cross breeding

[apistomaster]

It is a question of time, isn't really?

The collection/theoretical hybrid hot spot that has been there is essentially moving along the river further upstream over geological time but would still remain a collection point of every upstream species and recruitment of some Hypancistrus from nearby river systems down stream even if the location moves, it's basic biotope remains essentially stable the over time but undoubtedly punctuated by periods of climatic changes large enough to affect such a restricted location for extended periods of time. Rapids and water falls are usually relatively young geological features but they do often create species barriers so doesn't it follow that the present diversity of the Hypancistrus present are similarly young as species go? I wonder? Are these Hypancistrus converging into fewer species or diverging into newer species? It could be both but it seems like divergence means ever more refined evolution to fit narrowing niches but what could possibly be the force driving evolution in that direction? It would seem more likely that the evolutionary forces would favor more homogeneity and these fish's color patterns are probably not playing much role in any of this except as far as their appeal to us as aquarium fish. There are few signs of specialization. Only size seems very apparent to me. Some species are smaller; the others larger thus allowing for each to exploit some microniches within the same area more effectively. I doubt much, if any, hybridization occurs between larger Hypancistrus and smaller Hypancistrus species.
There has either been enough geological time passing to allow for species to blend or to diversify. It is a dynamic process and there is no reason preventing both from occurring simultaneously in the same area. Undoubtedly some periods of extremes have occurred over geological time that would have favored both extinction and diversification. The evolutionary "bottle necks"
These conditions and these Hypancistrus do have the makings for a lot of fascinating studies for science and continued confusion for aquarists for a long time to come.

Like I said, it's really all a question of time.

[racoll]

There must be some degree of reproductive isolation, otherwise these fishes would look identical. The strength of this reproductive isolation and the degree of hybridisation is the crucial factor.

Teasing apart the sympatric speciation from secondary contact hypotheses will require a robust phylogeny and a detailed outline of hydrological events in Amazon. A project on phylogeography and speciation in Hypancistrus would be fantastic.

I am half tempted to DNA barcode a few Hypancistrus spp. to get a quick and dirty idea of the amount of gene flow in the group, although I can't have too many personal projects piggybacking my PhD!

[Janne]

Larry,
The way you discuss evolution you assume that it takes millions of years to develope a new species I think? Is that the same for the species in the coral reefs too?

Hypancistrus species dont occur in the upper Rio xingu, the whole river have of course not been investigated but so far no Hypancistrus species have been found more south then the affluents between xingo and iriri and a small part of lower Rio Iriri.
More or less all Hypancistrus species is found from Altamira and down streams, the heavy rapids and waterfalls south of Belo Monte make migration extremely difficult or impossible, thats why no migrating species breed in Rio Xingu.

It could be both but it seems like divergence means ever more refined evolution to fit narrowing niches but what could possibly be the force driving evolution in that direction?

Competition.

These conditions and these Hypancistrus do have the makings for a lot of fascinating studies for science and continued confusion for aquarists for a long time to come.

No, if someone want to make real studies they must hurry, the construction of the Belo Monte dam has not yet started but when it does its to late. The whole stretch of rapids and waterfalls north of Altamira the whole way to the lake will be just a memory when the dam is a reality.

Janne

[Janne]

There must be some degree of reproductive isolation, otherwise these fishes would look identical.

Yes, many areas only 1 species is found but at Belo Monte you find them all.

Janne

[mummymonkey]

Perhaps the populations were once isolated but the river has moved course or something. If the hybrids are even a little less fertile this would allow for a stable "hybrid zone". Where I live a similar thing has happened with crows.

[Janne]

The latest larger geological change in Rio xingu was at the last iceage, under this time the lake didnt exist downstream Belo Monte but due to the high altitude differencies the lake become very deep after the latest iceage... much faster flow and much higher waterfalls then today made Rio xingu completely isolated.

Janne

[apistomaster]

Hi Janne,

No I do not think it takes millions of years for species to evolve.
I suspect all but the ancestral forms of Hypancistrus date back no more than the early to mid-Pliocene, rather recently, although I have not actually checked to see if any research supports my opinion.
I am quite aware that speciation can occur within very short time spans under conducive circumstances. I believe that is our shared point about the Rio Xingu's peculiar environment and it's Hypancistrus species.

