Examinando por Autor "Escudero, Adrián"

Mostrando 1 - 20 de 42

A dimmer shade of pale: revealing the faint signature of local assembly processes on the structure of strongly filtered plant communities
(Wiley, 2020-10-08) López-Angulo, Jesús; De la Cruz, Marcelino; Pescador, David S.; Sánchez, Ana M.; Escudero, Adrián
Trait-based ecology suggests that abiotic filtering is the main mechanism structuring the regional species pool in different subsets of habitat-specific species. At more local spatial scales, other ecological processes may add on giving rise to complex patterns of functional diversity (FD). Understanding how assembly processes operating on the habitat-specific species pools produce the locally observed plant assemblages is an ongoing challenge. Here, we evaluated the importance of different processes to community assembly in an alpine fellfield, assessing its effects on local plant trait FD. Using classical randomization tests and linear mixed models, we compared the observed FD with expectations from three null models that hierarchically incorporate additional assembly constraints: stochastic null models (random assembly), independence null models (each species responding individual and independently to abiotic environment), and co-occurrence null models (species responding to environmental variation and to the presence of other species). We sampled species composition in 115 quadrats across 24 locations in the central Pyrenees (Spain) that differed in soil conditions, solar radiation and elevation. Overall, the classical randomization tests were unable to find differences between the observed and expected functional patterns, suggesting that the strong abiotic filters that sort out the flora of extreme regional environments blur any signal of other local processes. However, our approach based on linear mixed models revealed the signature of different ecological processes. In the case of seed mass and leaf thickness, observed FD significantly deviated from the expectations of the stochastic model, suggesting that fine-scale abiotic filtering and facilitation can be behind these patterns. Our study highlights how the hierarchical incorporation of ecological additional constraints may shed light on the dim signal left by local assembly processes in alpine environments.
Additive effects of a potentially invasive grass and water stress on the performance of seedlings of gypsum specialists
(International Association of Vegetation Science, 2014-10-30) Matesanz, Silvia; Escudero, Adrián; Valladares, Fernando
Climate and small scale factors determine functional diversity shifts of biological soil crusts in Iberian drylands
(2014-04-03) Concostrina-Zubiri, Laura; Pescador, David S.; Martínez, Isabel; Escudero, Adrián
Understanding functional diversity is critical to manage and preserve biodiversity and ecosystem functioning in the face of global change. However, the efforts to characterize this functional component have been mostly directed to vascular vegetation. We sampled lichen-dominated biological soil crusts (BSCs) in semiarid grasslands along an environmental gradient in the Iberian Peninsula. We characterized five effect functional traits for 31 lichens species, and evaluated the influence of large scale (i.e. precipitation) and small scale factors (i.e. substrate type, shrub presence, Stipa tenacissima presence) on dominant trait values; i.e. community weighted means, and functional divergence; i.e. Rao quadratic entropy in 580 sampling quadrats. Across the gradient, we found multiple trait shifts and a general increase of functional divergence with increasing precipitation. We also observed that substrate type and small scale biotic factors determined shifts in all traits studied, while these factors affected less to functional divergence. Comparing functional diversity with taxonomic diversity, we found contrasting responses to both large and small scale factors. These findings suggest that BSC community trait composition is influenced by multi-scale abiotic and biotic factors with environmental filtering dominating at large spatial scales and limiting similarity at specific small scales. Also, our results emphasize the potential differences between taxonomic and functional diversity in response to environmental factors. We concluded that functional diversity of BSCs not only provides novel and critical knowledge of BSC community structure, but also it should be considered as a critical tool in biodiversity conservation strategies, ecosystem services assessment and ecological modelling.
