Spatial Scale Modulates the Effect of Habitat Amount on Diversity Patterns of Arachnid Assemblages Across Different Brazilian Ecosystems

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  Spatial Scale Modulates the Effect of Habitat Amount on Diversity Patterns of Arachnid Assemblages Across Different Brazilian Ecosystems ABSTRACT Aim We evaluated how native vegetation cover influences the diversity of arachnid assemblages across multiple spatial scales in major Brazilian ecosystems. Location Brazil (Amazon and Atlantic rainforests, Cerrado savanna and Caatinga dry forest). Taxon Arachnida (Opiliones, Pseudoscorpiones and Scorpiones). Methods We sampled arachnids at 120 sites using active search and litter sifting. Native vegetation cover was quantified at three spatial scales (100, 200 and 300 m buffers) using GIS data. Assemblage structure was assessed using abundance, species richness, and Hill numbers ( q  = 0, 1 and 2). Generalized linear mixed models were used to evaluate responses across taxonomic groups and ecosystems. Results We recorded 3986 individuals from 179 species. Diversity responses to native vegetation cover were taxon-, ecosystem- and scale-de...

Is predation by ants driving the evolution of tarantulas? First report of tarantulas (Araneae, Theraphosidae) actively using urticating setae against invertebrates

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Is predation by ants driving the evolution of tarantulas? First report of tarantulas (Araneae, Theraphosidae) actively using urticating setae against invertebrates

Abstract

The use of urticating setae by tarantulas from the Americas and the Caribbean has been known for centuries and is considered a defensive behavior against vertebrate predators. However, their passive use against invertebrates, such as parasitic fly maggots and ants, has also been recently proposed, but no active use of these setae against invertebrates has been observed or tested. In this study, eight tarantula specimens representing four different species from the family Theraphosidae were tested in twelve tests with the army ant Eciton burchelli and the carpenter ant Camponotus rufipes. Four spiders interacted with Eciton burchelli, and one interacted with Camponotus rufipes. The defensive behavior was distinct from that used against vertebrates, as the spider rubs the lower posterolateral region of the abdomen with downward and outward movements of the hind legs and uses silk threads. Scanning electron microscopy (SEM) demonstrated that the ants were entangled with urticating setae, primarily of type I morphology. Type I urticating setae are found exclusively in an important clade of theraphosine spiders, the tribe Theraphosini, which includes the largest known spiders. It is hypothesized here that protection against predation by ants due to the emergence of a specific type of urticating seta may be one of the factors responsible for the success of tarantulas in the New World.

Bertani, R. (2026). Is predation by ants driving the evolution of tarantulas? First report of tarantulas (Araneae, Theraphosidae) actively using urticating setae against invertebrates. Scientific Reports, 16(1), 23769. https://doi.org/10.1038/s41598-026-64167-7