I lean towards the belief that these lower Xingu and neighboring river systems have species that are actually so young that they are probably still very much in the process of speciation and therein lies so much of the difficulties in our attempts to identify many of them as being very distinct from one another.
Rapids and water falls just happen to change rapidly as geological time goes which is not in conflict with my above stated opinions on the youth of the Rio Xingu Hypancistrus species.

In the case of reef fish in general, I do not think they are evolving at a rate very close to that of the the Hypancistrus or indeed, most other Neotropical fish. But that being said, I have no doubt 1000's of reef species have formed during the same time but reef ecosystems have tended to be a bit more stable than that of the freshwater Neotropics throughout the Pliocene and did not evolve as much.

[Janne]

I lean towards the belief that these lower Xingu and neighboring river systems have species that are actually so young that they are probably still very much in the process of speciation and therein lies so much of the difficulties in our attempts to identify many of them as being very distinct from one another.

I think so too, but Rio xingu is unique. No other river systems in south america shows the same variety then they do in Rio xingu and only between Altamira and particular near Belo Monte, not at all the same variety uppstreams xingu. All other riversystems in Brazil have only few very stable species of Hypancistrus if there is any Hypancistrus species at all, what we know... maybe someone will find a few new species.

In the case of reef fish in general, I do not think they are evolving at a rate very close to that of the the Hypancistrus or indeed, most other Neotropical fish. But that being said, I have no doubt 1000's of reef species have formed during the same time but reef ecosystems have tended to be a bit more stable than that of the freshwater Neotropics throughout the Pliocene and did not evolve as much.

Like I said, there are a few really hot spots when it comes to coral reef, new "species" each year both of fishes and corals... in general no but at some extreme places yes, than I'm not sure this few new species would survive as species... but when a human find one of them it's a new species and how many have been missed that we did not find?
This is just speculation and not relevant, my point is that there are hot spots where things evolve faster then we think and one of very few of these could might well be around Belo Monte in Rio xingu... no one make any research today on these species of Hypancistrus in Rio xingu, why when everyone knows there is a time limit?

Janne

[apistomaster]

With the days of the free flowing Rio Xingu so few in number, about all I think I can do as an only an aquarist, is to do my best to contribute to the captive breeding of a handful of distinctly different Hypancistrus species/varieties and that is exactly what I am doing.

The environmental problem the Belo Monte project will cause exceeds my scope and abilities to influence. It is truly regrettable there is no time to perform thorough field studies and proper classification of all the species we might identify before the Hydro project permanently destroys any chances of doing that work.

I humbly attempt to maintain a half dozen Hypancistrus species and and try to recruit new breeders. I am networking with other breeders so I can coordinate my work with theirs so we cover as many Brazilian Hypancistrus species as possible That is all I can do as an individual.
I know I have offended a few people who wanted to buy a single specimen from me but I only sell my fish in lots of at least 6 because those who buy 6 or more fish are generally hopeful future breeders, more committed to breeding than the simple collectors of one of a kind. We need as many interested parties as we can get to help preserve the species we have in our tanks now for the future richness of the hobby. Eventually there will be surplus home bred Hypancistrus species which may be sold individually but I don't believe we breeders have reached that point yet with couple exceptions like L333 and H. zebra which seem to now be firmly established in the hobby. At least there are a number of hobbyists around the world who are trying. It doesn't matter if profit, personal satisfaction or both are their motivations so long as we save as many species as possible, even with all the flaws all captive breeding programs have, it is still better than doing nothing.
It takes more commitment to strive for Brazilian Hypancistrus species maintenance than it does to continue most tropical fish in the hobby because it takes many years to establish breeding colonies initially and thereafter.
My interest is much more recent in these Hypancistrus species maintenance projects than some others and a much greater test of my patience than when I have been involved with Killiefish species maintenance programs where many species are annuals and only live less than one year. I used to think that the generational time of Discus, one year, was a long time but it is not. Not compared to these damned little plecos.

