Cichlid Room Companion

Internet lectures

Cichlids as a model for evolution

By , 1996. printer
Published
Ad Konings, 2012

Classification: Evolution.

" Fishroom talk taking place on 1996-Mar-29 "

Severum bubbles: 20:00:40 FR time :)

Juanmi says: Well, welcome to the weekly installment of the Cichlid room meeting, tonight as you know we have another excellent speaker, we are honored to have Ad Konings who has specifically learned to move around in this MUD to give a talk to us, he will be chairing tonight on "Cichlids as a model for evolution"

There is a ripple and Konings appears!

Juanmi says: I will turn the PA on so Ad can run his talk without interruptions, questions will be at the end

JuanMi gives the mic to konings.

JuanMi has muted audible commands.

Konings says: hi all

Konings says: I hope that I'm doing this right. let's start

Konings says: Disclaimer: Although I'm a biologist, I'm not an evolutionary biologist or even a trained ichthyologist. I'm a geneticist and trained in DNA technology. But I have seen a lot of Cichlids in their natural environment and know something about their behaviour and distribution, and all my theories are based upon these observations. These are, of course, not all "my" theories but I favour those suggested previously that fit with my observations rather that fit with my observations rather than with, say, computer simulations.

Konings asks: Cichlids and evolution; why Cichlids and what is evolution?

Konings says: Cichlids, in particular those of Lakes Malawi, Tanganyika, and Victoria, have attracted the worldwide attention of evolutionary biologists because each of the lakes is inhabited by a unique set of Cichlid species which all seem to have evolved in their lake and are not found anywhere else. One of the interesting characters of these so-called species flocks is that there are numerous species many of which must be closely related. There are, of course, several scenarios leading to these flocks and the two obvious ones are that 1) there is either a fast turnover of species with thousands upon thousands of species extinct at present (bouts of mass speciation), or 2) species still present today ("ancestral" species) repeatedly "producing" new species when the environment changes (the type of speciation I favour).

Konings says: What is evolution? In my opinion there are two different processes which both are sometimes called evolution. One of the processes I call evolution and the other speciation. Evolution is the gradual change of the genetic material, the DNA, and speciation, the creation of new species, involves also a changed DNA but in my opinion these changes must be very specific for speciation to occur and not every group of organisms with a DNA different from another group is automatically a different species.

Konings says: The natural drift in the composition of the DNA occurs always and an ancient species may have an entirely different DNA profile than its forebearers millions of years ago, still it can be the same species (eg Crocodiles, Horseshoe Crab). Such changes are tiny alterations in the structure of the DNA which have no effect in the functioning of the organism and, important, no e organism and, important, no effect in the mate recognition system of that particular organism. The latter is very important because the speciation process in Cichlids is based on the compatibility of the interbreeding individuals. If an individual is excluded from the breeding process from the rest of the group it is not able to transfer and mix its DNA with the large gene pool of that group. So, if such individual was excluded because of a strange composition of its genes leading to an incompatibility (not being recognized by the other members of the group as a conspecific individual), such aberrant gene(s) are thus excluded and the gene pool kept "pure".

Konings says: Darwin thought that evolution automatically generates new species and that it would be very difficult to draw a line between a species and its predecessor, because evolution goes gradually. Nowadays not many evolutionary biologist believe in such a scenario any more and most think that speciation in Cichlids is based on the sexual selection process: when two individuals recognize each other as being of the same species and share their genetic products, they both belong to the same species. Their DNAs, however, may be quite different! In my opinion it is therefore useless to try to unravel the speciation events in a particular specie particular species flock by analyzing the DNA of the different forms, because what you measure is evolution (DNA drift) and not speciation.

Konings says: In 1992, during an expedition along the southern half of the Zairean shore of Lake Tanganyika, I found local variants of several species (eg. Ophthalmotilapia ventralis, , Tropheus annectens) which I knew were very similar in coloration to those found on the opposite shore (in Tanzania). The interesting observation was that these geographical variants were restricted in their distribution and did not at all link up (via the southern shores in Zambia) with those on the opposite those on the opposite coast. In fact OTHER variants of the same species were found along the southern shore. Knowing that the lake level fluctuated during the evolution of the lake, it is very plausible to assume that those very similar forms, now isolated by a deep lake, once formed a single population and were subsequently separated by the rising water. The places where we still find these variants today are steep rocky coasts which at any lake level are able to provide suitable habitat to those species. The newly accessible habitat (because of the rising water) in the south of the lake became gradually inhabited by wandering individuals from the old mother population.

