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

Diversity and mean specific leaf area of Mediterranean woody vegetation changes in response to summer drought across a double stress gradient: The role of phenotypic plasticity

Aim: Many aspects of vegetation response to increased drought remain uncertain but it is expected that phenotypic plasticity may be key to early adaptation of plants to environmental stress. In this work we observe the response of specific leaf area (SLA) of woody shrub vegetation to the summer drought typical of the Mediterranean climate. In addition, to observe the possible interaction between the impact of drought and the environmental characteristics of the ecosystems, communities from different edaphic and structural contexts distributed along the double stress gradient of the Mediterranean mountains (high temperature and low precipitation at low elevation; low temperature and high irradiation at high elevation) have been analysed. Location: Central Mountain range of the Iberian Peninsula. Methods: Along the entire altitudinal gradient, 33 shrub communities belonging to different habitat typologies (shrublands, rocky areas, hedgerows, understorey) were sampled before and after the passage of summer, both in 2017 and 2019. A total of 1724 individuals and 15,516 leaves were collected and measured to estimate the mean values and diversity of SLA of each community. Results: The community-weighted mean and functional divergence have inverse quadratic relationships with the environmental gradient. Shrub communities at both ends of the gradient have low mean SLA values and high functional divergence of this trait. Summer drought implies a generalised decrease in the mean SLA of the communities throughout the gradient, as well as an alteration in functional richness and uniformity. However, the effect of summer drought on the plant community is mediated by the microenvironmental characteristics of its habitat. Conclusions: Drought acclimatisation of shrub communities through phenotypic plasticity leads to rapid changes in their functional leaf structure. In the long term, our results point to an increase in plant conservative strategies, reduced ecosystem productivity, slower nutrient recycling and the reduction of communities of specific habitats as drought increasesAdministrative and financial support was received from the Autonomous Community of Madrid (Project REMEDINAL TECM S2018/EMT-4338) and Sierra de Guadarrama National Park, which provided the permits for the sampling within the park (ref 10/097831.9/18). Alejandro Carrascosa was supported by a grant for the Promotion of Research in UAM Master studies (UAM 2018– 2019), and Mariola Silvestre by an FPI grant from MINEC

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

A new host for a new Rossomyrmex minuchae population

Social parasites usually rely on chemical cues (cuticular hydrocarbons) to successfully invade and coexist with their hosts. Most ants that are obligate social parasites (slave-makers) can parasitize several related host species with different levels of chemical similarity although there are few exceptions where there is only a single host species. An example of the latter is Rossomyrmex minuchae, which was known to be only associated with Proformica longiseta. However, a recent discovery of a new R. minuchae population revealed that it can parasitize P. nasuta, a species with a separate distribution to P. longiseta. Chemical analyses of cuticular hydrocarbons show local adaptation of the parasite to its host in this new population, being more similar to P. nasuta than to other R. minuchae populations. In addition, genetic analyses evidence differences from the other known populations, from which it split 1.21 Mya during glacial and interglacial periods of the Pleistocene and remained separated to the present day. This historical genetic isolation and the chemical differences found between parasite populations may evidence a speciation process and support the local host–parasite coevolutionM Silvestre and FM Azcárate received administrative and fnancial support from the Spanish Ministry of Economy and Competitiveness (Project CGL2014-53789-R). Sierra de Guadarrama National Park provided the permits for the sampling (ref 10/101642.9/16). This work was also partially funded by the University of Jaén through the “Plan Operativo de Apoyo a la Investigación 2021-2022

¿Cómo coexisten las especies de hormigas y qué efecto tienen sus comunidades en las montañas mediterráneas? Un análisis a lo largo de un gradiente altitudinal en la Sierra de Guadarrama (Madrid)

Tesis doctoral inédita leída en la Universidad Autónoma de Madrid, Facultad de Ciencias, Departamento de Ecología. Fecha de lectura: 20-07-2020Esta tesis tiene embargado el acceso al texto completo hasta el 20-01-202