I have strayed far from the original subject of this thread with my ramblings but it is important, in view of our limited knowledge about which of our species are valid or merely naturally occurring variants, that we do our best to retain each in it's distinctiveness by avoiding indiscriminate hybridization which is all to easy, unfortunately, in aquariums. Serous breeders will always do their best to always distribute their bred fish with the most accurate designation as we have so far been able to define.

[Suckermouth]

I suspect all but the ancestral forms of Hypancistrus date back no more than the early to mid-Pliocene, rather recently, although I have not actually checked to see if any research supports my opinion.

Current evidence shows that some current genera were in existence in the Miocene in the Neotropics, with fossils of some familiar genera such as Arapaima, Phractocephalus, Brachyplatystoma, and Colossoma already present. The Miocene fish fauna was likely not that different from that today, however today's species were not necessarily present for that long. On the other hand, despite their bony plates, loricariid fossils are exceptionally rare, and there are no known examples of current loricariid genera in the fossil record. A fossil loricariid Taubateia piraiba is described from the late Oligocene-early Miocene.

In the case of reef fish in general, I do not think they are evolving at a rate very close to that of the the Hypancistrus or indeed, most other Neotropical fish. But that being said, I have no doubt 1000's of reef species have formed during the same time but reef ecosystems have tended to be a bit more stable than that of the freshwater Neotropics throughout the Pliocene and did not evolve as much.

Interestingly, many coral reef fish genera also go back to the Miocene, and even Eocene for some genera. Although oceans are certainly stable, the shallow reef habitat is fairly ephemeral; the Great Barrier Reef, one of the largest and likely oldest tropical coral reefs, has only existed since the Pleistocene.

There must be some degree of reproductive isolation, otherwise these fishes would look identical. The strength of this reproductive isolation and the degree of hybridisation is the crucial factor.

Teasing apart the sympatric speciation from secondary contact hypotheses will require a robust phylogeny and a detailed outline of hydrological events in Amazon. A project on phylogeography and speciation in Hypancistrus would be fantastic.

I am half tempted to DNA barcode a few Hypancistrus spp. to get a quick and dirty idea of the amount of gene flow in the group, although I can't have too many personal projects piggybacking my PhD!

There is a book in the works on biogeography of the Neotropics that'll contain chapters and information from numerous Neotropical ichthyologists. The main guy coordinating it, James Albert (a gymnotiform systematist), came to Auburn to talk about it and gave a seminar. One of the findings from the book is that speciation is almost entirely allopatric in the Neotropical rivers. Instances of congeners are secondary contact. Also, assemblages of related fish in the same locality are not each other's closest relatives.

[apistomaster]

Lack of fossils is to be expected and why like, racoll, I think it would be great to do the bar code of as many Hypancistrus as we have on hand and see what we can infer from those results.

[Mike_Noren]

Yes I know, but my point is; why cant similar hot spots exist in freshwater even if they are very rare.

Hybridization in animals typically reduces variation and causes coalescense of species, it does not normally increase variability or lead to speciation. The rare exceptions are hybrid species such as the Edible Frog (Rana esculenta) in Europe, a fertile hybrid between Rana lessonae and Rana ridibunda.
The most common reason for an area to be speciose is that it's an area which has remained relatively unchanged for a long time. Partly because that allows sufficient time for speciation, but also because such areas tend to have served as a refugium (place of refuge) for species during earlier changes in climate, ie glaciation cycles. This is why Spain, Italy and the Balkans are far richer in species than the rest of continental Europe.

My guess is that the Altamira area of Xingu is/was so full of endemic species because it, unlike most of the Amazon, has been pretty much unchanged for several million years.

Also some species-groups just speciate at the drop of a hat. The best studied is probably Salmonids who very quickly (thousands of years) tend to form multiple reproductively isolated and morphologically distinct populations/species in every lake and river they're found, but Loricariids certainly seem to be quick to speciate too as soon as some sort of reproductive barrier exists.

[Janne]

Hybridization in animals typically reduces variation and causes coalescense of species, it does not normally increase variability or lead to speciation. My guess is that the Altamira area of Xingu is/was so full of endemic species because it, unlike most of the Amazon, has been pretty much unchanged for several million years.

