Factors affecting pine processionary moth (Thaumetopoea pityocampa) incidence in Mediterranean pine stands: A multiscale approach

The occurrence of the pine processionary moth (Thaumetopoea pityocampa, hereafter PPM) in Mediterranean pine forests and plantations is of increasing concern as processes such as global warming and forest cover expansion have amplified the frequency and virulence of outbreaks. This study attempts to provide as complete an overview as possible of the different factors involved in pine forest susceptibility to PPM in 98 pine stands in Central Spain. A large study area (∼3,000 km2) was considered, including three different spatial scales (<1 ha, 1 ha, 10 ha) and four different pine tree species (Pinus pinaster, P. nigra, P. sylvestris, P. pinea), monitored over a 4-year period. Models were fitted for each of the three spatial scales, as well as for a combination of them (multiscale model). Pine species had a strong influence on vulnerability to PPM, with higher incidences in stands dominated by P. pinaster and P. nigra and lower for those dominated by P. sylvestris and P. pinea. Grazing pressure, a factor thus far disregarded, was also determining, with a prominent role at both the multiscale and the stand-scale levels. Other variables were highly influential at some of the spatial scales, showing a greater resistance in pine forests or plantations with a higher diversity of pine sizes, greater tree density, and a larger cover of non-host tree species. Open habitats also played a role in PPM incidence: we detected that, both at the locality and the plot scale, the presence of clearings occupied by bushes or rocky outcrops reduced vulnerability to PPM, while the clearings with a more simplified structure produced the opposite effect. We conclude that PPM incidence is greater in structurally simple pine forests, with strong grazing pressure and abundant open spaces without woody vegetation that may favour PPM pupation. To reduce damage by PPM, pine forest and plantations should be managed to avoid oversimplified forest structures. Patches of non-host tree species should be promoted, as well as some presence of shrubs in open areas. This implies avoiding overgrazing and other management models leading to an excessive increase in bare soil. Nevertheless, it should be noted that the implementation of these recommendations should consider the remaining challenges that need to be addressed in the current context of global change, such as the increased risk of wildfires and the emergence of other pests and diseasesThis work was supported by the European Social Fund managed by the Regional Government of Madrid (Remedinal TE-CM: S2018/EMT4338

Diverging facets of grassland ant diversity along a Mediterranean elevational gradient

1. We address associations of taxonomic diversity (TD), functional diversity (FD), and phylogenetic diversity (PD) of ant assemblages with gradients of elevation to assess whether energetic limitations or deterministic or stochastic niche-building processes are more relevant to the assembly of communities. 2. We sampled ant assemblages using pitfall traps in grassland habitats along an elevational gradient of 1712 m in the Guadarrama Mountains of Central Spain. The relationships of alpha and beta diversity metrics with soil temperature, productivity, elevation, and geographical distances were examined with generalised additive (mixed) models. 3. The facets of diversity showed strong and partially coincident responses to the gradients, but the responses and the similarities among them weakened or disappeared when the effects of species richness were factored out. TD and FD changed roughly in a similar manner with elevation and productivity, but PD did not show clear responses to those factors. Taxonomic and functional richness increased with productivity and decreased with elevation. Mean pairwise functional and phylogenetic dissimilarities did not change along the gradients. Elevation and productivity gradients accounted for much of the beta TD among assemblages but only explained a moderate variation of functional traits and phylogenetic relationships, while geographical distances were more explanatory of beta PD. 4. The partial redundancies among facets of diversity suggest that the spatial variation of diversity is mainly related to the sheer number of species. However, both environmental filtering and limiting similarity could be acting in concordance to reduce the number of species present in communitiesAdministrative and financial support was received from the Spanish Ministry of Economy and Competitiveness (Project CGL2014‐53789‐R) and Sierra de Guadarrama Park, which provided the permits for the sampling (ref 10/101642.9/16). Mariola Silvestre, Javier Seoane, and Francisco M. Azcárate work within the Madrid's Government research group network REMEDINAL3‐CM (S‐2013/MAE‐2719). Carlos P. Carmona was supported by the Estonian Research Council (PSG293) and the European Union through the European Regional Development Fund (Centre of Excellence EcolChange). Mariola Silvestre was supported by an FPI grant from MINECO. Special thanks to Héctor Miranda, Laura Morgado, and Miguel Blázquez for laboratory assistance and Violeta Hevia, Joaquin Calatayud, and Anders Forsman for your tips. Alberto González helped us to make the map and Xavier Espadaler to identify some species. We appreciate the use of data from Instituto Geográfico Nacional and Nuria Plaza for provided access with the satellite imager