Climate change and biocrust disturbance synergistically decreased taxonomic, functional and phylogenetic diversity in annual communities on gypsiferous soils
(Wiley, 2021) Sánchez, Ana M.; Peralta, Ana M. L.; Luzuriaga, Arantzazu L.; Prieto, María; Escudero, Adrián
Rainfall and biocrusts are important sources of temporal and spatial environmental heterogeneity and niche differentiation for annual plants, a major component of diversity in drylands. Therefore, global change processes comprising shifts in rainfall timing and drought exacerbation, together with biocrust disturbance may affect species coexistence and result in disrupted diversity patterns. In this study, we experimentally evaluated the effects of the rainfall amount and timing as well as physical biocrust disturbance and their interaction on the taxonomic, phylogenetic and functional diversity of annual plant communities on gypsum soil drylands. All diversity estimates were determined at different times during community development in each experimental unit (α), as the contribution of each experimental unit to the total diversity in each treatment (β) and as the total diversity in each treatment (γ). Rainfall timings led to changes in all diversity dimensions, with higher diversity under the typical timing. The community was quite resilient to moderate reductions in rainfall, but extreme droughts decreased the alpha and beta taxonomic, functional and phylogenetic diversities. In addition, the simultaneous occurrence of biocrust disturbance and extreme drought led to consistent collapses in all diversity dimensions, probably because the effects of water shortage were exacerbated. Observations of the community at different times during its development highlighted the importance of regenerative strategies for niche differentiation and species coexistence, and their strong dependence on global change drivers. Indeed, our experimental study demonstrated that rainfall patterns and biocrusts are key factors related to the maintenance of diversity in semiarid annual plant communities. In particular, our results highlight the key role of biocrusts in modulating the effects of drought on plant diversity and the need for integrative approaches that consider both plants and biocrusts in order to elucidate the influence of climate change on the diversity of drylands.
Climate seasonality and tree growth strategies in a tropical dry forest
(Wiley Online Library, 2019-11-16) García-Cervigón, Ana I.; Camarero, J. Julio; Cueva, Eduardo; Espinosa, Carlos I.; Escudero, Adrián
Questions: Do tree species in seasonally dry tropical forests differ in the timing oftheir secondary growth? And in their growth rates between consecutive years? If so,how are these contrasting patterns linked to seasonality in climatic variables (tem-perature, precipitation)? Which is the role of leaf phenology and functional traits asdrivers of stem radial increment responses to climate?Location: A Tumbesian tropical dry forest in southern Ecuador.Methods: We used a 12-year database of stem radial increments to characterizeintra- and inter-annual patterns of secondary growth in 13 co-existing dominant treespecies. For each species, we adjusted an additive model to describe intra-annualincrement patterns and created a mean series of annual increments to describe inter-annual changes. Adjusted increments were then correlated with monthly tempera-ture and rainfall data over the study period, and also with the crown percentagecovered by leaves. The role of functional traits (leaf area, wood density, maximumtree height, seed dry mass) was explored using average trait values per species.Results: We observed continuous variation in the seasonality of radial increments,ranging from species that started incrementing their diameter as early as first rainsoccurred in the season to species that showed delayed responses. Variability in intra-and inter-annual increment patterns was explained by functional traits (leaf area andseed dry mass, and maximum height and wood density, respectively) and leaf phenol-ogy, but this variation was not clearly matched with any functional trait configura-tion. This, combined with the absence of homogeneous responses of annual growthrates to climate, suggests the existence of contrasting strategies that virtually vary ina species-specific fashion.Conclusions: Co-existing tree species in seasonally dry tropical forests show differ-ent growth strategies to face intra- and inter-annual climate variations, which mayincrease the resilience of these forests against projected climatic variations.
Climbing route development affects cliff vascular plants more than subsequent climbing: A guide to evidence-based conservation management to regulate climbing
(Wiley, 2024-09-24) Morales-Armijo, Felipe; Sobrevilla-Covarrubias, Andrea; Estrada-Castillón, Eduardo; Escudero, Adrián; Scheepens, J. F.; Lorite, Juan; March-Salas, Martí
Cliff ecosystems provide refuge to 35%–66% of the world's endemic plants. However, they face growing threats from sport climbing. Evidence suggests that unclimbed cliffs harbour approximately twice the plant richness compared with climbed cliffs, with increasing impact as climbing intensity increases. Unfortunately, it remains unknown whether the climbing impact on cliff vegetation originates from the development (opening) of climbing routes or from temporal changes resulting from subsequent climbing. We recorded cliff vascular plants and lichens at the protected natural area of El Potrero Chico (Mexico) before and after the development of new climbing routes. Subsequently, we re-recorded the routes at sequential timepoints after 10, 20, and 30 ascents. Additionally, we examined whether the abundance of cliff vegetation influences the extent of climbing impact and whether the surroundings of the routes were also affected. We found that the