a test with ships' ballast.
abstract: Increasing empirical evidence indicates the number of released individuals (i.e. propagule pressure) and number of released species (i.e. colonization pressure) are key determinants of the number of species that successfully invade new habitats. In view of these relationships, and the possibility that ships transport whole communities of organisms, we collected 333 ballast water and sediment samples to investigate the relationship between propagule and colonization pressure for a variety of diverse taxonomic groups (diatoms, dinoflagellates and invertebrates). We also reviewed the scientific literature to compare the number of species transported by ships to those reported in nature. Here, we show that even though ships transport nearly entire local communities, a strong relationship between propagule and colonization pressure exists only for dinoflagellates. Our study provides evidence that colonization pressure of invertebrates and diatoms may fluctuate widely irrespective of propagule pressure. We suggest that the lack of correspondence is explained by reduced uptake of invertebrates into the transport vector and the sensitivity of invertebrates and diatoms to selective pressures during transportation. Selection during transportation is initially evident through decreases in propagule pressure, followed by decreased colonization pressure in the most sensitive taxa.
authors.affiliation: Great Lakes Laboratory for Fisheries and Aquatic Sciences, Fisheries and Oceans Canada, Burlington, Ontario, Canada, L7R 4A6. elizabeta.briski@dfo-mpo.gc.ca
authors.forename: Elizabeta
authors.initials: E
authors.lastname: Briski
authors.forename: Sarah A
authors.initials: SA
authors.lastname: Bailey
authors.forename: Oscar
authors.initials: O
authors.lastname: Casas-Monroy
authors.forename: Claudio
authors.initials: C
authors.lastname: DiBacco
authors.forename: Irena
authors.initials: I
authors.lastname: Kaczmarska
authors.forename: Colin
authors.initials: C
authors.lastname: Levings
authors.forename: Michael L
authors.initials: ML
authors.lastname: MacGillivary
authors.forename: Christopher W
authors.initials: CW
authors.lastname: McKindsey
authors.forename: Leslie E
authors.initials: LE
authors.lastname: Nasmith
authors.forename: Marie
authors.initials: M
authors.lastname: Parenteau
authors.forename: Grace E
authors.initials: GE
authors.lastname: Piercey
authors.forename: André
authors.initials: A
authors.lastname: Rochon
authors.forename: Suzanne
authors.initials: S
authors.lastname: Roy
authors.forename: Nathalie
authors.initials: N
authors.lastname: Simard
authors.forename: Maria C
authors.initials: MC
authors.lastname: Villac
authors.forename: Andréa M
authors.initials: AM
authors.lastname: Weise
authors.forename: Hugh J
authors.initials: HJ
authors.lastname: MacIsaac
mesh_terms: D000818:Animals; D057219:Biofouling; D017377:Diatoms / Q000145:classification / Q000502:physiology*; D004141:Dinoflagellida / Q000145:classification / Q000502:physiology*; D017753:Ecosystem; D019015:Geologic Sediments / Q000382:microbiology / Q000469:parasitology; D058865:Introduced Species; D007448:Invertebrates / Q000145:classification / Q000502:physiology*; D012623:Seawater / Q000382:microbiology / Q000469:parasitology; D012767:Ships