Ferns and Lycophytes of El Impenetrable National Park, Chaco, Argentina

Abstract

The Dry Chaco ecoregion faces severe degradation, making El Impenetrable National Park (EINP) a crucial biodiversity refuge. Despite its significance, botanical studies on ferns and lycophytes are scarce due to harsh climatic conditions and limited accessibility. This study addresses this gap through a comprehensive survey of the 128,000-hectare EINP to assess biodiversity and generate conservation data. Fieldwork conducted in February 2023 across four heterogeneous sites was complemented by reviewing specimens from BA, CTES, and LP herbaria and digital databases such as gbif.org and specieslink.net. We recorded 11 fern species and one lycophyte, distributed among eight families and 12 genera. Pteridaceae was the most diverse family (33.3% of species). Species showed specific adaptations to varied microhabitats: riparian forests supported epiphytes like Microgramma vacciniifolia; sandy paleochannels hosted desiccation-tolerant taxa such as Anemia tomentosa var. tomentosa, Cheilanthes obducta, and Selaginella sellowii; while seasonally flooded areas and water bodies contained Equisetum giganteum, Goniopteris tetragona, and Azolla filiculoides. Notable findings include the easternmost distribution limit for C. obducta and the discovery of G. tetragona in a humid lagoon forest. These results underscore the role of the Bermejo/ Teuco River system as a critical biological corridor and biodiversity refuge. Although diversity is lower than in humid regions, the species' remarkable adaptations to heterogeneous environments highlight the importance of conserving these microhabitats. This study provides an essential baseline for managing these understudied plant groups in the threatened Dry Chaco.