Examinando por Autor "Cruz, Marcelino de la"

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A method to incorporate the effect of taxonomic uncertainty on multivariate analyses of ecological data
(Wiley, 2011) Cayuela, Luis; Cruz, Marcelino de la; Ruokolainen, Kalle
Researchers in ecology commonly use multivariate analyses (e.g. redundancy analysis, canonical correspondence analysis, Mantel correlation, multivariate analysis of variance) to interpret patterns in biological data and relate these patterns to environmental predictors. There has been, however, little recognition of the errors associated with biological data and the influence that these may have on predictions derived from ecological hypotheses. We present a permutational method that assesses the effects of taxonomic uncertainty on the multivariate analyses typically used in the analysis of ecological data. The procedure is based on iterative randomizations that randomly re-assign non identified species in each site to any of the other species found in the remaining sites. After each re-assignment of species identities, the multivariate method at stake is run and a parameter of interest is calculated. Consequently, one can estimate a range of plausible values for the parameter of interest under different scenarios of re-assigned species identities. We demonstrate the use of our approach in the calculation of two parameters with an example involving tropical tree species from western Amazonia: 1) the Mantel correlation between compositional similarity and environmental distances between pairs of sites, and; 2) the variance explained by environmental predictors in redundancy analysis (RDA). We also investigated the effects of increasing taxonomic uncertainty (i.e. number of unidentified species), and the taxonomic resolution at which morphospecies are determined (genus-resolution, family-resolution, or fully undetermined species) on the uncertainty range of these parameters. To achieve this, we performed simulations on a tree dataset from southern Mexico by randomly selecting a portion of the species contained in the dataset and classifying them as unidentified at each level of decreasing taxonomic resolution. An analysis of covariance showed that both taxonomic uncertainty and resolution significantly influence the uncertainty range of the resulting parameters. Increasing taxonomic uncertainty expands our uncertainty of the parameters estimated both in the Mantel test and RDA. The effects of increasing taxonomic resolution, however, are not as evident. The method presented in this study improves the traditional approaches to study compositional change in ecological communities by accounting for some of the uncertainty inherent to biological data. We hope that this approach can be routinely used to estimate any parameter of interest obtained from compositional data tables when faced with taxonomic uncertainty.
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.
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.
Functional differences between herbs and woody species in a semiarid Mediterranean plant community: A whole-plant perspective on growth, nutrient-use and size
(Wiley, 2024-11-10) Illuminati, Angela; Matesanz, Silvia; Pías, Beatriz; Sánchez, Ana M.; Cruz, Marcelino de la; Ramos-Muñoz, Marina; López-Angulo, Jesús; Pescador, Daid S.; Escudero, Adrián
Despite decades of research, a comprehensive understanding of trait coordination at the whole-plant level remains elusive. Furthermore, while the link between above-ground growth rates and leaf traits related to nutrient use is well established, much less is known about the below-ground compartment. Herbs and woody species exhibit distinct above-ground growth and nutrient-use strategies, but whether these differences extend to root traits below-ground remains unclear. We carried out a common garden experiment with 23 perennials (7 herbs and 16 woody species) coexisting in a Mediterranean shrubland and measured 17 above-ground and below-ground traits related to growth, nutrient use and size. We analysed the links between growth rate and nutrient use focusing especially on roots and considering potential differences between herbs and woody species. We also combined plant size data from experimental juveniles and field-sampled adults to determine the effects of life stage on whole-plant phenotypic integration. We found a significant relationship between growth rates (both above-ground and below-ground) and root nutrient-use strategies. Root diameter was negatively associated to growth rate only in herbs. Specific root area and root tissue density were positively and negatively correlated with growth rate, respectively, in both herbs and woody species. Moreover, we found significant differences in roots traits between herbs and woody species. Plant growth rate and root nutrient-use strategies were both positively associated to plant size (height and above-ground diameter) in juveniles, while a negative relationship was observed in adults. Our work provides insights on the links between whole-plant growth rate and nutrient-use strategies in species from a dry Mediterranan shrubland. Specifically, we show that whole-plant growth rate is strongly associated to root traits, with more acquisitive root nutrient-use strategies related to faster growth rates, which in turn translated to greater plant size in juveniles but smaller in adults. Our results also highlight root functional differences and contrasting patterns of whole-plant phenotypic integration between herbs and woody species, offering deeper insights into species coexistence in species-rich dry Mediterranean environments
Functional traits explain both seedling and adult plant spatial patterns in gypsum annual species
(Wiley, 2023) Peralta, Ana L.; Escudero, Adrián; Cruz, Marcelino de la; Sánchez, Ana M.; Luzuriaga, Arantzazu L.
