Apistogramma

Abstract: Laboratory mate choice experiments have confirmed species status for cichlid fish in the African Great Lakes that differ in colour and little else. Colour differences between allopatric populations of the South American cichlid genus Apistogramma are known for many species, yet the status of such populations has not been previously tested. Analysis of the genetic relationships and mate choice characteristics of populations previously described as Apistogramma caetei from eastern Amazonia indicates genetic differentiation into at least three allopatric lineages, which also show strong prezygotic isolation through female mate choice, confirming them as Biological species. If future studies confirm that this result is indicative of a general trend, the species richness of the South American cichlid fishes may presently be seriously underestimated.

Abstract: Aim: The present study analyzed the spatial variation in fish species richness and composition in streams of the Ivinhema River basin, Upper Parana basin, determining the relationship between local and regional descriptors of the fish assemblage organization; Method: From 2001 to 2011 we sampled 200 stream stretches, using different sampling methods. Local species richness and composition were analyzed using univariate and multivariate methods to detect patterns of variation in the fish assemblage organization; Results: We identified 111 fish species in the streams, and estimated the occurrence of 117 fish species (CI α0.05 = 111 to 123) with lower species richness in headwater streams compared to the lower parts of the basin. The fish species recorded were predominantly of small size, and the mean size increased from the headwaters to the river mouth. The four most common species are widely distributed in the basin. However, 24 species are allocthonous to the Upper Parana basin, and two species (Chaetobranchopsis australis and Apistogramma commbrae) are recorded here for the first time in the Upper Parana basin. Altitude was the main determinant of local fish species richness and composition, and a discontinuity in assemblage organization (richness, composition, fish size) was detected at approximately 430 m a.s.l.; Conclusion: Streams of the Ivinhema River basin are inhabited mainly by small-sized fishes; and longitudinal variation, interacting with local characteristics, determines the fish assemblage patterns.