Adrián Escudero

The least‐cost economic theory of photosynthesis (LCE) postulates that leaf nitrogen (N) modulates the balance between carbon gain and water loss in plants, with N‐rich leaves exhibiting higher photosynthetic efficiency and lower transpiration rates than N‐poor leaves. However, the optimal balance of water and N acquisition and use may differ substantially among coexisting species, influenced by factors such as evolutionary history. Understanding how co‐occurring species balance water and nutrient use during photosynthesis, and how this shapes eco‐physiological performance and growth is ecologically relevant, particularly in water‐limited environments. Here, we investigate whether the LCE theory can explain differences in leaf water‐use traits among 23 naturally co‐occurring Mediterranean shrubland species growing under optimal, non‐limiting water and nutrient conditions. Specifically, we evaluated the effects of leaf N content on both inter‐ and intraspecific variation of three leaf traits related to water use: δ ¹³ C (proxy for intrinsic water‐use efficiency, WUEi), δ ¹⁸ O (proxy for stomatal conductance) and IMS, that is integrated metabolic strategy, (index integrating both isotopes to estimate leaf metabolic efficiency) accounting for potential phylogenetic constraints. We also examined how these traits influenced plant relative growth rate across species. Our 23 perennial species exhibited large interspecific variation in leaf traits related to water and nutrient use. Mean leaf N content ranged from 2.4 to 6% across species and was positively associated with both δ ¹⁸ O and IMS, revealing tighter stomatal regulation and enhanced metabolic efficiency in N‐rich leaves. Phylogenetic mixed models confirmed that leaf N was the main driver of variation in leaf water flux (δ ¹⁸ O) and metabolic efficiency (IMS) across individuals. Interspecific variation in plant growth rate was largely driven by leaf N and IMS. Synthesis. The large functional diversity in our dryland plant community results in significant variations in water and nutrient input mixture optimization across co‐occurring species. Our findings provide experimental evidence that increased nitrogen investment in leaves is associated, both across and within species, with enhanced photosynthetic efficiency and reduced water loss under controlled, non‐limiting conditions. Furthermore, they support IMS as an integrative index of the trade‐off between carbon assimilation and water loss.

The conservation of forest habitats in Europe is crucial for biodiversity conservation and human well-being. However, these habitats suffer a number of pressures that distance them from intact forest ecosystems. The European Union’s Habitats Directive (HD) set the path towards reversing this deterioration and protecting threatened habitats and species, dictating that all Member States should report every six years the conservation status of the natural habitats present in their territories. However, it presented a particularly static vision of what habitats were and how their conservation status should be evaluated. Here we created an indicator-based methodology to evaluate the conservation status of the forests of Spain using data of three consecutive Spanish National Forest Inventories and tracked its changes through a period of roughly 30 years. We also analyzed how this conservation status related to the dynamic nature of these habitats and the successional processes that affected them. While most of the habitats presented very low values of the conservation status and its attributes at the beginning of the study, this status has significantly improved since. However, we observed a slowdown of this improvement in the latest years, which seems correlated to an increase in extreme climate events —mainly droughts— due to the effects of climate change. Also, we observed very fast processes of species diversification and habitat succession that contradict the static vision that dominates the HD. We call for this dynamism to be considered both in the definition of the habitats and the evaluation of their conservation status.

Summary: Predicting coexistence in species‐rich plant communities requires understanding the role of functional traits in species interactions and the stability of these associations to environmental variation. In a manipulative factorial field experiment in an annual community (> 45 500 individuals and 45 species), we followed plant associations from seedling to adult on both preserved and altered biological soil crust (BSC) over 2 yr with contrasting weather conditions. Neighborhood models quantified how among‐species differences in key functional traits affected coexistence and how these effects varied in response to ontogenetic stage, environmental variation, and spatial scale. Trait‐based models revealed a prevalent negative relationship between functional differences and species associations, but these relationships varied predictively with ontogenetic stage, environment, and spatial scale. Functional dissimilarity in traits, such as specific leaf area, seed mass, and reproductive‐to‐vegetative biomass ratio consistently mediated species segregation, especially during wet years and among seedlings, while BSC disturbance altered trait‐mediated associations differently at fine and coarse spatial scales. Trait‐mediated species associations shift predictably with environmental variation, suggesting that coexistence reflects a dynamic balance between environmental filtering and competitive interactions. This work provides novel experimental evidence of when, where, and which traits predict community assembly, which has implications for forecasting biodiversity responses to global environmental change.

