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© 2018 Flores et al. ; [Background]: The study of biodiversity spatial patterns along ecological gradients can serve to elucidate factors shaping biological community structure and predict ecosystem responses to global change. Ant assemblages are particularly interesting as study cases, because ant species play a key role in many ecosystem processes and have frequently been identified as useful bioindicators. ; [Methods]: Here we analyzed the response of ant species richness and assemblage composition across elevational gradients in Mediterranean grasslands and subsequently tested whether these responses were stable spatially and temporally. We sampled ant assemblages in two years (2014, 2015) in two mountain ranges (Guadarrama, Serrota) in Central Spain, along an elevational gradient ranging from 685 to 2390 m a.s.l. ; [Results]: Jackknife estimates of ant species richness ranged from three to 18.5 species and exhibited a hump-shaped relationship with elevation that peaked at mid-range values (1100–1400 m). This pattern was transferable temporally and spatially. Elevation was related to ant assemblage composition and facilitated separation of higher elevation assemblages (> 1700 m) from the remaining lower elevation species groups. Ant assemblages were nested; therefore species assemblages with a decreased number of species were a subset of the richer assemblages, although species turnover was more important than pure nestedness in all surveys. The degree of nestedness changed non-linearly as a cubic polynomial with elevation. These assembly patterns coincided more clearly over time than between the two study regions. ; [Discussion]: We suggest double environmental stressors typical of Mediterranean mountains explained species richness patterns: drought at low elevations and cold temperatures at high elevations likely constrained richness at both extremes of elevational gradients. The fact that species turnover showed a dominant role over pure nestedness suggested current ant assemblages were context-dependent and highly vulnerable to global change, which threatens the conservation of present day native ant communities, particularly at high elevations. ; The study received most economical support from Ministerio de Economía y Competitividad (MINECO) and partial support by the Madrid's Government research group network REMEDINAL3-CM (S-2013/MAE-2719, https://remedinal.wordpress.com/). There was no additional external funding received for this study. This is a contribution to project CGL2014-53789-R. ; Peer Reviewed

Agri-environmental schemes (AES) of the Common Agricultural Policy (CAP) aims at reversing the negative effects of agricultural intensification on biodiversity and ecosystem services. Landscape context may modulate, and even constraint, AES effectiveness. We evaluate AES effectiveness on ant abundance, diversity and community composition. Ants are an ecologically dominant group whose response to conservation efforts in farmland has been rarely evaluated, despite its role in weed control, particularly in Mediterranean farmland. Ants were sampled in the edge and in the centre of paired cereal fields, managed with and without AES in three study areas along a landscape complexity gradient. AES application had no significant effects on ant species richness or ant community composition. Richness increased in fields and landscapes with higher amounts of complex edges and decreased towards the centre of the fields. Specialist granivorous ants (harvester ants, Messor spp.) were the most abundant. Abundance of foraging ants increased with the amount of complex edges around fields and in the landscape. AES application increased ant abundance close to field edges but not in field centers. AES fields had less specialist granivorous foraging in their centers than in control field centers. Ant communities in Mediterranean cereal cropland were mostly constrained by the availability of complex edges, needed for nest building. AES increased the abundance of foraging ants, mostly specialist harvester ants, and its potential service of weed control, but close to field edges mainly. Measures promoting the abundance of stable edges rather than of ephemeral headlands in the landscape are essential to enhance the potential of AES for increasing ant-mediated ecosystem services of weed control ; This paper is a contribution to the EU Project QLK5-CT-2002–1495 'Evaluating current European Agri-environment Schemes to quantify and improve Nature Conservation efforts in agricultural landscapes (EASY)'

This work was supported by the European Union FEDER INTERREG SUDOE program (Project POLL-OLE-GI, SOE1/P5/E0129), MINECO and FEDER (INIA-RTA2017-00051-C02-00 to MM and JAS), and a FPI-INIA CPD2015-0059 fellowship to RMS. This study also received funding from: (1) the Simbiosis Api- project Agro funded by the European Union, the Spanish Ministry of Agriculture, Food and the Environment and the Madrid Regional Government under the Rural Development Programme (RDP-CM 2014-2020) (2) the European Union´s Horizon 2020 research and innovation program under grant agreement N 81819, and (3) the R&D projects for young researchers at the Autonomous University of Madrid by providing funds for this research through SAVIA project (ref SI1/PJI/2019-00444). We thank Alicia Mart?nez and Marina Vara for field assistance, and all respondents who dedicated their time to respond to the questionnaire.