opening of climbing routes exerted the strongest negative effects on cliff plants, reducing species richness by 38%, while subsequent ascents generated a minimal impact. Worryingly, route opening affected not only species richness in the route itself but also the surroundings of the routes. After 30 ascents, cliff plant abundance decreased by 60.6% within the bolted routes, whereas it decreased by 42.3% in the surroundings. However, this impact depended on the original cliff vegetation abundance. Lichen cover showed a gradual decrease, indicating that cliff-dwelling lichens are affected not only by the opening of the route but also by subsequent ascents. Synthesis and applications: Given the almost non-existent regulation of outdoor climbing activities in most countries, we urge the implementation of a conservation management protocol that defines clear strategies to regulate climbing activities and preserve pristine cliffs. On yet unclimbed cliffs with narrow endemic, rare, or threatened species, we propose banning the establishment of new climbing areas. On climbed cliffs lacking protected species, dynamic management actions should be implemented, such as setting a maximum number of routes that can be established and defining limits of acceptable change as climbing intensity increases. The proposed conservation management should help to halt the loss of unique cliff biodiversity and safeguard pristine cliff ecosystems
Contrasting adaptive trait variation in response to drought in two Mediterranean shrubs
(Elsevier, 2023) Blanco-Sánchez, Mario; Franks, Steven J.; Ramos-Muñoz, Marina; Pías, Beatriz; Ramírez-Valiente, José Alberto; Escudero, Adrián; Matesanz, Silvia
Adaptive evolution and phenotypic plasticity are key mechanisms of climate change responses. However, we still lack a detailed understanding of the strategies different species use to cope with climatic changes such as increased droughts, particularly for species with special edaphic requirements and limited dispersal such as gypsum endemics. In this study, we assessed phenotypic and genotypic selection, phenotypic plasticity and genetic variation in traits potentially related to drought response in two dominant gypsum Mediterranean species, Helianthemum squamatum and Centaurea hyssopifolia. We established a common garden in which 524 plants from 79 maternal families from both species were grown under two contrasting watering treatments. Our results revealed that selection was stronger under drought than well-watered conditions for both species, but we found contrasting adaptive strategies and genetic variation. In H. squamatum, a drought-escape strategy with advanced reproductive phenology and faster growth rates was positively associated with fitness under dry conditions, and most adaptive traits exhibited quantitative genetic variation. In contrast, in C. hyssopifolia, selection under dry conditions favored a drought-tolerance strategy with thicker leaves and longer phenologies, but all traits lacked quantitative genetic variation, indicating that their evolutionary potential may be limited. Most traits exhibited significant plasticity in response to drought and genetic variation for trait plasticity in both species, indicating that trait plasticity can evolve independently of the evolution of trait means in these gypsophiles. Our results show that these gypsum endemic species vary in strategies and adaptive potential in response to drought, which contributes to our understanding of potential adaptive responses to climate change in such edaphic specialists.
Critical predictors of functional, phylogenetic, and taxonomic diversity are geographically structured in lichen epiphytic communities
(Wiley, 2019-04-11) Hurtado, Pilar; Prieto, Maria; Aragón, Gregorio; Escudero, Adrián; Martínez, Isabel
Assessing the response of biological communities to contrasting environmentalconditions is crucial to predict the effects of global change drivers. The influenceof multiple environmental factors may differ depending on the diversity facetconsidered, which emphasizes the need to simultaneously evaluate the functional(FD), phylogenetic (PD) and taxonomic (TD) diversity.2. To examine how these facets of biodiversity respond to environmental changes,we studied lichen epiphytic communities across 47 beech forest fragments fromtwo biogeographic regions. We applied structural equation modelling to relatehabitat fragmentation, climate and habitat quality with FD, PD and TD. We com‐pared the community response to contrasting climatic conditions by analysing in‐dependently Atlantic and Mediterranean communities.3. We found different major drivers of biodiversity patterns across biogeographicregions. Habitat fragmentation performed the highest effect on lichen communi‐ties, with a reduction of FD, PD and TD at both regions. However, the influenceof climate was stronger in the Atlantic region than in the Mediterranean region,where the effect of habitat quality was superior. The effect of the environmentalpredictors over PD and TD was both direct and indirect through the differentcomponents of FD, and their intensity and sign differed across regions. Changesin PD were not related to changes in TD.4. Synthesis. Our results evidenced that the major environmental drivers affect‐ing epiphytic communities were geographically structured. These drivers modi‐fied the diversity of the epiphytic community directly but also indirectly throughchanges in FD, which emerged as a causal but not unique determinant of PD andTD. Our findings also showed the difficulty for inferring TD through PD. Theseresults emphasize the essential role of FD predicting part of the response of lichencommunities to global change drivers but also highlight the importance of con‐sidering multiple biodiversity facets to understand the effects of environmentalchange on community structure.
