The spatial scaling of species interaction networks

Galiana N., Lurgi M., Claramunt-López B., Fortin M.-J., Leroux S., Cazelles K., Gravel D., Montoya J.M. (2018) The spatial scaling of species interaction networks. Nature Ecology and Evolution. 2: 782-790.
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Doi: 10.1038/s41559-018-0517-3

Resumen:

Species-area relationships (SARs) are pivotal to understand the distribution of biodiversity across spatial scales. We know little, however, about how the network of biotic interactions in which biodiversity is embedded changes with spatial extent. Here we develop a new theoretical framework that enables us to explore how different assembly mechanisms and theoretical models affect multiple properties of ecological networks across space. We present a number of testable predictions on network-area relationships (NARs) for multi-trophic communities. Network structure changes as area increases because of the existence of different SARs across trophic levels, the preferential selection of generalist species at small spatial extents and the effect of dispersal limitation promoting beta-diversity. Developing an understanding of NARs will complement the growing body of knowledge on SARs with potential applications in conservation ecology. Specifically, combined with further empirical evidence, NARs can generate predictions of potential effects on ecological communities of habitat loss and fragmentation in a changing world. © 2018 The Author(s).

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The effects of space and diversity of interaction types on the stability of complex ecological networks

Lurgi M., Montoya D., Montoya J.M. (2016) The effects of space and diversity of interaction types on the stability of complex ecological networks. Theoretical Ecology. 9: 3-13.
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Doi: 10.1007/s12080-015-0264-x

Resumen:

The relationship between structure and stability in ecological networks and the effect of spatial dynamics on natural communities have both been major foci of ecological research for decades. Network research has traditionally focused on a single interaction type at a time (e.g. food webs, mutualistic networks). Networks comprising different types of interactions have recently started to be empirically characterized. Patterns observed in these networks and their implications for stability demand for further theoretical investigations. Here, we employed a spatially explicit model to disentangle the effects of mutualism/antagonism ratios in food web dynamics and stability. We found that increasing levels of plant-animal mutualistic interactions generally resulted in more stable communities. More importantly, increasing the proportion of mutualistic vs. antagonistic interactions at the base of the food web affects different aspects of ecological stability in different directions, although never negatively. Stability is either not influenced by increasing mutualism—for the cases of population stability and species’ spatial distributions—or is positively influenced by it—for spatial aggregation of species. Additionally, we observe that the relative increase of mutualistic relationships decreases the strength of biotic interactions in general within the ecological network. Our work highlights the importance of considering several dimensions of stability simultaneously to understand the dynamics of communities comprising multiple interaction types. © 2015, Springer Science+Business Media Dordrecht.

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Five Years of Experimental Warming Increases the Biodiversity and Productivity of Phytoplankton

Yvon-Durocher G., Allen A.P., Cellamare M., Dossena M., Gaston K.J., Leitao M., Montoya J.M., Reuman D.C., Woodward G., Trimmer M. (2015) Five Years of Experimental Warming Increases the Biodiversity and Productivity of Phytoplankton. PLoS Biology. 13: 0-0.
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Doi: 10.1371/journal.pbio.1002324

Resumen:

Phytoplankton are key components of aquatic ecosystems, fixing CO2 from the atmosphere through photosynthesis and supporting secondary production, yet relatively little is known about how future global warming might alter their biodiversity and associated ecosystem functioning. Here, we explore how the structure, function, and biodiversity of a planktonic metacommunity was altered after five years of experimental warming. Our outdoor mesocosm experiment was open to natural dispersal from the regional species pool, allowing us to explore the effects of experimental warming in the context of metacommunity dynamics. Warming of 4°C led to a 67% increase in the species richness of the phytoplankton, more evenly-distributed abundance, and higher rates of gross primary productivity. Warming elevated productivity indirectly, by increasing the biodiversity and biomass of the local phytoplankton communities. Warming also systematically shifted the taxonomic and functional trait composition of the phytoplankton, favoring large, colonial, inedible phytoplankton taxa, suggesting stronger top-down control, mediated by zooplankton grazing played an important role. Overall, our findings suggest that temperature can modulate species coexistence, and through such mechanisms, global warming could, in some cases, increase the species richness and productivity of phytoplankton communities. © 2015 Yvon-Durocher et al.

