title: Fronts, jumps and secondary introductions suggested as different invasion patterns in marine species, with an increase in spread rates over time.
abstract: Not all introduced (invasive) species in a region will spread from a single point of introduction. Long-distance dispersal or further introductions can obscure the pattern of spread, but the regional importance of such processes is difficult to gauge. These difficulties are further compounded when information on the multiple scale process of invasive species range expansion is reduced to one-dimensional estimates of spread (e.g. km yr(-1)). We therefore compared the results of two different metrics of range expansion: maximum linear rate of spread and accumulation of occupied grid squares (50 x 50 km) over time. An analysis of records for 54 species of introduced marine macrophytes in the Mediterranean and northeast Atlantic revealed cases where the invasion process was probably missed (e.g. Atlantic Bonnemaisonia hamifera) and suggested cases of secondary introductions or erratic jump dispersal (Dasysiphonia sp. and Womersleyella setacea). A majority of species analysed showed evidence for an accumulation of invaded sites without a clear invasion front. Estimates of spread rate are increasing for more recent introductions. The increase is greater than can be accounted for by temporally varying search effort and implies a historical increase in vector efficiency and/or a decreased resistance of native communities to invasion.
authors.affiliation: School of Biological Sciences, Medical Biology Centre, 97 Lisburn Road, Belfast BT9 7BL, UK.
authors.forename: Frédéric
authors.initials: F
authors.lastname: Mineur
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Davies
authors.forename: Christine A
authors.initials: CA
authors.lastname: Maggs
authors.forename: Marc
authors.initials: M
authors.lastname: Verlaque
authors.forename: Mark P
authors.initials: MP
authors.lastname: Johnson
mesh_terms: D001267:Atlantic Ocean; D044822:Biodiversity; D056890:Eukaryota / Q000502:physiology*; D005843:Geography; D008522:Mediterranean Sea; D012044:Regression Analysis; D013997:Time Factors
references.citation: Science. 1998 Jan 23;279(5350):555-8
references.pmid: 9438847
references.citation: Ecol Lett. 2006 Jun;9(6):663-72
references.pmid: 16706911
references.citation: Mar Pollut Bull. 2002 Jan;44(1):32-8
references.pmid: 11883681
references.citation: Proc Natl Acad Sci U S A. 2005 Jan 25;102(4):1088-91
references.pmid: 15657121
references.citation: Proc Natl Acad Sci U S A. 2003 Mar 18;100(6):3321-3
references.pmid: 12615995