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Topic: Drift migration

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	PopGen: Models (Site not responding. Last check: 2007-11-04)
		Migration, which refers to the movement of the individuals between subpopulations, is the "glue" that holds subpopulations together, that sets a limit to how much genetic divergence can occur.
		If the subpopulations are finite in size, then genetic drift may result in random differences among them even with migration.
		If migration is restricted to adjacent populations, then movement forms a stepping stone pattern.
	cc.oulu.fi /~jaspi/popgen/models.htm (375 words)

	Bird migration - Wikipedia, the free encyclopedia
		Many species of land birds migrate very long distances, the most common pattern being for birds to breed in the temperate or arctic northern hemisphere and winter in warmer regions, often in the tropics or the southern hemisphere.
		An interesting example where a change of migration route has occurred because of such a geographical barrier is the trend for some Blackcaps in central Europe to migrate west and winter in Britain rather than cross the Alps.
		An example is the migration of continental populations of Swainson's Thrush, which fly far east across North America before turning south via Florida to reach northern South America; this route is believed to be the consequence of a range expansion that occurred about 10,000 years ago.
	en.wikipedia.org /wiki/Bird_migration (2367 words)

	Migration of Birds
		Fall migration in coastal Louisiana and the evolution of migration patterns in the Gulf region.
		Migration routes of the Arctic Tern (Sterna paradisaea Brunnich).
		The role of migration and winter mortality in the life history of a temperate-zone migrant, the Dark-eyed Junco, as determined from demographic analyses of winter populations.
	www.npwrc.usgs.gov /resource/othrdata/migratio/bibliog1.htm (1530 words)

	Bird migration (Site not responding. Last check: 2007-11-04)
		Many species of land birds migrate very long distances, the most common pattern beingfor birds to breed in the temperate or arctic northernhemisphere and winter in warmer regions, often in the tropics or the southern hemisphere.
		An interesting example where a change of migration route has occurred because ofsuch a geographical barrier is the trend for some Blackcaps in central Europe tomigrate west and winter in Britain rather than cross the Alps.
		Drift migration of birds blown off course by the wind can result in "falls" of large numbers ofmigrants at coastal sites.
	www.therfcc.org /bird-migration-19757.html (2022 words)

	Evolutionary Genetics
		In this view, four evolutionary forces (mutation, random genetic drift, natural selection, and gene flow) acting within and among populations cause micro-evolutionary change and these processes are sufficient to account for macro-evolutionary patterns, which arise in the longer term from the collective action of these forces.
		The force of migration or gene flow has effects on genetic variation that are the opposite of those caused by random genetic drift.
		Despite the not infrequent occurrence of small population sizes where drift would be expected to be most efficacious, random genetic drift was considered an irrelevant evolutionary force in ecological genetics because natural selection was viewed as being particularly strong during periods of population decline.
	plato.stanford.edu /entries/evolutionary-genetics (6345 words)

	[No title]
		Migration and selection are complimentary - if the number of migrants with a genotype is large and natural selection favors that phenotype, it will increase rapidly in the population, especially if the migration is a recurring one.
		Genetic drift occurs in populations of all sizes, but its effects are much more pronounced in small populations, where the genetic composition of a few individuals makes a significant impact on the gene pool.
		An example of the effects of random genetic drift on natural populations is provided by a study of the fish occupying warm springs in the Death Valley region of California and Nevada.
	www.gwu.edu /~darwin/BiSc150/PopGen/Drift.htm (1889 words)

	Bird migration (Site not responding. Last check: 2007-11-04)
		The Whinchat Saxicola rubetra of Europe is a long-distance migrant wintering in the tropics, whereas its close relative, the Stonechat Saxicola torquata is resident in most of its range, and moves only short distances from the colder north and east.
		Those which have long distance migrants in the same family, like the Chiffchaff, are species of southern hemisphere origins which have progressively shortened their return migration so that they stay in the northern hemisphere.
		The same considerations about barriers and detours that apply to long distance land bird migration apply to water birds, but in reverse: a large area of land without bodies of water that offer feeding site is a barrier to a water bird.
	www.sciencedaily.com /encyclopedia/bird_migration (2161 words)

	Drift and migration of juvenile Atyoida bisulcata, an endemic Hawaiian amphidromous shrimp - NABS Communication ...
		Both drift and migration occurred throughout the summer, with peaks in late April and early July, and both appeared to be influenced by lunar phase.
		Drift and migration were correlated and both were nearly zero in mid May, mid June and mid August.
		Drift fell in late July, while migration was greatest on the same sampling date, which may be explained by sampling error.
	www.benthos.org /database/allnabstracts.cfm/db/Athens2003abstracts/id/373 (262 words)

	Evolutionary Analysis Chapter 6 -- Text Answers--Genetics II (migration, drift, non-random mating) (Site not responding. Last check: 2007-11-04)
		Migration causes a small population's gene frequencies to move toward the large population's.
		The allele can then be maintained in the new small populaton for many years (and genetic drift while the population is small may even increase the frequency of the allele, in spite of selection against the disease).
		Migration, genetic drift, and inbreeding have greater effects in small populations.
	cwx.prenhall.com /bookbind/pubbooks/freemanea2/chapter6/custom1/deluxe-content.html (1141 words)

