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Re: Paraguay and Amazonas


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:


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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