congresos y reuniones científicas
Insights about the evolutionary history of the southern black ant, Acromyrmex lobicornis, a widely distributed species in western Argentina
Congreso; XXIII Simpósio de Mirmecologia An International Ant Meeting; 2017
The southern black ant, Acromyrmex lobicornis, is a species of leaf-cutting ant with a wide distribution in southern South America. Mostly distributed in Argentina, it?s range extends from southern Brazil, Bolivia and Paraguay to the province of Chubut in Patagonia, and it is apparently in the process of a southwestern expansion into Chile. It?s adaptability to colonize different environments is explained by the capacity to tolerate extreme climatic conditions, their dome-shaped nests that minimize environ-mental variability, thereby maintaining optimum temperature and internal humidity for the survival of the fungus. A. lobicornis has four valid subspecies differentiated by variations in coloration and sculp-turing. However, these characters seem ambiguous and make it difficult to ascertain if these variants really correspond to different subspecies or just represent phenotypic variability of the species. Defin-ing the limits and range of species variation is essential to maintain reliable biological information, es-pecially those species with economic importance like this one. Samples from different populations of A. lobicornis from throughout their distribution range were sequenced for two mitochondrial genes in or-der to explore the distribution of genetic variation among their populations, resolve the status of the subspecies and determine historical demographic processes that could be related to a possible adap-tation to lower temperatures and lower rainfall. We found the geographical distribution of A. lobicornis to be disjunct, with populations distributed along the ecoregión of El Monte in Argentina and popula-tions distributed in rocky and dry zones near the Atlantic Forest in the south of Brazil and Uruguay, with scarce intermediate populations in the ecoregion of El Espinal, Argentina. Our preliminary results for the Argentinian populations indicate that A. lobicornis forms a well-supported monophyletic clade and suggest that A. lobicornis is composed by differentiated clades located at lower latitudes (areas with higher temperature, which is more similar to the tropics) and clades distributed at higher latitudes. In spite of some widespread haplotypes within the distribution range, at least three to four distinguisha-ble haplogroups can be recognizable: one corresponding to El Monte, a second group to southernmost populations in Patagonia, and a third group to populations of El Espinal and the north of the distribution range. Understanding the evolutionary history of the southern black ant will provide insights into the evolutionary history of leaf-cutting ants in southern South America and the role of historical geo-climatic processes in their diversification. (CONICET, PICT-FONCyT).