Coreids massol 171107
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Understanding properties of food webs, such as their topology or stability, and the rules underlying food web structure, has been a key issue in ecology for now more than half a century. Because obtaining data on food webs has long been a hard task by itself, this research field has progressed slowly, and its dynamical aspects have seldom been empirically considered. However, technical advances, like next generation sequencing or the possibility of retrieving past ecosystems in sediment cores, have paved the way for massive data and the analysis of time series on food webs, while new models allow better predictions about food web dynamics. Making use of such existing data sets, this working group aimed at assessing the effects of biological invasions on food web topology, the fluxes of energy and nutrients throughout the network, and its ultimate effects on biodiversity. The working group has provided an integrative view on this topic, simultaneously tackling empirical, theoretical and applied aspects of biological invasions in food webs. Obvious applications will arise both from the numerous transports of invasive species and from the reshuffling of natural communities that is expected under global change scenarios. The working group comprised theoreticians and empiricists, biological invasion specialists as well as food web and host-parasite network experts, and benefited from existing experience in the field of ecoinformatics and massive data management in ecology.
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Coreids massol 171107
- 1. COREIDS Predicting community resilience to invasions from diversity and network structure 2014 – 2017 Project leaders: Patrice DAVID & François MASSOL Post-docs: Grégory MOLLOT & Jelena PANTEL
- 2. Rabbit Orycolagus cuniculus Water lily Eicchornia crassipes Nile perch Lates niloticus Zebra mussel Dreissena polymorpha A worldwide revolution in ecosystems and a major component of global change Concerns all kinds of organisms and habitats Large impacts on biodiversity but largely unpredictable biodiversity.europa.eu Biological invasions
- 3. Networks of species interactions Impacts of invasions depend on interactions with resident species Interactions are organized in networks (e.g. food webs) What properties make networks sensitive to invasion?
- 4. COREIDS project summary • Assess the effects of invaders on biodiversity • Understand which food webs are more likely to be invaded • Predict the effects of invaders based on invaded food web and invader properties • Reveal perturbation synergies between anthropogenic pressures and invasions
- 5. The COREIDS group A group of scientists working on invasions and/or networks in France, Canada, New Zealand Field biologists, experimental biologists, statisticians, theoreticians Syntheses, meta-analysis, modelling
- 7. The COREIDS timeline 01/09/2014 2015 2016 20172014 meetings finalreport G. Mollot J. Pantel midreport Advances in Ecological Research issues 56 & 57 N. Poulain
- 8. The COREIDS meetings Four meetings (Jan 2015, Sept 2015, March 2016 & Oct 2016) At the CESAB 9-13 persons per meeting (total = 19) Meeting #1: presentations, general discussions Meeting #2: preparation of AER 56-57, tentative chapters Meeting #3: update & work on chapters (small groups) Meeting #4: updates on theoretical projects, presentations
- 12. Deliverables: wrap-up Various reviews Meta-analysis Theoretical models Statistical toolbox To do
- 13. Four types of local impacts of invaders on food webs I 1. Top-down Invasive predator Resident prey Euglandina rosea (predatory “wolf” snail) Endemic Partula spp (tree snails) Direct predation is responsible for most species extinctions following invasions (Moorea island) R
- 14. Four types of local impacts of invaders on food webs I R1 2. Exploitative competition R2 Invasive species Resident prey Resident competitor Locally cultivated fruit (La Réunion island) Endemic Ceratitis catoirii C. Capitata Introd 1939
- 15. Four types of local impacts of invaders on food webs I R1 2. Exploitative competition R2 Invasive species Resident prey Resident competitor Locally cultivated fruit (La Réunion island) Endemic Ceratitis catoirii C. Capitata Introd 1939 C. rosa Introd 1955
- 16. Four types of local impacts of invaders on food webs I R1 2. Exploitative competition R2 Invasive species Resident prey Resident competitor Endemic Ceratitis catoirii C. Capitata Introd 1939 Locally cultivated fruit C. rosa Introd 1955 Bactrocera zonata Introd 1991 - Invasive competitors often arrive in successive series - Resident species are reduced or displaced more often than they go extinct (La Réunion island)
- 17. Four types of local impacts of invaders on food webs R 3. Bottom-up - Resident predators may limit populations of invasive species (biotic resistance) - Invasive species usually have positive effects on their predators Invasive Gobies Neogobius melanostomus Endemic water snake Nerodia sipedon insularum (Lake Erie) I Invasive prey Resident predator
