Assessing the Relationship Between Propagule Pressure and Invasion Risk in Ballast Water (2011) / Chapter Skim
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3 Sources of Variation Influencing the Probability of Invasion and Establishment
3 Sources of Variation Influencing the Probability of Invasion and Establishment
Pages 55-71
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From page 55... ...
Further influencing the outcome of propagule release is a host of factors that include both species traits and the recipient region's environmental traits. The following equation reflects the complex and uncertain relationship between propagule pressure, other variables, and the probability of establishment: PE = f (PP, ε)
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From page 56... ...
These sources of variation shown in Figure 3-1 are reviewed below. This overview is not a comprehensive list of all factors that can influence invasion success, but is intended to illustrate significant sources of variation that are likely to influence the relationship between propagule supply and invasion outcome.
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From page 57... ...
Sources of Variation Influencing the Probability of Invasion and Establishment 57 FIGURE 3‐1 Examples of variables altering establishment probability (PE) of nonindigenous species released in ballast water and sediments. Processes in the right hand column impact the outcome of survival, reproduction, and establishment.
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From page 58... ...
The underlying mechanisms may include differences in physiological tolerance, competitive ability, and life history. For example, it has been suggested that biota from some geographic regions may be more successful in invading, compared to others, due to competitive superiority or particular suites of life history characteristics that have evolved in those regions (Vermeij, 1991, 1996)
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From page 59... ...
SPECIES TRAITS Species traits that influence the density and quality of propagules upon discharge (discussed above) include a host of characteristics that describe the life history, genetics, biology, and eventual population abundance of a species should it survive initial release.
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From page 60... ...
versus releasing planktonic larvae, sexual versus asexual reproduction, and the ability to form resting stages. An example of direct development facilitating an invasion is the recent establishment of the North Atlantic rocky shore snail Littorina saxatilis in San Francisco Bay (Carlton and Cohen, 1998)
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From page 61... ...
, these new individuals, the first to be born in the new location, could, in turn, form dispersed metapopulations with a lowered probability of the newly colonizing species going extinct. The processes that influence the fates of both the initial founder population and F1 reflect the entire suite of species traits and environmental traits already discussed that influence the probability of colonization, including the variables of demographic stochasticity discussed in Chapter 4.
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From page 62... ...
The differences are perhaps most striking when comparing biota from open-ocean, coastal marine bays and estuaries, and freshwater, which can differ in taxonomic groups, functional groups, species life histories, and species environmental tolerances. Such large inter-habitat differences are thought to result in major barriers to invasions.
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From page 63... ...
ENVIRONMENTAL TRAITS A number of abiotic and biotic processes play a significant role in determining the invasion success of organisms in discharged ballast water. These are discussed below, focusing first on abiotic characteristics of the recipient region, followed by biotic interactions between invaders and species in recipient regions, and finally the role of disturbance regimes. Scale of Habitat Fragmentation or Connectivity Several characteristics of coastlines and bays/estuaries are likely to influence the likelihood of establishment and spread of propagules introduced by
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From page 64... ...
. The differences in life history coupled with the spatial separation of low salinity estuaries along the west coast may have provided an effective obstacle to subsequent spread for mitten crabs but not for green crabs.
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From page 65... ...
could facilitate invasion, particularly if the species involved represent novel trophic modes in the recipient system. Further facilitating establishment could be the presence of species that would provide food or refugia for invading propagules.
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From page 66... ...
Inocula with high genetic variability may also be favored. Further favoring establishment are biological characteristics such as being eurytopic and euryphagic, and life history characteristics such as direct development, asexual reproduction, and/or the ability to form resting stages.
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From page 67... ...
While it is extremely difficult to quantitatively prioritize all of these variables that vary across species, space, and time, initial habitat compatibility and propagule retention are likely to be critical. The importance of the latter two variables underscore the relative role of inoculum density: very low inocula that match these two scenarios along with the other "best-case" criteria above could lead to highly successful invasions.
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From page 68... ...
1995. Introduction, dispersal and po tential impacts of the green crab Carcinus maenas in San Francisco Bay, California.
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From page 69... ...
2005. Alteration of wetland ecosystems in San Francisco Bay by Spartina hybrid invasion.
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From page 70... ...
2005. A life history model for the San Francisco Estuary population of the Chinese mitten crab, Eriocheir sinensis (Decapoda : Grapsoidea)
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From page 71... ...
2000. Fish and ships: relat ing dispersal frequency to success in biological invasions.
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