It has been isolated since maybe 60 million years if we can trust the geological history, if there is a hotspot similar like is found on a few places in the oceans the variety should be great until the nature make the selection how will survive as a new species.
It's an ongoing process in front of our eyes, even if there are 50 or 100 varieties right now at this moment, there maybe only will be a few of these surviving as a new stable specie.

Janne

[apistomaster]

Hi Mike and All,

My other passion is fly fishing for trout and I have studied more about Cutthroat Trout, Oncorhynchus clarki and it's 10-14 subspecies than any other fish. The classification of this species took the "splitter's" route which I am generally a little uncomfortable with but it is one of the best studied of all North American Trout species.
Yet the facts remain that there are many different distinct and geographically isolated forms and some rarely grow more than 12 inches while one subspecies native to large ancient remnant desert lakes have evolved to survive in mineral rich waters so saline and high in carbonates and sulfates that only a few minnows that co-evolved are the only fish able to tolerate the extreme chemistry. These Lahontan cutthroats, Oncorhynchus clarki henshawi, historically exceeded 40 lbs.
It is believed that the ancestral form, which is still extant, is the Sea Run Cutthroat, Oncorhynchus clarki clarki.(One of my favorite quarry).
The Cutthroat Trouts are one the two native Trout west of the Mississippi River and are found on both the east and west slope of the Rocky Mountains. The Rainbow is only native west of the Rocky Mountains.
The Westslope cutthroat trout O. c. lewisi, is "my" local native Trout. I fish for them in Idaho's Lochsa River which is a high mountain stream. I have tested it's waters pH and TDS. The pH was only 5.1 and the TDS was only 15 ppm. I was amazed at the relative purity of the water and this limits it's productivity although I have caught fish up to 18 inches and a few have been caught that exceed 20 inches. It may take 8+ years or them to reach that size in this pure and relatively biologically unproductive water. They share this river with only the Sea Run Rainbow trout, aka Steelhead, Oncorhynchus mykiss. The Steelhead smolts migrate downstream so they do not compete strongly with the native resident Cutthroat trout.

I only brought up this much detail about a sports fish because I have thought a lot about how the many divergent types which are clearly Cutthroat Trout were classified as subspecies but if they were Hypancistrus species I think they would have been classified as many separate species. I don't think I have ever mentioned implying that maybe there are many subspecies of only a few Hypancistrus superspecies in the Rio Xingu because I figured that idea would go over like a lead balloon so I'm glad you provided me an opportunity to expand on this a little. It has always been something of a mystery to me as to what fish merit subspecies designation while others apparently just as similarly related are given full species status.

My local subspecies is restricted to only some of the very pure high mountain rivers of the Rocky Mountain Westslope.
Within their rivers they often are cogeners with Rainbow Trout but each prefers different parts of the river. The Cutthroats prefer runs of 2-6 feet of water while Rainbows prefer rougher water, rapids with boulder pockets. Both are spring spawning fish but originally the native populations rarely hybridized although once non-native populations of Cutthroat trout or Rainbow Trout were introduced to either species native waters, the alien species and/or strains began to easily hybridize with the other and the resulting fertile hybrids are commonly called "Cuttbows". They can have phenotype that represents any point on the continuum between both traits of each species being expressed to varying degrees. Agencies have stopped stocking programs and now manage native trout fisheries much more prudently. Much damage has been done to the purity of both the native Rainbow and cutthroat trout in much of the range of these two species during the years of stocking hatchery produced fish for harvest. Catch and release regulations and wild trout management programs have salvaged some populations like "mine."
Here are a few photos showing the same river and typical Cutthroat habitat and typical rainbow habitat for comparison and one gratuitous photo of one of the many lovely wild West Slope Cutthroats I caught and released on an outing last fall.

