Functional links and robustness in food webs

Abstract

The robustness of ecosystems to species losses is a central question in ecology, given the current pace of extinctions and the many species threatened by human impacts, including habitat destruction and climate change. Robustness from the perspective of secondary extinctions has been addressed in the context of food webs to consider the complex network of species interactions that underlie responses to perturbations. In-silico removal experiments have examined the structural properties of food webs that enhance or hamper the robustness of ecosystems to species losses, with a focus on the role of hubs, the most connected species. Here we take a different approach and focus on the role of the connections themselves. We show that trophic links can be divided into functional and redundant based on their contribution to robustness. The analysis of empirical webs shows that hubs are not necessarily the most important species as they may hold many redundant links. Furthermore, the fraction of functional connections is high and constant across systems regardless of size and interconnectedness. The main consequence of this scaling pattern is that ecosystem robustness can be considerably reduced by species extinctions even when these do not result in any secondary extinctions. This introduces the possibility of tipping points in the collapse of ecosystems.

Effect of multiple disturbances on food web vulnerability to biodiversity loss in detritus‐based systems

“…Dunne et al (2002) and Allesina et al (2009) observed that there exists a core, minimum set of secondary extinctions that are predictable in any case. Caused by the lack of food items for a specific consumer, they are easily deducible from a food web description.…”

Spatio-temporal variability of benthic macrofauna in a coastal lagoon assessed by ecological interaction networks

“…Such large and highly connected networks are considered more robust against disturbances ( Allesina et al 2009). Although "deposit feeders" and "herbivores" seem to have an important role in shaping species interactions within the benthic community, "carnivores" and "suspension feeders" were restricted only to the radial part of the networks due to the fact that their abundance did not increase enough in order to occupy a central position.…”

Neutral theory of biodiversity: Controversies and a transvaluation of species conservation

“…Se a teoria neutra de Hubbell se aplica por completo ou não na natureza, é uma dúvida que persiste (Poulin, 2004;McGill et al, 2006;Connolly et al, 2017), porém a possibilidade de aplicação desta teoria demonstra que as justificativas de estudos ecológicos precisam mudar da simples necessidade de "conservar" para uma motivação mais voltada para a aquisição de conhecimento e a busca pela compreensão do funcionamento da natureza e autopreservação. Essa necessidade também é reforçada pelo fato de muitas interações tróficas serem redundantes e não necessariamente funcionais, característica que dá certa robustez às comunidades biológicas diante de certas alterações ambientais ou enfraquecê-las diante daquelas cumulativas ou constantes (Allesina et al, 2009;Valiente--Banuet et al, 2015) remetendo, de certa forma, à equivalência trófica de Hubbell.…”