Mammal diversity and conservation in Argentina
De Mendoza CONICET
Argentina is the most extensive temperate country in South America. The wide expanse of its continental area (2,779,741 km²), as well as its varied topographical, climatic and vegetational features, are essential to the formation of one of the most diverse mammal faunas in the southern Neotropics. Argentina shows a wide range of macrohabitats across elevation and climatic gradients, from 7,000 m to the coastal plains, and from subtropical to polar climates. Among them are the subtropical forests belonging to the Amazonian domain (Yungas and Paranense forests), the Monte Desert, the Chacoan forest and savanna, the humid Pampas grasslands, the cold deserts of Patagonia and Puna, and the humid Subantarctic Nothofagus forest, belonging to the Subantarctic domain (see ecoregions of Argentina).
Mammals in Argentina belong to two major biogeographic divisions: the Brazilian and the Patagonian subregions. The former contributes the tropical elements of the Amazon basin which reach their southern distribution in northern Argentina, particularly through the Yungas and Paranense forests. The Patagonian subregion, on the other hand, has the cosmopolitan and authoctonous temperate elements, typical of the arid and semiarid landscapes of the region. The concurrence of tropical and temperate groups, and "old" and modern mammal lineages, results in a scenario of great diversity in South America.
The mammal fauna in Argentina is composed of 15 orders, 43 families, 176 genera and 356 species. Of the total families, 20 are endemic to the Neotropical region. Hystricognath rodents contribute 10 families. The other 10 families are distributed among Microbiotheria (1), Didelphimorphia (2), Paucituberculata (1), Cingulata (1), Vermilingua (1), Tardigrada (1), Chiroptera (2), and Primates (1) .
The highest richness, at the genus level, is found in rodents (61 genera), which along with bats and carnivores, amount to more than 60% of the existing genera. As for species, 36 are marine mammals, while 57 and 263 belong to volant and non-volant mammals.
Species density over the continental area is 1,15 x 10-4 species/km2. Species/area relationship shows that species richness is higher in Argentina than in Australia, while species density in Argentina is 6 times as high as that in North America. In contrast, bat richness is remarkably lower than it is in other South American countries like Venezuela, Colombia and Peru. This pattern may be explained by the greater habitat complexity of tropical forests, which occupy only a small area in Argentina.
The highest species richness is found in the Chacoan region (118 species), followed by the humid subtropical forests (Yungas, 97, and Paranense, 95). The biomes exhibiting the lowest species richness are the Puna desert (36 species) and the Subantarctic forest (37 species).
The total number of mammal species is significantly correlated with macrohabitat heterogeneity. Therefore, mammal diversity in each biome could be accounted for, in the first place by its heterogeneity, and secondly by its area.
Similarity analysis among mammal assemblages of the different biomes shows five groups. One of them corresponds to the fauna of warm and cold deserts (Monte and Patagonia); another one is related to the semiarid and humid biomes (Chaco, Pampa and Yungas forest). The three remaining groups correspond to the cold Puna desert, the Paranense forest, and the Subantarctic forest.
The number of species endemic to Argentina is 77 (24%). The biome showing the highest endemicity is the Monte Desert, followed by the Chacoan and Yungas forests. The Patagonian desert shows a high number of endemic species as well. The Paranense forest, despite its high species richness, exhibits the lowest endemicity.
Mammals in Argentina show contracted distribution ranges, local extinction, fragmentation and reduced populations. The hasty habitat degradation and a strong hunting pressure stand out among the causative factors. The dissappearance of forest corridors along the major northern rivers, logging of forests, extensive agriculture, overgrazing, livestock mismanagement, salinization, the advance of agricultural frontiers, road opening, and oil exploration are, among others, the causes of landscape deterioration.
Taking the number of species (richness) in each biome as the criterion for conservation, the main conservation units should correspond to species-rich macrohabitats such as the subtropical and semiarid Chacoan, Yungas and Paranense forests. Based on this criterion most of the biomes in Argentina are poorly protected. On the other hand, considering the number of endemic species, conservation priorities should focus on both arid-semiarid (Monte, Chaco, Patagonia) and humid (Pampas, Yungas) biomes. Finally, the index of conservation priorities for each biome [IPB: taking into account endemicity, vulnerability and taxonomic singularity] evidences that the most urgent conservation priorities are those of the Monte, Chaco, Patagonia, Pampa and Yungas. This by no means implies that conservation of biodiversity in Puna, Subantarctic and Paranense forests is already fully guaranteed.
Reca et al. proposed 37 endangered mammal species for Argentina, while SAREM (2000) includes 83 species. In general terms both classifications agreed on highlighting marsupials, primates,carnivores and ungulates as the most vulnerable taxa.
Some of the issues to be addressed in order to give solid answers to biodiversity conservation are the conflicting taxonomic status for a large number of species, the few and localized data on population abundance, and the poorly known areas of extension and occurrence. This situation is shared by most Latin American countries. The current available information on natural history does not meet, in most cases, the requirements demanded by international conservation organizations on evaluating the categories of threat faced by the mammals of Argentina. Unless some of these issues are timely solved, great part of the Neotropical biodiversity will eventually be lost.
extracted from Mamiferos de Argentina, Pp. 23-63, by RA. Ojeda, C.E. Borghi & V.G. Roig, in Diversidad & Conservación de los Mamiferos Neotropicales (Ceballos,G. & J. Simonetti, eds.). CONABIO-UNAM, Mexico, 582 pp.