1. Prime Cutthroat trout habitat. Lochsa River, Idaho


2. Prime Rainbow Trout habitat. Lochsa River, Idaho, only about 150 meters down steam from the Cutthroat water.


3. A female in excellent condition of Wild West Slope Cutthroat prior to release.
a

http://en.wikipedia.org/wiki/Cutthroat_trout
http://en.wikipedia.org/wiki/Rainbow_trout

[Carp37]

Interesting points raised by Frank and Janne. I'm not especially up on Hypancistrus, due to their being expensive, requiring specialist conditions just to keep, let alone adjusting water parameters for breeding, plus they're fairly nocturnal. I know many of them look much the same shape to the untrained eye, but are any of them morphologically almost identical? I suppose I'm trying to get a handle on how similar these species/subspecies/races are, despite variations in colouring.

[Mike_Noren]

Hybridization in animals typically reduces variation and causes coalescense of species, it does not normally increase variability or lead to speciation. My guess is that the Altamira area of Xingu is/was so full of endemic species because it, unlike most of the Amazon, has been pretty much unchanged for several million years.

It has been isolated since maybe 60 million years if we can trust the geological history, if there is a hotspot similar like is found on a few places in the oceans the variety should be great until the nature make the selection how will survive as a new species.
It's an ongoing process in front of our eyes, even if there are 50 or 100 varieties right now at this moment, there maybe only will be a few of these surviving as a new stable specie.

I'm honestly doubtful there exist any freshwater bodies on the planet as old as 60 million years. The oldest lakes on the planet - Tanganyika and Baikal - are 10 - 20 million years old, and in a class pretty much all their own with regards not only to age, but also biodiversity. Parts of some rivers are no doubt older, though I do not know how old Xingu is.

You're right that extinction will play a role in making the species distinct.

@Apistomaster: Yes, the situation is pretty much the same with salmonids all over the arctic: they are in the middle of an explosive radiation, and even though many forms live in areas which were scoured clean by the inland ice sheet just a few thousand years ago, they are highly morphologically distinct, differing wildly in size and pigmentation. However, if you sequence their DNA they're nearly identical - COI barcoding typically can't tell a population of minnow-like silvery 5" arctic charr from a population of two foot long dark brown fish eaters. Even though reproductively isolated, the populations/morphs/species are simply too young, their DNA haven't diverged enough for detection.
Even weirder is that those tiny minnow-likes and the big browns can live in the same lake, and the only barrier to hybridization is their choice in spawning area or spawning time.
The species concept used on "exploding" groups like these vary with who's doing the identifying. One researcher told me that if the same species concept was used for salmonids in Scandinavia as is used for salmonids in mainland Europe, there would be some 800 more species of salmonid.

I do not know if loricariids are quite as extreme as salmonids, but it may well turn out that barcoding wont help resolve relationships among many closely related species.

[Shane]

Just a couple of comments in general.

1) Speciation can happen very fast. Lake Nabugabo only became separated from Lake Victoria 5,000 years ago (by a sand bar). It now has half a dozen endemic cichlids. I would love to gather data from the various catfishes there and compare this data to populations collected in Lake Victoria. How different are the two catfish populations already?

2) Loricariids are "fast evolvers" which is born out by the pure number of genera and spp. It is the most speciose family of catfishes for a reason.

3) Variation will be the largest at the epicenter of an evolutionary event. There is a good chance that the epicenter of Hypancistrus evolution is near/at Altamira. Hypancistrus is a relative new comer as evidenced by its absence from drainages created by the eruption of the Andes. They are absent from the Magdalena, Maracaibo, Pacific coastal and Caribbean coastal drainages. They are also absent from all the southern cone drainages to my knowledge. They clearly thus have not been around as long as Ancistrus, Chaetostoma, Panaque, Rineloricaria, and other genera that inhabit all of these drainages.

-Shane

[racoll]

It has always been something of a mystery to me as to what fish merit subspecies designation while others apparently just as similarly related are given full species status.

Now that is the $1,000,000 question Larry.

First off, I do have to do a lot more reading to do on the subject of subspecies, but here are my current thoughts (please forgive the ranting).

Subspecies were created to describe intraspecific variation under the biological species concept, where species were proposed to be entities that are unable to produce viable offspring.

Now, I don't like the biological species concept one bit, as it recognises diversity far too late in the process of divergence, ignoring evolutionary independent lineages which are clearly different, but may well hybridise. The subspecies concept was created to recognise this problem for those entities within a biological species that are morphologically different, but would be able to breed together and produce offspring given the opportunity.

