Suchergebnisse

Este artículo contiene 12 páginas, 7 figuras, 2 tablas. ; The relative benefts of group foraging change as animals grow. Metabolic requirements, competitive abilities and predation risk are often allometric and infuenced by group size. How individuals optimise costs and benefts as they grow can strongly infuence consumption patterns. The shoaling fsh Sarpa salpa is the principal herbivore of temperate Posidonia oceanica seagrass meadows. We used in-situ observations to describe how ontogeny infuenced S. salpa individual feeding behaviour, shoaling behaviour and group foraging strategies, and its potential consequences to seagrass meadows. Shoaling was strongly infuenced by body length: shoals were highly length-assorted and there was a clear positive relationship between body length and shoal size. Foraging strategies changed dramatically with shoal size. Small shoals foraged simultaneously and scattered over large areas. In contrast, larger shoals (made of larger individuals) employed a potentially cooperative strategy where individuals fed rotationally and focused in smaller areas for longer times (spot feeding). Thus, as individuals grew, they increased their potential impact as well, not merely because they consumed more, but because they formed larger shoals capable of considerably concentrating their grazing within the landscape. Our results indicate that ontogenetic shifts in group foraging strategies can have large ecosystem-wide consequences when the species is an important ecosystem modifer. ; Te Spanish Ministry of Science funded this research through RECCAM project (CMT2013-48027-C03-R). Te Spanish National Research Council supported Rohan Arthur's visitorship with the Memorandum of Understanding between CEAB-IMEDEA-NCF. Jordi F. Pages acknowledges fnancial support from the Welsh Government and Higher Education Funding Council for Wales through the Sȇr Cymru National Research Network for Low Carbon, Energy and Environment and from the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant Agreement No 795315. Te work was supported by UMBRAL National Project CTM2017-86695-C3-3-R. ; Peer reviewed

Invasive species pose a major threat to global diversity, and once they are well established their eradication typically becomes unfeasible. However, certain natural mechanisms can increase the resistance of native communities to invaders and can be used to guide effective management policies. Both competition and herbivory have been identified as potential biotic resistance mechanisms that can limit plant invasiveness, but it is still under debate to what extent they might be effective against well-established invaders. Surprisingly, whereas biotic mechanisms are known to interact strongly, most studies to date have examined single biotic mechanisms separately, which likely influences our understanding of the strength and effectiveness of biotic resistance against invaders. Here we use long-term field data, benthic assemblage sampling, and exclusion experiments to assess the effect of native assemblage complexity and herbivory on the invasion dynamics of a successful invasive species, the alga Caulerpa cylindracea. A higher complexity of the native algal assemblage limited C. cylindracea invasion, probably through competition by canopy-forming and erect algae. Additionally, high herbivory pressure by the fish Sarpa salpa reduced C. cylindracea abundance by more than four times. However, long-term data of the invasion reflects that biotic resistance strength can vary across the invasion process and it is only where high assemblage complexity is concomitant with high herbivory pressure, that the most significant limitation is observed (synergistic effect). Overall, the findings reported in this study highlight that neglecting the interactions between biotic mechanisms during invasive processes and restricting the studied time scales may lead to underestimations of the true capacity of native assemblages to develop resistance to invaders. ; Funding for this project was obtained from the Spanish Ministry Project ANIMA (CGL2016-76341-R, MINECO/FEDER, UE), the European Union's EMFS Program, AFRIMED (EASME/EMFF/2017/1.2.1.12/S4/01/SI2.789059), the Spanish Autonomous Organism of National Parks through the project BIGPARK (project 2017-2462), and the Padi Foundation to FT (CGA App: 5134). JS received the support of a fellowship from "La Caixa" Foundation (ID 100010434) with code (LCF/BQ/DE17/11600001).

Este artículo contiene 9 páginas, 5 figuras, 1 tabla. ; Seagrass meadows, key ecosystems supporting fisheries, carbon sequestration and coastal protection, are globally threatened. In Europe, loss and recovery of seagrasses are reported, but the changes in extent and density at the continental scale remain unclear. Here we collate assessments of changes from 1869 to 2016 and show that 1/3 of European seagrass area was lost due to disease, deteriorated water quality, and coastal development, with losses peaking in the 1970s and 1980s. Since then, loss rates slowed down for most of the species and fast rowing species recovered in some locations, making loss rate in seagrass area experience a reversal in the 2000s, while density metrics improved or remained stable in most sites. Our results demonstrate that decline is not the generalised state among seagrasses nowadays in Europe, in contrast with global assessments, and that deceleration and reversal of declining trends is possible, expectingly bringing back the services they provide. ; This research was supported by the COST Action ES0906. C.B.d.l.S. acknowledges the support by the Short-Term Scientific Missions (COST-STSM-ES0906-06377, -06441 and -06419) and the Portuguese Foundation for Science and Technology (FCT) fellowship (SFRH/BPD/119344/2016). C.B.d.l.S. and R.S. acknowledge the support of FCT through the projects UID/Multi/04326/2013 and FCT UID/MAR/00350/2018. N.M. was supported by Spanish Ministry of Economy, Industry and Competitiveness (MedShift, CGL2015-71809-P), by the European Union (M&M's, EVK3-CT-2000–00044 and WISER 226273), by the Fundación BBVA (Proyecto Praderas), and the Spanish Government (MEDEIG. CTM2009–07013). King Abdullah University of Science and Technology (KAUST) supported C.M.D. through baseline funding. J.M.R. acknowledges the project Monitoring network of Posidonia oceanica meadows and global climate change of the Murcia Region funded by the Autonomous Government of the Murcia Region (General Directorate of Livestock and Fishery), the European Fishery Fund (EFF 2007–2013), and European Maritime and Fisheries Fund (EMFF 2014–2020). ; Peer reviewed