Multiple Assembly Rules Drive the Co-Occurrence of Orthopteran And
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Multiple assembly rules drive the co-occurrence of orthopteran and plant species in grasslands: Combining network, functional and phylogenetic approaches Bertrand Fournier, Arnaud Mouly, François Gillet To cite this version: Bertrand Fournier, Arnaud Mouly, François Gillet. Multiple assembly rules drive the co-occurrence of orthopteran and plant species in grasslands: Combining network, functional and phylogenetic approaches. Frontiers in Plant Science, Frontiers, 2016, 7, pp.1224. 10.3389/fpls.2016.01224. hal- 01429221 HAL Id: hal-01429221 https://hal.archives-ouvertes.fr/hal-01429221 Submitted on 7 Jan 2017 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. fpls-07-01224 August 12, 2016 Time: 15:24 # 1 ORIGINAL RESEARCH published: 17 August 2016 doi: 10.3389/fpls.2016.01224 Multiple Assembly Rules Drive the Co-occurrence of Orthopteran and Plant Species in Grasslands: Combining Network, Functional and Phylogenetic Approaches Bertrand Fournier1, Arnaud Mouly1,2 and François Gillet1,3* 1 Laboratoire Chrono-Environnement UMR 6249 CNRS, Université Bourgogne Franche-Comté, Besançon, France, 2 Jardin botanique de la ville de Besançon et de l’Université de Franche-Comté, Besançon, France, 3 Ecological Systems Laboratory, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland Understanding the factors underlying the co-occurrence of multiple species remains a challenge in ecology. Biotic interactions, environmental filtering and neutral processes are among the main mechanisms evoked to explain species co-occurrence. However, they are most often studied separately or even considered as mutually exclusive. This Edited by: Ivan Hiltpold, likely hampers a more global understanding of species assembly. Here, we investigate Western Sydney University, Australia the general hypothesis that the structure of co-occurrence networks results from Reviewed by: multiple assembly rules and its potential implications for grassland ecosystems. We Martin Zimmer, Leibniz Center for Tropical Marine surveyed orthopteran and plant communities in 48 permanent grasslands of the French Ecology, Germany Jura Mountains and gathered functional and phylogenetic data for all species. We Ângela Cristina Lomba, constructed a network of plant and orthopteran species co-occurrences and verified Research Centre in Biodiversity and Genetic Resources, Portugal whether its structure was modular or nested. We investigated the role of all species in the *Correspondence: structure of the network (modularity and nestedness). We also investigated the assembly François Gillet rules driving the structure of the plant-orthopteran co-occurrence network by using [email protected] null models on species functional traits, phylogenetic relatedness and environmental Specialty section: conditions. We finally compared our results to abundance-based approaches. We This article was submitted to found that the plant-orthopteran co-occurrence network had a modular organization. Agroecology and Land Use Systems, a section of the journal Community assembly rules differed among modules for plants while interactions with Frontiers in Plant Science plants best explained the distribution of orthopterans into modules. Few species had a Received: 28 April 2016 disproportionately high positive contribution to this modular organization and are likely to Accepted: 02 August 2016 Published: 17 August 2016 have a key importance to modulate future changes. The impact of agricultural practices Citation: was restricted to some modules (3 out of 5) suggesting that shifts in agricultural Fournier B, Mouly A and Gillet F practices might not impact the entire plant-orthopteran co-occurrence network. These (2016) Multiple Assembly Rules Drive findings support our hypothesis that multiple assembly rules drive the modular structure the Co-occurrence of Orthopteran and Plant Species in Grasslands: of the plant-orthopteran network. This modular structure is likely to play a key role in the Combining Network, Functional response of grassland ecosystems to future changes by limiting the impact of changes in and Phylogenetic Approaches. Front. Plant Sci. 7:1224. agricultural practices such as intensification to some modules leaving species from other doi: 10.3389/fpls.2016.01224 modules poorly impacted. The next step is to understand the importance of this modular Frontiers in Plant Science | www.frontiersin.org 1 August 2016 | Volume 7 | Article 1224 fpls-07-01224 August 12, 2016 Time: 15:24 # 2 