In reality I would guess that only a handful of creatures have ever been described on the basis of breeding experiments, and these were certainly carried out in captivity, which does not reflect natural conditions. This to me makes the biological species concept irrelevant, with essentially untestable hypotheses.

So, what has happened , especially in birds and insects, is the species rank used when "large" differences are clear, while the subspecies rank being ascribed to variation that is only "slightly" different. These relative, and totally subjective differences are basically used as a proxy for whether something is capable of producing fertile offspring or not. This I think is poor science.

There has been a few papers criticising the recognition of many avian subspecies, pointing to lack of reciprocal monophyly as evidence of misleading classification; i.e. that subspecies should be monophyletic, and indicating that workers have been describing local populations with slightly different morphologies as different subspecies.

My first choice would be to recognise all independently evolving, monophyletic groups as separate species, no matter how small the difference is, and providing data are presented and defended in concordance with our current knowledge of the systems involved. There is no need for subspecies therefore, as the species rank becomes the smallest unit of formal biodiversity. I am glad that most if not all current ichthyologists agree with this idea, and therefore do not use the subspecific taxon.

However, I can see a case for recognising a subspecies in certain circumstances, but not how it has been used historically. If one wants to name local populations that have not demonstrated an independent evolutionary history, but look different in some way, then perhaps the subspecific taxon name could be used for this? An excellent example for you Larry is the discus (Symphysodon spp.). Perhaps one species and three subspecies would reflect the incipient speciation process of this group?

One researcher told me that if the same species concept was used for salmonids in Scandinavia as is used for salmonids in mainland Europe, there would be some 800 more species of salmonid.

There are many that would say "great, we'd better get on with describing them then", so, is the large number a reason not to recognise them?. The radiation of rift lake cichlids have received a full taxonomic approach, and a lot of study effort, so why not the post-Pleistocene salmonid radiation? In Kottelat and Freyhof's European freshwater fishes book, they speak of people's denial of biological reality regarding these fishes.

In conclusion, although I doubt there will ever be an objective way to delineate all living creatures into species, methods such as the phylogenetic species concept are more inclusive of evolutionary theory, and are therefore eminently more applicable to hypothesis testing in a scientific context.

[Janne]

I'm honestly doubtful there exist any freshwater bodies on the planet as old as 60 million years. The oldest lakes on the planet - Tanganyika and Baikal - are 10 - 20 million years old, and in a class pretty much all their own with regards not only to age, but also biodiversity. Parts of some rivers are no doubt older, though I do not know how old Xingu is.

Lakes is much younger then the oldest rivers. The biodiversity in Amazonia is far far more higher than Tanganyika and Baikal together.

The Guyana shield and the Brazilian shield is one if not the oldest rocks in the world dated at least 590 million years old, for >160 million years ago the amazon river was floating to the west out in the Pacific ocean. Between 160 to 60 million years ago the amazon was probably the largest lake ever existed on earth when the Andean mountain raised in the west, for 60 million years ago the Guyana shield and the Brazilian shield moved apart and the lake start to drainage into the Atlantic ocean and the Amazon river was born. Of course there have been large geografical changes since then but many of the Amazons tributaries have similar age, the Amazon river needs to be fed just like all other river systems even at that time. I maybe not have the exactly time scale but very close I think.

3) Variation will be the largest at the epicenter of an evolutionary event. There is a good chance that the epicenter of Hypancistrus evolution is near/at Altamira. Hypancistrus is a relative new comer as evidenced by its absence from drainages created by the eruption of the Andes. They are absent from the Magdalena, Maracaibo, Pacific coastal and Caribbean coastal drainages. They are also absent from all the southern cone drainages to my knowledge. They clearly thus have not been around as long as Ancistrus, Chaetostoma, Panaque, Rineloricaria, and other genera that inhabit all of these drainages.

I think Hypancistrus species is one of the youngest if not the youngest genus within Loricariidae (Ancistrinae), compairing the reproduction behaviour and the genital papilla between the relatives in the genus Peckoltia and Panaque (Panaqolus) I would say that Panaque is the oldest, than Peckoltia and last Hypancistrus if they share some common ancestors.


