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.EnlaceDoi: 10.1038/s41559-018-0517-3
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).
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.EnlaceDoi: 10.1111/j.1600-0706.2013.00859.x
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.
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.EnlaceDoi: 10.1098/rstb.2012.0239
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.
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.EnlaceDoi: 10.1098/rstb.2012.0238
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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