Spatial distribution, habitat suitability, and threat status of Diponthus crassus (Orthoptera: Romaleidae: Romaleini)

Abstract Diponthus crassus is a grasshopper distributed across Argentina, Brazil, and Paraguay, and despite its broad geographic range, little is known about its habitat preferences, climatic requirements, or vulnerability to land‑use change. Understanding how climate and landscape structure jointly shape its distribution is crucial to assess extinction risk and guide conservation planning. We compiled 152 occurrence records (1985–2022) and modeled the species’ climatic and landscape suitability using eight algorithms within an ensemble modeling framework. Climatic predictors were combined with seven land‑use/land‑cover metrics to classify areas into four suitability categories (+/+ favorable climate and landscape; +/- favorable climate only; -/+ favorable landscape only; -/- neither favorable). Habitat loss was quantified by comparing historical potential suitability (assuming no human land‑cover change) with current conditions. We also evaluated the overlap between fully suitable habitats and protected areas. Historical fully suitable habitats (+/+) totaled 184,364 km², but only 41,814 km² remain today, representing a 77% reduction. Habitat loss was most pronounced in Brazil (90%) and Paraguay (86%), whereas Argentina retained 76% of its historically suitable area. Only 13% of remaining fully suitable habitats lie within protected areas, with strong regional variation. The Paraná and Araucaria Forests remain the main refugia, whereas all suitable habitats were lost in Esteros del Iberá. The Chaco province was the only region exhibiting increased suitability through time. The severe loss and fragmentation of suitable habitats suggest high conservation concern for D. crassus , especially in Paraguay, where the species may meet IUCN criterion B2b(iii) for a threatened category. Prioritizing unprotected areas that retain both climatic and landscape suitability is essential, particularly within the Paraná dominion and the Chaco, which may function as emerging refugia under changing land‑use dynamics. Implications for insect conservation Our findings reveal substantial declines in habitat availability for D. crassus , highlighting an urgent need to protect the remaining climatically and structurally suitable areas. These results underscore the importance of integrating landscape structure into conservation planning to mitigate ongoing habitat loss for grasshoppers and other terrestrial insects in South America.