Janne

[Mike_Noren]

The Guyana shield and the Brazilian shield is one if not the oldest rocks in the world dated at least 590 million years old, for >160 million years ago the amazon river was floating to the west out in the Pacific ocean. Between 160 to 60 million years ago the amazon was probably the largest lake ever existed on earth when the Andean mountain raised in the west, for 60 million years ago the Guyana shield and the Brazilian shield moved apart and the lake start to drainage into the Atlantic ocean and the Amazon river was born. Of course there have been large geografical changes since then but many of the Amazons tributaries have similar age, the Amazon river needs to be fed just like all other river systems even at that time.

Scandinavia largely consists of 1.8 billion year old rock, yet is one of the species-poorest temperate areas on earth because it was scoured clean by the inland ice; it's not how old the rock is, it's how long the environment has been roughly unchanged. In the case of Amazonia it partly dries and becomes savannah every glaciation cycle, with rainforest organisms surviving in small scattered refugia, spreading out again when climate became wetter. I wouldn't be surprised if Xingu, which is unusually rich in endemic species also of other groups (snails, cichlids, tetras... there was even a frog endemic to Altamira) has remained fairly unchanged for an unusually long time.

[Janne]

Scandinavia largely consists of 1.8 billion year old rock, yet is one of the species-poorest temperate areas on earth because it was scoured clean by the inland ice; it's not how old the rock is, it's how long the environment has been roughly unchanged.

Ok, in that case the Guyana shield and the Brazilian shield is one if not the oldest rocks in the world dated at least 590 million years old that not have been cleaned by the inland ice ;)

In the case of Amazonia it partly dries and becomes savannah every glaciation cycle, with rainforest organisms surviving in small scattered refugia, spreading out again when climate became wetter.

Eh, only small areas on the highlands was probably because we don't know for sure partly dried, there are many oil reservoars at quite high altitude in the Amazon. The form and shape of the large "lakes" in the mouth of Rio tocantins, Rio xingu and Rio tapajos was created under the glaciation cycles, these rivers must be very very old. The lowland of Amazonas was probably never dried out and have remain quite intact.

A study have been made of the fish biodiversity in Rio xingu, very small parts under a couple of months was investigated and they found 480 species and 1 Hypancistrus species H. zebra It's not only a high variety among Hypancistrus in this river, there are at least 5 different "Golden Nugget" varieties, 3 other Baryancistrus species, around 8-10 different Oligancistrus varieties/species and so on; there are at least 100 species of Loricariidae in this river and that is a low number.

Hypancistrus is a relative new comer as evidenced by its absence from drainages created by the eruption of the Andes. They are absent from the Magdalena, Maracaibo, Pacific coastal and Caribbean coastal drainages. They are also absent from all the southern cone drainages to my knowledge. They clearly thus have not been around as long as Ancistrus, Chaetostoma, Panaque, Rineloricaria, and other genera that inhabit all of these drainages.

All these species and some other or their ancestors must have been spread to all other drainages before the Amazon turned around to the east direction, at that time Hypancistrus did'nt exist.

Janne

[Suckermouth]

A study have been made of the fish biodiversity in Rio xingu, very small parts under a couple of months was investigated and they found 480 species and 1 Hypancistrus species H. zebra It's not only a high variety among Hypancistrus in this river, there are at least 5 different "Golden Nugget" varieties, 3 other Baryancistrus species, around 8-10 different Oligancistrus varieties/species and so on; there are at least 100 species of Loricariidae in this river and that is a low number.

Are you saying that there is only one Hypancistrus in the Rio Xingu? I'm confused.

Any idea who did the study and where the specimens might be stored?

[Janne]

Are you saying that there is only one Hypancistrus in the Rio Xingu? I'm confused.

No, I'm saying they are incompetent. The study was made for some years ago of the university in Belém... I have to find it again to tell if it was the UFPA (University Federal PARA) or a local university. I do understand the difficulties to investigate the whole Rio xingu drainage, it's 504.000 km2 or the size of France; I can collect the same amount of species in one week only around Altamira and Belo Monte with small tributaries where all nice tetras and Apistogramma species is hiding. PM or use my email for a copy.

