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Unraveling the cavity-nesting network at large spatial scales: The biogeographic role of woodpeckers as ecosystem engineers

Alaniz, Alberto J.1; Carvajal, Mario A.1; Quiroz, Madelaine1; Vergara, Pablo M.1; Marquet, Pablo A.2; Fierro, Andres1; Sieving, Kathryn E.3; Moreira-Arce, Darío1; Hidalgo-Corrotea, Claudia1; Rodríguez-San Pedro, Annia4; Allendes, Luis5; Machuca, Katerine1

Published Dec 11, 2023 on Dryad. https://doi.org/10.5061/dryad.zs7h44jdj

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Dec 11, 2023 version files 659.14 KB

Abstract

Aim: Cavities are usually a limiting resource for several forest-dwelling vertebrates, with effects that propagate through ecological networks. Although diverse assemblages of primary excavators (e.g., woodpeckers) are assumed to increase cavities, other forest resources can also limit populations of primary excavators and cavity users, thus undermining the ecological role of excavators over different scales. We aim to test the biogeographical-scale relationships between primary excavators and cavity users by distinguishing the contribution of forest characteristics.

Location: Southern South America

Methods: We used species distribution models, which combine bioclimatic and remote sensing derived variables, to map the richness of vertebrates composing the cavity network of temperate and Mediterranean forests of South America. Based on a resampling procedure for ensuring spatial independence, we fitted structural equation models to estimate causal relationships between forest characteristics and cavity-user vertebrates.

Results: Secondary cavity users (obligated, habitat generalists and forest specialists) were positively and strongly influenced by the richness of primary excavators, while mammal richness was more influenced by tree richness. The richness of trees and Nothofagus tree species influenced positively the richness of primary excavators and secondary cavity users. Canopy height and net primary productivity affected positively secondary cavity users.

Main conclusions: Our results confirm the role of primary excavators as ecosystem engineers but highlight the importance of considering large spatial scales when analyzing cavity-nesting networks. Biogeographical patterns of tree diversity and forest structure can be important drivers of cavity-nesting networks that remain hidden when studies are conducted over fine spatial scales.