Testing the Limits of Morphology: A Comprehensive Morphometric Study of the Sister Lineages Lasiocyano Galleti-Lima, Hamilton, Borges and Guadanucci, 2023 and Lasiodora C. L. Koch, 1850 (Theraphosidae, Mygalomorphae)

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  Testing the Limits of Morphology: A Comprehensive Morphometric Study of the Sister Lineages Lasiocyano Galleti-Lima, Hamilton, Borges and Guadanucci, 2023 and Lasiodora C. L. Koch, 1850 (Theraphosidae, Mygalomorphae) ABSTRACT Morphological conservatism and homoplasy pose significant challenges for the systematics of mygalomorph spiders, limiting the number of reliable morphological characters available for species identification, particularly in Theraphosidae. Closely related taxa frequently display high phenotypic similarity, which limits the resolution of morphology-based approaches. In this study, we conducted the most extensive morphometric analysis to date within Theraphosidae, with the objective of explicitly testing how much morphological information is retained within the  Lasiocyano sazimai  and  Lasiodora  lineage. We applied a morphometric framework combining linear morphometry and geometric morphometry, including multivariate statistics, discrimina...

Reliance on blue, green, and brown energy channels drives a shift in the trophic position of riparian spiders

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Reliance on blue, green, and brown energy channels drives a shift in the trophic position of riparian spiders

Abstract

Understanding the mechanisms shaping food chain length (FCL) has long been central to food web ecology. FCL is a key determinant of stability, energy flow efficiency, and biodiversity maintenance, but there is an ongoing debate about its underlying drivers. It is particularly important in meta-ecosystems, where predator trophic position (TP) is influenced by multiple energy channels. In this study, we focused on spiders in riparian ecosystems, which rely on resources linked to distinct energy channels: blue (algal herbivory), green (terrestrial herbivory), and brown (terrestrial detritivory). We applied nitrogen isotope analysis of amino acids to estimate the TP of both spiders and their prey. This method is a powerful tool for determining TP from a single sample and even allows for capturing decomposer trophic steps. However, the TP estimate requires special care for riparian spiders, as spiders show a specific trophic discrimination factor (TDFGlx-Phe), and that energy channel use can confound the TP estimate. Our detailed food web resolution supports the use of specific parameters for spiders, particularly the low trophic discrimination factor (TDFGlx-Phe ~ 2‰), and raises caution about the importance of estimating resource use of predators to estimate their TP. We show that the primary factor driving variation in spider TP is the energy channel they utilize, from blue (TP ~ 2.9) to green (TP ~ 3.6) to brown (TP ~ 4.1). This increase was largely due to prey omnivory in green channels, and microbial and fungal decomposers serving as an initial trophic step between litter and invertebrate detritivores in brown channels. We propose that this pattern is likely influenced by differences in basal nutritional quality, which increases from brown (low) to green (medium) and to blue (high) sources. This suggests that shifts in energy channels within meta-ecosystems in the course of global change (e.g., climate warming, eutrophication and land-use change) may significantly impact FCL, with significant consequences for trophic interactions, nutrient fluxes, and biomagnification processes.

Saboret, G., W. Drost, B. J., Kowarik, C., Ilić, M., Gossner, M. M., & Schubert, C. J. (2026). Reliance on blue, green, and brown energy channels drives a shift in the trophic position of riparian spiders. Ecology, 107(1), e70264. https://doi.org/10.1002/ecy.70264