Broad-Scale Climatic Gradients Drive Multiple Facets of Scorpion Beta Diversity in Northeastern Brazil

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  Broad-Scale Climatic Gradients Drive Multiple Facets of Scorpion Beta Diversity in Northeastern Brazil ABSTRACT Aim Beta diversity analyses clarify mechanisms structuring ecological communities, but their multidimensional facets remain poorly explored in arthropods. Here, we quantified taxonomic, phylogenetic, and functional beta diversity in scorpions, partitioned these facets into species replacement and richness differences, and evaluated the relative importance of spatial structure and environmental conditions in driving community assembly. Location Northeastern Brazil, South America. Taxon Scorpions (Arachnida: Scorpiones). Methods Taxonomic beta diversity was estimated using species presence across 70 sites in northeastern Brazil. Phylogenetic turnover was calculated from a multi-locus molecular tree, and functional beta diversity was derived from morphometric and ecological traits. All beta diversity facets were decomposed into replacement and richness-difference component...

Circadian rhythms of locomotor activity in the New World tarantula Neoholothele incei (Araneae: Theraphosidae)

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Circadian rhythms of locomotor activity in the New World tarantula Neoholothele incei (Araneae: Theraphosidae)

Abstract

Circadian rhythms in behavior are intrinsically linked to organismal fitness, supporting the theory that Earth’s near 24 h day selects against dissonant rhythms. However, in arthropods, particularly spiders, circadian free-running periods (FRPs) exhibit significant population variation. Some spider species possess rhythms that deviate by up to 5–6 h from 24 h. These findings are restricted to a large clade of web-building spiders, leaving it unknown whether this chronobiological strategy extends beyond that group. To explore this, we monitored the locomotor activity of a distant outgroup species, the New World tarantula Neoholothele incei F.O. Pickard-Cambridge, under a controlled photic cycle. Our efforts determined that its bimodal diel activity is governed by circadian (endogenous) components. Spiders usually had both a diurnal and nocturnal peak in locomotor activity. Each peak showed strong support for its regulation by endogenous circadian control under constant conditions. FRPs averaged within an hour of 24 h but ranged from ~ 21 to 25 h, similar to the variation observed in some insects and spiders. These results offer initial evidence that FRP variation, though not always extreme deviations from 24 h, is a common strategy among spiders.

Giulian, J., Toporikova, N., Petko, J. et al. Circadian rhythms of locomotor activity in the New World tarantula Neoholothele incei (Araneae: Theraphosidae). J Ethol (2025). https://doi.org/10.1007/s10164-025-00842-y