Urbanization is a global phenomenon inducing rapid and permanent land‐use changes. These transformations have significant impacts on biodiversity and ecosystem functioning, primarily through the filtering of specific functional and/or morphological traits. In animals, body size is a critical functional trait linked to ecosystem functioning because it affects metabolism, dispersal and trophic interactions. Moth communities are particularly sensitive to urbanization, often exhibiting reduced species diversity due to non‐random species loss. However, body size responses to urbanization remain ambiguous, as contrasting eco‐evolutionary processes may drive shifts in opposite directions. The Urban‐Heat‐Island effect (UHI) predicts a reduction in body size—following Atkinson's temperature‐size rule—due to increased metabolic costs, whereas habitat fragmentation may favour larger individuals with greater dispersal ability. Here, to test these hypotheses, we sampled geometrid moths along an urbanization gradient in a tropical Andean city and analysed body size variation at both community and population levels in relation to UHI intensity. At the community level, our results revealed a reduction in body size at high levels of UHI, consistent with the temperature‐size rule. However, at the population level, phenotypic changes were consistent with opposing pressures associated with urban warming and habitat fragmentation, depending on the species. Hence, our study suggests that urban environments can filter species idiosyncratically within communities and individuals within species, but through different mechanisms.

El fenómeno del despoblamiento en áreas rurales se ha convertido en uno de los motores de cambio global de mayor impacto. Es especialmente relevante en los llamados países desarrollados, aunque también se da en regiones tropicales. El despoblamiento tiene consecuencias muy importantes en los ámbitos social y ambiental, manifestando la existencia de importantes desequilibrios territoriales. En los últimos años este fenómeno ha ganado importancia en la opinión pública y ya forma parte de la agenda política, especialmente en su vertiente sociológica. El análisis del despoblamiento, así como las estrategias y actuaciones encaminadas a revertirlo, o al menos a mitigarlo, se basan mayoritariamente en valoraciones económicas y sociológicas, pero también culturales, ya que el despoblamiento rural comporta una elevada carga emocional fundamentada en nuestra historia y en la supervivencia de los valores culturales asociados al territorio. Sin embargo, las implicaciones ecológicas suelen ser obviadas, a pesar de ser evidentes y de que el cambio de uso del suelo es uno de los grandes conductores de las alteraciones de los sistemas naturales, muy en particular en contextos mediterráneos. En este monográfico tratamos sobre las implicaciones ecológicas del despoblamiento en áreas rurales.

SUMMARY: Predicting coexistence in species-rich plant communities requires understanding the role of functional traits in species interactions and their resilience to environmental variation. In a manipulative factorial field experiment in an annual community (>45,000 individuals and 45 species), we followed plant associations from seedling to adult on both preserved and altered biological soil crust over two years with contrasting weather conditions. Neighborhood models quantified how among-species differences in key functional traits affected coexistence and how these effects varied in response to ontogenetic stage, environmental variation and spatial scale. Trait-based models revealed a prevalent negative relationship between functional differences and species associations, but these relationships varied predictively with stage, environment and spatial scale. Functional dissimilarity in traits such as specific leaf area, seed mass, and reproductive-to-vegetative biomass ratio consistently mediated species segregation, especially during wet years and among seedlings, while biological soil crust disturbance altered trait-mediated associations differently at fine and coarse spatial scales. Trait-mediated species associations shift predictably with environmental variation, suggesting that coexistence reflects a dynamic balance between environmental filtering and competitive interactions. This work provides novel experimental evidence of when, where, and which traits predict community assembly, which has implications for forecasting biodiversity responses to global environmental change.

