4 



Among the taxa with Hmited distributions, three main species associations were identified that are 

 associated with unique habitats: 1. species inhabiting hilly ecosystems, 2. species associated with the 

 southern coastal plains, and 3. species restricted to the northwest of Uruguay. 



The first of these species associations consists of Bufo sp., Melanophryniscus atroluteus, M. 

 devincenzii, M. orejasmirandai, M. sanmartini, Phyllomedusa iheringii, Hyla minuta, H. uruguaya, Scinax 

 fuscovariiis, Leptodactylus furnarius, Limnomedusa macroglossa, and Physalaemus riograndensis. In this 

 group of species stands out the endemism of the genus Melanophrysniscus (M orejasmirandai and M 

 sanmartini); their unique distribution suggests mechanisms of allopatric speciation in the genus. 



The second group consists of species associated with sandy environments on the shores of the Rio de 

 La Plata and the Atlantic Ocean. This group includes Chthonerpeton indistinctum, Melanophryniscus 

 montevidensis, Argenteohyla siemersii, and Ceratophrys ornata. Among these species M. montevidensis 

 had a significant reduction of its distribution probably caused by the increase coastal urbanization of its 

 habitat (Langone, 1995) and Ceratophrys ornata, the last record of which corresponds to specimens 

 collected in 1982 (Maneyro & Langone, 2001). 



The species with geographic distribution restricted to the northwest of Uruguay are: Bufo paracnemis, 

 Lysapsus limeUus, Hyla nana, Scinax nasicus, Leptodactylus chaquensis, and L. podicipinus. These taxa 

 are associated to the ecosystem of the Rio Uruguay basin, their presence in Uruguay represent the southern 

 limits of their distributions. 



A detailed map shows all localities from which specimens are deposited in collections and allows 

 identification of areas of geographic priority to carry out further collecting. Tables 1 and 2 summarize the 

 amphibian richness by Department and locality (only localities with more than 15 species are included), 

 respectively. Table 2 shows a bias in the richness of localities from Artigas and Salto, Departments that 

 were heavily sampled in the 70's, as well as in Rivera, which was intensively sampled during the 2000- 

 2001 period to evaluate the impact of non-native forest plantations. The other localities with high richness 

 are all located in the south and southeastern part of Uruguay, areas with easy sampling access. 



AGRADECIMIENTOS 



A Santiago Carreira y Monica Brandimarti por el manejo informatico, a Federico Achaval por 

 bibliografia y ayuda en la detemiinacion de las coordenadas. Lucia Ziegler colaboro con la 

 revision de la Coleccion de Anfibios de la Facultad de Ciencias. Gustavo Carrizo y Esperanza 

 Varela de Olmedo del Museo Argentino de Ciencias Naturales "Bernardino Rivadavia", por el 

 acceso a la coleccion del Instituto Nacional Malbran . A Marcelo Loureiro por la ayuda en la 

 traduccion del manuscrito. 



