What is the difference between active and passive dispersal

In general, active dispersal is a density-dependent process. The magnitude of the process mainly depends on local population size, resource competition, and habitat quality and size. Snails and slugs show active dispersal and their dispersal is mainly influenced by population density, habitat complexity, climatic conditions and individual characteristics such as body size or behaviours. Passive dispersal is a mode of dispersal in which organisms need assistance to move from one place to another place.

Seeds of plants mainly disperse by passive dispersal. Marine invertebrates such as sponge and corals use passive dispersal. Those are sessile organisms. Hence, they utilize passive dispersal. Passive dispersal in seeds occurs in different ways. Seeds use water to disperse. Moreover, they can disperse by the wind. In order to disperse by wind, seeds and fruits have wings, hairs, or inflated processes.

Also, sticky seeds stick to clothes of animals and disperse. Furthermore, when animals feed on seeds and fruits, passive dispersal takes place. Similar to seeds, spores use wing and water to disperse.

Using passive dispersal, plants colonize new areas and habitats. At the population level, patterns of emigration and immigration within and among habitat patches associated with local population density, among other factors, drive temporal and spatial cycles of colonization and extinction. The form of such movements, such as stepping-stone versus one-way migration, ultimately determines the genetic structure of populations, wherein genetic differentiation is directly proportional to the amount of gene flow among populations.

For populations exhibiting frequent dispersal, ongoing gene flow within and among populations results in those populations becoming genetically similar to one another and ultimately evolving as a single unit. Finally, over evolutionary time frames, a lack of dispersal among populations impacts organisms at the species level.

If dispersal between populations ceases, these newly isolated populations accumulate novel genetic attributes via genetic drift or natural selection potentially leading to local adaptation. Insurmountable landscape features, such as mountains and rivers, typically drive such processes, and in cases where genetic differentiation persists even after dispersal between formerly isolated populations could resume, such entities can then be designated as separate species Figure 3.

Figure 3: Phylogenetic relationships of hypothetical populations that became isolated via dispersal Uppercase letters represent taxa, roman numerals represent geographic areas, black arrows represent dispersal events. All rights reserved. Species exhibit geographic distributions that are constrained by a range of environmental variables — outside of which individuals may experience reduced survival and reproduction due to physical and physiological constraints.

For example, species are often accustomed to particular temperature ranges, and dispersal to regions with temperatures outside those ranges reduces fitness. Additionally, resources necessary for population persistence may be insufficient at range edges and outside the range.

Physical barriers to dispersal consist of landscape features that prevent organisms from relocating. Mountains, rivers, and lakes are examples of physical barriers that can limit a species' distribution.

Anthropogenic barriers, like roads, farming, and river dams, also function as impediments to movement. It has been suggested that anthropogenic barriers are the most serious threats to dispersal. These barriers can effectively divide up a species' range into isolated fragments, and dispersal from one habitat patch to another can prove difficult. Creating dispersal corridors has been suggested as a means to maintain connectivity between habitat patches.

For example, Banff National Park in Alberta, Canada, contains 22 underpasses and 2 overpasses to facilitate wildlife dispersal within the park across a busy four-lane highway the Trans-Canada Highway. Similarly, wildlife crossings, specifically designed for Florida panthers, were constructed along a forty-mile stretch of Interstate 75 in Florida.

Corridors are not just for large mammals either: Salamanders have also benefited from miniature underpasses to facilitate dispersal. Additionally, recent research has focused on using modeling techniques to analyze available habitat to designate potential dispersal pathways for species whose ranges have been fragmented Figure 4. Source populations in the West were as follows: A. Badlands, ND; B. Black Hills, SD; C. Kimble County, TX. Anabrus simplex with radio transmitters attached see Lorch et al.

Direct methods can be somewhat easier to use in larger animals simply because tracking the smallest organisms e. However, tracking devices are becoming increasingly more advanced and useful in small organisms Figure 5. Interpretation of results from direct measurement can sometimes prove difficult though. Low accuracy of spatial position, disproportionate mortality of marked individuals, labor intensity, and high costs are all deterrents to using direct measurement methods.

