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The London Underground Mosquito: Evolution In Action

Updated on September 8, 2012
The Gary Larson-esque Mosquito Monument in Suwon City, South Korea
The Gary Larson-esque Mosquito Monument in Suwon City, South Korea | Source
Photo of a C. pipiens molestus mosquito feasting on human blood in its subterranean London habitat. (Okay, not really, but the close-up photos of mosquitoes sucking blood were giving me the creeps, so please accept this substitute.)
Photo of a C. pipiens molestus mosquito feasting on human blood in its subterranean London habitat. (Okay, not really, but the close-up photos of mosquitoes sucking blood were giving me the creeps, so please accept this substitute.) | Source

One of the more frequent science-denialist arguments against evolution is the claim that the evolution of a new species has never been observed. Besides being an illogical argument that ignores the preponderance of forensic evidence in favor of the theory, it is falsified by a number of examples of observed speciation within the span of recent history. One of the most interesting of these examples comes from a rather infuriating creature: The London Underground mosquito.

This sub-species of mosquito, named Culex pipiens molestus by biologists, appears to have branched off from an above-ground population of Culex pipiens pipiens mosquitoes around the time the London Underground was being dug in the mid-19th Century and subsequently adapted to the warm subterranean climate of this newly-created environment.

Mind The Allele Gap

The existence of these underground pests has been known for many decades, having been a particular annoyance to Londoners seeking refuge from the Blitz bombings of World War II. Behavioral differences between these underground mosquitoes and their above-ground brethren had been observed for many years. Above-ground Culex pipiens pipiens in London feed primarily on birds, mate openly in large swarms, and live seasonal lifestyles - lying dormant in warm, sheltered areas during the winter. The below-ground Culex pipiens molestus feed on humans and rats, have very private sex lives, and are active year-round in the moist and temperate environment of the subway system.

The exact relationship between the two species - and indeed whether they were truly different species or just two populations of the same species - has remained a mystery for many years.

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Some major clues to this mystery were found in the late 1990s, when geneticist Richard Nichols of Queen Mary and Westfield College at the University of London, and his then-doctoral student Katherine Byrne began performing genetic analysis of the underground and above-ground populations of mosquito at multiple London locations.

The results showed that all the alleles found in the Underground variety of mosquito were also found in the above-ground species, suggesting that Culex pipens molestus was indeed a descendant of London's native Culex pipiens pipiens. Had the underground variety been a foreign import, perhaps brought from mainland Europe as a stowaway in an unsuspecting traveller's luggage, it would have had some completely unique foreign alleles.

The C. molestus populations at different tube stations also showed far more genetic similarity to each other than they did to the corresponding above-ground population of C. pipiens, suggesting that the C. molestus mosquitoes began their conquest of the London Underground in one location and spread via subway tunnels rather than establishing individual colonies at each station.

Perhaps most important to the question of speciation was whether the above ground and underground populations could interbreed, as this is one of the critical determinants of a new species. Byrne and Nichols (mostly Byrne) collected eggs from the breeding mosquitoes at multiple underground and above -ground locations, raised the sample populations to maturity, and attempted to interbreed them. While the Underground mosquitoes from different locations all readily interbred with each other, they could not produce viable offspring with their above-ground counterparts.

The data indicates that the London Underground mosquito is in all likelihood a descendant of a local above-ground population, demonstrating how speciation can occur between populations that are reproductively isolated.

Molestus on the Move

More recent studies on underground mosquito populations in other cities in Europe, North Africa, the Middle East, and Asia, using genome analysis of mitochondrial DNA, have shown remarkable genetic similarity between all of these widespread C. molestus populations.

Though one interpretation of this data is that the molestus variety is much older than the London findings suggested - dating back thousands of years rather than hundreds, another is that these underground mosquitoes radiated from a single recent population, their larvae carried along international trade routes before settling in underground niches in their new locations. In either case, the speciation event would have occurred well within the span of human history.