More for less: Sampling strategies of plant functional traits across local environmental gradients

This is the peer reviewed version of the following article: Functional Ecology 29.4 (2015): 579-588, which has been published in final form at http://dx.doi.org/10.1111/1365-2435.12366. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-ArchivingEcologists use approaches based on plant functional traits to tackle several fundamental and applied questions. Although a perfect characterization of functional trait structure requires the measurement of all the individuals in communities, this is prohibitively resource-consuming. Consequently, the general practice is to average the trait values of a reduced number of individuals per species. However, there are different alternatives regarding the number, identity and spatial location of the individuals chosen to calculate species-averaged trait values. In this study, we compared different strategies for sampling functional traits, using community-weighted mean trait values (CWM) and the Rao index of functional diversity (FD). We intensively sampled the functional trait structure along a topographical gradient in a Mediterranean grassland, obtaining accurate estimations of the 'real' values of these indices (CWMI and FDI) for three traits (height, leaf area and specific leaf area). We simulated three different sampling strategies differing in the spatial location of the individuals used to estimate species-mean trait: (i) average of the whole gradient (GLO), (ii) average of the sampling unit in which the abundances of species maximize (MAX) and (iii) average of a reduced number of individuals per species and sampling unit (LOC). For each strategy, we simulated different sampling intensities (number of individuals sampled). For each trait, we examined the ability of each strategy and sampling intensity to accurately estimate CWMI and FDI, as well as their ability to detect changes in functional trait structure along the topographical gradient. LOC outperformed the other strategies in terms of accuracy and bias, and was much more efficient to describe changes along the gradient, regardless of the traits and indicators considered. Furthermore, LOC was the only strategy that improved consistently as sampling intensity increased, especially at low levels of intensity. Our results indicate that the impact of considering intraspecific variability in trait values can be greater than commonly assumed. Strategies that neglect this source of variability can result in inaccurate or biased estimations of the functional trait structure of plant communities. Most importantly, we show that intraspecific variability can be taken into consideration without any increases in the total number of individuals measuredFinancial support was received from the Spanish Ministry of Science (Project CGL2011-24871), the Madrid Regional Government (Project REMEDINAL3), and the Spanish Ministry of Education (FPU AP2012-2849 for CR). CPC was supported by a Marie Curie Intra-European Fellowship within the 7th European Community Framework Programme (TANDEM; project id. 626392

Spatial patterns of species richness and nestedness in ant assemblages along an elevational gradient in a Mediterranean mountain range

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 elevation

Landscape and agri-environmental scheme effects on ant communities in cereal croplands of central Spain

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 controlThis 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)

Herbivore corridors sustain genetic footprint in plant populations: a case for Spanish drove roads

Habitat fragmentation is one of the greatest threats to biodiversity conservation and ecosystem productivity mediated by direct human impact. Its consequences include genetic depauperation, comprising phenomena such as inbreeding depression or reduction in genetic diversity. While the capacity of wild and domestic herbivores to sustain long-distance seed dispersal has been proven, the impact of herbivore corridors in plant population genetics remains to be observed. We conducted this study in the Conquense Drove Road in Spain, where sustained use by livestock over centuries has involved transhumant herds passing twice a year en route to winter and summer pastures. We compared genetic diversity and inbreeding coefficients of Plantago lagopus populations along the drove road with populations in the surrounding agricultural matrix, at varying distances from human settlements. We observed significant differences in coefficients of inbreeding between the drove road and the agricultural matrix, as well as significant trends indicative of higher genetic diversity and population nestedness around human settlements. Trends for higher genetic diversity along drove roads may be present, although they were only marginally significant due to the available sample size. Our results illustrate a functional landscape with human settlements as dispersal hotspots, while the findings along the drove road confirm its role as a pollinator reservoir observed in other studies. Drove roads may possibly also function as linear structures that facilitate long-distance dispersal across the agricultural matrix, while local P. lagopus populations depend rather on short-distance seed dispersal. These results highlight the role of herbivore corridors for conserving the migration capacity of plants, and contribute towards understanding the role of seed dispersal and the spread of invasive species related to human activities.Peer reviewe

Exploring the effect of soil management intensity on taxonomic and functional diversity of ants in Mediterranean olive groves