In contrast to direct methods, indirect methods infer the degree of dispersal without actually having to observe the dispersal movement. Typically, indirect methods involve utilizing molecular markers to measure gene flow and deduce dispersal patterns based on within and among population genetic differences.

Specifically, the differences in allele or genotype frequencies resulting from gene flow between populations reveal patterns and levels of dispersal. Indirect methods are increasingly being used to infer dispersal because of the difficulties involved with direct measurement. Human activities have facilitated and impeded dispersal in many ways.

As stated previously, anthropogenic barriers in the form of human development have disrupted natural dispersal patterns in a variety of species. Conversely, humans have also facilitated dispersal, both deliberately and accidentally. A common inadvertent way organisms have been dispersed is through their transport in the ballast water of ships. Ships emptying ballast water may release foreign organisms.

For example, zebra mussels, a freshwater mollusk native to the lakes of southeast Russia, were accidentally introduced into the Great Lakes of North America where they have caused major economic problems by clogging water treatment and power plants through ballast water discharge.

As a result of the potential for introduction of non-native organisms via ballast water, new standards have been proposed for ballast tank cleaning. Humans have also transported organisms to areas outside their native ranges for deliberate reasons. The seeds of attractive plants native to areas outside North America are routinely used in gardens and have the capacity to disperse to wild areas if conditions are suitable e.

Also, bighead and silver carp originating from China were introduced to catfish farm ponds in the United States to control algal growth. Fish accidentally escaped from these ponds and have subsequently colonized the Mississippi, Missouri, Illinois and Ohio rivers where they have had significant negative impact on the native fauna Figure 6. Dispersal is a common process undertaken by individuals at different stages of the life cycle and in response to various factors.

Morphological adaptations make dispersal achievable but with varying degrees of success due to anthropogenic and natural barriers. These barriers modify the level of dispersal and consequently exert effects on population dynamics and genetic structure. As environments are altered, through stochastic events and global climate change, it will become increasingly important to assess how such changes will affect dispersal at the individual, population, and species levels.

Avise, J. Phylogeography: The History and Formation of Species. Freeze, M. North American Journal of Fisheries Management 2 , — doi Johnson, C. Mortality risk increases with dispersal distance in American martens. Larue, M. Modelling potential dispersal corridors for cougars in midwestern North America using least-cost path methods. Ecological Modelling , — doi Lorch, P. Radiotelemetry reveals differences in individual movement patterns between outbreak and non-outbreak Mormon cricket populations.

Ecological Entomology 30 , — doi Mate, B. Satellite-monitored movements of the northern right whale.

Journal of Wildlife Management 61 , — Mix, C. Regional gene flow and population structure of the wind-dispersed plant species Hypochaeris radicata Asteraceae in an agricultural landscape. Molecular Ecology 15 , — doi Matthysen, E. Density-dependent dispersal in birds and mammals.

Ecography 28 , — doi: Penrod, K. Sorensen, A. Seed dispersal by adhesion. Annual Review of Ecology and Systematics 17 , — Sword, G. Biogeography of microscopic organisms. Wharton DA. Curr Biol. Survival in extreme environments—on the current knowledge of adaptations in tardigrades. Acta Physiol. Jenkins DG, et al. Does size matter for dispersal distance? Glob Ecol Biogeogr. Dormancy in invertebrates. Invert Biol. Alpert P. The limits and frontiers of desiccation-tolerant life.

Int Comp Biol. Watanabe M. Anhydrobiosis in invertebrates. Appl Entomol Zool. CAS Google Scholar. Diapause in monogonont rotifers. Biology, Ecology and Systematics 2nd ed. In: HJF D, editor. Ghent: Kenobi Productions; On dormancy strategies in tardigrades. J Ins Physiol. McSorley R. Adaptations of nematodes to environmental extremes.