Konings says: A similar thing happened in lake Malawi where we find several species and geographical variants of species on opposite coasts of the lake (eg Pseudotropheus sp. "tropheops red fin", Aulonocara stuartgranti "Usisya", Labeotropheus trewavasae "Lion's Cove", Ps. fainzilberi), and also these do not form continuous populations. So also in Lake Malawi it looks like there are species which are older than others and with every increase in lake level these species gave and will give rise to new ones.

Konings asks: How is it possible that so many species could evolve in a single body of water.

Konings says: Cichlids are primarily substrate-dwelling fishes and rarely venture far from the bottom. Both lakes Malawi and Tanganyika are so deep that the water layer below 200 meters is void of oxygen which means that fish cannot live there or deeper. So, the suitable habitat for Cichlids is thus restricted to a rather narrow band along the shore where the lake is not deeper than 150-200 meters. Many of the species are restricted to rocky habitats, especially the smaller ones. Rocks provide shelter. So the rock-dwelling species are never, or let say extremely rarely, found on the sand for instance. The type of coast of both lakes Malawi and Tanganyika alternates from rocky to sandy both lakes Malawi and Tanganyika alternates from rocky to sandy and from rocky to muddy. The further some rocky stretches are apart the longer it takes for the rock-dwellers to cross the unsuitable habitat in between. New species can be formed when new habitat gets (during rising water level) by a few founder individuals.

Konings says: Some scientists argue that there are far too many closely related species, in Lake Malawi for instance, to all have originated on isolated stretches of rocky coast; they therefore postulate that there are also other ways of speciation, namely so-called sympatric speciation. This means that a new species is formed in the full presence of the species from which it is derived. In this way they want to explain the presence of eg 25 different Rhamphochromis species in the southern part of Lake Malawi, because Rhamphochromis is normally found in the free water column and appears not to be bound by the substrate. Since Lake Malawi has in the past always been a single body of water it is indeed difficult to imagine how new Rhamphochromis species could evolve when all individuals of all populations seem to be able to move around the lake. In other words there seems to be no room for a scenario where some populations were geographically isolated from others.

Konings says: There are, of course, several explanations and sympatric speciation is just one of them. Since I cannot imagine how sympatric speciation can occur, I favour other possibilities. It is not very unlikely that during breeding Rhamphochromis migrate to their particular breeding grounds and they can thus be isolated from other Rhamphochromis species in the lake, or that they have different breeding seasons. The most plausible explanation, however, is that there are no 25 different species because to be able to define a species we need to know about their behaviour (species recognition) and up to now Rhamphochromis has been collected in gill nets or deep trawls and only morphological data could be gathered from them. The same can be true for many other species as well: there are no 2000 Cichlid species in Lake Malawi or 1000 in Lake Victoria, but maybe 500 in Malawi and 300 in Lake Victoria. Maybe w Malawi and 300 in Lake Victoria. Maybe we still have to learn a lot about the Cichlid's ability of species recognition and about themorphological variation within a species.

Juanmi says: Well, we are now going for the questions

JuanMi has released muting.

MrKillie applauds enthusiastically.

Dev applauds.

Severum bubbles enthusiastically.

Sabrina applauds

Rickdf applauds

Konings says: thank you, I hope it was not too dry

MrKillie says: what are your feelings about the notion of 'explosive speciation', we sometimes hear about when rift lake Cichlids are mentioned as a way to explain the # of species in the relatively short life of the lake

MrKillie says: isn't it the case that Lake Victoria is maybe 10,000 years old, yet hundreds of Cichlid species in addition to everything else that's there?

Konings says: I think that a basic Cichlid has many different "bauplans" in its genes and can quickly generate these when the environment requires

Konings says: Lake Victoria is indeed a very young lake and we may be looking here at speciation in the process

Konings says: I think that speciation is usually triggered by the presence of similar species living off the same resources and preferring similar habitats

MrKillie asks: and your basic pupfish, then, is the other end of the spectrum?

