Search

Insect faunas from the latest Cretaceous are poorly known worldwide. Particularly, in the Southern Hemisphere, there is a gap regarding insect assemblages in the Campanian-Maastrichtian interval. Here we present an insect assemblage from the Maastrichtian Chorrillo Formation, southern Argentina, represented by well-preserved and non-deformed, chitinous microscopic remains including head capsules, wings and scales. Identified clades include Chironomidae dipterans, Coelolepida lepidopterans, and Ephemeroptera. The assemblage taxonomically resembles those of Cenozoic age, rather than other Mesozoic assemblages, in being composed by diverse chironomids and lepidopterans. To the best of our knowledge, present discovery constitutes the first insect body fossils for the Maastrichtian in the Southern Hemisphere, thus filling the gap between well-known Early Cretaceous entomofaunas and those of Paleogene age. The presented evidence shows that modern clades of chironomids were already dominant and diversified by the end of the Cretaceous, in concert with the parallel radiation of aquatic angiosperms which became dominant in freshwater habitats. This exceptional finding encourages the active search of microscopic remains of fossil arthropods in other geological units, which could provide a unique way of enhancing our knowledge on the past diversity of the clade. An insect assemblage gathered from the Chorrillo Formation in Argentina constitutes an important set of insect body fossils for the Maastrichtian interval in the Southern Hemisphere. [ABSTRACT FROM AUTHOR]

The Monte, one of the main arid regions in Argentina, is affected by degradation processes that impact the biological communities. Arthropods are the most diverse component of the Monte fauna and play important roles in several ecosystem processes. The study of interactions between native plants and arthropods, two key elements of the Monte biodiversity, contributes to our understanding of how this ecosystem functions. Our objective was to compare the plant-dwelling arthropod assemblages associated with representative shrub species of the southern Monte and to analyse the relationship between plant architecture and the assemblage structure. We sampled arthropods using the beating method on three evergreen shrub species (Chuquiraga avellanedae, Schinus johnstonii and Larrea divaricata) at six sites during two consecutive spring seasons. We recorded shrub height, canopy area, volume and an index of canopy openness. Our results showed that native shrub species host different arthropod assemblages, partially explained by both the shrub species identity and shrub architecture (mainly canopy openness). The arthropod assemblage that lives in S. johnstonii showed the highest diversity, probably related to the plant's intermediate canopy openness, which may determine favourable microhabitats that provide protection against adverse climatic conditions and predators. The assemblage in C. avellanedae had the lowest diversity. The closed canopy of C. avellanedae could be beneficial for a few very abundant taxa that dominate the assemblage associated with it. Implications for Insect Conservation: Our results show that these native shrubs support a wide range of arthropod taxa and guilds, contributing to maintaining the biodiversity in the southern Monte. [ABSTRACT FROM AUTHOR]