Evolution: still very speculative, but extremely exciting

We know only a little about the evolution of the genus Parosphromenus. The striking similarity of these fish throughout the whole genus in a vast geographical area, with only two obvious exceptions, the two slim forms parvulus and ornicaudata, has, for a long time until the discovery of significantly different forms, led to the assumption that it would only be one single species (“deissneri”).

This suggests to consider an evolutionary hypothesis, which has already been verified for a major group of plants, the Cryptocorynes. This group of plants, playing a major role in the aquarium hobby, is partly coming from the same area. Intense genetic research on these plants shows the development of bio-diversity through adaptive radiation. This means the insulating effect of habitats, which were formerly connected. If these habitats are separated, different genetic developments occur in the individual habitats, although they have the same starting population. The originally identical species gradually develops genetically separated populations and later probably subspecies or even distinct species. The river basins of the former Sundaland looked different in former times. Geological processes (uplift, surface subsidence, etc.) have opened or closed corridors, the current picture is a snapshot of the evolutionary events, which occur somewhere in the scenario.

We know this form of species development from the aquarium plants Cryptocoryne, which is distributed partly in the same area and occurs in forms with different genetic distance, either with ongoing or with already completed hybridisation. For these plants the adaptive radiation has been verified by the investigation of many gene sequences. For the Licorice Gouramis probably the same is true, but we can not prove it. Their striking similar variety of forms certainly shows us a snapshot of a still ongoing evolutionary process: a complex picture of various stages of species development.

(PF)