Florida Ent. Developmental stages in diapausing eggs: an investigation across monogonont rotifer species. Modes, mechanisms and evidence of bet hedging in rotifer diapause traits. Dormancy and dispersal as mediators of zooplankton population and community dynamics along a hydrological disturbance gradient in inland temporary pools.

The monopolization hypothesis and the dispersal-gene flow paradox in aquatic organisms. Acta Oecol. Shurin JB. Dispersal limitation, invasion resistance, and the structure of pond zooplankton communities. Spatial autocorrelation and dispersal limitation in freshwater organisms.

PubMed Google Scholar. The metacommunity concept: a framework for multi-scale community ecology. Body size and dispersal mode as key traits determining metacommunity structure of aquatic organisms.

Morphological response of a bdelloid rotifer to desiccation. J Morphol. Anhydrobiosis: the extreme limit of desiccation tolerance. Invert Surv J. Tunnacliffe A, Wise MJ. The continuing conundrum of the LEA proteins. Foreign genes and novel hydrophilic protein genes participate in the desiccation response of the bdelloid rotifer Adineta ricciae. J Exp Biol. Rebecchi L. Dry up and survive: the role of antioxidant defences in anhydrobiotic organisms.

J Limnol. Gateway to genetic exchange? DNA double-strand breaks in the bdelloid rotifer Adineta vaga submitted to desiccation. J Evol Biol. Ricci C, Pagani M. Desiccation of Panagrolaimus rigidus Nematoda : survival, reproduction and the influence on the internal clock. Ricci C, Covino C. Anhydrobiosis of Adineta ricciae : costs and benefits. Anhydrobiosis in tardigrades and its effects on longevity traits.

J Zool. Ricci C. Traunspurger W. The biology and ecology of lotic nematodes. Freshwat Biol. Nelson DR. Current status of the Tardigrada: evolution and ecology. Wilson C, Sherman P. Anciently asexual bdelloid rotifers escape lethal fungal parasites by drying up and blowing away. Grewal PS. Anhydrobiotic potential and long-term storage of entomopathogenic nematodes Rhabditida: Steinernematidae.

Int J Parasitol. The anhydrobiotic potential and molecular phylogenetics of species and strains of Panagrolaimus Nematoda, Panagrolaimidae. Anhydrobiotic capabilities of bdelloid rotifers. Colonising strategies and diapause of planktonic rotifers Monogononta, Rotifera during aquatic and terrestrial phases in a floodplain lower Oder Valley, Germany.

Int Rev Hydrobiol. Ricci C, Caprioli M. Anhydrobiosis in bdelloid species, populations and individuals. Wright JC. Desiccation tolerance and water-retentive mechanisms in tardigrades. Dynamics of long-term anhydrobiotic survival of lichen-dwelling tardigrades. Variation in anhydrobiotic survival of two eutardigrade morphospecies: a story of cryptic species and their dispersal. Horizontal gene transfer in bdelloid rotifers is ancient, ongoing and more frequent in species from desiccating habitats.

BMC Biol. Survival and DNA degradation in anhydrobiotic tardigrades. Antioxidant defences in hydrated and desiccated states of the tardigrade Paramacrobiotus richtersi. Anhydrobiosis in tardigrades—the last decade.

J Insect Physiol. Hatching phenology and resting eggs in tardigrades. Long-term survival of microscopic animals under desiccation is not so long. Long-term anhydrobiotic survival in semi-terrestrial micrometazoans. Experiences with dormancy in tardigrades. A molecular study of the tardigrade Echiniscus testudo Echiniscidae reveals low DNA sequence diversity over a large geographical area.

Steiner G, Albin FM. Resuscitation of the nematode Tylenchus polyhypnus , n. J Wash Acad Sci. Fielding MJ. Observations on the length of dormancy in certain plant infecting nematodes. Proc Helminth Soc Wash. Studies on genetic variations of the rotifer Brachionus plicatilis O. PhD Thesis, Nagasaki University. Dynamics of rotifer and cla- doceran resting stages during copper pollution and recovery in a subalpine lake.

