Re: Paraguay and Amazonas

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

Per,

I am not sure what you consider is a "highly specialized" species. There 
are actually very few truly specialized species. A. diplotaenia is 
specialized in its body and breeding to life in open river systems. A. 
sp. Mouthbrooder has a specialized form of breeding. Many species have 
adapted to extreme water values & temperature ranges, but on the whole 
are fairly generalized.

What might surprise the average apistophile is that species in many of 
the older species-groups appear to be specializing by becoming more 
cryptic in shape and color. That means there is a trend to becoming 
smaller, less colorful, and having less ornate fins. On first 
consideration, this does not appear logical. One would think that the 
original fish would be small, less colorful fish without exaggerated 
features, but let us consider Dr. Kullander's South American cichlid 
phylogeny. In it he lists Apistogramma & Gymnogeophagus as sibling 
genera with a common ancestor. If we look at physical features of the 2 
genera we actually see some of these similarities. Some of these 
features include a small to moderate size; moderately elongate & 
moderately laterally compressed body; vertical bars on the body (these 
bars are often split on displaying fish); broad stripes through the eyes 
(suborbital & supraorbital); a prominent spot in the mid-flank area 
(often surrounded by a pale halo - especially in Gymnogeophagus); a 
caudal spot; a relatively narrow lateral band; caudal fin often squared 
off or double tipped (commonly with alternating dark and light stripes); 
dorsal & anal fins moderate in height and showing slight serrations; 
metallic markings on face & flank scales (often brighter in the 
centers). Not all of these features are common to only these 2 genera, 
of course, but appear on many other geophagines. If we consider all of 
these features, we can now guess what the ancestral Apistogramma might 
possibly look like.

The ancestral apisto was probably large for an apisto, with moderately 
high, serrated dorsal and anal fin spines. The caudal fin was probably 
squared off  or double tipped and probably was striped. It probably had 
well developed facial markings, especially pronounced cheek & forehead 
stripes. The body probably showed dark edged, metallic scales, a narrow 
lateral band, a caudal spot, a flank spot surrounded by a light halo, & 
broad vertical bars that would split in threat display. Now let us look 
for present day apisto that combines most of these features. Those with 
more of these ancestral features (plesiomorphs) are probably closer to 
the ancestral species than those that have fewer. There are many that 
show most of these features. Of all of the presently know species, the 
species of the steindachneri-group show the most of them.

Let us consider A. steindachneri as a present day species that most 
closely represents this ancestral species. A. steindachneri is a large 
apisto, reaching over 8 cm/3½" in length. It is moderately elongate & 
laterally compressed. The dorsal & anal fins are relatively high with 
serrated spines. The tail is double tipped and cross striped. The body 
is covered with metallic scales, whose darker edges give it a net like 
appearance. Dark markings on the flanks include a small caudal spot 
separated from a narrow lateral band; mid-flank, on & above the the 
lateral band, is a large flank patch surrounded by a narrow pale halo. 
The vertical bars split on the posterior bars when the fish display. The 
face is covered with metallic stripes and prominent head stripes, 
especially the cheek and forehead stripes. In having so many features 
that I consider derived from the ancestral apisto (plesiomorphs), A. 
steindachneri appears to be a very primitive species in the genus. 
Compare A. steindachneri with species like Gg. meridionalis & Gg. 
rhabdotus. There are some fairly obvious similarities. There are obvious 
differences in them, too. That is why they are in different genera. 
Other species in the steindachneri-group show fewer plesiomorphs, 
particularly their reduction in size & less spectacular finnage. Now let 
us look at other species-groups.

In the regani-lineage (which includes the regani-, macmasteri-, & 
Rotpunkt-groups as well as A. borellii), the eunotus complex would be 
considered the most primitive (showing the most plesiomorphs). These 
include moderately large size; more deep bodied but laterally 
compressed; moderately high, serrated dorsal spines; light colored 
scales with slightly darker edges; separate caudal spot; round to 
squared off (sometimes with short double tips) caudal fin; split 
vertical bars in the posterior flanks. Other complexes in the 
regani-group have species that show lower finnage, usually round tails, 
& smaller size. Species of the macmasteri-group show similar 
plesiomorphs to the eunotus-complex (except no split vertical bars) and 
probably is an offshoot of the eunotus- or cruzi-complex. Over its range 
of species of this group shows little change from what its ancestor 
probably looked like. This could be due to less need for speciation, 
since they appear to have been the only species-group in the Orinoco 
until recent invasions from the Rio Negro. The Rotpunkt-group shows 
several reductions in plesiomorphs from its possible macmasteri-group 
ancestor: low, even dorsal; round caudal fin.