Agricultural intensification is one of the major drivers behind biodiversity loss in Mediterranean agroecosystems. The intensification of olive groves as monoculture in large areas of the southern Spain has had important effects on biodiversity and ecological processes. In the present study, we explore the olive grove soil management practices effects on taxonomic and functional diversity of ants along a gradient of soil management intensity. We predict that both species richness and functional diversity decrease with an increasing intensification of olive grove soil management. We used pitfall traps to sample ants in 24 olive groves subject to different soil management regimes in southern Spain, and then compared ant species richness and functional diversity (FD). Nonploughed organic farms showed higher species richness. Ploughing was observed to be the soil management practice with the greatest negative effect on ant species richness. Three functional traits significantly responded to soil management intensity, with tibia length and head width showing a higher FD in organic farms and diet showing a lower FD in ploughed farms. The results of the present study highlight the negative effects of olive grove ploughing on ant biodiversity and provide novel evidence of the nonploughing organic farming role with respect to maintaining higher levels of ant functional diversityFinancial support was received from the Spanish Ministryof Economy and Competitiveness (Project CGL2014-53782-P

Abiotic controls, but not species richness, shape niche overlap and breadth of ant assemblages along an elevational gradient in central Spain

Niche overlap and breadth are fundamental characteristics of ecological niches that have been hypothesized to relate both to environmental conditions and to biotic interactions within a community. Abiotic factors and interspecific competition may have opposing effects on those niche characteristics by respectively filtering out species from the niche space and limiting among-species similarity. Here we set out to assess niche overlap and breadth of ant assemblages in Mediterranean grasslands along a 1668-m elevational gradient in the Guadarrama range (Central Spain). We carried out an outdoor cafeteria experiment considering two niche dimensions on resource acquisition: food type and period of aboveground activity. We compared metrics describing niche overlap and breadth to null models and related the metrics to elevation, temperature at ground level and a proxy of interspecific competition (species richness) with general linear models. Pianka's niche overlap indexes were higher than those calculated with random assemblages, but differences among observed and random assemblages were only significant at mid-elevations and were unrelated to the explanatory variables. Overlap along elevation seemed more due to overlap in period of activity. Niche breadth at the assemblage level was significatively smaller than null expectations and was related to elevation (negatively) and to species richness (positively). These were significantly larger than estimates for the species level. These results show that ant assemblages exploit a subset of available conditions, in a pattern only partially coincident with a scenario of abiotic control. Moreover, their constituent species share time of activity and, to a lesser extent, food resources, in spite of the interspecific competition structuring communities that is often assumed. Overall, the patterns we recorded suggest that other mechanisms should be acting to promote species coexistence, such as trade-offs among ecological functionsThis work was supported by the Spanish Ministry of Economy and Competitiveness [Project 469 CGL2014-53789-R and grant BES-2015-075124 (MS)] and the research group network 470 REMEDINAL3-CM (S-2013/MAE-2719). The Sierra de Guadarrama National Park provided 471 administrative support. Arantxa Aguilar and Celia Santos contributed to the field work and Xavier 472 Espadaler helped to identify some species

Exploring the effect of landscape composition and agroecological practices on wild bees in horticultural farms

How farms and the surrounding landscape are managed locally substantially affects biodiversity, with consequent impacts on the supply of certain ecosystem services, such as pollination. Wild bees provide pollination services for small-scale horticultural farming, and are key to determining and improving farm production, as well as maintaining ecosystem-level diversity. Here, we investigated how landscape composition and agroecological practices affect wild bee community in small-scale horticultural farms. The study was conducted at 16 horticultural farms in the northern part of Madrid. The pan-trapping method was used to collect wild bees during the flowering period of horticultural plants. We interviewed farmers to identify which agroecological practices were primarily adopted to attain a resilient ecosystem. The most common practices adopted were weed control methods, natural fertilizer usage, pest control, and crop diversification. In total, 109 wild bee species were identified, and included individuals from all six bee families present on the Iberian Peninsula. One genus (Lasioglossum) was highly abundant, accounting for 68% of individuals, and is a known ground nester. Areas of sparse vegetation and bare soil and forested areas primarily enhanced the richness of bee species. On the other hand, abundance of wild bees is enhanced by pasture and forest areas. The presence of these habitats in areas surrounding farms might represent the potential nesting sites with important resources for wild bees. Small-scale horticulture production promotes landscape diversity, which strongly promotes the potential of different ecosystem services, including pollination and wild bees. Thus, implementing agroecological practices could transcend farms, and individual fields, to the landscape level, providing long-term sustainability of ecosystemsThis work was supported by the “Simbiosis api-agro” project funded by the European Union, the Spanish Ministry of Agriculture, Food and the Environment and Madrid Regional Government under the Rural Development Programme (rdp-cm 2014-2020); and SAVIA-Sowing Alternatives for Agroecological Innovation project, which was supported by the Madrid Government under the Multiannual Agreement with Universidad Autónoma de Madrid, in the context of the V PRICIT (Regional Programme of Research and Technological Innovation) (SI1/PJI/2019-00444