Determinants of high mountain plant diversity in the Chilean Andes: From regional to local spatial scales
(2018-07-06) López-Angulo, Jesús; Pescador, David S.; Sánchez, Ana M.; Mihoč, Maritza A.; Cavieres, Lohengrin A.; Escudero, Adrián
Mountains are considered excellent natural laboratories for studying the determinants of plant diversity at contrasting spatial scales. To gain insights into how plant diversity is structured at different spatial scales, we surveyed high mountain plant communities in the Chilean Andes where man-driven perturbations are rare. This was done along elevational gradients located at different latitudes taking into account factors that act at fine scales, including abiotic (potential solar radiation and soil quality) and biotic (species interactions) factors, and considering multiple spatial scales. Species richness, inverse of Simpson’s concentration (Dequiv), beta-diversity and plant cover were estimated using the percentage of cover per species recorded in 34 sites in the different regions with contrasted climates. Overall, plant species richness, Dequiv and plant cover were lower in sites located at higher latitudes. We found a unimodal relationship between species richness and elevation and this pattern was constant independently of the regional climatic conditions. Soil quality decreased the beta-diversity among the plots in each massif and increased the richness, the Dequiv and cover. Segregated patterns of species co-occurrence were related to increases in richness, Dequiv and plant cover at finer scales. Our results showed that elevation patterns of alpine plant diversity remained constant along the regions although the mechanisms underlying these diversity patterns may differ among climatic regions. They also suggested that the patterns of plant diversity in alpine ecosystems respond to a series of factors (abiotic and biotic) that act jointly at different spatial scale determining the assemblages of local communities, but their importance can only be assessed using a multi-scale spatial approach.
Dispersal syndrome influences the match between seed rain and soil seed bank of woody species in a Neotropical dry forest
(Wiley, 2020-11) Jara-Guerrero, Andrea; Espinosa, Carlos I.; Méndez, Marcos; De la Cruz, Marcelino; Escudero, Adrián
Aims Plant recruitment may occur immediately after seed dispersal from the mother plant, or be delayed through the formation of soil seed banks. These strategies are known to be mediated by adaptations of seed dispersal and reproductive phenology, which if analyzed together can provide valuable information about the regeneration strategies of species. We explored whether dispersal syndrome and/or seed dispersal phenology control the similarity between standing vegetation, seed rain and soil seed bank in a seasonally dry tropical forest (SDTF) in Southern Ecuador. Location Arenillas Ecological Reserve, Southwestern Ecuador, the biogeographic region of Pacific Coastal Ecuador. Methods We recorded standing vegetation of woody species in a 9-ha permanent plot and sampled soil seed bank from 265 cores of 0.06 m2. Additionally, we sampled seed rain from 265 seed traps of 0.64 m2 for one year. We evaluated similarity in species composition, species richness, and abundance between the three components for all species and for each dispersal syndrome. Results The community we studied showed a high similarity in species composition between components. The similarity was influenced by dispersal syndrome and the seed dispersal phenology. Similarity between seed rain and standing vegetation was high in species that dispersed in the rainy season, such as zoochorous species, while for autochorous species, compared with the other dispersal syndromes it was higher between seed bank and standing vegetation. Conclusions In our SDTF, dispersal phenology seemed to influence whether seeds had direct germination or entered the soil seed bank and influenced the match between seed rain and soil seed bank, suggesting different regeneration strategies related to dispersal ability.