Further study will be needed to answer some of the outstanding questions of exactly how and when the London Underground mosquito evolved, and if indeed this creature can be officially classified as a new species or simply a sub-species of the existing Culex pipiens mosquito. As useful as Linnaean taxonomy was in 1735, it doesn't adequately capture the complexities of changing life forms as they can be measured today with modern genetic analysis. However, the example of the London Underground mosquito clearly provides an excellent demonstration of the mechanisms of evolution and speciation at work as life occupies a new, artificial ecosystem.

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    • profile image

      Biggerhass 

      3 years ago

      Nicomp - you'll find language like "suggest" and "most likely" in most primary sources in scientific research papers. It is because of the humility of scientists, there is always space for new evidence, all conclusions are tentative. Don't mistake this to mean we don't have a great deal of certainty; if we did not, then we couldn't fly planes, drive cars or take medicine. Whether evolution occurs or not, is as much as a done debate as there can be in science. The theory of evolution is more understood than the theory of gravity. The objection seems to be people don't want evolution to be true due to religious bias or some other personal reason, rather than legitimate scientific objections. It's confirmation bias - pick superficial holes in evolutionary theory & ignore the overwhelming evidence collected over a century in order to hold to one's religious beliefs. Once we started to learn about genes and DNA, that could've been the nail in the coffin of evolution- rather, it only confirmed it. To deny evolution is to deny the body of knowledge collected in genetics, molecular biology, archeology, geology, biochemistry, comparative biology, embryology and so forth. There is no other theory in biology that has this breadth of evidence.

    • profile image

      Bob 

      3 years ago

      So the two forms are of different species (or subspecies) apparent from the inability of the two to reproduce fertile offspring. However, they are nearly indistinguishable in appearance and they "seem" to be well adapted for the underground environment.

      They also claim that it is unlikely that this underground form migrated from another geographical region due to the lack of alleles that are only known to exist in mosquitoes outside of Britain.

      How else can this data be interpreted besides the underground population splitting from the above ground population and adapting over time to those conditions? And how would you test this alternative hypothesis against the hypothesis proposed by the authors?

    • nicomp profile image

      nicomp really 

      4 years ago from Ohio, USA

      Your theory doesn't work, but that's OK. If your benchmark is whomever claims to get there first, it's all good.

      The London Underground Mosquito is not an example of any information being created. Yes, it's a different species than the London Above-ground mosquito, but so is a ferret.

    • scottcgruber profile imageAUTHOR

      scottcgruber 

      4 years ago from USA

      There's a Nobel Prize waiting for you if you manage to come up with an alternative theory to evolution that explains the diversity of life on Earth. I mean, nobody has done so in the past 150 years, but who knows - maybe you'll be the first!

      Until you produce your alternate theory, I'll stick with evolution. It works. The London Underground Mosquito is an example of it working.

    • nicomp profile image

      nicomp really 

      4 years ago from Ohio, USA

      Wow. Since there is only one theory then it must, by definition, be correct?

      OK. Can't argue with that type of logic.

    • scottcgruber profile imageAUTHOR

      scottcgruber 

      4 years ago from USA

      The debate is over - there is no competing theory other than evolution to explain the diversity of life on Earth.

    • nicomp profile image

      nicomp really 

      4 years ago from Ohio, USA

      "suggest."

      "Most likely"

      "more consistent."

      And you extrapolated that to "The debate is over."

    • scottcgruber profile imageAUTHOR

      scottcgruber 

      4 years ago from USA

      "The genetic distances measured by the present study between the Underground and surface populations (0.07–0.24) would suggest that the relationship between the two population types is between that of local populations and subspecies"

      And

      "The data are more consistent with local populations being the source of molestus populations in the Underground. However, Fig. 1 shows that there is no association between individual Underground populations and local surface populations, which suggests that multiple independent colonizations are unlikely or, at least, that such events are rare. The most parsimonious explanation is a single colonization."

      Surface populations are culex pipiens. Underground populations are culex molestus. The results of the study were that above-ground populations of c. pipiens were the most likely source for the underground c. molestus populations. In other words, c. molestus evolved from c. pipiens.