Ann Limnol — Int J Limnol. Age and survivorship of diapausing eggs in a sediment egg bank. Hairston NG Jr. Zooplankton egg banks as biotic reservoirs in changing environments. Limnol Oceanogr. Invertebrate biodiversity in Antarctic dry valley soils and sediments. Determining habitat suitability for soil invertebrates in an extreme environment: the McMurdo dry valleys.

Antarctica Antarct Sci. Exceptional tardigrade-dominated ecosystems in Ellsworth Land. Antarctica Ecology. The geographic distribution of metazoan microfauna on East Antarctic nunataks. Polar Biol. Diversity gradients of rotifer species richness in Antarctica.

Macrotrachela quadricornifera featured in a space experiment. Tardigrades survive exposure to space in low earth orbit. Extreme stress tolerance in tardigrades: surviving space conditions in low earth orbit. J Zool Syst Evol Res.

Fontaneto D, Hortal J. At least some protist species are not ubiquitous. Mol Ecol. Niches and distributional areas: concepts, methods, and assumptions. Thermophilic bacteria in cool temperate soils: are they metabolically active or continually added by global atmospheric transport? Appl Microbiol Biotechnol. Variation in algal dispersal and recruitment: the importance of episodic events. Ecol Monogr.

Reducing redundancy in invasion ecology by integrating hypotheses into a single theoretical framework. Divers Distrib. Rotifera, Chapter 4. In: Schmidt-Rhaesa A, editor. Handbook of Zoology, Gastrotricha, Cycloneuralia and Gnathifera. Volume 3, Gastrotricha and Gnathifera. Berlin: De Gruyter GmbH; Gilabert A, Wasmuth JD. Unravelling parasitic nematode natural history using population genetics. Trends Parasitol. Dispersal of Ramazzottius and other tardigrades in relation to type of reproduction.

Invert Reprod Dev. Dispersal in freshwater invertebrates. Annu Rev Ecol Syst. Are distribution patterns linked to dispersal mechanisms? An investigation using pond invertebrate assemblages.

Nathan R. Long-distance dispersal of plants. Ronce O. How does it feel to be like a rolling stone? Ten questions about dispersal evolution. Annu Rev Ecol Evol Syst. Ecological methods. Oxford, UK: Blackwell; Maguire B. The passive dispersal of small aquatic organisms and their colonization of isolated bodies of water. Bonte D, Dahirel M. Dispersal: a central and independent trait in life history.

Krishnan A, et al. Funct Ecol. Passive external transport of freshwater invertebrates by elephant and other mud-wallowing mammals in an African savannah habitat.

Freshwat Biol ;— Dispersal patterns and behaviour of the nematode Phasmarhabditis hermaphrodita in mineral soils and organic media. Soil Biol Biochem. The passive dispersal of viable algae, protozoans, and fungi by aquatic and terrestrial Coleoptera. Ann Ent Soc Am.

The dispersal of microorganisms by a hemipteran, Lethocerus uhleri Montandon. Trans Am Micr Soci. Zoochorous dispersal of freshwater bivalves: an overlooked vector in biological invasions? Knowl Manag Aquat Ecosyst. News records of phoresy and hyperphoresy among treefrogs, ostracods, and ciliates in bromeliad of Atlantic forest.

Biodivers Conserv. Bryophyte dispersal by flying foxes: a novel discovery. Dispersal of freshwater invertebrates by large terrestrial mammals: a case study with wild boar Sus scrofa in Mediterranean wetlands. Invertebrate dispersal by aquatic mammals: a case study with nutria Myocastor coypus Rodentia, Mammalia in southern France. Role of human-mediated dispersal in the spread of the pinewood nematode in China. PLoS One. Unintentional dispersal of aquatic invertebrates via footwear and motor vehicles in a Mediterranean wetland area.

Aquatic Conserv. Implications of waterbird ecology for the dispersal of aquatic organisms.