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Potential issues with Cameroon P. taeniatus populations

tjudy

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While in Gabon I was able to have several lengthy discussions with Anton Lamboj and Cyrille Dening (a Cameroon fish exporter) about the status of 'aberrant' P. taeniatus populations in Cameroon. Two populations in particular, Muyuka and Njanje, appear to be the result of artificial introductions from Southern Cameroon fish.

An ex-pat Austrian living in Cameroon is known to have released fish from the Kribi area into waters closer to his home in east-central Cameroon (Kumba... near Lake Barombi Mbo) so that collecting them for export would be easier. A month ago, some fish of the Muyuka strain were collected from a stream the Austrian directed the collectors to east of Kumba... way outside the natural range of any P. taeniatus. The area of Muyuka is also far inland from the natural ranges of the species, and it is now suspected that this person established the Muyuka population many years ago (he has been in Cameroon for a very long time).

When hobbyist/scientist collectors 'discovered' the fish in the stream near the town of Muyuka, they labeled it as a new population. We now suspect that it is not a valid variation. One of the clues pointing to this comes from some recent comprehensive work done with DNA comparisons of the Cameroon populations. There are three different groups of P. taeniatus that are clearly defined if the data from Muyuka and Njanje are ignored: the Moliwe population, the Wouri population and the Kribi/Lobe area populations. The Njanje and Muyuka fish just plain do not fit the pattern, and are more closely related to the southern races than the relatively nearby Wouri and Moliwe populations.

So... the circumstantial evidence is piling up to support the theory that Muyuka and Njanje are probably not real populations:

1) We know the Austrian ex-pat sprinkled fish around the area.
2) We have an aberrant pattern in the distributions.
3) We know that the physical locations of the Njanje and Muyuka populations are many kilometers outside the natural range of all other valid populations (which are all found close to the coast or tidal waters).

I still think that the Njanje is the prettiest P. taeniatus to show up in a long time... but it is probably a strain derived from Dehane or Kienke pioneers.
 

Shernutz

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Sublocale taeniatus spp.

Do we know when this Austrian ex-pat started this "sprinkling?"

If it was decades ago, ? possible the the Muyuka and Njanje have branched out to their own spp?

This is all very interesting.

Who is funding the DNA project?

Where (journal) will the findings be published?

When you were there, did you find areas where previously found fish are no longer or more rare because of development? Which P. taeniatus spp. most at risk?

I ask too many questions. Answer (or not ) at your leisure. Hope your jetlag has disappeared!

Lisa
 

tjudy

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The DNA work is being done as a part of the revision of the genus that Anton Lamboj is making (maybe it will be published this year). The original population found at Muyuka is known to have disappeared about ten years ago, and the recent imports of 'Muyuka' were collected many kilometers east of that location by Cyrille Dening. Cyrille was directed to the location he collected them at by Victor, the Austrian ex-pat living in Kumba (who seeded the fish into the stream about ten years ago).

Jeff (aquaticclarity) was able to get two pairs of these 'Muyuka'. He and I both have a pair (only 7 pairs, according to Cyrille, were sent to Toyin here in the USA).

It takes many thousands of years for a geographically isolated population to become a new species. That is one of the theories of evolution, speciation, that is very very difficult to observe... probably impossible to observe in a wild population of a vertebrate (or large invertebrate) organism. However, the fish introduced to these locations were probably a mix of fish from different locations in southern Cameroon, and the pioneers represented only a small sample of the gene pools of the original populations. Inbreeding, hybridization and different selective pressures have probably resulted in color patterns that are not the same, but not too different either, from the original pioneers. And there is likely a lot of variation in the introduced populations.

None of the known wild populations of P. taeniatus in Cameroon are at risk. Though the ecosystems in some areas are changing rapidly. Moliwe, for example, is now surrounded by oil palm groves and the stream is not as shaded as it used to be. But there are still a lot of fish there.

All of the known natural populations of P. taeniatus are found in soft, fresh water, but within only a few kilometers of the ocean. Only the Wouri River population seems not to adhere to than, BUT the Wouri River is a huge tidal river that has brackish water many kilometers inland. The distance of the cichlids to that brackish estuary follows the patter. The locations of Njanje and Muyuka (new and old) are 50 - 150 km east of the inland-most range of the any other P. taeniatus in Cameroon.
 

aquaticclarity

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I got it 3 pair of the "Muyuka"-1pr went to Ted and I have the other two.

2 of the 3 males looked alike in terms of color, patterning, and occeli. The other male lackd any occeli in the caudal. The females also had some variation. 2 females have a black dot in the caudal while the third doesn't.

Now I expect, and often see, some variation (not a set number of spots or occeli) from fish to fish in a given population of wild taeniatus but having 2 males with occelii and a 3 with out any is very odd.
 

tjudy

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A note on DNA comparisons.... there is an art to this science. What DNA comparisons do is show molecular relationships between species, or possibly populations between species. Since it is the genes that are inherited from one generation to the next, two species that have a lot of DNA 'markers' in common are considered to be closely related. But that only tells part of the story.