- 18. Four types of local impacts of invaders on food webs 3. Bottom-up - Invasive species usually have positive effects on their predators - … but these benefits are sometimes outweighed by competition with more profitable resident prey - This situation is common with invasive plants e.g. Caulerpa taxifolia, Rubus alceifolius >> herbivore diversity decreases R2 Resident competitor Horned Lizard Phrynosoma coronatum Argentine ant Linepithema humile Native ant Crematogaster californica (California) R Invasive prey Resident predator I
- 19. Four types of local impacts of invaders on food webs 4. Apparent competition Golden eagle Aquila chrysaetos Island fox Urocyon littoralis Feral pig Sus scrofa - Invasive species may benefit local generalist predators and indirectly affect local species (California channel islands) R2 Resident prey R Invasive prey Resident predator I
- 20. • ASYMMETRY: Invaders tend to have more impact (often strong) on natives than natives have on invaders; they are fiercer predators, better-defended prey, and stronger competitors The filter hypothesis
- 21. Predation efficiency coevolved Not coevolved Frequency Example of predator introduction • ASYMMETRY: Invaders tend to have more impact (often strong) on natives than natives have on invaders; they are fiercer predators, better-defended prey, and stronger competitors • LACK OF COEVOLUTION: Invaders and residents are evolutionary naive to each other : their interactions may often be extreme • FILTER: Only species that happen to be tolerant to resident species successfully invade • Major outcomes The filter hypothesis
- 22. • ASYMMETRY: Invaders tend to have more impact (often strong) on natives than natives have on invaders; they are fiercer predators, better-defended prey, and stronger competitors • LACK OF COEVOLUTION: Invaders and residents are evolutionary naive to each other : their interactions may often be extreme • FILTER: Only species that happen to be tolerant to resident species successfully invade • Major outcomes Predation efficiency coevolved Not coevolved Mean natives Invasion fails Invasion succeeds Mean invaders Frequency Example of predator introduction The filter hypothesis
- 23. Propagation of effects in the recipient network: attenuation or amplification? I
- 24. Theoretical predictions • Theoretical models: construction of model food webs by addition of species and evolution of trophic traits (e.g. body size) or classic models of food web simulation (niche model) • Introduce virtual invaders, measure probability of success and impact • Diversity >> filling of niche space >> fewer invasions and lower impacts • Connectance: decrease probability of invasion, but potentially more negative effects if invasion succeeds
- 25. Theoretical predictions Distribution of robustness (=% of persistent species after invasion attempt) by connectance
- 26. Theoretical predictions Distribution of robustness (=% of persistent species after invasion attempt) by connectance & by type of invader All impacts At least one species lost
- 27. Theoretical predictions Extinction cascades depend on food web topology
- 28. Empirical data: Three cases of far-reaching impact of species introduction 1) Trophic cascades in lakes Favored by the relatively low diversity and high efficiency of primary consumption of phytoplankton (unlike in many plant-based terrestrial ecosystems) http://www.lmvp.org
- 29. Empirical data: Three cases of far-reaching impact of species introduction 2) Disequilibrium - Recent human modification: eutrophication, elimination of top predators, replacement of native forest by agriculture or secondary habitat >> low diversity, lots of unexploited resource - Evolutionary immaturity: remote islands lacking particular groups >> idem http://www.lmvp.org Guam island Tree snake Boiga irregularis
- 30. Empirical data: Three cases of far-reaching impact of species introduction 3) Ecosystem engineering - Large modification of habitat: sessile filter-feeders; water clarification, creation of habitats - Attracts many new species, limits many others, deeply reorganizes energy and matter fluxes in lake ecosystem (pelagic >> benthic) http://ian.umces.edu Zebra mussel Great Lakes
- 31. Some invaders have more effect
- 32. Some ecosystems are more affected
- 33. Some regions are more affected
- 34. Lessons for ecosystem conservation • Fight against causes of invasions rather than invasions themselves: pollution, perturbation, predator removal • Islands are hypersensitive due to past isolation: prevent introductions, especially of generalist predators • Eradication is usually costly and ineffective: resident communities often change ecologically and evolutionarily after invasions, there is often no way back. Look for mitigation rather than eradication.
- 35. Thank you for your attention