Structural complexity and prey availability shape spider communities under retention forestry

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 Abstract Retention forestry is promoted as a conservation-oriented management strategy to sustain forest biodiversity by preserving key structural elements, such as single old trees and deadwood. However, the effectiveness of this approach in conserving the diversity of spiders as generalist predators remains unclear, particularly because the effect of structural elements under retention forestry on spiders may be mediated by its effect on prey availability. We sampled spiders (Araneae) and potential prey (Diptera, Hemiptera, Collembola) in 55 1-hectare plots across mixed temperate forests of the Black Forest, Germany. We used pitfall traps targeting species active on the forest floor. We studied spider abundance, taxonomic diversity, ecological diversity (combined measure of functional and phylogenetic distance) and community composition along gradients of forest structure (canopy cover, proportion of conifers, stand structural complexity, volume of lying deadwood, herb cover and...

Rapid Distribution Updates for Arachnids of Conservation Concern through Citizen Collaboration: the Case of the Spider Macrothele calpeiana (Walckenaer, 1805) (Mygalomorphae: Macrothelidae)

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Rapid Distribution Updates for Arachnids of Conservation Concern through Citizen Collaboration: the Case of the Spider Macrothele calpeiana (Walckenaer, 1805) (Mygalomorphae: Macrothelidae)

Despite the severe decline that arthropod communities are experiencing worldwide, there are still basic scientific knowledge deficits that are preventing policymakers from implementing optimal decisions for their conservation. Chorological maps, fundamental conservation tools, are not available for most species or are not updated periodically. Limited funding or an unaffordable workforce are some of the impediments to surveying species distribution. To address these challenges in the near term, several solutions have been proposed. One option involves engaging citizens in the collection of data, a method not commonly employed for studying spiders. Here, the distribution of the only spider species protected by EU legislation, the elusive Iberian endemism Macrothele calpeiana Walckenaer, 1805 (Macrothelidae) is updated by using traditional sources, but mostly citizen records, both in its native range and for the whole European continent, given that the species has been frequently exported to diverse countries. The native range has been slightly expanded and currently occupies 156 UTM 10 x 10 grid cells, which means ca. 2.7% of the total area of the Iberian Peninsula. Citizen collaboration proved decisive, especially to generate recent information in a short period of time: over just the last 10 years, data from third parties covered 35 grid cells, 17 of them new to science. On the other hand, M. calpeiana has been reported as non-native in eight different countries. In some of them, such as France and Italy, the reports are recurrent. The outcomes of methodology used in the study were highly encouraging, showcasing its potential for implementation by budget-constrained administrations to effectively monitor this species of conservation concern.

Cortés-Fossati F. 2025. Rapid distribution updates for arachnids of conservation concern through citizen collaboration: the case of the spider Macrothele calpeiana (Walckenaer, 1805) (Mygalomorphae: Macrothelidae). Zool Stud 64:52. doi:10.6620/ZS.2025.64-52.