Examinando por Autor "Iriondo, Jose M"

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Addition of nocturnal pollinators modifies the structure of pollination networks
(Scientific Reports, 2024-01-12) García, Yedra; Giménez-Benavides, Luis; Iriondo, Jose M; Lara-Romero, Carlos; Marcos, Méndez; Morente-Lopez, Javier; Santamaría, Silvia
Although the ecological network approach has substantially contributed to the study of plant-pollinator interactions, current understanding of their functional structure is biased towards diurnal pollinators. Nocturnal pollinators have been systematically ignored despite the publication of several studies that have tried to alleviate this diurnal bias. Here, we explored whether adding this neglected group of pollinators had a relevant effect on the overall architecture of three high mountain plant-pollinator networks. Including nocturnal moth pollinators modified network properties by decreasing total connectivity, connectance, nestedness and robustness to plant extinction; and increasing web asymmetry and modularity. Nocturnal moths were not preferentially connected to the most linked plants of the networks, and they were grouped into a specific “night” module in only one of the three networks. Our results indicate that ignoring the nocturnal component of plant-pollinator networks may cause changes in network properties different from those expected from random undersampling of diurnal pollinators. Consequently, the neglect of nocturnal interactions may provide a distorted view of the structure of plant-pollinator networks with relevant implications for conservation assessments.
Direct and indirect effects of shrub encroachment on alpine grasslands mediated by plant-pollinator interactions
(2016-01-21) Lara-Romero, Carlos; Cristina, Gar; Morente-Lopez, Javier; Iriondo, Jose M
1. Mutualistic interactions structure ecological communities and they are strongly influenced by the combined effect of different drivers of global change. Land-use changes and global warming have elicited rapid shrub encroachment in alpine grasslands in recent decades, which may have detrimental outcomes for native alpine forbs. In spite of the importance of this process, we lack knowledge about how shrub encroachment modifies community-wide patterns of plant–pollinator mutualistic interactions. 2. Based on the functional biodiversity hypothesis (FBH), which predicts higher pollinator biodiversity in species-rich plant communities, we asked whether the increase in nutritional resources available for pollinators due to shrub expansion modifies pollinator niche breadth and species richness, and whether these changes affect plant–plant interactions. 3. For this purpose, we compared quantitative plant–flower visitor interaction network assemblages at replicated plots in two habitat types in dry cryophilic grasslands of Sierra de Guadarrama (Spain): (i) encroached pastures (EP) and (ii) pastures dominated by forb species where shrub species are absent (PA). 4. As predicted by FBH, flower visitor richness increased in EP, but their niche breadth did not vary. Furthermore, shrubs had more interactions with flower visitors and received more visits per plant than forbs in EP in agreement with their significantly higher linkage and strength. 5. Overall, results revealed that moderate levels of shrub encroachment affected the flower visitation patterns of forb species in alpine grasslands as flower visitor diversity increased and plant–plant competition for shared flower visitors became greater. These findings highlight the need to use an integrative approach to study the cascading effects of global change drivers on species interactions and their impact on the structure and functioning of threatened ecological communities.
Evaluating the structure of commensalistic epiphyte–phorophyte networks: a comparative perspective of biotic interactions
(Oxford University Press on behalf of the Annals of Botany Company, 2019-03-03) Naranjo, Carlos; Iriondo, Jose M; Riofrio, María L; Lara-Romero, Carlos
. Epiphytic vascular plants comprise an essential part of the tropical flora and are a key component for ecosystem functioning. Some recent studies have used a network approach to investigate the interaction of epiphytes with host phorophytes at the community level. However, knowledge on commensalistic epiphyte–phorophyte network structure still lags behind with regard to other biotic interaction networks. Our goal was to provide a more complete overall perspective on commensalistic epiphyte–phorophyte interaction and its placement with respect to other better studied mutualistic interactions. We hypothesized that the intensity of the fitness effect of the different types of biotic interactions would determine the degree of specialization of the interacting organisms. Thus, commensalistic epiphyte–phorophyte interactions would have lower specialization than mutualistic interactions. We compiled and analysed the structural properties (nestedness, network specialization and modularity) of 12 commensalistic epiphyte–phorophyte networks and compared them with the same metrics to 11 ant–myrmecophyte, 86 pollination and 13 seed dispersal mutualistic networks. Epiphyte–phorophyte networks were nested and modular with regard to the corresponding null models and had greater nestedness than mutualistic networks, whereas specialization and modularity were significantly lower. Commensalistic epiphyte–phorophyte networks of interactions are both nested and modular, and hence, are structured in a similar way to most other types of networks that involve co-evolutionary interactions. Nevertheless, the nature and intensity of the ecological processes involved in the generation of these patterns is likely to differ. The lower values of modularity in commensalistic epiphyte–phorophyte networks are probably due to the low levels of specialization and the lack of co-evolutionary processes between the interacting partners.
