London Underground mosquito
Encyclopedia
The London Underground mosquito is a species of mosquito
in the genus Culex
found in the London Underground
. It is thought to have evolved
from the overground species Culex pipiens recently. Biologist
s named the London Underground mosquito Culex pipiens molestus due to its voracious biting. Notably the London C.p. molestus assaulted Londoners sleeping in the Underground during the Blitz
, although similar populations were already known. The name seems to already have been given to a species of mosquito found in Australia
, named as long ago as 1775. The London Underground mosquito, although first discovered in the London Underground
system, has been found in underground systems around the world. It is suggested that it may have adapted to human-made underground systems since the last century from local above-ground Culex pipiens
, although more recent evidence suggests that it is a southern mosquito variety related to Culex pipiens
that has adapted to the warm underground spaces of northern cities.
The evidence for this mosquito being a different species
from Culex pipiens comes from research by Kate Byne and Richard Nichols. The species have very different behaviours, are extremely difficult to mate, and with different allele frequency
consistent with genetic drift
during a founder event. More specifically, this mosquito, Culex pipiens molestus, breeds all-year round, is cold intolerant, and bites rats, mice, and humans, in contrast to the above ground species Culex pipiens
that is cold tolerant, hibernates in the winter, and bites only birds. When the two varieties were cross-bred the eggs were infertile suggesting reproductive isolation.
Since that paper more information has accumulated. The fundamental results still stand: the genetic data indicate that the molestus form in the London Underground appeared to have a common ancestry, rather than the population at each station being related to the nearest above-ground population (i.e. the pipiens form). Byrne and Nichols' working hypothesis was that adaptation to the underground environment had occurred locally in London once only – since there are many hurdles to jump in order to become adapted to the subterranean environment, it is understandable that it would occur rarely. This hypothesis implies that local adaptation would be expected in different locations around Europe and beyond, as each local pipiens population evolved an offshoot that overcame the problems of living underground.
However, more recently-collected genetic evidence suggests that a single molestus form has spread throughout Europe and beyond, since populations over a large area share a common genetic heritage. These widely separated populations are distinguished by very minor genetic differences, which suggest that the molestus form developed recently: a single mtDNA difference shared among the underground populations of ten Russian cities; a single fixed microsatellite difference in populations spanning Europe, Japan, Australia, the middle East, and Atlantic islands. This worldwide spread might have occurred after the last glaciations or be even more recent, due to the insects hitch hiking on world trade routes. One possibility is the international second-hand tire trade. The tires retain water in which the larvae can survive (Completely removing water from an old tire can be difficult).
What has always been more intriguing about the molestus story was that the reproductive isolation in north European populations appears to be almost complete, whereas there is clearly gene flow
between them in populations to the south. Byrne and Nichols attributed this pattern to the inability of the underground form (and perhaps their hybrids) to survive above ground in harsh northern winters.
Now it appears that the persistence of hybrids in northern climates may be another evolutionary problem that can be solved but only rarely: the Fonseca paper obtained genetic evidence that the recent colonization of America by Culex mosquitoes actually involves a strain derived from a rare successful hybridization between pipiens and molestus. They suggest that hybridization may explain why the American form bites both birds and humans (this interpretation is controversial, see letter from Spielman et al. and the response that follows it in Science
). The consequences of this more indiscriminate feeding hit the news in 1999 with the outbreak of human encephalitis in New York, caused by West Nile virus. It was the first documented introduction of this virus into the Western Hemisphere; perhaps because in the longer established populations the old world northern above-ground pipiens almost exclusively bite birds, the human biting ones being incarcerated below ground.
in the borough
of Manhattan
, New York City
. The mosquito is well known for being in commonly found in sewers of New York and thrive throughout the year feeding off of humans. Residents of older brownstones
found the mosquitoes coming from the underground into basements and then through air vents and other openings into the homes. The city government did not make this infestation of the pest a top priority because they tested negative for West Nile Virus
and the high cost of mosquito control.
Mosquito
Mosquitoes are members of a family of nematocerid flies: the Culicidae . The word Mosquito is from the Spanish and Portuguese for little fly...
in the genus Culex
Culex
Culex is a genus of mosquito, and is important in that several species serve as vectors of important diseases, such as West Nile virus, filariasis, Japanese encephalitis, St. Louis encephalitis and avian malaria....
found in the London Underground
London Underground
The London Underground is a rapid transit system serving a large part of Greater London and some parts of Buckinghamshire, Hertfordshire and Essex in England...
