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Glossary  See Carlton and Ruiz (2005) for a framework for the standardization of terms and definitions associated with vector science. Allee effects — density-dependent phenomena that can cause the per-capita rate of population growth to decline with decreasing population size (Kramer and Drake, 2010) ballast water exchange — transfer of water from a ship’s ballast systems to the environment, with concomitant (“continuous exchange” method) or subsequent (“empty-refill” method) uptake of water; generally intended to take place in off- shore (open ocean) waters (cf. salt-water flushing) with a goal or removing or reducing the original contents and associated biota from coastal or nearshore habitats. Note that the target for exchange (100 percent for empty refill or 300 percent flow-through by volume) is intended to achieve 95 percent replacement of the original water. ballast water management — (1) in the context of reducing invasions, ballast- ing practices designed to minimize the uptake or discharge of living organisms; techniques or treatments designed to remove, kill or inactivate prior to their dis- charge, organisms inadvertently taken up when water is brought into tanks or ballasted holds; (2) independent of invasion biology considerations, the move- ment of water into and out of ships’ ballast tanks and ballasted holds in such a way as to maximize stability and safety of the ship, its crew, and cargo. cryptogenic — a species that cannot be reliably demonstrated as native or non- indigenous. diapausing — describes a period during which physiological activity is sus- pended. discharge standard — criteria for the maximum concentration of living organ- isms that may be discharged by a ship when discharging ballast; the value is established by a regulatory or governing body. donor region — dispersal hub within which a species interfaces with a transport mechanism (Carlton, 1996); synonymous with “source region.” establishment probability — used interchangeably herein with “invasion risk”; the chance that one or more individuals establishes a self-maintaining popula- tion.   137 

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138    Glossary    euryphagic — a species exhibiting broad feeding range. eurytopic — a species exhibiting broad habitat and physiological breadth. founder effect — a reduction in genetic diversity occurring when a novel popu- lation is established by a relatively small number of colonists. holoplankton — organisms having their entire life history in the planktonic (free-swimming) state. inoculum density (ID or DI) —the total number of organisms in the inoculum (NI) divided by the volume of the inoculum (VI) (Minton et al., 2005), i.e., DI = NI / VI. initial population size — the initial number of organisms released into the envi- ronment in a given location at a given time, i.e., the inoculum number (NI). In its simplest formulation, the organisms’ density in the environment (DE) is given as the number of organisms released (NI) divided by the volume of water in the environment (VE), i.e., DE = NI / VE. invasion rate — the number of nonindigenous species that establish in a given region per unit time. invasion risk — see establishment probability. invasive species — a broad term for a nonindigenous species to which is attri- buted environmental, ecological, economic, or societal harm, or a combination of these. lecithotrophic — refers to planktonic larvae whose nutrition is yolk derived from their egg. meroplankton — defined as organisms having planktonic life stages for part of their life history. metapopulations — spatially separated populations of the same species that are linked by dispersal. microorganism — a wide variety of microscopic organisms consisting of a sin- gle cell or cell cluster; includes viruses, which are not cellular (Madigan and Martinko, 2006); synonymous with “microbe.” models — conceptual, graphical, or mathematical descriptions of a phenomenon or process. Here we define two major categories that are not mutually exclu-

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Glossary  139    sive, but which represent very different modeling philosophies and goals: de- scriptive models represent the shape of the relationship, often in graphic form; mechanistic models define the processes generating the relationship (e.g., Drake and Jerde, 2009) and consist of two general classes, probabilistic statements and dynamic, demographic models. nonindigenous species — a species not naturally (historically) found in a par- ticular geographic location or region; synonymous with non-native, alien, intro- duced, exotic, and foreign (cf. invasive species). parthenogenetic — describing a form of reproduction in which an unfertilized egg develops into a new individual, occurring commonly among insects and certain other arthropods. pathway — a term used to encompass (a) why a species is transported, whether accidentally or deliberately (cause), (b) the geographic path over which a spe- cies is transported (route) and (c) how a species is transported (vector) (Carlton and Ruiz, 2005). polyvectic — species transported by more than one vector (Carlton and Ruiz, 2005); cf. vector. probability of establishment (PE) — probability of establishing a self- sustaining population. propagule — any living biological material (particles, cells, spores, eggs, lar- vae, and mature organisms) transported from one location to another. propagule pressure — a general term expressing the quantity, quality, and fre- quency with which propagules are introduced to a given location. Propagule pressure is a function of a suite of variables reflecting the nature of the species and the transport vector. recipient region — endpoint of dispersal spoke at which a species is released (initial point of inoculation) (Carlton, 1996); synonymous with target region. risk–release relationship — the relationship between invasion risk and propa- gule pressure for a single or multiple species. It expresses the number of spe- cies that establish as a function of the large-scale release of a varying number of varying species at varying densities. The relationship between invasion risk and propagule pressure is generally held to be positive although the shape of the curve may vary considerably.

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140    Glossary    salt-water flushing — the input of salt water to a ship’s seemingly empty or partially filled ballast tank with the intent of (1) imposing a lethal physiological shock to organisms therein or (2) removing residual living organisms and sedi- ments, which are then pumped back out into the open sea (“rinse and spit”) (cf. ballast water exchange). vector — how a species is transported, that is, the physical means or agent (such as ballast, hulls, or movement of commercial oysters) (Carlton and Ruiz, 2005) (cf. polyvectic). vector strength — the relative number or rate of established invasions that re- sult within a specified time period from a given vector in a particular region (Carlton and Ruiz, 2005). virus — A genetic element containing either DNA or RNA that replicates in cells but is characterized by having an extracellular state (Madigan and Martin- ko, 2006). REFERENCES Carlton, J. T., and G. M. Ruiz. 2005. Vector science and integrated vector management in bioinvasions ecology: conceptual frameworks. Pp. 36–58 In: Invasive Alien Spe- cies. A New Synthesis. Mooney H. A., Mack R. N., McNeely J. A. , Neville L. E. , Schei P. J., Waage J. K., editors. Scope 63. Washington, DC: Island Press. Carlton, J. T. 1996. Pattern, process, and prediction in marine invasion ecology. Biolog- ical Conservation 78:97–106. Drake, J. M., and C. Jerde. 2009. Stochastic models of propagule pressure and estab- lishment. Chapter 5 In: Bioeconomics of invasive species: integrating ecology, eco- nomics, policy, and management. Keller, R. P., Lodge, D. M, Lewis, M. A., and Shogren, J. F. (editors). New York: Oxford University Press. Kramer, A. M., and J. M. Drake. 2010. Experimental demonstration of population ex- tinction due to a predator-driven Allee effect. Journal of Animal Ecology 79:1365– 2656. Madigan, M. T., and J. M. Martinko. 2006. Biology of Microorganisms. Upper Saddle River, NJ: Pearson Prentice Hall. Minton, M. S., E. Verling, A. W. Miller, and G. M. Ruiz. 2005. Reducing propagule supply and coastal invasions via ships: Effects of emerging strategies. Frontiers in Ecology and the Environment 3:304–308.