Gene flow effects on populations inhabiting marginal areas: origin matters.
(British Ecological Society, 2020-06-24) Morente Lopez, Javier; Lara-Romero, Carlos; Garcia-Fernández, Alfredo; Rubio Teso, Maria L.; Prieto-Benitez, Samuel; Iriondo, Jose M
The evolutionary potential of populations inhabiting marginal areas has been extensively debated and directly affects their conservation value. Gene flow is one of the main factors influencing selection, adaptive potential and thus, local adaptation processes in marginal areas. The effects of differential gene flow provenance are still not well understood, since studies on gene flow between marginal populations have been underrepresented in the literature. This kind of gene flow can be especially beneficial because it can provide both adaptive allelic combinations originated under similar environmental conditions and genetic variation on which selection can act.
Geography and Environment Shape Landscape Genetics of Mediterranean Alpine Species Silene ciliata Poiret. (Caryophyllaceae)
(2018-11-27) Morente Lopez, Javier; García, Cristina; Lara-Romero, Carlos; Garcia-Fernández, Alfredo; Draper, David; Iriondo, Jose M
Individual spatial aggregation correlates with between-population variation in fine-scale genetic structure of Silene ciliata
(2016-05) Lara-Romero, Carlos; Garcia-Fernández, Alfredo; Robledo-Arnuncio, Juan J.; Roumet, Marie; Morente-Lopez, Javier; Lopez-Gil, Angela; Iriondo, Jose M
Fine-scale genetic structure (FSGS) can vary among populations within species depending on multiple demographic and environmental factors. Theoretical models predict that FSGS should decrease in high-density populations and increase in populations where individuals are spatially aggregated. However, few empirical studies have compared FSGS between populations with different degrees of individual spatial aggregation and microhabitat heterogeneity. In this work, we studied the relationship between spatial and genetic structure in five populations of alpine specialist Silene ciliata Poiret (Caryophyllaceae). We mapped all individuals in each population and genotyped 96 of them using 10 microsatellite markers. We found significant FSGS consistent with an isolation-by-distance process in three of the five populations. The intensity of FSGS was positively associated with individual spatial aggregation. However, no association was found between FSGS and global population density or microhabitat heterogeneity. Overall, our results support theoretical studies indicating that stronger spatial aggregation tends to increase the magnitude of FSGS. They also highlight the relevance of characterizing local plant distribution and microhabitat to better understand the mechanisms that generate intraspecific variation in FSGS across landscapes.
Past selection shaped phenological differentiation among populations at contrasting elevations in a Mediterranean alpine plant
(Elsevier B.V., 2020-06-14) Morente Lopez, Javier; Scheepens, JF; Lara-Romero, Carlos; Ruiz-Checa, Raquel; Tabarés, Pablo; Iriondo, Jose M
Flowering phenology is an important life-history trait strongly influenced by the environment that directly affects plant fitness. Climate change is bringing about shifts in flowering time caused by adaptive evolution and phenotypic plasticity, but their relative contributions and effects are poorly understood. This is especially critical in Mediterranean alpine species, which experience steep environmental gradients at short distances characteristic of alpine environments and an intense summer drought period derived from the Mediterranean climate. Moreover, tracking climate change through migration to higher elevations is not always possible for alpine species since many already find their optimal niche at mountain summits. In this study, we aimed to determine if flowering phenology is genetically differentiated among populations inhabiting contrasting environmental conditions and ascertain if it has been subjected to past selection. This knowledge is crucial to understanding adaptation of alpine plants to current environmental gradients and to provide insight about what adaptations may be necessary to cope with future and ongoing climate warming. We used a common garden experiment to analyze genetic differentiation in phenological traits of nine populations of Silene ciliata Pourret (Caryophyllaceae) distributed at two environmentally differentiated areas (optimal and marginal habitat suitability) in three mountain ranges of Central Spain. Environmentally optimal areas for this species are close to the mountain tops, whereas marginal areas are found at the lower distribution edge. We also studied the relation between neutral genetic differentiation (FST) and quantitative trait differentiation (PST) to infer past selection on characters under contrasting environmental conditions. We found genetic differentiation for the onset, peak and end of flowering between populations in optimal and marginal areas in the presence of substantial gene flow. This finding highlights the strong diverging selection pressures between the different Mediterranean alpine environments. We also found evidence of past diversifying selection for flowering peak and end of flowering. This evidence of past adaptation in addition to adaptive phenotypic plasticity to advance flowering dates under warmer temperatures suggest that adaptation of flowering phenology to current and future warming should be feasible, especially for populations inhabiting optimal areas.