	Population Genetics
		Chance genetic fluctuations, called random genetic drift, result in dispersion of gene frequencies of small, genetic isolates as time goes on.
		Migration among subpopulations counteracts the genetic differentiation caused by genetic drift.
		If a founder happens to be a carrier of an otherwise rare allele and has many descendants, the allele - be it harmful or not - may reach an appreciable frequency as a result of genetic drift.
	www.thecanadianencyclopedia.com /index.cfm?PgNm=TCE&Params=A1SEC644163 (455 words)

	Encyclopedia: Bird migration (Site not responding. Last check: 2007-11-04)
		The Northern Hemisphere is the half of a planets surface (or celestial sphere) that is north of the equator (the word hemisphere literally means half ball).
		Reverse migration is a phenomenon in bird migration.
		Chart of ocean surface temperature anomaly [Â°C] during the last strong El NiÃ±o in December 1997 El NiÃ±o and La NiÃ±a (Spanish for the boy and the girl, often written in English as El Nino and La Nina) are major temperature fluctuations in the tropical Pacific Ocean.
	www.nationmaster.com /encyclopedia/bird-migration (4924 words)

	Spurn - Wikipedia, the free encyclopedia
		The mud flats are an important feeding ground for wading birds, and the area has a bird observatory, for monitoring migrating birds and providing accommodation to visiting birdwatchers.
		Their migration is assisted by east winds in autumn, resulting in drift migration of Scandinavian migrants, sometimes leading to a spectacular "fall" of thousands of birds.
		Material is washed down the coast by longshore drift and accumulates to form the long, narrow embankment in the sheltered waters inside the mouth of the Humber estuary.
	www.wikipedia.org /wiki/Spurn (523 words)

	Genetic drift (Site not responding. Last check: 2007-11-04)
		Genetic drift is a mechanism of evolution that acts in concert with natural selection to change the characteristics of species over time.
		Like selection, it acts on populations, altering the frequency of alleles and the predominance of traits amongst members of a population, and changing the diversity of the group.
		Drift is observed most strongly in small populations and results in changes that need not be adaptive.
	www.kiwipedia.com /en/genetic-drift.html (98 words)

	Overview
		To evolutionary biologists, migration means gene flow, the transfer of alleles from the gene pool of one population to the gene pool of another population.
		Migration can be caused by anything that moves alleles far enough to go from one population to another.
		The actual amount of migration among populations in different species varies enormously, depending on how mobile individuals or populations are at various stages of the life cycle.
	wps.prenhall.com /esm_freeman_evol_3/0,8018,849200-,00.html (587 words)

	Continental drift (Site not responding. Last check: 2007-11-04)
		The concept was initially ridiculed by most geologists, who felt that an explanation of how a continent drifted was a prerequisite and that the lack of one made the idea of drifting continents wholly unreasonable.
		The hypothesis of continental drift became part of the larger theory of plate tectonics.
		Fossil patterns across continents Evidence for continental drift is now extensive, in the form of plant and animal fossils of the same age found around different continent shores, suggesting that these shores were once joined.
	www.kiwipedia.com /en/continental-drift.html (663 words)

	[No title]
		The reason is not evolution; rather it is migration during periods of glaciation which pushed the biomes toward the equator.
		The wobbling of planet Earth causes periods of glaciation and continental drifting towards and away from the equator influences climate.
		Once the colonists have established themselves and built up their population size, some individuals may migrate either to different habitats within the same island or to other nearby islands and become isolated long enough the evolve into a new species.
	www.holycross.edu /departments/biology/whealy/notes_text/e.text (4314 words)

	Drift migration (Site not responding. Last check: 2007-11-04)
		Drift migration is the phenomenon in which migrating birds are blown off course by the winds at the time they arein flight.
		Drift is assisted by disorientating conditions such as mist or drizzle, and can result in large numbers of birds arrivingtogether in an area in which they are not normally seen.
		An example would be an east wind in September blowing Scandinavian migrants such as Bluethroats, Wrynecks and the continental race of Robin onto the eastcoast of England and Scotland, leadingto temporary concentrations of these species at headlands like Spurn.
	www.therfcc.org /drift-migration-155320.html (162 words)

	Ch 6. Migration, Genetic Drift, Non-Random Mating (Site not responding. Last check: 2007-11-04)
		Founder effect" is a special case of genetic drift: the small size of a founder population almost guarantees that its allele frequencies will not be identical to the parent population.
		Migration - "In an evolutionary sense, the movement of alleles between populations" (p.
		Migrations reduces diversity among populations of intermediate age.
	faculty.buffalostate.edu /penaloj/bio405/outline6.html (1089 words)

	Workpackage: Migration/drift
		Recent work (2000) has involved allowing the proportions which migrate between areas to vary from year to year, yet in a time series fashion, so that too much variability in migration is penalised.
		A baseline model for migration of capelin was set up and parameters connected to year-to-year migration of immature capelin were estimated in order to test the software.
		A model for migration where the individual migration vector depends on temperature and current will be built and tested on migration of pre-spawning capelin in the above period in the course of 2002.
	www.hafro.is /dst2/report2/node20.html (725 words)

