Scientists Discover Fish in Act of Evolution in Africa’s Greatest Lake
In what could be a first in the world, a fish species in the cichlid family has been observed by scientists in the act of splitting into two distinct species in Lake Victoria, Africa’s largest lake and one of the world’s biggest fresh water bodies.
This may be remarkable because what is causing them to diverge are adaptations to their vision as animals and plants try to cope with increased pollution and the effects of climate change. The change is also happening without geographical isolation, which was thought to be a precursor for evolution.
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The Pundamilia nyererei is a haplochromine type cichlid native to areas in the Mwanza Gulf region of Lake Victoria. This region consists of many islands where each island region has its own color variant of the fish.
In a report published in the journal Nature, researchers from Tokyo’s Institute of Technology and the Swiss Federal Institute of Aquatic Science and Technology have observed the cichlid evolve into a new species better adapted in sighting its prey and predator.
But the scientists have also tabled evidence indicating that it is not pollution and over-fishing alone that are responsible for the disappearance of some fish species in Lake Victoria and the evolving of others like the cichlid into new species.
The report summarizes that new species may be born because of vision differences and what fish see at least in one African lake could be the driving force that causes them to evolve into new species.
This may explain the very rapid loss of pundamilia in Lake Victoria over the past 30 years. The study says the eye adaptations have also affected mating patterns.
Researchers looked at two species, conspicuous by their red or blue colours. They determined through lab experiments that certain genetic mutations helped some fish adapt their vision at deeper levels to see the colour red and others in shallower water to recognise shades of blue.
The researchers showed that the eyes have adapted to this difference so that fish that live in deeper water have a pigment in their eyes that is more sensitive to red light, while shallow-water fish were sensitive to blue.
Generally, the evolutionary process of speciation (the formation of new species) occurs when one species is split by a physical distance or barrier, allowing each group to develop different traits. The observations of Lake Victoria’s cichlids provide evidence of an unusual form of evolution known as sympatric speciation, which occurs without the physical separation of a population group.
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Image credit: Erica Marshall at Flickr under a Creative Commons license.
“The change is also happening without geographical isolation, which was thought to be a precursor for evolution.”
Allopatric speciation is certainly not the only precursor to evolution. Sympatric speciation is extremely well documented and these two particular fish are in most college biology text books. I really thing the person who wrote this needs to study their basic biology a lot more along with many of the people commenting on here.
These two species are reproductively isolated (unless in an environment with monochromatic lighting) so speciation has occurred. Populations evolve not individuals.
Sadly, this is an inaccurate and poorly evidenced post. It refers to an article in the October 2nd issue of Nature (volume 455 - pages 620 - 626), titled Speciation through sensory drive in Cichlid dish.
First of all, speciation simply refers to the genetic divergence of a species, part of the evolutionary process. Secondly, geographical isolation has played a large role in much of evolution but the author seems to incorrectly stress that this is somehow rare (or even the first) evidence of another type of evolution. Even Darwin didn’t believe geographic isolation was recquired for evolution.
What the authors are poiting out here, is sensory driven speciation, the genetic divergence of a species based on sensory preferences. As opposed to say, Galapagos finches that find evolutionary niches based on the size of the seeds they can eat, this species of fish seems to be splitting based on mate preferences infuenced by differing visual recognition among females - some see red more vividly, and the others blue - combined with a corresponding shift in coloration among males towards the color associated with the female choice. They note the genetic shifts among the populations at locations in the genome not resposible for these traits and indicate the process of reporductive isolation , a hallmark of speciation - the point at which the two populations can no longer mate effectively (a liger is the result of ineffective mating here).
Below is the abstract of the paper (I had some technical difficulties connecting to the Nature site through my subscriber’s proxy)
“Theoretically, divergent selection on sensory systems can cause speciation through sensory drive. However, empirical evidence is rare and incomplete. Here we demonstrate sensory drive speciation within island populations of cichlid fish. We identify the ecological and molecular basis of divergent evolution in the cichlid visual system, demonstrate associated divergence in male colouration and female preferences, and show subsequent differentiation at neutral loci, indicating reproductive isolation. Evidence is replicated in several pairs of sympatric populations and species. Variation in the slope of the environmental gradients explains variation in the progress towards speciation: speciation occurs on all but the steepest gradients. This is the most complete demonstration so far of speciation through sensory drive without geographical isolation. Our results also provide a mechanistic explanation for the collapse of cichlid fish species diversity during the anthropogenic eutrophication of Lake Victoria.”
PubMed ID (PMID): 18833272
Link to PubMed: http://www.ncbi.nlm.nih.gov/pubmed/18833272?ordinalpos=1&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_DefaultReportPanel.Pubmed_RVDocSum
Sadly the ignorant cretins (Creationist, Christofascist) etc that deny Evolution don’t understand that you must have “micro” evolution before you get “Macro” evolution.
One is simply a “step” in a very long series of steps for the other.
Evolution has been PROVEN well beyond any reasonable doubt.
It sure is great to see how much blatant ignorance is being posted in the comments section here by people who obviously have no clue what evolution is. Spouting nonsense like ‘micro-’ and ‘macro-evolution’, making false dichotomies between adaptation and evolution and making use of species without, apparently, appreciating that ’species’ is a rather arbitrary distinction and that such Linnaean taxonomy has been replaced in all serious discussion with the more robust and accurate use of Cladistics. (More robust and accurate because it places emphasis on objective, quantitative analysis and genetics and not apparent resemblances between organisms.)
This does not seem to be a true example of sympatric speciation. It is true that one species of fish is adapting to different environmental conditions, but speciation would not occur unless the two forms become reproductively isolated. Also, geographic isolation was not considered a “precursor” of evolution, because we have known about sympatric evolution for quite some time, for example, in apple maggot flies.
As I’m Dutch, English isn’t my native tongue, but the word precursor in the 2nd paragraph strikes me as wrong. Wouldn’t the author better use ‘prerequisite’?
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“This is an example of a natural mutation (or adaptation) - not evolution. There’s a HUGE difference between the two. It’s adapting to environment changes - not evolving into a completely different creature.”
I have to agree with Mike (comment #3) on this one.
go science!!
silly christians.
“This is an example of a natural mutation (or adaptation) - not evolution. There’s a HUGE difference between the two. It’s adapting to environment changes - not evolving into a completely different creature.”
Are you seriously that pathetic. I mean could that have sounded more ignorant if you had actual bovine fecal matter spewing out of your mouth? You know what, probably not.
Learn about something before you act like you are an expert. An entire institution has been working with these fish and an entire field is dedicated to this kind of research. Somehow you think you’ve got it figured out better than they do? If you aren’t a creationist, then you are even more pathetic than before because at least they have fear of eternal damnation to make them act like idiots.
Evolution does not, at least as far as we have seen, say that species A turns into species B in one generation. Species A mutates, an action you admit happens. Over time, more and more of these mutations occur. This is where it might get tricky for you. Addition of mutations = greater and greater gene variance so bada-bing two different species.
Oh yeahi forgot to mention that the primary reason species EVOLVE is because of ENVIRONMENTAL ADAPTATION. I mean what else do you think is supposed to trigger that change? Magic?