Re: Paraguay and Amazonas

["Nuno Prazeres" <nprazeres@vodafone.pt>]

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 :-( 

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? 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.

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

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?

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?

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?

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

Nuno Prazeres



-----Mensagem original-----
De:	owner-apisto@v2.listbox.com em nome de Mike & Diane Wise
Enviada:	qui 18-03-2004 17:14
Para:	apisto@v2.listbox.com
Cc:	
Assunto:	Re: Paraguay and Amazonas

Nuno Prazeres wrote:

>Dear friends,
>
>Can somebody clarify one doubt I have.
>
>This two systems seem to connect in the Bolivian/Brazilian border just like Amazonas and Orinoco connect in the upper Rio Negro.
>
No. At present there is not linkage between the Amazon system and the 
Paraguay system. In the past it appears that this was not the case. It 
is even possible that the Rio Guaporé once connected with of the 
Paraguay system. We see apisto species that had their origins in the 
Amazon now living in the Paraguay system.

>
>Is the A. trifasciata (or trifasciatum?) the only registered species that shares the two systems?
>
A. trifasciata & A. inconspicua are found in both the Paraguay & Rio 
Guaporé (Amazon) drainages.

>
>Are A. borellii, A. commbrae and A. trifasciata the only Paraguay system apistos?
>
A. pleurotaenia is also believed to come from the Rio Paraguay, but no 
precise collecting locality is known for this enigmatic species.

>Is there any known collection data of A. borellii in the Guapore section where A. taeniata and A. incospicua (appart form A. trifasciata) apparently occur?
>
No. A. borellii is found only in the Paraguay drainage. Many 
morphological and behavioral features of A. borellii are atypical of the 
'normal' member of the genus (whatever that is). This species is not a 
typical forest dwelling apisto. It, like its closest (but not very 
close) relatives in the macmasteri-group generally inhabit savanna 
biotopes. In many respects the macmasteri-group & A. borellii mirror the 
geographic distribution of the Rams (Mikrogeophagus). They probably 
migrated into the Orinoco system at the same time. How they did this is 
a good question.

Mike Wise

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