    • nicomp profile image

      nicomp really 

      4 years ago from Ohio, USA

      In all seriousness, read your own references. http://www.nature.com/hdy/journal/v82/n1/full/6884... has nothing to do with your premise that one species evolved from the other. Your leap of logic is dizzying.

      Morphology does not prove (or disprove) homology .

    • scottcgruber profile imageAUTHOR

      scottcgruber 

      4 years ago from USA

      Stomp,

      "Microevolution" and adaptation ARE evolution. There is no actual scientific distinction between "microevolution" and "macroevolution." These terms are only used by Creationists who are trying desperately to hold on to their mythology in the face of overwhelming evidence.

      Similarly, the "no new information" talking point is one that only Creationists use to deny reality. Demonstrating "new information" is not necessary to prove evolution - though mutations can certainly create new "information" by insertion.

      The fact of evolution - that living things change over time - has already been proven beyond all reasonable doubt. The evolution of culex pipiens molestus described above is just one example of this. It doesn't "prove" evolution, it IS evolution.

      The London Underground Mosquito does lend more evidence to the theory of evolution, however, as it demonstrates a recent example of natural selection driving speciation through evolutionary adaptations, just as the theory predicts.

    • profile image

      Stomp 

      4 years ago

      It is just about microevolutionary changes and adaptation. No new information has been created here. Is this proof of evolution? Yes, but just about microevolution. Microevolution need no more evidence, it has been know long time now.

    • nicomp profile image

      nicomp really 

      6 years ago from Ohio, USA

      Thanks for the suggestion. Evidently you haven't read it, the abstract conflicts with your article.

    • scottcgruber profile imageAUTHOR

      scottcgruber 

      6 years ago from USA

      1. Read it for yourself. I'm not going to waste my time doing it for you. The Byrne and Nichols paper is linked above.

      2. Adaptation. The underground species adapted so they would thrive in the new environment.

    • nicomp profile image

      nicomp really 

      6 years ago from Ohio, USA

      1. What was the mutation?

      2. What is the evolutionary advantage of the two different species?

    • scottcgruber profile imageAUTHOR

      scottcgruber 

      6 years ago from USA

      Nicomp: This demonstrates the method of speciation. A population split into two geographically-isolated groups. The groups evolved different traits through mutation and natural selection, and now they can no longer interbreed. That's the only "feature" that matters.

    • nicomp profile image

      nicomp really 

      6 years ago from Ohio, USA

      I don't see any proof of evolution in the particles-to-people sense. One species of mosquito is found to be similar but different to another species of mosquito. So what?

      The science is cool, but nothing has been proven pertaining to the classic definition of macro-evolution: 'small changes' over time to get from one species to another. What features and functionality were added? Just as important: what features and functionality were lost?

    • LetitiaFT profile image

      LetitiaFT 

      6 years ago from Paris via California

      I wonder if they've traveled via Eurostar to France. I live in Paris over a metro vent and the last few years we've become infested with mosquitoes, even in winter!

    • scottcgruber profile imageAUTHOR

      scottcgruber 

      6 years ago from USA

      It must be so nice to be a Creationist, unbound by nuance or complexity. The black-and-white world of False Dichotomy would be a refreshing change from having to think critically all the time.

      Nah, I'd probly hate it.

    • parrster profile image

      Richard Parr 

      6 years ago from Australia

      "The speedy changes have nothing to do with the production of any new genes by mutation, but result mostly from selection of genes that already exist. Here we have real, observed evidence that (downhill) adaptive formation of new forms and species from the one created kind can take place rapidly. It doesn’t need millions of years. Informed creationists have long stressed that natural selection can easily cause major variation in short time periods, by acting on the created genetic information already present. But this does not support the idea of evolution in the molecules-to-man sense, because no new information has been added."

      http://creation.com/speedy-species-surprise

    • scottcgruber profile imageAUTHOR

      scottcgruber 

      6 years ago from USA

      Highly recommended. And don't forget to MIND THE GAP.

    • kateperez profile image

      kateperez 

      6 years ago from pasadena, tx

      What an interesting hub. If I ever make it to London, I'll be sure to wear my long sleeves...

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