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Theoretical frameworks of terrestrial community assembly often focus on single trophic levels (e.g. plants) without considering how complex interdependencies across different trophic levels influence assembly mechanisms. Yet, when multiple trophic levels are considered (e.g. plant–pollinator, plant–microbe interactions) the focus is typically on network analyses at local spatial scales. As spatial variation in biodiversity (β‐diversity) is increasingly being recognized for its relevance in understanding community assembly and conservation, considering how β‐diversity at one trophic level may be influenced by assembly processes that alter abundance and composition of interacting communities at a different trophic level (multitrophic dependency) is critical. Here, we build on single trophic level community assembly frameworks to explore the assembly processes affecting β‐diversity in multitrophic communities comprising flowering plants, their bee pollinators, and the corresponding bee‐gut microbiota to better understand the importance of multitrophic dependency in community assembly. Using distance‐based redundancy analysis and variation partitioning, we investigated community assembly processes across three interconnected trophic levels in two ecological regions in southern California: the Santa Monica Mountains and three islands of the Channel Island Archipelago. We found that the deterministic effects of multitrophic dependency are stronger on directly connected trophic levels than on indirectly connected trophic levels (i.e. flowers explain bee communities and bees explain bee‐gut bacteria communities, but flowers weakly explain variation in bee‐gut bacteria communities). We also found notable regional variation, where multitrophic dependency was weaker on the Channel Islands as ecological drift was more pronounced. Our results suggest that integrating the influence of multitrophic dependency on community assembly is important for elucidating drivers of β‐diversity and that multitrophic dependency can be determined by the regional context in which β‐diversity is measured. Taken together, our results highlight the importance of considering multiscale perspectives – both multitrophic and multiregional – in community assembly to fully elucidate assembly processes.
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Experimental evidence of the importance of multitrophic structure for species persistence
Ecological theory predicts that species interactions embedded in multitrophic networks shape the opportunities for species to persist. However, the lack of experimental support of this prediction has limited our understanding of how species interactions occurring within and across trophic levels simultaneously regulate the maintenance of biodiversity. Here, we integrate a mathematical approach and detailed experiments in plant–pollinator communities to demonstrate the need to jointly account for species interactions within and across trophic levels when estimating the ability of species to persist. Within the plant trophic level, we show that the persistence probability of plant species increases when introducing the effects of plant–pollinator interactions. Across trophic levels, we show that the persistence probabilities of both plants and pollinators exhibit idiosyncratic changes when experimentally manipulating the multitrophic structure. Importantly, these idiosyncratic effects are not recovered by traditional simulations. Our work provides tractable experimental and theoretical platforms upon which it is possible to investigate the multitrophic factors affecting species persistence in ecological communities.
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- Award ID(s):
- 2024349
- PAR ID:
- 10217610
- Publisher / Repository:
- Proceedings of the National Academy of Sciences
- Date Published:
- Journal Name:
- Proceedings of the National Academy of Sciences
- Volume:
- 118
- Issue:
- 12
- ISSN:
- 0027-8424
- Page Range / eLocation ID:
- Article No. e2023872118
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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