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Invasions cause biodiversity loss and community simplification in vertebrate food webs

Galiana N., Lurgi M., Montoya J.M., Lopez B.C. (2014) Invasions cause biodiversity loss and community simplification in vertebrate food webs. Oikos. 123: 721-728.
Enlace
Doi: 10.1111/j.1600-0706.2013.00859.x

Resumen:

Global change is increasing the occurrence of perturbation events on natural communities, with biological invasions posing a major threat to ecosystem integrity and functioning worldwide. Most studies addressing biological invasions have focused on individual species or taxonomic groups to understand both, the factors determining invasion success and their effects on native species. A more holistic approach that considers multispecies communities and species' interactions can contribute to a better understanding of invasion effects on complex communities. Here we address biological invasions on species-rich food webs. We performed in silico experiments on empirical vertebrate food webs by introducing virtual species characterised by different ecological roles and belonging to different trophic groups. We varied a number of invasive species traits, including their diet breadth, the number of predators attacking them, and the bioenergetic thresholds below which invader and native species become extinct. We found that simpler food webs were more vulnerable to invasions, and that relatively less connected mammals were the most successful invaders. Invasions altered food web structure by decreasing species richness and the number of links per species, with most extinctions affecting poorly connected birds. Our food web approach allows identifying the combinations of trophic factors that facilitate or prevent biological invasions, and it provides testable predictions on the effects of invasions on the structure and dynamics of multitrophic communities. © 2014 The Authors.

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On the dimensionality of ecological stability

Donohue I., Petchey O.L., Montoya J.M., Jackson A.L., Mcnally L., Viana M., Healy K., Lurgi M., O'Connor N.E., Emmerson M.C. (2013) On the dimensionality of ecological stability. Ecology Letters. 16: 421-429.
Enlace
Doi: 10.1111/ele.12086

Resumen:

Ecological stability is touted as a complex and multifaceted concept, including components such as variability, resistance, resilience, persistence and robustness. Even though a complete appreciation of the effects of perturbations on ecosystems requires the simultaneous measurement of these multiple components of stability, most ecological research has focused on one or a few of those components analysed in isolation. Here, we present a new view of ecological stability that recognises explicitly the non-independence of components of stability. This provides an approach for simplifying the concept of stability. We illustrate the concept and approach using results from a field experiment, and show that the effective dimensionality of ecological stability is considerably lower than if the various components of stability were unrelated. However, strong perturbations can modify, and even decouple, relationships among individual components of stability. Thus, perturbations not only increase the dimensionality of stability but they can also alter the relationships among components of stability in different ways. Studies that focus on single forms of stability in isolation therefore risk underestimating significantly the potential of perturbations to destabilise ecosystems. In contrast, application of the multidimensional stability framework that we propose gives a far richer understanding of how communities respond to perturbations. © 2013 Blackwell Publishing Ltd/CNRS.

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Climate change impacts on body size and food web structure on mountain ecosystems

Lurgi M., López B.C., Montoya J.M. (2012) Climate change impacts on body size and food web structure on mountain ecosystems. Philosophical Transactions of the Royal Society B: Biological Sciences. 367: 3050-3057.
Enlace
Doi: 10.1098/rstb.2012.0239

Resumen:

The current distribution of climatic conditions will be rearranged on the globe. To survive, species will have to keep pace with climates as they move. Mountains are among the most affected regions owing to both climate and land-use change. Here, we explore the effects of climate change in the vertebrate food web of the Pyrenees. We investigate elevation range expansions between two time-periods illustrative of warming conditions, to assess: (i) the taxonomic composition of range expanders; (ii) changes in food web properties such as the distribution of links per species and community size-structure; and (iii) what are the specific traits of range expanders that set them apart from the other species in the community-in particular, body mass, diet generalism, vulnerability and trophic position within the food web. We found an upward expansion of species at all elevations, which was not even for all taxonomic groups and trophic positions. At low and intermediate elevations, predator: prey mass ratios were significantly reduced. Expanders were larger, had fewer predators and were, in general, more specialists. Our study shows that elevation range expansions as climate warms have important and predictable impacts on the structure and size distribution of food webs across space. © 2012 The Royal Society.

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Novel communities from climate change

Lurgi M., López B.C., Montoya J.M. (2012) Novel communities from climate change. Philosophical Transactions of the Royal Society B: Biological Sciences. 367: 2913-2922.
Enlace
Doi: 10.1098/rstb.2012.0238

Resumen:

Climate change is generating novel communities composed of new combinations of species. These result from different degrees of species adaptations to changing biotic and abiotic conditions, and from differential range shifts of species. To determine whether the responses of organisms are determined by particular species traits and how species interactions and community dynamics are likely to be disrupted is a challenge.Here, we focus on two key traits: body size and ecological specialization.We present theoretical expectations and empirical evidence on how climate change affects these traitswithin communities. We then explore howthese traits predispose species to shift or expand their distribution ranges, and associated changes on community size structure, food web organization and dynamics.We identify three major broad changes: (i) Shift in the distribution of body sizes towards smaller sizes, (ii) dominance of generalized interactions and the loss of specialized interactions, and (iii) changes in the balance of strong andweak interaction strengths in the short term. We finally identify two major uncertainties: (i) whether largebodied species tend to preferentially shift their ranges more than small-bodied ones, and (ii) how interaction strengths will change in the long term and in the case of newly interacting species. © 2012 The Royal Society.

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