Geographic location is also taken into account. Two populations of closely related species SHOULD have a high number of correlating markers, if the two now separate species shared a common ancestor. That does not always bear out. Sometimes, when several species DNA are compared to each other, two species that are far apart share the most DNA in common. There are lots of hypotheses that try to explain this, with the most reasonable being that there was once a widely distributed species in a genus that radiated into several species. It just happens that two of those new species are still very similar. This is being observed in Hemichromis. The DNA work on that genus is also progressing.

Back to P. taeniatus... The genus has proven to be surprisingly predictable with regards to geographic range and DNA correlation. What scientists do is make a hypothesis, then test (using DNA as part of the diagnostics) to see if that hypothesis is valid. The population called 'Muyuka' does not follow the pattern. Anton Lamboj described the revision of P. taeniatus as being 'easy', except that the form at Muyuka makes no sense. If that data set were not in the comparisons the data would draw a distribution map that clearly indicated three different species in Cameroon that are geographically isolated from each other. With the Muyuka data in the mix there are a problems. If Muyuka is a natural population, then it may not be possible to separate northern (Moliwe and Wouri forms) from the southern forms. If it can be proven that Muyuka is NOT a natural population beyond any shadow of doubt, the data can be tossed out and the revision of the genus can proceed very quickly, and what is currently one species in Cameroon will become three.

The current designation of P. taeniatus for all Cameroon fish was published in the 1960's. At that time there were only two locational varieties from Cameroon used, both from the southern region. If Muyuka existed in the 50's it was not used, and neither were the Moliwe or Wouri populations.
 

ed seeley

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It takes many thousands of years for a geographically isolated population to become a new species.

Not necessarily true. One of the newer theories about evolution is that it happens in bursts that can occur surprisingly quickly and fundamental changes that can reproductively separate populations can occur in only a few generations. Colour changes and female preference can be a key driver of these rapid speciations. For instance if a yellow male were to occur in an otherwise blue population and a female were to inherit a preference for that colour you could easily end up with a population of yellow males and yellow preferring females in an otherwise blue / blue-preferring species. As soon as they are reproductively isolated according the biological species concept they are a new species and they are then free to drift apart from the parent species in other characteristics.
 

tjudy

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Punctuated equilibrium is a hypothesis that has been around for a long time, though the entire hypothesis is directed at species diversity and mass extinctions more so than individual populations. A more directly associated example was provided by ornithologists:

Studies on the Galapagos Islands with finches indicate that the frequency of specific phenotypes in a population can swing rapidly from year to year depending upon the effect of environmental factors. In dry years finches of a species with large beaks are more successful, but in wet years birds of the same species with small bills are better off. After tracking literally every bird on the island of Daphne for over 20 year (and multiple wet/drought cycles), the penotypic ratios in the population from year to year swung wildly, but after 20 years the overall frequencies were rather steady. The genes were still in the birds. Both phenotypes were being born, but in some years they live and in others they die.

The definition of biological species suggested by Ernst Mayr is almost 70 years old (1942), and the debate over the validity of that definition continues. Even Dr. Mayr, in the 1990's, said that his original concept would not stand up to modern knowledge. (Cool side story.... some of my students were debating the definition, and I challenged them to ask Dr. Mayr directly. They found his email, he responded and continued to communicate with the kids for weeks about evolution and the definition of species. Very nice man.) Reproductive isolation is a one of the factors stated as needed to support the hypothesis of adaptive radiation, which is suggested to be one avenue for eventual speciation. But reproductive isolation alone cannot be the only factor causing speciation, especially in the short term (say less time that what we have records for). If isolation were the only factor, the English house sparrows and English starlings found in North America would be different species from those found in Europe... but they are not. I have never been anywhere humans are at in a temperate or tropical climate and NOT seen English house sparrows. If populations that are found in places isolated from each other in different habitats speciate quickly, why has Passer domesticus not changed somewhere in the world? Translocate birds from either population and they will fit right in with their new communities.

In our hobby (and in the field of ichthyology) there is a tendency to try to split species (and even genera) on the slightest difference. Personally, I think that this is short-sighted (though I am not a taxonomist). That does not mean that I am in favor of crossing fish from known different populations. A part of the allure of the fish we keep is that there are differences between the species in on stream and from another.

If the populations of Muyuka and Njanje P. taeniatus are not naturally-occuring, and we do not know what the pioneer populations were (they may have even been a mix of populations), then trying to predict if they will be a new species someday generates an interesting debate, but in the end it will have little basis in reality.... not in our lifetime anyway. I will keep them separate from all my other strains (and from each other), but for the time being I am not going to let them out of the fishroom without including the back story. I think that they are really no different than a tank strain, and should be treated as such. The evidence that they are not natural populations is circumstantial, but it is all the evidence we have to go on, and the evidence is pretty strong.

I love these types of discussion!!!! :biggrin:
 

ed seeley

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Ted I meant that isolation can lead to rapid speciation but there are loads of factors that govern it, not just the isolation alone. Over time random genetic drift may slowly create new species from isolated populations but that process will take ages. However drop in a selective factor in a small and isolated population and you can see rapid changes.

