Abstract
Two new species of Australoheros Rican and Kullander are described. Australoheros ykeregua sp. nov. is described from the tributaries of the rio Uruguay in Misiones province, Argentina. Australoheros angiru sp. nov. is described from the tributaries of the upper rio Uruguai and middle rio Iguacu in Brazil. The two new species are not closely related, A. ykeregua is the sister species of A. forquilha Rican and Kullander, while A. angiru is the sister species of A. minuano Rican and Kullander. The diversity of the genus Australoheros is reviewed using morphological and molecular phylogenetic analyses. These analyses suggest that the described species diversity of the genus in the coastal drainages of SE Brazil is overestimated and that many describedspecies are best undestood as representing cases of intraspecific variation. The distribution patterns of Australoheros species in the Uruguay and Iguazu river drainages point to historical connections between today isolated river drainages (the lower rio Iguazu with the arroyo Urugua-i, and the middle rio Iguacu with the upper rio Uruguai). Molecular clocks are used to date these and other biogeographic patterns.
NSTL