Re: Paraguay and Amazonas]

[Mike & Diane Wise <apistowise@bewellnet.com>]

Nuno Prazeres wrote:

> Thank u Mike for your grat help! So I guess I can not use Nannostumus 
> trifasciatus and other amazonic species with A. borellii in my biotope 
> :-( 

If you are trying for an accurate biotope aquarium, then no. I know of 
no pencilfish (or any lebiasinid for that matter) that comes from the 
Paraguay system.

> I have been studying collection data from Paraguay system and a few 
> days ago came across some info about the Guapore bassin. It is indeed 
> amazing that a fair number of Characidae species seem to prosper on 
> both systems showing that the two must have been in fact connected not 
> too long time ago.
> Does this mean the speciation process that created A. borellii occured 
> after the loss of the connection?

I personally believe that A. borellii was the first apisto to enter the 
Paraguay system. It entered long before the Guaporé-derived species.

> The non specialization of A. borellii should have provided the 
> oportunity for expantion to the North. Another interesting fact in my 
> humble opinion is that A. commbrae and its close cousin A. incospicua 
> seem to be very primitive Apistos and that shows the genera existed 
> there for quite a long time.

I consider A. borellii to be a savanna specialized species. One 
possibility why it is found only in the Paraguay system is, that during 
one of the dry periods during the Pleistocene Epoch the eastern Amazon 
Basin was mostly savanna instead of rain forest. In such an environment 
the ancestors of both A. borellii and the macmasteri-group possibly 
inhabited this region. Once another pluvial period started, savannas in 
the eastern Amazon were replaced by rain forest, forcing the savanna 
species out of the region. From there they might have spread into 
savanna biotopes in the Paraguay & Orinoco systems. This scenario has 
problems, however. If A. borellii has inhabited the Paraguay system for 
so long, why has it not speciated into other forms? One possibility is 
that A. borellii was restricted to a small part of it present range for 
most of the time. If this area had stable biotopes and were all 
interconnected, then there would be no need for speciation to occur. 
Later it was able to invade the southern part of the Paraguay system 
only recently. There are many questions with this scenario & it probably 
is not entirely accurate. It might not be accurate at all.

I think one thing that we are fairly certain about is that species of 
the commbrae-complex are very closely related to those of the 
resticulosa-complex. It appears likely that the commbrae- and 
urteagai-complexes are derived from species of the older 
resticulosa-complex. I, too, once thought the commbrae-complex species 
were rather primitive apistos. But after reading Kullander's ideas of 
phylogeny in South American cichlids & discussing them with Koslowski, I 
can see that what we once thought of as ancestral features on apistos 
actually are not.

If we look at where we find representatives of most Apistogramma 
species-groups closely associated, then we probably have found the point 
where apistos first arose from non-apisto ancestors and then radiated 
outward. One good source is the southern foot hills of the Brazilian 
highlands in the upper Rio Madeira drainage. There we find members of 
the steindachneri-group, regani-group (including to supposedly most 
primitive complex, the eunotus-complex), the pertensis-group, the 
cacatuoides-group (including the most primitive, A. staecki), and the 
agassizii-group. I feel that this is the source area for at least all 
species-group found in the western Amazon Basin. The species-group in 
the eastern part of the Amazon Basin seem to be older, except for 
species from western groups that have recently invaded the area. These 
groups of species (caetei-, Xingu-, & possibly regani-complexes & A. 
borellii) appear to have derived from species farther east, in the Mato 
Grosso area.

> Can the similarities with the macmasteri group be explained only by 
> some kind of environmental triggered convergence?

Convergence is certainly a good possibly. It even happens with species 
from different families & orders of fish. It does not explain why the 
genus Mikrogeophagus, which has a similar range, came to be so widely 
separated, too.

> I dont know anything about ichtiology :-( but I would say that some 
> external characteristics of Apistogrammoides pulcapensis look quite 
> similar to A. borellii. Cd it be a offshot of an A. borelli ancestor 
> just like T. candidi is by some said to be an offshot of A. agassizii?

I think that Apistogrammoides pucallpaensis has many feature similar to 
those of urteagai-complex species. Taeniacara candidi actually appears 
to be more closely related to A. elizabethae.

> By the way... Is this late statement true?
> Aggies seem to be quite "recent" apistos giving the number of 
> sub-orbital pores. And if this is true how fast could an ancestor 
> aggie become a diferent genera?

As I said, Taeniacara candidi actually appears to be more closely 
related to A. elizabethae. I even have a photo of a fish from a Japanese 
aquarium magazine that appears to be a bridge between A. elizabethae & 
T. candidi. Genera are based on features considered by the taxonomist to 
be sufficiently different as to not easily fit into a previously 
established genus. Taeniacara is significantly different from 
Apistogramma primarily due to the loss of a lateral line. Is this 
sufficient enough to put it into another genus? It is up to the 
taxonomists to decide. Kullander considered Taeniacara & 
Apistogrammoides so close to Apistogramma that he did not even list them 
in his cichlid phylogeny. Taeniacara was also described as an 
Apistogramma species - A. weisei - only a few months after being placed 
in its own genus. Imagine if this description had been earlier than the 
T. candidi description. Do you think that it would now be called A. 
weisei? Probably. In truth, A. borellii has features (especially 
behavioral ones) sufficiently different as to be considered in a 
different genus, too. Should it be in its own genus separate from 
Apistogramma? Possibly yes, but it is just speculation.

> I think there is a niche of oportunity for someone to build up a 
> computer model showing the evolution of the 3 big river systems of 
> South Am at least since the last glaciation. This models do exist for 
> the ocean but the change in level would be much more dramatic there I 
> would say.


> All the understanding about speciation and cladistic relationships in 
> apistos and other genera will gain a lot.


> Better than that the model might help us to predict the future 
> dynamics of the bassins and how they would cope with global warming, 
> deflorestation and other human induced factors. Anybody looking for a 
> great PhD subject?

Sounds good to me. Who has the money & time to research this? 
Additionally, the geologic history of the area, the Amazon in 
particular, is so poorly understood that we cannot actually understand 
past biotopes until we know the history of the area. Right now DNA 
studies are the rage. These appear to provide faster & less expensive 
means of determining interrelationships.

> Maybe my ignorance became much more evident after posing this 
> questions but this matter is fascinating enough for one to risk 
> exposing his stupidity :-)

In this regard I think that we are all ignorant (we lack sufficient data 
to produce a workable theory). Only by first asking the questions can we 
try to answer them.

Mike Wise

> Best regards to all
>
> Nuno Prazeres
>
>
>
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