The butterflies of a Cerrado-Atlantic Forest ecotone at Laguna Blanca reveal underestimation of Paraguayan butterfly diversity and need for conservation

The insect diversity of Paraguay remains poorly studied despite its position at the meeting point of some of South America's most diverse biomes and has obscured the true level of diversity and conservation value of the species present. Here, we investigate the butterfly species present across a disjunct Cerrado-Atlantic Forest ecotone in the fragment of natural habitat at Laguna Blanca in an otherwise entirely deforested landscape, after 7 years of collection. We found 290 species (33% of species known from Paraguay), of which 47 (16%) were new records and four undescribed. They constituted a unique mix of species typical of the Atlantic forest, Cerrado, Pampas and Chaco, with 28% endemic to these regions, with half-a-dozen interior mesophytic forest specialists and even equatorial species. Diversity was higher in the forests compared to the Cerrado, contradicting trends from similar ecotones in Brazil and is likely the result of it's nutrient-poor soils, supporting lower species diversity. We estimate the actual number of species present in Paraguay to be around 1500 with around half remaining undetected. The high richness and conservation value of the species present at Rancho Laguna Blanca makes its protection critical for the persistence of these species and is especially urgent considering the imminent threats to its existence. It also indicates that other fragments of natural habitat may also still support significant levels of diversity. Their protection provides a 'silver-bullet' strategy to protect species from a variety of different biodiversity hotspots in a single area.