I'm a splitter by tendency, especially when it comes to fish kept in captivity, as I think it's all too easy to lump populations together and then they are crossed in captivity as people don't bother about the populations. Or the flip side is killifish where each population collected is kept completely isolated, even from later collections from the same places, when, if they were classed as a species people might mix them and possibly create a better genetic pool from different collections from the same location.

Genetic data now being used is throwing an extra spanner into these kinds of questions. I read one study recently on two Tangayikan rockdwelling species where the genetic data has been used to lump together two different species as they said the populations were polyphyletic. However the problem is the DNA they used (D-loop mitochondrial) is slow to change and I think these two species are an example of two isolated species that changed enough so that they don't, or rarely, interbreed when mixed that have then got mixed around different sites when the lake level has changed leaving one species at each place. However the DNA hasn't kept up with the species preferences so are they one species or two? By naming them all Neolamprologus pulcher (rather than keeping N.pulcher and N.brichardi) I think we will end up with a mongrel captive population of both species.
 

tjudy

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What makes sense to me is to link bottle-necking of gene pools to rapid divergence. When large portions of a population are lost to natural (or otherwise) disasters, then there is a chance that some specific traits may have been lost... possibly purely by chance. Creating a new population from a few pioneer individuals in a new place mimics the effect of bottle-necking. It is possible that only a small percentage of the gene pool is actually relocated. BUT... genes that are in the pioneer population are still in the original population. Divergence from that point in time is dependent upon a lot of factors (I think it can be assumed the the environmental factors acting upon each population are going to be different).

When we get fish for our aquariums we are forcing extreme bottle-necking. Especially if all we do is get a pair or two, and doubly so if we get siblings from a captive spawn. A good example would be albinism in a species in which that color is a recessive trait. Suppose a friend has a spawn and there are some albinos in the fry. You beg for the albinos and take them all home. Since the gene is recessive, the dominant gene is not in the gene pool of the fish you take home. So long as you do not outcross the line you should never get the dominant gene back (short of a random mutation.... very rare to have that happen to get back to wild type). But the gene for albinos is still somewhere in the original population. Does the fact that your population is albino and your friend's wild type mean that the two populations are diverging?

I am actually in favor of outcrossing to new stock from the same collection location whenever possible. That will maintain the genetic integrity of the captive population and reduce the effect of bottle necks.
 

ed seeley

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I am actually in favor of outcrossing to new stock from the same collection location whenever possible. That will maintain the genetic integrity of the captive population and reduce the effect of bottle necks.

Me too, as long as the populations are identified properly! I think elevating different populations to a specific level will help with that too though as many people don't think twice about crossing two P.taeniatus but would maybe not cross two different species But then that's one reason why I'm a splitter! :biggrin:
 

tjudy

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One of the problems is how people define 'location'. If I collect fish from the same stream 5 km apart from each other, am I collecting in the same location? What if I collect a killie from the main channel of a stream and from 1 km up a small tributary of that main channel? The P. taeniatus 'Moliwe' we get are from any of several streams in one specific coastal watershed. Are all the small streams in that watershed that hold cichlids difference locations?
 

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How mobile are the species you are mentioning? Will populations move up and down a small river system, or do populations tend to stay in a very small area? Do the species move as a colony or do fish move about as individuals.
 

ed seeley

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One of the problems is how people define 'location'. If I collect fish from the same stream 5 km apart from each other, am I collecting in the same location? What if I collect a killie from the main channel of a stream and from 1 km up a small tributary of that main channel? The P. taeniatus 'Moliwe' we get are from any of several streams in one specific coastal watershed. Are all the small streams in that watershed that hold cichlids difference locations?

Sorry Ted, I've only just seen this post - must have got marked read by mistake by me at some point!

That is a very good point and I agree. Killie keepers are maniacal in allocating collection codes to fish within the same stream but at different points in the stream. We would have to rely on the people who collect in these locations to inform us of whether there is access for the fish at different points to mix, if they can tell. Unfortunately it's a very complicated issue as to what isolates different populations. I have heard that on some stretches of the Congo river there are different species and forms on the different banks of the main river as the small fish can't get across the river to mix! Yet they are in the same body of water! It parallels the situation of rock dwellers in the big rift lakes.
 

ed seeley

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How mobile are the species you are mentioning? Will populations move up and down a small river system, or do populations tend to stay in a very small area? Do the species move as a colony or do fish move about as individuals.

Good point and it will vary species by species and even between individuals within a population. We have all seen in broods of fish that some are just more inquisitive and it would be easy to assume that those inquisitive individuals (if they don't get eaten) would wander more widely and spread their genes more than other indviduals.

From a genetics point of view whether colonies or individuals move is irrelevant really, it's the rate of genetic transfer that matters and similar rates of effect could be achieved by a few genetically quite distinct individuals entering a fairly isolated, different population or a lot of individuals moving into an already fairly mixed, similar population.
 

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