MrKillie asks: very stable, unchanging despite severely limited habitat?

Konings says: I have no idea about pupfishes but I can imagine that there are no other similar fishes present in their habitat with whom they have to compete

MrKillie says: yet, sometimes there are more than 1 sp. of pupfish in same habitat. Though that may be a 'modern effect' due to loss of habitat

Konings says: Indeed, but Cichlids may have a far larger scenario of possibilities in their genes than pupfish

Juanmi says: Yes Matt, In Yucatán three different species of pupfish (Cyprinodon maya, C. labiosus, C. Simus) developed from an ancient one (Cyprinodon Beltrani) those new took advantage of new resources and different habitats within the same lake (Laguna Chichancanab).

MrKillie nods his head in understanding.

MrKillie asks: but there are also goodeidae in that lake, too, right?

Juanmi says: Not that I know Matt, goodies are restricted to the triangle México-Durango-San Luis Potosi, with their evolution center in Lerma system

MrKillie asks: so, the only competition the pupfish have is other pupfish?

Juanmi says: Yes

Konings says: Yes and this triggers speciation

Juanmi says: Consider also Herichthys minckleyi, in the process of speciation, now polymorphic species, they diverge taking advantage of different food sources present in the same habitat

MrKillie says: true, with the mutable dentition (and *seriously* nasty attitude in captivity)

MrKillie says: let me see if I understood this properly:

MrKillie says: different species will have different DNA signatures but the same species may have different DNA signatures, too?

Konings says: yes, that's what I think

MrKillie asks: so, how do you reliably identify a species?

Konings exclaims: good question, gut feeling!!!

MrKillie says: the old saw of whether the offspring were fertile doesn't work and you can't look at the DNA and trust it, either

Konings says: right

MrKillie wonders if there's just one, say,

MrKillie says: with lots of color forms - leptosoma, nigripinnis,

Konings says: No because when you have syntopic forms (different species/forms living side by side) and do not interbreed we can say for certain they these belong to different species

Konings says: The problem are the so-called allopatric forms which do not share the habitat

MrKillie thinks he's been monopolizing the questions and will go raid the icebox

MrKillie is afk (Away From Keyboard)

Konings says: I can try answering questions on a lighter note

Konings says: yes, horus

Horus asks: what are some of the newer importations we can look forward to coming out of lake Tanganyika?

Konings says: difficult question because there are not that many New species in Tanganyika left

Konings says: I think that species from the southern Tanzanian coast can be expected in a not too far distance. If you are interested in Tropheus then don't expect anything spectacular

Horus says: also, I was wondering, ad, if you have noticed in the wild any problems with blindness and

Konings says: Very rarely I have seen fishes with ONE eye blinded but totally blind fish have little chance of survival

Konings says: I can't remember Cyprichromis with white eyes in the wild, but could be.

MrKillie raises his hand.

Konings says: yes, Mrkillie

MrKillie asks: Will there be a 2d edition of your Tanganyikan cichlid book, like the Malawi one that's recently been out in the U.S?

ARCAS says: good question...:)

Konings says: Yes, due out in TWO years, but there will be a small interim book out September this year

ARCAS asks: the interim include updated stuff?

Konings says: yes updated stuff

MrKillie asks: may I ask a killie question?

Konings says: Killie question? I know extremely little about killies but other may help

MrKillie says: Have you noticed a lot of variation in the Lamprichtys populations in Lake Tanganyika, or no variation, or something in between...

Konings says: I have not seen any variation in the Lamprichthys populations, don't think there are

MrKillie asks: hmm.. Are they distributed throughout the lake?

Konings says: yes, they are

MrKillie says: hmm. such a huge distribution, especially in killie terms, yet, so similar....

Horus asks: what do you mean so similar?

MrKillie says: look alike

MrKillie says: no, say, red forms or green forms, or...

MrKillie says: lots of other killies in much smaller ranges show a *lot* of variation

Konings says: The Lamprichthys is found in the upper few feet of the water column and juveniles in the upper inches where they form huge schools and are thus able to migrate from place to place without needing a particular type of habitat

MrKillie wonders just how far they migrate in their lifetimes...