Drivers of phenotypic variation and plasticity to drought in populations of a Mediterranean shrub along an environmental gradient
(Elsevier, 2024-10-18) Ramos-Muñoz, Marina; Castellanos, María Clara; Blanco-Sánchez, Mario; Pías, Beatriz; Ramírez-Valiente, José Alberto; Benavides, Raquel; Escudero, Adrián; Matesanz, Silvia
Assessing the factors driving intraspecific phenotypic variation is crucial to understand the evolutionary trajectories of plant populations and predict their vulnerability to climate change. Environmental gradients often lead to phenotypic divergence in functional traits and their plasticity across populations. We studied the entire environmental range of the Mediterranean gypsum endemic shrub Helianthemum squamatum to evaluate the factors underlying quantitative population differentiation and phenotypic plasticity to drought, using a common garden with 16 populations that covered the main geographic and the entire climatic range of the species. Sampling followed a hierarchical approach to assess trait genetic variation within and among four distinct geographical regions. We found high but similar plastic responses across populations, which were consistent with adaptive plasticity to drought, including advanced phenology, more sclerophyllous leaves, higher water use efficiency and larger seeds in dry conditions. Despite these generally similar plastic responses, we found significant population differentiation in quantitative traits, part of which was structured at the regional scale. Such differentiation was not associated with environmental variation, including differences in climate and soil conditions. This suggests that non-adaptive processes might have had a role on genetic differentiation in H. squamatum, likely due to the island-like configuration of gypsum habitats and the lack of effective seed dispersal of the study species. Our results emphasize the role of phenotypic plasticity in adaptive drought response and the importance of considering both adaptive and non-adaptive processes shaping intraspecific phenotypic variation, which is crucial for predicting plant population vulnerability to climate change
Ecological drivers of fine-scale distribution of arbuscular mycorrhizal fungi in a semiarid Mediterranean scrubland
(Oxford Academic, 2023-06) López-Angulo, Jesús; Matesanz, Silvia; Illuminati, Angela; Sánchez Pescador, David; Sánchez, Ana María; Pías, Beatriz; Chacón-Labella, Julia; De la Cruz, Marcelino; Escudero, Adrián
Background and Aims Arbuscular mycorrhizal (AM) fungi enhance the uptake of water and minerals by the plant hosts, alleviating plant stress. Therefore, AM fungal–plant interactions are particularly important in drylands and other stressful ecosystems. We aimed to determine the combined and independent effects of above- and below-ground plant community attributes (i.e. diversity and composition), soil heterogeneity and spatial covariates on the spatial structure of the AM fungal communities in a semiarid Mediterranean scrubland. Furthermore, we evaluated how the phylogenetic relatedness of both plants and AM fungi shapes these symbiotic relationships. Methods We characterized the composition and diversity of AM fungal and plant communities in a dry Mediterranean scrubland taxonomically and phylogenetically, using DNA metabarcoding and a spatially explicit sampling design at the plant neighbourhood scale. Key Results The above- and below-ground plant community attributes, soil physicochemical properties and spatial variables explained unique fractions of AM fungal diversity and composition. Mainly, variations in plant composition affected the AM fungal composition and diversity. Our results also showed that particular AM fungal taxa tended to be associated with closely related plant species, suggesting the existence of a phylogenetic signal. Although soil texture, fertility and pH affected AM fungal community assembly, spatial factors had a greater influence on AM fungal community composition and diversity than soil physicochemical properties. Conclusions Our results highlight that the more easily accessible above-ground vegetation is a reliable indicator of the linkages between plant roots and AM fungi. We also emphasize the importance of soil physicochemical properties in addition to below-ground plant information, while accounting for the phylogenetic relationships of both plants and fungi, because these factors improve our ability to predict the relationships between AM fungal and plant communities.
Environmental heterogeneity blurs the signature of dispersal syndromes on spatial patterns of woody species in a moist tropical forest
(Public Library of Science, 2018-02) Ramón, Pablo; Velázquez, Eduardo; Escudero, Adrián; De la Cruz, Marcelino
We assessed the relative importance of dispersal limitation, environmental heterogeneity and their joint effects as determinants of the spatial patterns of 229 species in the moist tropical forest of Barro Colorado Island (Panama). We differentiated five types of species according to their dispersal syndrome; autochorous, anemochorous, and zoochorous species with small, medium-size and large fruits. We characterized the spatial patterns of each species and we checked whether they were best fitted by Inhomogeneous Poisson (IPP), Homogeneous Poisson cluster (HPCP) and Inhomogeneous Poisson cluster processes (IPCP) by means of the Akaike Information Criterion. We also assessed the influence of species’ dispersal mode in the average cluster size. We found that 63% of the species were best fitted by IPCP regardless of their dispersal syndrome, although anemochorous species were best described by HPCP. Our results indicate that spatial patterns of tree species in this forest cannot be explained only by dispersal limitation, but by the joint effects of dispersal limitation and environmental heterogeneity. The absence of relationships between dispersal mode and degree of clustering suggests that several processes modify the original spatial pattern generated by seed dispersal. These findings emphasize the importance of fitting point process models with a different biological meaning when studying the main determinants of spatial structure in plant communities.
