New mathematical framework reveals architecture of biotic interactions

• An interdisciplinary team with IFISC participation has developed a model that integrates multiple types of biotic interactions in a single framework.
• What is innovative about this mathematical framework is that it is not limited to ecological networks, but can be extended to other complex systems related to genetics or economics.

An international research team with the participation of the Consejo Superior de Investigaciones Científicas (CSIC), an agency of the Ministerio de Ciencia, Innovación y Universidades (MICIU), has developed an innovative mathematical framework that integrates various types of interactions between different species of plants, animals and fungi, providing a deeper and more complete view of the complexity of ecosystems. The work, published in the journal Nature Communications, is the result of the collaboration of scientists from the Instituto de Física Interdisciplinar y Sistemas Complejos (IFISC-CSIC-UIB) and the Institut Mediterrani d'Estudis Avançats (IMEDEA-CSIC-UIB).

Until now, most studies on ecological complexity have focused on specific interactions between species that mediate a single ecological function, such as pollination or herbivory. This perspective has overlooked the fundamental role that species play in simultaneously participating in multiple ecological functions. This new approach overcomes this limitation by integrating multiple types of species interactions into a single model, allowing for a more comprehensive analysis of functional patterns and their relationship to ecosystem biodiversity and resilience.

The key to maintaining ecosystem equilibrium

The study introduces a multi-layered approach, which integrates different species interaction networks, providing a deeper understanding of how multifunctionality impacts the ecosystem. To test this model, more than 1,500 interactions between 691 plant, animal and fungal species were analyzed on the islet of Na Redona in the Balearic Islands, a small island community that, due to its relative simplicity and isolation, offers an ideal setting for testing this innovative methodological framework. These species participated in six ecological functions: pollination, herbivory, seed dispersal, decomposition, nutrient uptake and fungal pathogenicity. 

“Comparing a plant species pollinated by two animals with one that interacts with dozens of fungi is not always straightforward. However, by quantifying the likelihood of these interactions, we can make more precise comparisons between a plant's pollination and its saprophytic interactions. This ability to compare was fundamental for the next steps in our research”, highlights Sandra Hervías-Parejo, IMEDEA researcher and author of the paper. The new framework of this study also allows us to identify not only the key species in the community but also the key functions in it, notes Anna Traveset (IMEDEA), also an author of the paper.

The study reveals that interactions do not occur randomly, but are organized in a structured way. In addition, both species and key functions were identified, such as woody plants and fungal decomposition, which are essential to maintain the balance of the ecosystem. The disappearance of these species could cause a significant impact on the extinction of other organisms by triggering species extinction cascades. “A provocative idea emerging from our research is the exploration of the species-function duality,” reveals Mar Cuevas-Blanco, IFISC researcher and author of the study. “We propose to consider ecological functions not only as connectors between species, but also as elements that, by themselves, are subject to evolution and extinction,” notes Lucas Lacasa, also an IFISC scientist and author of the paper.

Applications beyond ecology

The innovative aspect of this framework is that it is not only limited to ecological networks, but can be extended to other complex systems. For example, it can be applied to genetics to understand how genes interact to generate phenotypes or to the economic domain, to study how goods are traded between countries in different economic sectors.

This dual approach, from species and function perspectives, opens up new possibilities for quantifying the complexity of ecosystems and better understanding the influence of multifunctionality on their functioning and biodiversity.

In future research, it is proposed to apply this model to diverse environments and examine their spatial and temporal dynamics. This will provide a more comprehensive and in-depth view of ecosystems, thus providing a more effective guide for conservation efforts in the face of stressors such as climate change and for mitigating biodiversity loss.

Photo: Podarcis lilfordi (Balearic lizard, endemic to the Balearic Islands) visiting the flowers of Lavatera maritima on the islet of Na Redona (Cabrera Archipelago National Park).  Toni Escandell

Hervías-Parejo, S., Cuevas-Blanco, M., Lacasa, L., Traveset, A., Donoso, I., Heleno, R., Nogales, M., Rodríguez-Echeverría, S., Melián, C.J., & Eguíluz, V.M. On the structure of species-function participation in multilayer ecological networks. Nature Communications. DOI: 10.1038/s41467-024-53001-1.

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