Janne

[Mike_Noren]

A study have been made of the fish biodiversity in Rio xingu, very small parts under a couple of months was investigated and they found 480 species and 1 Hypancistrus species H. zebra It's not only a high variety among Hypancistrus in this river, there are at least 5 different "Golden Nugget" varieties, 3 other Baryancistrus species, around 8-10 different Oligancistrus varieties/species and so on; there are at least 100 species of Loricariidae in this river and that is a low number.

When was that diversity study done? Some time ago I tried to see how many species were reported from the various rivers scheduled to be dammed in the Amazon, and found only ridiculously low numbers, e.g. 34 species for Rio Madeira (even scandinavian lakes have more species than that!), apparently because Brazil does not share biodiversity data.

[Janne]

The study was made under 2001 and 2002, by UFPA and listed 467 species.
I find the paper if someone want a copy, send me a mail or pm.

I think Rio Madeira have ~500 species listed and an estimation made around 700 species of fishes if I can find the right paper.

Janne

[Bas Pels]

Lakes is much younger then the oldest rivers. The biodiversity in Amazonia is far far more higher than Tanganyika and Baikal together.

I wonder, lake Tanganyica has a lot of species, but mostly cichlids. Lake Malawi is even more extreme - 80 % of the species in thatr lake are cichlids

If one would count species, the description of another cichlid in lake Malawi would increase the recorded biodiversity - but it is still mostly cichlids

The Amazon river has cichlids, catfish, a lot of tetras and other Charicins (I hope I wrote this correctly ) which results in much more different designs

If one would count designs instead of species, the outcome might be that some rivers are much less interesting

[Janne]

I wonder, lake Tanganyica has a lot of species, but mostly c*****ds. Lake Malawi is even more extreme - 80 % of the species in thatr lake are c*****ds

If one would count designs instead of species, the outcome might be that some rivers are much less interesting

You can stop wonder, the amazon have much more biodiversity than Baikal, Tanganyica AND Malawi together.

Only Brazil stands for 12% of the whole worlds biodiversity and that only counted scientific described species, 3000 fish species only in Brazil official... I can ensure you, that you need to double that number to even get close to the correct number. Even if we would put together all the Ichthyologists in the world make them work in Brazil they would not be finished under their lifetime.

Janne

[Bas Pels]

I intended another opinion: What is biodiversity?

is it just the total of species, or does it mean the variety? 2 kinds of Hypancistrus will be quite similar, much more similar than a Hypancistrus and a Pimelodus

Both the above contain 2 species, but the second is much more divers - thus the diversity is larger

[Janne]

Bas Pels,
I do understand that 2 different genus is more diverse than 1 genus, but whats your point? That 2 different Mbunas is more diverse than other genus from south america?

Janne

[Shane]

the amazon have much more biodiversity than Baikal, Tanganyica AND Malawi together.

Also, in all fairness, the Amazon in terms of water volume (i.e. fish living space) is greater than the Ganges, Congo, Orinoco, Yangtze, Mississippi, Volga, Nile, and Mekong systems combined. Let that sink in a bit. If you break it down this way it looks a bit different. Sure the Mekong has less spp than the Amazon, but it is also only 7% the Amazon's size in volume.

I am not sure we can say the Amazon has more biodiversity than say Lake Tanganyika. Break it down by volume of water divided by number of sp and Lake Tanganyika will come out far ahead. This is not to belittle the incredible richness of the Amazon, just to point out that there are many ways to measure biodiversity and a straight count of described spp is not one when comparing bodies of water of such disparate sizes.

I see Bas Pels point. His point is related to my comments above with regard to measuring biodiversity. If we count number of spp per 1,000 cubic liters of water (or some such thing) Tanganyika has a greater diversity than the Amazon. However, in Tanganyika, 90% of the spp present all belong to the same family (Cichlidae), not nearly as impressive as the dozens of unrelated families that make up the Amazon's fishes.

As Mark Twain said, "There is lies, damn lies and statistics."

-Shane