Estimating belowground plant abundance with DNA metabarcoding
(Wiley, 2019-09) Matesanz, Silvia; Pescador, David S.; Pías, Beatriz; Sánchez, Ana M.; Chacón-Labella, Julia; Illuminati, Angela; De la Cruz, Marcelino; López-Angulo, Jesús; Marí-Mena, Neus; Vizcaíno, Antón; Escudero, Adrián
Most work on plant community ecology has been performed above ground, neglecting the processes that occur in the soil. DNA metabarcoding, in which multiple species are computationally identified in bulk samples, can help to overcome the logistical limitations involved in sampling plant communities belowground. However, a major limitation of this methodology is the quantification of species’ abundances based on the percentage of sequences assigned to each taxon. Using root tissues of five dominant species in a semi-arid Mediterranean shrubland (Bupleurum fruticescens, Helianthemum cinereum, Linum suffruticosum, Stipa pennata and Thymus vulgaris), we built pairwise mixtures of relative abundance (20%, 50% and 80% biomass), and implemented two methods (linear model fits and correction indices) to improve estimates of root biomass. We validated both methods with multispecies mixtures that simulate field-collected samples. For all species, we found a positive and highly significant relationship between the percentage of sequences and biomass in the mixtures (R2 = .44–.66), but the equations for each species (slope and intercept) differed among them, and two species were consistently over- and under-estimated. The correction indices greatly improved the estimates of biomass percentage for all five species in the multispecies mixtures, and reduced the overall error from 17% to 6%. Our results show that, through the use of post-sequencing quantification methods on mock communities, DNA metabarcoding can be effectively used to determine not only species’ presence but also their relative abundance in field samples of root mixtures. Importantly, knowledge of these aspects will allow us to study key, yet poorly understood, belowground processes.
Every bit helps: The functional role of individuals in assembling any plant community, from the richest to monospecific ones
(Wiley, 2021) Matesanz, Silvia; Escudero, Adrián; Valladares, Fernando; Cruz, Marcelino de la; Pescador, David; Cavieres, Lohengrin
Plant trait-based ecology is a powerful extension of the attempt of community ecologists to unveil assembly mechanisms. However, the two main expected determinants of community assembly, niche and neutral processes, can be confused under this framework. Here, we propose to move from trait-based to phenotype-based community ecology, accounting for the variation between individuals (phenotypes affected by the abiotic and biotic environment, and vice versa), and explicitly considering their ability to compete with or facilitate its neighbours. This would shift our focus from species’ niche responses to niche specialization of phenotypes, reducing the space for neutrality at the finest scales. The current assembly framework, based mainly on niche complementarity and using species-average functional traits, has been developed exploring mega-diverse communities, but it fails at describing poor plant communities. Under this framework, monospecificity would be interpreted as an arena where functionally similar individuals compete, consequently leading to regular patterns, which are rarely found in nature. Our niche specialization framework could help explaining coexistence in rich plant communities, where the higher fraction of functional variation is found between species, whereas the intraspecific trait variation dominates in poor species and monospecific communities. We propose a guide to conduct massive phenotyping at the community scale based on the use of visible and near-infrared spectroscopy. We also discuss the need to integrate the so-called plant's eye perspective based on the use of spatial pattern statistics in the current community ecology toolbox.
Every little helps: the functional role of individuals in assembling any plant community, from the richest to monospecific ones
(Wiley, 2021-09) Escudero, Adrián; Matesanz, Silvia; Pescador, David S.; De la Cruz, Marcelino; Valladares, Fernando; Cavieres, Lohengrin A.