Phenology drives species interactions and modularity in a plant - flower visitor network
(Springer Nature, 2018-06-20) Morente Lopez, Javier; Lara-Romero, Carlos; Ornosa, Concepción; Iriondo, Jose M
Phenology is often identifed as one of the main structural driving forces of plant – fower visitor networks. Nevertheless, we do not yet have a full understanding of the efects of phenology in basic network build up mechanisms such as ecological modularity. In this study, we aimed to identify the efect of within-season temporal variation of plant and fower visitor activity on the network structural conformation. Thus, we analysed the temporal dynamics of a plant – fower visitor network in two Mediterranean alpine communities during one complete fowering season. In our approach, we built quantitative interaction networks and studied the dynamics through temporal beta diversity of species, interaction changes and modularity analysis. Within-season dissimilarity in the identity of interactions was mainly caused by species replacement through time (species turnover). Temporal replacement of species and interactions clearly impacted modularity, to the extent that species phenology emerged as a strong determinant of modularity in our networks. From an applied perspective, our results highlight the importance of considering the temporal variation of species interactions throughout the fowering season and the requirement of making comprehensive temporal sampling when aiming to build functionally consistent interaction networks.
What causes conspecific plant aggregation? Disentangling the role of dispersal, habitat heterogeneity and plant–plant interactions
(2016) Lara-Romero, Carlos; de la Cruz, Marcelino; Escribano Avila, Gema; Garcia-Fernández, Alfredo; Iriondo, Jose M
Spatial patterns of plant species are determined by an array of ecologica factors including biotic and abiotic environmental constraints and intrinsic species traits. Thus, an observed aggregated pattern may be the result of short-distance dispersal, the presence of habitat heterogeneity, plant–plant interactions or a combination of the above. Here, we studied the spatial pattern of Mediterranean alpine plant Silene ciliata (Caryophyllaceae) in five populations and assessed the contribution of dispersal, habitat heterogeneity and conspecific plant interactions to observed patterns. For this purpose, we used spatial point pattern analysis combined with specific a priori hypotheses linked to spatial pattern creation. The spatial pattern of S. ciliata recruits was not homogeneous and showed small-scale aggregation. This is consistent with the species’ shortdistance seed dispersal and the heterogeneous distribution of suitable sites for germination and establishment. Furthermore, the spatial pattern of recruits was independent of the spatial pattern of adults. This suggests a low relevance of adultrecruits interactions in the spatial pattern creation. The difference in aggregation between recruits and adults suggests that once established, recruits are subjected to self-thinning. However, seedling mortality did not erase the spatial pattern generated by seed dispersal, as S. ciliata adults were still aggregated. Thus, the spatial aggregation of adults is probably due to seed dispersal limitation and the heterogeneous distribution of suitable sites at seedling establishment rather than the presence of positive plant–plant interactions at the adult stage. In fact, a negative density-dependent effect of the conspecific neighbourhood was found on adult reproductive performance. Overall, results provide empirical evidence of the lack of a simple and direct relationship between the spatial structure of plant populations and the sign of plant–plant interactions and outline the importance of considering dispersal and habitat heterogeneity when performing spatial analysis assessments.