In the pertensis-lineage (pertensis-, velifera-, & iniridae-groups as 
well as the Balzfleck assemblage) the pertensis-group appears to be the 
most primitive. Probably the most  primitive species in the 
pertensis-group is the Eartheater/Erdfresser Apisto. This species is 
elongate, but deeper bodied than most species in the group. The dorsal 
fin is moderately high with some serrated spines anteriorly. The tail is 
double (sometimes triple) tipped and cross striped. The lateral band is 
narrow & ends in front of a caudal spot. The lateral spot is large, 
especially on displaying fish. Dark edged flank scales form a net like 
pattern on the body. This lineage is a central Amazonian group of 
species that (if you believe the geological data given in Frailey, et 
al. 1988) have only entered the region in the past 2000 years, & only 
then had the opportunity to speciate. If we look at this lineage we see 
species that have moved in two directions. Some entered less hospitable 
(blackwater) areas where fewer predators occur. These blackwater species 
have developed features (higher finnage for the most part) that make 
them more visible to prospective mates & also used to make them look 
larger to potential enemies. Species living in white/clearwater biotopes 
(e.g. Balzfleck assemblage), however, have much lower fins & smaller size.

The trifasciata-lineage (brevis-, trifasciata-, cacatuoides-groups  & 
related species) all inhabit the western Amazon Basin. I consider the 
species in this lineage to be fairly recent for the most part. They are 
probably derived from an uaupesi-like species in the upper Negro. They 
have not modified their basic form except for A. sp. Tiquié which is 
very small, with low, even dorsal fins.

The agassizii-lineage (gibbiceps-, elizabethae-, bitaeniata- & 
agassizii-groups, & related species) is another recent lineage probably 
derived from the iniridae-group. Little modification in their basic form 
has occurred except a trend toward lower dorsal fins and rounder caudal 
fins.

From all this (worthless?) information, we can see that older 
plesiomorphic features are larger sizes & more ornate bodies & finnage. 
The more specialized features (small size, less ornate finnage & dull 
colors) appear to be the result of apistos specializing to live in 
shallow biotopes where being inconspicuous is important.

To answer you last question, I believe that A. borellii or its ancestor 
(& Mikrogeophagus species) entered the area that is now the Pantanal 
Matogrossense (a flat frequently swampy area that lies between the upper 
Paraguay and upper Tapajós drainages) sometime during the last glacial 
(= dry) age 10,000+ years b.p. At that time the area from the Amazon & 
Paraguay Basins was all savanna & higher above sea level (sea level was 
actually 100m/300ft lower). This was a time of increased erosion in the 
headwaters, and stream piracy would be a common occurrence. Steam 
priracy of some of the headwater streams of the Rio Tapajós over the 
last few thousand years probably brought A. borellii into the Paraguay 
System, where it has expanded through most of this drainage. The other 
Rio Paraguay species probably entered through the head waters of the Rio 
Guaporé. These fish apparently originated in the lower Mamoré/Guaporé 
drainages, moved upstream into headwaters that only recently (past few 
thousand years) have been pirated by the Paraguay system.

Disclaimer: These are my opinions - and may be in part (probably) or 
entirely (unlikely) all wrong. :-)

Mike Wise

Per Wigstal wrote:

> Hi
>
> Was reading your conversation with big interest. I have been thinking about this since I´m very interested in the southern species as Borellii, Commbrae and Trifasciata.
> I would like to have some comments to my thoughts below.
>
> As I understand the development of species within a genera moves in the direction of more and more specialized species. And would say that the amazon basin inhibit a lot of highly specialized apisto species, while the paraguay/ parana basin is not.
>
> The three endemic species (Borellii, Commbrae and Trfasciata) in the paraguay/ Parana basin are regarded as non-specialised highly oppurtunistic species. (As far as I understand).
>
> Wouldn´t  that also confirm the theory that these species have migrated from north to south in a relatively late period?
>
> Best regards/ Per
>
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