Plant trait-based ecology is a powerful extension of the attempt of community ecologists to unveil assembly mechanisms. However, the two main expected determinants of community assembly, niche and neutral processes, can be confused under this framework. Here, we propose to move from trait-based to phenotype-based community ecology, accounting for the variation between individuals (phenotypes affected by the abiotic and biotic environment, and vice versa), and explicitly considering their ability to compete with or facilitate its neighbours. This would shift our focus from species’ niche responses to niche specialization of phenotypes, reducing the space for neutrality at the finest scales. The current assembly framework, based mainly on niche complementarity and using species-average functional traits, has been developed exploring mega-diverse communities, but it fails at describing poor plant communities. Under this framework, monospecificity would be interpreted as an arena where functionally similar individuals compete, consequently leading to regular patterns, which are rarely found in nature. Our niche specialization framework could help explaining coexistence in rich plant communities, where the higher fraction of functional variation is found between species, whereas the intraspecific trait variation dominates in poor species and monospecific communities. We propose a guide to conduct massive phenotyping at the community scale based on the use of visible and near-infrared spectroscopy. We also discuss the need to integrate the so-called plant's eye perspective based on the use of spatial pattern statistics in the current community ecology toolbox.
Evidence of functional species sorting by rainfall and biotic interactions: A community monoliths experimental approach
(Wiley, 2019) Peralta, Ana M.L.; Sánchez, Ana M.; Luzuriaga, Arantzazu L.; de Bello, Francesco; Escudero, Adrián
1. Different abiotic and biotic sources of environmental heterogeneity have been proposed as determinants of community assembly, but few experimental studies have identified the processes and functional traits through which they operate. Thus, we aimed to experimentally determine the relationships between variations in functional structure according to spatiotemporal environmental heterogeneity to understand how biotic and abiotic drivers affect the highly dynamic nature of annual plant communities. 2. Entire annual plant communities were subjected to experimental manipulation of rain regimes (timing and amount) and perturbation of the biological soil crust (BSC; intact vs. perturbed) in a community common garden. We surveyed the experimental assemblages at different life stages (seedlings to reproductive adults) and characterized their functional structure (community weighted means and Rao) based on key functional traits. 3. We found an important filtering effect of rain timing and amount on the composition and functional structure. Drought conditions limited the community weighted means and diversity to better functionally equipped species in terms of stress resistance (high leaf dry matter content and low specific leaf area) and resource economy (short species with low reproductive ratios and higher root:shoot ratios), although the timing of drought could determine the intensity of the filtering effect. BSC acted as a filter on germination via seed mass and as a ‘biotic buffer’ in later stages by minimizing the stressful conditions during severe droughts decreasing evapotranspiration. 4. Synthesis. We found clear cause–effect relationships among abiotic and biotic factors and their interaction, and the experimental communities in terms of species composition and functional structure. We demonstrated the importance of rain regimes for shaping annual plant communities and identified germination as the main process determining the community assembly, suggesting phenotypic integration of a complete set of functional traits for resisting drought throughout the whole life cycle. The BSC–annual plant relationship shifted from negative by acting as a germination filter to positive by acting as a biotic buffer in later stages. We demonstrate the importance of evaluating these relationships at multiple 37 plant stages. The temporal and spatial heterogeneity related to the factors considered are key sources of niche differentiation that promote species coexistence.
Fencing promotes fast recovery of demographic processes after grazing-driven collapse in Bursera graveolens forests
(Elsevier, 2021-11-01) Patiño, Jorge; Ramón, Pablo; Gusmán-Montalván, Elizabeth; Escudero, Adrián; De la Cruz, Marcelino
Global change pressures are jeopardizing the functioning and structure of most tropical forests and clouding the future for their biodiversity and provided services. Although the impact of direct destruction through deforestation and fragmentation is currently in the research portfolio, overgrazing, which is more diffuse and generalized but chronic, especially in the seasonal dry forests, has been by far less addressed. Overgrazing can lead to a dramatic change in natural regeneration, often triggering the collapse of dominant species. The almost monospecific dry forests of Bursera graveolens, one of the most representative forest of the Tumbesian region, are on the verge of extinction due to both direct destruction and chronic overgrazing and regeneration collapse in forest remnants. Here, we evaluated the impact of a very simple measure, the installation of fences, on the regeneration of ecological processes affecting the dominant species. We mapped and measured all Bursera individuals with a height greater than or equal to 30 cm in six 1-ha plots, 3 within and 3 outside fenced areas. Using spatial point pattern analysis, we inferred the importance of demographic and ecological processes affecting adults and juveniles in fenced and unfenced areas. The spatial structure of adults was similar in fenced and unfenced areas, varying from random to aggregated patterns, showing that fences did not interfere with ecological processes affecting adult trees. On the contrary, we found 2765 juveniles in the three fenced plots but none in free ranging areas. Juveniles showed heterogeneous clustered patterns, and their distribution and growth were negatively influenced both by the presence and the height of adult trees. On average, there was an exclusion zone of 10 m around adult trees were recruitment of juveniles was limited. Competition among juveniles appeared to be negligible. All in all, these results suggest that, in addition to recruitment, two of the main mechanisms that rule tree population dynamics in tropical forests, i.e., dispersal limitation and a Janzen-Connell-like mechanism favoring recruiting far from adult trees have been immediately restored in the fenced area. This shows that fencing is a viable tool for a fast regeneration and conservation of Bursera forests.
