Even without any special knowledge within systematic I do agree with you, special the area from Altamira downstreams couple of miles north of Belo Monte. If we start at Altamira, we will find a few species with quite good distance between each of them (Hypancistrus) the more north and closer to Belo Monte the more "species" we will find and both south and north of Belo Monte you find many different L-numbers of Hypancistrus at the same locality. Around Belo Monte you find L46, L66, L173, L236, L333, L399, L400, L287 and L345 is mysterious... probably mixed up with other L-number of the guy that put these L-number. What is called Hypancistrus sp "Lower rio xingu" in the Cat-eLog is also from the same area around Belo Monte.Larry wrote:How do we know whether or not many of the Hypancistrus spp. found in nature, say those of the Rio Xingu, are not actually hybrids between fewer species than we currently believe are endemic to that river? There are many forms that appear to be intermediates between better defined species. The genus could still be in considerable flux, especially those from the same or nearby streams. It would explain why it is often so difficult to identify many of them.
It looks to me like many Hypancistrus spp are are recent, in geological time, and still very much undergoing radiative speciation.
The reproductive barriers between species appear to be low. Low enough to question whether or not there are as many species as there are Hypancistrus L-numbers.
The only species that have several other localities of these above is L46, L66, L236 and L333, the first two is found upstreams almost to Altamira and there we find L174 also together with a mimic Hypancistrus species lacking any L-number. At the mouth of Rio xingu at Porto de Moz we find L236 and L333, no other known Hypancistrus. If I would be an scientist working in this field I would call this area between Altamira and Belo Monte for a "Hot spot", where natural crossbreeding and natural creating of new species is comparable with the hot spots in some coral reafs in the pacific. To use DNA barcoding for these species I think will be impossible, to close relationship between them.
Janne