Preliminary study of the myrmecofauna of El Impenetrable National Park (Chaco, Argentina)

In the Chaco region, we can find one of the biggest protected areas of northern Argentina, the “El Impenetrable” National Park, with a surface nearing 130,000 ha. It provides multiple habitats that sustain notable plant and animal diversity, in which formicid assemblages are included. Ants are the most abundant arthropods in tropical forests and represent an important part of ecosystems, due to them providing important ecosystemic services. They are excellent bioindicators of anthropogenic perturbations; their diversity in tropical forests is associated with the forest’s canopy coverage. Despite this, no published studies of formicid diversity in “El Impenetrable” National Park evaluate canopy coverage in this important protected area of the subtropical region. A formicid survey was conducted following the recommendations of the ALL protocol, developed as a fast and standardized way of surveying ant populations in forests. True diversity (Hill numbers) for each forest and β-diversity between forests (Sörensen index) were assessed, and rank--abundance curves were constructed. D0 and D1 showed that diversity is positively correlated with coverage increase. Rank--abundance curves indicated higher dominance in forests with high and intermediate coverage, while low-coverage ones exhibited a more even abundance distribution. The βSOR indexes were higher than 50%, suggesting differences between the ant assemblages of each forest, with species turnover being the larger contributor (46%). We can conclude that canopy coverage directly influences the richness and diversity of ants.