. It is thought to have evolved
Evolution
Evolution is any change across successive generations in the heritable characteristics of biological populations. Evolutionary processes give rise to diversity at every level of biological organisation, including species, individual organisms and molecules such as DNA and proteins.Life on Earth...
from the overground species Culex pipiens recently. Biologist
Biologist
A biologist is a scientist devoted to and producing results in biology through the study of life. Typically biologists study organisms and their relationship to their environment. Biologists involved in basic research attempt to discover underlying mechanisms that govern how organisms work...
s named the London Underground mosquito Culex pipiens molestus due to its voracious biting. Notably the London C.p. molestus assaulted Londoners sleeping in the Underground during the Blitz
The Blitz
The Blitz was the sustained strategic bombing of Britain by Nazi Germany between 7 September 1940 and 10 May 1941, during the Second World War. The city of London was bombed by the Luftwaffe for 76 consecutive nights and many towns and cities across the country followed...
, although similar populations were already known. The name seems to already have been given to a species of mosquito found in Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
, named as long ago as 1775. The London Underground mosquito, although first discovered in the London Underground
London Underground
The London Underground is a rapid transit system serving a large part of Greater London and some parts of Buckinghamshire, Hertfordshire and Essex in England...
system, has been found in underground systems around the world. It is suggested that it may have adapted to human-made underground systems since the last century from local above-ground Culex pipiens
Culex pipiens
Culex pipiens is a species of blood-feeding mosquito of the family Culicidae. It is a vector of some diseases, such as Japanese encephalitis, meningitis, Urticaria...
, although more recent evidence suggests that it is a southern mosquito variety related to Culex pipiens
Culex pipiens
Culex pipiens is a species of blood-feeding mosquito of the family Culicidae. It is a vector of some diseases, such as Japanese encephalitis, meningitis, Urticaria...
that has adapted to the warm underground spaces of northern cities.
The evidence for this mosquito being a different species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
from Culex pipiens comes from research by Kate Byne and Richard Nichols. The species have very different behaviours, are extremely difficult to mate, and with different allele frequency
Allele frequency
Allele frequency or Gene frequency is the proportion of all copies of a gene that is made up of a particular gene variant . In other words, it is the number of copies of a particular allele divided by the number of copies of all alleles at the genetic place in a population. It can be expressed for...
consistent with genetic drift
Genetic drift
Genetic drift or allelic drift is the change in the frequency of a gene variant in a population due to random sampling.The alleles in the offspring are a sample of those in the parents, and chance has a role in determining whether a given individual survives and reproduces...
during a founder event. More specifically, this mosquito, Culex pipiens molestus, breeds all-year round, is cold intolerant, and bites rats, mice, and humans, in contrast to the above ground species Culex pipiens
Culex pipiens
Culex pipiens is a species of blood-feeding mosquito of the family Culicidae. It is a vector of some diseases, such as Japanese encephalitis, meningitis, Urticaria...
that is cold tolerant, hibernates in the winter, and bites only birds. When the two varieties were cross-bred the eggs were infertile suggesting reproductive isolation.
Since that paper more information has accumulated. The fundamental results still stand: the genetic data indicate that the molestus form in the London Underground appeared to have a common ancestry, rather than the population at each station being related to the nearest above-ground population (i.e. the pipiens form). Byrne and Nichols' working hypothesis was that adaptation to the underground environment had occurred locally in London once only – since there are many hurdles to jump in order to become adapted to the subterranean environment, it is understandable that it would occur rarely. This hypothesis implies that local adaptation would be expected in different locations around Europe and beyond, as each local pipiens population evolved an offshoot that overcame the problems of living underground.
However, more recently-collected genetic evidence suggests that a single molestus form has spread throughout Europe and beyond, since populations over a large area share a common genetic heritage. These widely separated populations are distinguished by very minor genetic differences, which suggest that the molestus form developed recently: a single mtDNA difference shared among the underground populations of ten Russian cities; a single fixed microsatellite difference in populations spanning Europe, Japan, Australia, the middle East, and Atlantic islands. This worldwide spread might have occurred after the last glaciations or be even more recent, due to the insects hitch hiking on world trade routes. One possibility is the international second-hand tire trade. The tires retain water in which the larvae can survive (Completely removing water from an old tire can be difficult).