Fournier et al. Drivers of Plant-Orthopteran Co-occurrences structure for the long-term maintenance of grassland ecosystem structure and functions as well as to develop tools to integrate network structure into models to improve their capacity to predict future changes. Keywords: coexistence, competition, environmental filtering, functional traits, grasshoppers, grassland- invertebrate interactions, null models INTRODUCTION pressure forcing the displacement of functional traits where sufficiently different species can coexist (limiting similarity) Understanding the rules underlying species assembly is a (MacArthur and Wilson, 1967; Wilson, 2007; Wilson and Stubbs, key challenge in ecology (HilleRisLambers et al., 2012). In a 2012). When functional traits are phylogenetically conserved, foodweb, species interact hierarchically with species from other communities are expected to be composed by functionally trophic levels through trophic interactions (producer-consumer, dissimilar and phylogenetically unrelated species. Neutral drift of predator-prey, and parasite-host). Within trophic levels, different species abundance can also occur and support coexistence over theories such as the competition, the environmental filtering and extended periods (Hubbell, 2001). In this case, the functional the neutral theories describe species assembly into ecological and phylogenetic similarity among species is expected to be communities (sensu Hubbell, 2001). Practically, assembly rules random. within and among trophic levels were mainly considered In this paper, we explore the possibility of combining separately. Studies have investigated the importance of among- functional and phylogenetic analyses of assembly rules with guild interactions including plant-pollinator (Olesen et al., ecological network approaches to go beyond the view of a 2007), trophic networks (Dunne et al., 2002a) or host-parasite single mechanism driving a whole assemblage. Our hypothesis networks (Vázquez et al., 2005) without considering within- is that co-occurrence networks constitute a directly observable guild processes. Similarly, studies focusing on within-guild outcome of species assembly whose structure results from assembly rules have mainly focused on answering which of different assembly rules. We focus here on two well-documented competition, environmental filtering and neutral processes network structure: nestedness and modularity (Fortuna et al., could explain observed ecological assemblages (Cottenie, 2005). 2010). Nestedness and modularity plays a key role for the However, a growing body of evidence suggests that different stability of species-rich ecosystems and their response to global species assembly mechanisms can operate simultaneously and change (Bascompte and Stouffer, 2009). Modularity refers to the that they should be placed along a continuum (Amarasekare organization of a network into modules or groups where species et al., 2004; Mouquet et al., 2005; Gravel et al., 2006; Leibold co-occur more frequently within than among modules (Newman, and McPeek, 2006; Fournier et al., 2016). Understanding this 2006). Modularity can retain the impact of perturbations or complexity of processes is key to better predict and manage land use changes within few modules thereby minimizing the species assemblages and their associated functions and services impact on other modules (Krause et al., 2003; Teng and McCann, (Balvanera et al., 2006; Cadotte et al., 2011) and becomes 2004). Well-known examples include pollination network in increasingly critical in the current context of global change and tropical high-altitude grasslands (Danieli-Silva et al., 2012) and biodiversity crisis (Koh et al., 2004). However, it remains difficult the hummingbird–plant networks across the Americas (Martín to assess multiple assembly rules from species distribution or González et al., 2015). Nestedness describes the organization co-occurrence data (Fournier et al., 2016). Here, we explore of a network where species-poor assemblages are a subset of to what extent the combination of species co-occurrence species-rich assemblages. It can make the community more network and functional and phylogenetic approaches can provide robust to both random extinctions (Memmott et al., 2004; Burgos new insights on how multiple rules interact to shape species et al., 2007) and habitat loss (Fortuna and Bascompte, 2006). assembly. Nestedness was first described for insular fauna where island size Phylogenetic relatedness and functional traits are strong strongly determines the total diversity. Examples