Ant-butterfly symbiosis in the Riodinidae caterpillars range from free-living trophobiont herbivores to carnivory and social parasitism within ant-nests. Aricoris is a riodinid genus typical of Neotropical Cerrado savanna and has several social parasitic species. The life cycles of these species depend on specific multitrophic interactions between plants, ants and honeydew-producing hemipterans. Over the past few decades, the Cerrado has been devastated by the expansion of agribusiness and the abuse of pesticides, accelerating global climate change and leading to the extinction of local species. Due to high specificity, it is expected social parasitic Aricoris species to be more affected by local extinctions than free-living ones. Data on the presence of Aricoris in Cerrado areas in Diamantino, Mato Grosso state, Brazil were compiled in three periods: 1978-1979 (80 hour/net), 1996-1997 (20 hour/net) and recent 2013-2019 (120 hour/net). Based on phylogenetic position and natural history data, Aricoris species were classified in free-living trophobionts or social parasites. Interpolation and extrapolation analyze were performed to compare the abundance and richness between different periods and life cycle style. Sampling in the 1970s recorded 13 Aricoris species in Diamantino, of which 11 were social parasites. Over time, there was a marked reduction in the abundance and richness of Aricoris, mainly in social parasitic ones. In recent years, even with a greater sampling effort, only four species were recorded, just one being a social parasite. The Diamantino region can be considered an Aricoris-biodiversity hotspot. Among the 13 Aricoris species recorded, five are undescribed and one has been recorded only in this locality, last seen in 1970s, when they were relatively common. Since the arrival of agribusiness in Mato Grosso, in the late 1970s, this region has converted most of its original area into monocultures. However, there remain some fragments of pristine Cerrado in the region, including areas where several common species of Aricoris were previously recorded. These results show that species with complex social parasitic life cycles are more susceptible to local extinctions than free-living herbivorous species, suggesting unexpected coextinction cascades. Social parasitic caterpillars have a specialized morphology and occupy a high trophic position. Therefore, the extinction of these lineages can result in great losses in terms of functional and phylogenetic diversity. Paradoxically, the same diversity of interactions that provided the diversification of these butterflies seems to be related to their susceptibility to extinction.
Myrmecophily, Mutualism, Formicidae, Hemiptera, extinction, Aricoris, immature stages, Brazil