Fine-scale spatial patterns and genetic structure of two co-occurring plant congeners: fingerprints of coexistence?
(Willey, 2011) Matesanz, Silvia; Gimeno, Teresa E.; Cruz, Marcelino de la; Escudero, Adrián; Valladares, Fernando
1.¿The spatial distribution of individual plants within a population and the population¿s genetic structure are determined by several factors, like dispersal, reproduction mode or biotic interactions. The role of interspecific interactions in shaping the spatial genetic structure of plant populations remains largely unknown. 2.¿Species with a common evolutionary history are known to interact more closely with each other than unrelated species due to the greater number of traits they share. We hypothesize that plant interactions may shape the fine genetic structure of closely related congeners. 3.¿We used spatial statistics (georeferenced design) and molecular techniques (ISSR markers) to understand how two closely related congeners, Thymus vulgaris (widespread species) and T. loscosii (narrow endemic) interact at the local scale. Specific cover, number of individuals of both study species and several community attributes were measured in a 10 × 10 m plot. 4.¿Both species showed similar levels of genetic variation, but differed in their spatial genetic structure. Thymus vulgaris showed spatial aggregation but no spatial genetic structure, while T. loscosii showed spatial genetic structure (positive genetic autocorrelation) at short distances. The spatial pattern of T. vulgaris¿ cover showed significant dissociation with that of T. loscosii. The same was true between the spatial patterns of the cover of T. vulgaris and the abundance of T. loscosii and between the abundance of each species. Most importantly, we found a correlation between the genetic structure of T. loscosii and the abundance of T. vulgaris: T. loscosii plants were genetically more similar when they were surrounded by a similar number of T. vulgaris plants. 5.¿Synthesis. Our results reveal spatially complex genetic structures of both congeners at small spatial scales. The negative association among the spatial patterns of the two species and the genetic structure found for T. loscosii in relation to the abundance of T. vulgaris indicate that competition between the two species may account for the presence of adapted ecotypes of T. loscosii to the abundance of a competing congeneric species. This suggests that the presence and abundance of close congeners can influence the genetic spatial structure of plant species at fine scales.
Focusing on individual species reveals the specific nature of assembly mechanisms in a tropical dry-forest
(Elsevier, 2018-10) Gusmán-M., Elizabeth; De la Cruz, Marcelino; Espinosa, Carlos I.; Escudero, Adrián
We employed an individual-species approach based on the plant’s eye perspective to disentangle the effects of individual species on community assembly in a dry tropical forest of southern Ecuador. We completely mapped a forest plot of 9 ha, and measured several functional traits (leaf area, specific leaf area, wood density, seed mass and maximum height) for tree and shrub species. To account for stochastic and habitat filtering effects, we fitted spatial point processes for the 23 more abundant species in the plot, which confirmed that all species responded to plot scale habitat filtering and 14 were dispersal-limited. We tested the hypothesis that facilitative interactions would be prevalent in this dry forest. For this, we compared the distribution of taxonomic (TD), functional (FD) and phylogenetic (PD) diversity in the neighborhood of the studied species with the diversity expected under a null model combining habitat filtering and stochastic assembly. We found that in the fine spatial scales where species interactions are expected to occur (i.e., neighborhoods of 1–20 m) eight species did not show any significant pattern for TD, FD or PD. Eleven species showed evidences of facilitation (i.e., accumulated more TD than expected) but in some cases the facilitated neighborhoods had more FD or PD than expected, suggesting the joint effect of facilitation and competition based on niche differences. One species showed less TD than expected, accompanied by lower FD and higher PD, suggesting competition based on fitness differences. Our study shows that in this dry tropical forest, where abiotic stress is prevalent, the assembly of diversity is controlled by environmental heterogeneity and both facilitative and competitive biotic processes, all of them acting simultaneously and at the same scale in the same neighborhoods.