What has always been more intriguing about the molestus story was that the reproductive isolation in north European populations appears to be almost complete, whereas there is clearly gene flow
Gene flow
In population genetics, gene flow is the transfer of alleles of genes from one population to another.Migration into or out of a population may be responsible for a marked change in allele frequencies...
between them in populations to the south. Byrne and Nichols attributed this pattern to the inability of the underground form (and perhaps their hybrids) to survive above ground in harsh northern winters.
Now it appears that the persistence of hybrids in northern climates may be another evolutionary problem that can be solved but only rarely: the Fonseca paper obtained genetic evidence that the recent colonization of America by Culex mosquitoes actually involves a strain derived from a rare successful hybridization between pipiens and molestus. They suggest that hybridization may explain why the American form bites both birds and humans (this interpretation is controversial, see letter from Spielman et al. and the response that follows it in Science
Science (journal)
Science is the academic journal of the American Association for the Advancement of Science and is one of the world's top scientific journals....
). The consequences of this more indiscriminate feeding hit the news in 1999 with the outbreak of human encephalitis in New York, caused by West Nile virus. It was the first documented introduction of this virus into the Western Hemisphere; perhaps because in the longer established populations the old world northern above-ground pipiens almost exclusively bite birds, the human biting ones being incarcerated below ground.
New York outbreak
In the summer of 2011, an invasion of Culex Pipiens Molestus appeared on the Upper West SideUpper West Side
The Upper West Side is a neighborhood in the borough of Manhattan, New York City, that lies between Central Park and the Hudson River and between West 59th Street and West 125th Street...
in the borough
Borough (New York City)
New York City, one of the largest cities in the world, is composed of five boroughs. Each borough now has the same boundaries as the county it is in. County governments were dissolved when the city consolidated in 1898, along with all city, town, and village governments within each county...
of Manhattan
Manhattan
Manhattan is the oldest and the most densely populated of the five boroughs of New York City. Located primarily on the island of Manhattan at the mouth of the Hudson River, the boundaries of the borough are identical to those of New York County, an original county of the state of New York...
, New York City
New York City
New York is the most populous city in the United States and the center of the New York Metropolitan Area, one of the most populous metropolitan areas in the world. New York exerts a significant impact upon global commerce, finance, media, art, fashion, research, technology, education, and...
. The mosquito is well known for being in commonly found in sewers of New York and thrive throughout the year feeding off of humans. Residents of older brownstones
Brownstone
Brownstone is a brown Triassic or Jurassic sandstone which was once a popular building material. The term is also used in the United States to refer to a terraced house clad in this material.-Types:-Apostle Island brownstone:...
found the mosquitoes coming from the underground into basements and then through air vents and other openings into the homes. The city government did not make this infestation of the pest a top priority because they tested negative for West Nile Virus
West Nile virus
West Nile virus is a virus of the family Flaviviridae. Part of the Japanese encephalitis antigenic complex of viruses, it is found in both tropical and temperate regions. It mainly infects birds, but is known to infect humans, horses, dogs, cats, bats, chipmunks, skunks, squirrels, domestic...
and the high cost of mosquito control.
See also
- Nylon-eating bacteriaNylon-eating bacteriaNylon-eating bacteria are a strain of Flavobacterium that is capable of digesting certain byproducts of nylon 6 manufacture. This strain of Flavobacterium, Sp...
- E. coli long-term evolution experimentE. coli long-term evolution experimentThe E. coli long-term evolution experiment is an ongoing study in experimental evolution led by Richard Lenski that has been tracking genetic changes in 12 initially identical populations of asexual Escherichia coli bacteria since 24 February 1988...
- Radiotrophic fungusRadiotrophic fungusRadiotrophic fungi are fungi which appear to use the pigment melanin to convert gamma radiation into chemical energy for growth. This proposed mechanism may be similar to anabolic pathways for the synthesis of reduced organic carbon in phototrophic organisms, which capture photons from visible...
- Urban wildlifeUrban wildlifeUrban wildlife is wildlife that can live or thrive in urban environments. Some urban wildlife, such as house mice, are synanthropic, ecologically associated with humans. Different types of urban area support different kinds of wildlife...