Scatterhoarder abundance and advantages of seed burial drive dynamics of a tree–rodent interaction

• Published in: The Journal of ecology 2024-09, Vol.112 (9), p.1940-1951
• Main Authors: Zwolak, Rafał, Celebias, Paulina, Zduniak, Milena, Bogdziewicz, Michał, Wróbel, Aleksandra
• Format: Article
• Language: English
• Subjects: Abiotic factors; Abiotic stress; Abundance; Animal models; Antagonism; Apodemus flavicollis; Caching; conditional mutualism; Density dependence; Dispersal; drought; Mice; Monitoring; Mutualism; Overexploitation; Poland; Population density; Quercus robur; Recruitment; Rodents; Seed dispersal; seed predation; Seedlings; Seeds; Symbiosis; synzoochory
• ISSN: 0022-0477; 1365-2745
• DOI: 10.1111/1365-2745.14356

Theoretical models suggest that species abundance plays a crucial role in mutualism; high densities can lead to overexploitation. Additionally, mutualistic benefits are expected to increase under abiotic stress. We investigated the interplay between density dependence and abiotic factors in conditional mutualism, focussing on the interactions between yellow‐necked mice (Apodemus flavicollis) and common oaks (Quercus robur) across 3 years. We controlled for seed abundance, while mouse densities varied. Our approach included monitoring mouse abundance, measuring seed removal, determining the fate of harvested seeds and conducting seedling emergence trials to assess the advantages of seeds caching. We found that mouse abundance exerted a strong influence on all studied aspects of seed dispersal. Higher densities led to increased seed removal and greater dispersal distances. However, they also decreased the probability of seed caching and increased seed consumption, degrading dispersal quality and shifting the interaction towards antagonism. Furthermore, the reliance of seedling recruitment on burial varied over time, likely becoming more critical during dry conditions. This indicates that plants face the worst conditions when high abundance of mice coincides with abiotic stress. Synthesis: Our results supports the notion that increased rodent abundance reduces plant recruitment, revealing the conflicting interests of the interacting species. However, the dynamics of rodent–oak interactions are shaped not only by the density‐dependent foraging decisions of rodents, but also by the benefits of seed burial under stress. These findings illustrate how the interplay between population density and abiotic factors jointly dictate the costs and benefits of mutualistic interactions. Abstrakcyjny Modele teoretyczne sugerują, że liczebność populacji oddziałujących ze sobą gatunków odgrywa kluczową rolę w mutualizmie; wysokie zagęszczenie może prowadzić do nadmiernego eksploatowania partnera. Dodatkowo, zakłada się, że korzyści z mutualizmu rosną w warunkach stresu abiotycznego. Zbadaliśmy oddziaływania pomiędzy zagęszczeniem, a czynnikami abiotycznymi w warunkowym mutualizmie, skupiając się na interakcjach pomiędzy myszami leśnymi (Apodemus flavicollis), a dębami szypułkowymi (Quercus robur). Badania objęły trzy lata zmiennych zagęszczeń myszy, przy kontrolowanej przez nas, stałej dostępności nasion. Przeprowadziliśmy monitoring liczebności gryzoni, zmierzyliśmy tempo us