	Drift and migration
		is the migration rate, the fraction of individuals in a population that is composed of immigrants.
		Normally we'd think about the forwards migration rate, i.e., the probability that a randomly chosen individual with go to a different population in the next generation, but backwards migration rates turn out to be more convenient to work with in most population genetic models.
		In populations with only ten individuals, drift will be operating much more quickly, so it takes a large proportion of immigrants to keep populations from diverging.
	darwin.eeb.uconn.edu /eeb348/lecture-notes/mutation-drift/node4.html (557 words)

	Estimating Effective Population Size and Migration Rates From Genetic Samples Over Space and Time -- Wang and Whitlock ...
		of migration in the estimation of demographic parameters from
		The populations are assumed to have no previous migration (case A) or be at drift-migration equilibrium (case B) when the first sample from the focal population is taken.
		equilibrium between drift and migration (Fig 1 and Fig 2).
	www.genetics.org /cgi/content/full/163/1/429 (7066 words)

	Biology 301 - Lecture 5
		The intensity of this process of random genetic drift is dependent upon population size.
		Small populations drift a great deal from one generation to the next, and large populations drift little.
		If P is the proportion of A alleles in the surrounding habitat, then "A" alleles migrate into the local area each generation when fraction "m" of the surrounding population migrates in.
	www.biol.sc.edu /%7Ewethey/301/drift_migration_mutation.html (694 words)

	WP 2.1 Migration and drift models
		The noise distribution is dependent on the difference between actual velocity and that required to arrive at the preferred location, ie the closer their velocity to the destination, the closer to uniform the noise is. The preferred direction could be due to a feeding migration, temperature gradient, food gradient etc.
		The aims of this are to aid the assessment of which type of model could be used in a more general prediction model, test which factors might control migration, test assumptions about importance of external parameters.
		It is a continuous counterpart to the previous discrete model and a counterpart to the compartmentalised model.
	www.hafro.is /dst2/report2/node173.html (690 words)

	LECTURE 2
		Drift is the result of random choice of gametes that will participate in the next generation.
		Migration thus tends to avoid complete homogeneity due to drift.
		If migration is a once only phenomenon, and involves a group of some size, which operates a resettlement to a new area where there are favorable chances of giving rise to a successful colony, and therefore there is population increase after the initial bottleneck at migration time, then the result is the opposite.
	www.unipv.it /iuss/safi/wang/lezione2.htm (1539 words)

	Bird migration (Site not responding. Last check: 2007-11-04)
		An interesting example where a change of migration route has occurred because of such a geographical barrier is the trend for some Blackcaps in central Europe to migrate west and winter in Great Britain rather than cross the Alps.
		The climate of the breeding area is important, and few species can cope with the harse winters of inland Canada or northern Eurasia.
		The most pelagic species, mainly in the order Procellariiformes, are great wanderers, and the albatrosses of the southern oceans may circle the globe as they ride the "roaring forties" outside the breeding season.
	www.portaljuice.com /bird_migration.html (1714 words)

	Population Genetics Glossary
		Drift is one of the major forces of evolutionary change (along with natural selection, mutation, genetic migration, and non-random mating).
		The equilibrium/balance between drift and mutation is a major focus of much of population genetics.
		Thus, a 'migrating' warbler does not cause any migration (in the genetic sense) by moving from breeding grounds in Wyoming to wintering grounds in Mexico and then returning to breed in the same Wyoming locale.
	www.uwyo.edu /dbmcd/popecol/Maylects/PopGenGloss.html (3420 words)

	MIGRATION/DRIFT BALANCE
		But here we must make the assumption that the islands are at equilibrium between drift and migration.
		This assumption is dubious because the islands may in fact be slowly diverging since colonization, and there may be no migration at all.
		In other words drift and migration are not at equilibrium.
	www.ucl.ac.uk /~ucbhdjm/courses/b242/MigEvol/Fst=1over1+4Nm.html (607 words)

	Study and Review
		Define migration in the context of evolutionary biology.
		Explain the role of selection and migration in the maintenance of polymorphism in banding patterns in island forms of the Lake Erie water snake.
		When genetic drift is the only mechanism of evolution operating, what is the relationship between the rate of evolution, the rate of substitution, and the mutation rate?
	wps.prenhall.com /esm_freeman_evol_3/0,8018,849217-,00.html (676 words)

	UGa Statistics: Abstract (Site not responding. Last check: 2007-11-04)
		A simple two-locus drift model for cytonuclear systems is developed, in which the stochastic dynamics of cytonuclear genotypic frequencies are specified.
		Trajectories for the first two moments of both genotypic and allelic disequilibria are given under three scenarios: (i) random drift alone; (ii) random drift with mutation; and (iii) random drift with migration.
		The utility of this simple two-locus drift model in testing the neutrality of mitochondrial DNA markers in artificial hybrid zones is briefly illustrated.
	www.stat.uga.edu /tech_reports/tech.rpt.abs/94/94-42.html (98 words)

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