Konings says: I guess killies in other habitats are restricted to the creeks and puddles they inhabit and have difficulty moving from one habitat to the next

MrKillie says: but they support your theory in that there is no variation -> because of no competition

MrKillie says: Lamprichthys is in the group that's rapids-dwelling

MrKillie says: like Aplocheilicthys, Procatopus, Plataplocheilus

Konings says: I don't think they migrate far in their lifetime but very few individuals may..

Conrad says: Whoa There are a lot of people in here.

Horus asks: what is the lifespan of l. tanganicanus in the wild?

Konings says: Just a guess: I think two-three years

Konings says: males are territorial and defend their "cracks in the rock" aggressively against conspecifics

MrKillie says: you see, that then implies they don't migrate much

Konings says: Their continuous fights and display may burn them out in a few months, I don't know

MrKillie says: they live a while in captivity, if well cared for

Horus says: my oldest specimen is 2.25 years old, 10cm

MrKillie just has a hard time envisioning Lamprichthys as the pupfish living in the largest spring in the world :-)

Konings says: In my opinion the most obvious way to create a new race or species is to found a whole new population and this is likely to take place in brand new habitats which could not be settled before

Horus asks: ad, do you know by what mechanism the mastacelbelus sp. spawn?

Konings says: I haven't clue referent Mastacembelus breeding. They are very common in the lake but never seen even babies. They may breed in the shallow swampy surrounding of the lake and not in the lake proper

Horus says: thanks.

MrKillie says: are there any threats to Lake Tanganyika? I've heard rumors of pollution in Malawi...

Konings says: the biggest threat in any lake is overfishing by the locals

MrKillie says: do they eat all the fish they catch? I thought they were mostly after the larger Cichlids

Konings says: nowadays they eat everything they catch also the tiny fishes, because the larger ones are getting scarce...

Horus asks: is it called "sushi" over there as well?

Horus says: :)

Konings says: no it is burnt in the fire

Horus asks: one more question...do syn. Multipunctatus reproduce in the wild by any method other than "cuckoo spawning"?

Konings says: Not that I know but the sometimes large schools of Syn. Make you wonder

MrKillie raises his hand.

Severum bubbles: what plant species are in the lake?

Konings says: yes, Mr Killie

MrKillie defers to Severum

Severum thanks MrKillie.

Konings says: the most common in Malawi and Tanganyika is Vallisneria and Ceratophyllum

Severum nods his head in understanding.

Konings says: there are a few others but in far lower number near swampy shores

MrKillie asks: did all the Cichlids in the lake come from one ancestor, or many?

Konings says: in Malawi probably very few 2-3 in Lake Tanganyika probably up to 10

Melissa says: Ultimately, they all did :)

Konings says: yes but not in the lake

Melissa says: I know

MrKillie says: what is the 'oldest' Cichlid in the lake, I guess I mean most primitive...

Konings says: the lake was likely invaded by several different species

Melissa says: My morp class last quarter was by a prof whose main interest is fish and fish evolution

MrKillie asks: did you use that book edited by Keenleyside?

Melissa asks: Me?

MrKillie nods his head in understanding.

Melissa says: No, he changed the book because too many students complained about heavy fish content :(

Melissa says: Didn't stop me. I did my project on tilapias :)

Konings says: the oldest is not necessarily the most primitive. In Malawi it could be Astatotilapia calliptera

Dev raises his hand.

Konings says: yes dev

Dev says: Ad, how selective are Tropheus when it comes to diet (being aufwuchs feeders) in the lake, since captive fish have a tendency to eat just about anything, regardless of content

Konings says: You are right in the wild ANY Cichlid eats the most attractive or easiest available food

Konings says: Tropheus is specialized on algae because other fishes have eaten the juicy bugs before them

Dev asks: so Tropheus sp. and other aufwuchs feeders like Eretmodus / Spathodus simply reside in high "green" parts of the lake and less available prey?

Konings says: but if they get the opportunity to eat worms, beef heart or chocolate for that matter, they will

Dev nods his head in understanding.

Melissa asks: Do you know of an algae eater that does not have bi- or tri-cupsid teeth?

Konings says: Eretmodus , Spathodus and Tanganicodus have unicuspid teeth in the outer row

Melissa says: Thanks.