Un nuevo árbol y género de la familia Araliaceae ha sido registrada por primera vez en Ecuador. El hallazgo de varios ejemplares se realizó en bosques semideciduos piemontanos del Catamayo - Alamor y en bosques semideciduos montano bajo del Catamayo – Alamor de la provincia de Loja, cantónes: Macará, Paltas y Gonzanamá, específicamente en la reserva natural Laipuna (Propiedad de Naturaleza y Cultura Internacional), ubicada a unos 20 km de Macará, a una altitud de 1120 m.s.n.m. Durante una expedición botánica (noviembre 2009), se colectó un árbol de aproximadamente 7 metros de altura, desconocido por los habitantes locales. Tras su análisis en herbarios ecuatorianos (LOJA. QCNE, QCA) y consulta con especialistas taxónomos del país, se confirmó que se trataba de Aralia soratensis Marchal, una especie distribuida típicamente en la parte central y al Pacífico en el continente sur americano, especialmente en el norte de Argentina, el suroeste de Bolivia y el sur del Perú. En este último país, hay una colección realizada en el noroeste, dentro del área protegida Cerros de Amotape, en el departamento de Tumbes. En Ecuador, además del registro en la reserva Laipuna en el cantón Macará, se han identificado ejemplares en otros cantones de la provincia de Loja, como Gonzanamá sector Sacapalca (1350 m s.n.m.), y con mayor frecuencia en Paltas, particularmente en la parte baja del cerro Pisaca (1857 m. s.n.m.). Durante investigaciones y seguimiento a las plantas identificadas se ha determinado que Aralia soratensis, florece entre noviembre - enero cuando inicia el periodo de lluvias y fructifica entre enero – marzo; hasta ahora se ha identificado 2 poblaciones con pocos individuos en los cantones Macará como Paltas, creciendo en lugares húmedos o lechos de quebradas secas donde encuentra su nicho favorable para su desarrollo.

A new species of Malvaceae, Spirotheca zapotillana , is described from the Equatorial Pacific region of South America. The species occurs in seasonally dry tropical forests of El Oro and Loja provinces in southern Ecuador. It is characterized by a strictly tree-like habit, elliptical leaflets with acute apices, glandular floral receptacles, glabrous styles, oblong capsules, and reniform seeds. A morphological description of the new species is provided, along with data on its habitat and distribution, an assessment of its conservation status, and an updated key for the genus.

Water scarcity is the main selective pressure determining the performance of Mediterranean plant populations, with climate change predicted to increase the intensity and duration of droughts. However, drought rarely acts in isolation. Climate change also involves substantial warming in this region and may disrupt natural processes, including biotic interactions. Phenotypic plasticity allows plants to cope with rapid and multifaceted environmental changes. Although our knowledge of plastic responses to drought in Mediterranean plants has increased in recent years, how co‐occurring simultaneous stressors interact to produce additive, synergistic, or antagonistic effects that enhance or constrain adaptive plastic responses to drought is still unknown. Using a factorial experimental approach based on a multivariate common garden, we assessed whether adaptive phenotypic plasticity to drought and population differentiation in traits related to drought response were affected by the occurrence of other key simultaneous stressors, warming and intraspecific competition, in a Mediterranean gypsum endemic shrub. In response to drought, plants expressed adaptive plastic responses associated with a mixed resource‐use strategy, combining conservative (sclerophyllous leaves with higher water use efficiency) and acquisitive (advanced phenology) phenotypic responses. Although the response to drought was modified by synergistic and antagonistic interactions with warming and competition, these interactions did not change the direction or reduce the extent of adaptive plasticity to drought. This suggests that plastic responses to drought may also provide benefits against warming and competition. Finally, we detected significant population differentiation in all functional traits, but phenotypic differences in reproductive biomass were significantly reduced under combined drought and warming. Our results emphasize the robustness of adaptive plasticity to drought under complex stress scenarios and underscore the importance of realistic, multifactorial experimental approaches to predict whether adaptive responses of plant populations will remain effective in a climate change context and influence their future ecological and evolutionary dynamics.

Climate change and land use changes in urban landscapes exacerbate the runoff generation which produces economic losses and socio-environmental impacts. Urban rivers serve as blue–green infrastructure (BGI) offering ecosystem services (ESs), including runoff control and mitigation that helps in climate change adaptation, especially in arid regions where flash floods are devasting and climate models predict an increase in frequency and intensity. This study uses the InVEST urban flood risk mitigation (UFRM) model to estimate the runoff generated during precipitation events, applied to the urban section of the Chili River in Arequipa, an arid region south of Peru. The model requires information on land use/land cover, rainfall depth, and hydrological soil groups. Results from 1984 and 2022 demonstrate there is a significant reduction in runoff retention, specially in the northern section, where areas decreased their runoff retention capacity from 70–80% to 20–30%. The results highlight the river’s critical role in mitigating flash flood risks in a dessert region. The methodology used can help estimate run-off mitigation provided by urban rivers as BGI and supports the conservation and restoration of urban rivers as ecological corridors, enhancing urban resilience.