Michael Oliver wrote:As for the jaws, actually, most specimens we examined are not strongly prognathous - the lower jaw projects only a little, or not at all in some specimens, forward beyond the upper jaw. (Genyochromis mento -- now that's prognathous.)
We discuss the similarities to Labidochromis in detail (see the sections on Autapomorphies, and Comparisons with other mbuna genera). It's unclear if the similarities are convergent or homologous; as we discuss, A. labrosus is outside the range of variation of Labidochromis in several respects. I don't see its behavior as particularly Labido-like; the lack of a fixed territory, the wandering habits, are quite odd. Anyway, an intriguing fish!
Tachymarptis wrote:I observed specimens where this feature [prognathous lower jaw] is really strong. Maybe it depends on geographical location, and also on age and size.
Tachymarptis wrote:According to my own aquarium observations (of course, these are "only" aquarium observations), A. labrosus and L. caeruleus behave similarly, they are not territorial and their aggressive behavior is similar. This is not the case in all Labidochromis, but I am convinced that Labidochromis sensu Lewis is a polyphyletic group. The labido-like jaws are likely to have evolved more than one time in mbunas.
Michael Oliver wrote:Maybe, but we had specimens from 5 localities well distributed along the lake, and a wide range of fish lengths including all the wild-collected museum specimens we could find.
I'm not so sure it's polyphyletic - Labidochromis is one of the more distinctive genera of mbuna - but I certainly can agree there is a rather wide range of variation in it. Until there is a defensible cladogram of mbuna and other Malawi cichlids (one with character evidence, not just bootstrap statistics and such), questions like the monophyly or polyphyly of Labidochromis cannot be answered except by "feeling" (not science). As you saw, even though most of us "feel" confident that the mbuna are a real group, not a single adequate character to define them has been found yet.
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