MrKillie raises his hand.

Konings says: yes, MrKillie

MrKillie says: Is Eretmodus easily bred in captivity? I've heard widely varying anecdotal info on it, supposedly very tricky

MrKillie says: e.g. E. cyanostictus

Konings says: Eretmodus can easily be bred if you provide a PAIR ample space and very oxygen-rich water

Dev asks: do Eretmodus have a reduced swim bladder like Steatocranus sp.?

Konings says: yes

Dev nods his head in understanding.

Spawn asks: anyone tell me how I can get my hands on so good literature on pike Cichlids?

Mox says: Any book by Ad Konings

Spawn asks: is that right?

Shamu grins.

Konings says: Pike Cichlids: Frank Warzel is working on a book due out end next year with ALL pikes

horus raises his hand with one last question.

Konings says: yes, horus

Horus asks: here in the states, there are "rumors" about "all the good fish" coming out of Europe, Germany, etc. and on the purchasing end, that all the "good stuff" is being snagged immediately by the Europeans and Japanese and the "crap" is what eventually makes it to the states. how true is this?

Konings says: this is not all true. Good stuff gets into the US but people can only get when they pay the European price..

Horus asks: in other words, to get the "good stuff", we have to purchase from a source in Europe?

Konings says: no not necessary to buy in Europe, Old World in Miami has the largest selection of Cichlids that I know of...

MrKillie raises his hand.

Konings asks: what is wrong with your fin, Severum?

(Editor note: before this Severum was heavily waving everyone getting in with his fins and suddenly and unexpectedly stopped, waving have been left out this transcript for readers comfort)

Severum tries to grin but his mouth shape prevents it.

Severum had to rest it. also changed trigger sets. :)

MrKillie says: Ad, some of us were threatening Severum with de-scalation if he didn't turn his fins off

James smiles.

Melissa grins.

(Editor note: again, Severum fins started to wave, also left out) Konings says: glad to see your fin again

MrKillie sighs deeply.

Severum tries to grin but his mouth shape prevents it.

MrKillie sharpens his sushi knife and looks meaningfully at Severum.

Severum nips at MrKillie.

James grins.

Timh grins.

Jasonang smiles.

MrKillie asks: Ad, how important is it to establish captive breeding programs for rift lakers other than Victoria?

Konings says: I feel captive breeding is just creating an excuse to destroy the habitat even more

Mox asks: But with the poverty of the region, is their any hope of conservation?

Konings says: Conservation in Africa? Very little hope...

Konings says: we have to try hard to persuade the local population to conserve but when your stomach is empty.....

MrKillie asks: So, if no conservation, and no captive breeding, will we have F0 Cichlids from Lake Tanganyika 25 years from now?

Konings exclaims: yes!

Konings says: Lake Tanganyika is biiiiig

horus is very glad to hear that.

James nods his head in agreement.

MrKillie ponders.

Mox asks: How about Malawi?

Konings says: still Cichlids in 25 years, yes, but maybe not the variety we see now

Timh asks: what effect will the nile perch have do you think?

Konings says: the effect it had was disastrous enough, a few percent left over of the haplochromines in lake Victoria is a rather dramatic wipe-out

Timh ponders

Severum bubbles: how do you feel about Burundi pond raised fish?

Konings says: Burundi raised fish are OK and comparable to those bred in Florida farms

Severum nods his head in understanding.

Konings says: I have enjoyed being here tonight. Thank you all

MrKillie exclaims: THANK YOU!

Timh says: thank you

Horus says: thank you very much, ad.

Severum nods his head in agreement.

James thanks Konings for visiting FishRoom :)

MrKillie thanks JuanMi for arranging the visit.

Severum bubbles: muchas gracias

Timh hopes he can return again

Dev says: thank you very much Ad

James throws a carrot at the link-mabeast...

Konings says: My pleasure. Juan Miguel just walked out and I haven't a clue how to log off

MrKillie says: type 'quit'

Mox says: I guess you'll be on a lot then.

Spawn laughs.

Konings has left FishRoom.

Citation

Konings, Ad. (May 27, 1996). "Cichlids as a model for evolution". Cichlid Room Companion. Retrieved on October 17, 2017, from: https://www.cichlidae.com/article.php?id=283.