Ecological processes such as seed dispersal or plant–plant interactions and environmental constraints such as climate or soil heterogeneity are known to influence establishment, and thus the spatial patterns of plant communities and populations. In this study, we hypothesized that key functional traits such as the specific leaf area (SLA), reproductive ratio (reproductive/vegetative biomass), seed mass and maximum plant height would influence the spatial patterns of individual species in annual, gypsophilous plant communities, and that these effects would be modulated by both the soil surface structure (biocrust) and climate (precipitation) conditions.We mapped the spatial patterns of all plants found in six 1 × 1 m plots (more than 1000 individuals per plot) in both the seedling (autumn) and adult stages (spring) under two biocrust experimental conditions (intact vs. disturbed biocrust) during two consecutive years which were contrasted in term of precipitation (dry year and wet year). To assess the spatial patterns of seedlings and adults, we fitted four different spatial point pattern models (i.e. Poisson, inhomogeneous Poisson, Poisson cluster and inhomogeneous Poisson cluster processes) to each of the 242 populations of the 26 most abundant species that had more than 15 individuals per plot.Most seedling populations exhibited clustered spatial patterns that persisted in the adult stage, which suggests that short-distance dispersal is an adaptive trait for soil specialists such as gypsophilous plants. One-third of the populations fitted an inhomogeneous model best but the physical structure of the biocrust was not related to them. More importantly, we found a connection between the functional strategies of species and the spatial distribution of plants. In particular, during the dry year, irrespective of the biocrust conditions, species with a high SLA and high Rep/Veg mainly exhibited clustered spatial patterns, whereas low SLA and low Rep/Veg were associated with random distributions. Species with heavy and light seed masses had random and clustered patterns, respectively. In both the dry and wet years, species with lower maximum heights had clustered patterns, whereas taller species exhibited random patterns. In addition, species with heavier seeds and greater maximum heights had the largest cluster sizes.Our results confirm that the spatial patterns of seedlings and adult plants are significantly determined by the functional strategy of each species.Read the free Plain Language Summary for this article on the Journal blog.
Phenotypic integration does not constrain phenotypic plasticity:differential plasticity of traits is associated to their integrationacross environments
(Wiley, 2021) Matesanz, Silvia; Ramos-Muñoz, Marina; Blanco-Sánchez, Mario; Cruz, Marcelino de la; Benavides, Raquel; Escudero, Adrián
Understanding constraints to phenotypic plasticity is key given its role on the response oforganisms to environmental change. It has been suggested that phenotypic integration, thestructure of trait covariation, could limit trait plasticity. However, the relationship betweenplasticity and integration is far from resolved. Using a database of functional plasticity to drought of a Mediterranean shrub that included20 ecophysiological traits, we assessed environmentally-induced changes in phenotypic inte-gration and whether integration constrained the expression of plasticity, accounting for thewithin-environment phenotypic variation of traits. Furthermore, we provide the first test ofthe association between differential trait plasticity and trait integration across an optimumand a stressful environment. Phenotypic plasticity was positively associated with phenotypic integration in both environ-ments, but this relationship was lost when phenotypic variation was considered. The similarityin the plastic response of two traits predicted their integration across environments, with inte-grated traits having more similar plasticity. Such variation in the plasticity of traits partlyexplained the lower phenotypic integration found in the stressful environment. We found no evidence that integration may constitute an internal constraint to plasticity.Rather, we present the first empirical demonstration that differences in plastic responses mayinvolve a major reorganization of the relationships among traits, and challenge the notion thatstress generally induces a tighter phenotype.