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Many angiosperms rely on vertebrates for seed dispersal via gut passage, an interaction that has been traditionally classified as a mutualism. The seed dispersal effectiveness (SDE) framework provides a mechanistic approach to evaluate evolutionary and ecological characteristics of animal-mediated seed dispersal, by synthesising the quantity and the quality of the dispersal that a plant species receives from each of its animal dispersers. However, the application of the SDE framework has been largely restricted to plant–frugivore interactions, whereas animal-mediated seed dispersal results from plant–disperser interactions that cover a continuum from pure mutualisms to antagonisms. This biases ecological and evolutionary knowledge on plant–disperser interactions. Here, we propose an extended SDE framework (‘eSDE') that allows comparing plant–disperser interactions in the full mutualism–antagonism continuum ranging from pure mutualisms (frugivores) to conditional mutualisms (scatter-hoarding granivores and folivores) and antagonisms (pure granivores). We present the eSDE framework, and use examples to illustrate how it can be applied to compare effectiveness among plant–disperser interaction types. Our initial comparison based on available data suggests that vertebrate species differ more in the number of seeds they deposit away from the mother plant (quantity), than in the effects such dispersal processes have on seed fate (quality). Scatter-hoarding granivores provide the most effective dispersal due to high removal rates, closely followed by frugivores due to high deposition rates. Folivores and pure granivores provide low quantity dispersal, but of high and moderate quality, respectively. These early comparative insights illustrate the necessity and usefulness of more standardized data collection protocols, for which we provide recommendations. Applying the eSDE framework can reveal broad-scale patterns across and within plant–disperser interaction types, which w

Seed dispersal by frugivorous bird species involves a fine temporal tuning between fruiting plants and birds. However, this interaction may be severely threatened by anthropogenic climate and land-use change, which may result in phenological mismatches and pervasive ecological consequences for avian communities. In this study, we evaluate changes at long (~40 years) and short-time (seasonal) spans in an avian frugivore community using a snapshot resampling. Particularly, we focus on changes in composition, abundance, migratory timing (i.e. phenology) and physical condition in relation to variations in fruit supply. We used bird and fruit data collected during 1981–1983 and 2019–2021 in a Mediterranean scrubland site in Doñana Natural Area, SW Spain. Our findings indicate a profound transformation of species composition, bird phenology and body condition: in ~40 years, the avian community showed a 66% and 18.4% decrease of the abundance of wintering and seed-disperser species, respectively. Seasonal abundance peaks were advanced for at least one month in the 9 out of 11 frugivorous bird species included in the analyses. Avian body condition during the migratory passage has worsened, with fewer individuals showing a high-fat percentage now than in the past. Finally, we report a fruit production decrease of almost half in 2019–2021 compared to 1981–1983, probably linked to habitat encroachment by pine trees and replacement of fleshy-fruited shrubs. Vegetation encroachment and climate change are the most plausible explanations for the observed changes in the avian community, but the relative importance of these factors is yet unknown. Our results at a local scale mirror the dramatic consequences of global change affecting the diversity, phenology and physical condition of frugivorous bird species reported in multiple studies across the globe. The loss of frugivores may trigger feedback mechanisms in which seed dispersal is disrupted, leading to impaired recruitment of f

Many angiosperms rely on vertebrates for seed dispersal via gut passage, an interaction that has been traditionally classified as a mutualism. The seed dispersal effectiveness (SDE) framework provides a mechanistic approach to evaluate evolutionary and ecological characteristics of animal-mediated seed dispersal, by synthesising the quantity and the quality of the dispersal that a plant species receives from each of its animal dispersers. However, the application of the SDE framework has been largely restricted to plant–frugivore interactions, whereas animal-mediated seed dispersal results from plant–disperser interactions that cover a continuum from pure mutualisms to antagonisms. This biases ecological and evolutionary knowledge on plant–disperser interactions. Here, we propose an extended SDE framework (‘eSDE') that allows comparing plant–disperser interactions in the full mutualism–antagonism continuum ranging from pure mutualisms (frugivores) to conditional mutualisms (scatter-hoarding granivores and folivores) and antagonisms (pure granivores). We present the eSDE framework, and use examples to illustrate how it can be applied to compare effectiveness among plant–disperser interaction types. Our initial comparison based on available data suggests that vertebrate species differ more in the number of seeds they deposit away from the mother plant (quantity), than in the effects such dispersal processes have on seed fate (quality). Scatter-hoarding granivores provide the most effective dispersal due to high removal rates, closely followed by frugivores due to high deposition rates. Folivores and pure granivores provide low quantity dispersal, but of high and moderate quality, respectively. These early comparative insights illustrate the necessity and usefulness of more standardized data collection protocols, for which we provide recommendations. Applying the eSDE framework can reveal broad-scale patterns across and within plant–disperser interaction types, which w

Question: How does habitat degradation affect recruitment limitation and its components (seed limitation versus establishment limitation) of woody plant communities in a Mediterranean landscape? Location: 1600-1900 m a.s.l. in the Sierra Nevada National Park, southern Spain. The landscape is a mosaic composed of native forest and two degraded landscape units: reforestation stands and shrubland. Methods: We evaluated fruit production, seed rain, seedling emergence and seedling survival in two consecutive years with contrasting rainfall patterns. Seed and seedling data were used to calculate values of seed and establishment limitation. Results: In general, the woody community was both severely seed- and establishment-limited. Species were less seed-limited in the landscape units with higher adult density (i.e. shrub species in shrubland, Pinus spp. in reforestation stands). In contrast, degradation did not exacerbate establishment limitation, which was severe in all landscape units. This general pattern was modulated by the biogeographical distribution, dispersal type, and life form of the species. Boreo-alpine species were more limited in establishment than species with a typical Mediterranean distribution. Zoochorous species were less seed-limited in the landscape units preferred by dispersers (i.e. native forest). Tree species were more establishment-limited than shrub species, irrespective of the landscape unit. Seed limitation, and especially establishment limitation, varied among years, with establishment being almost nil in the very dry year. Conclusion: In the case of Mediterranean landscapes, when degradation from human impact involves a reduction in the adult abundance of the woody plant community (trees and shrubs), seed limitation increases, although establishment limitation is generally high in all landscape units, especially for boreo-alpine species. Conservation and restoration strategies should take into account our results showing that tree species we

Understanding seedling performance across resource gradients is crucial for defining the regeneration niche of plant species under current environmental conditions and for predicting potential changes under a global change scenario. A 2-year field experiment was conducted to determine how seedling survival and growth of two evergreen and two deciduous Quercus species vary along gradients of light and soil properties in two Mediterranean forests with contrasting soils and climatic conditions. Half the seedlings were subjected to an irrigation treatment during the first year to quantify the effects on performance of an alteration in the summer drought intensity. Linear and non-linear models were parameterized and compared to identify major resources controlling seedling performance. We found both site-specific and general patterns of regeneration. Strong site-specificity was found in the identity of the best predictors of seedling survival: survival decreased linearly with increasing light (i.e. increasing desiccation risk) in the drier site, whereas it decreased logistically with increasing spring soil water content (i.e. increasing waterlogging risk) in the wetter site. We found strong empirical support for multiple resource limitation at the drier site, the response to light being modulated by the availability of soil resources (water and P). Evidence for regeneration niche partitioning among Quercus species was only found at the wetter site. However, at both sites Quercus species shared the same response to summer drought alleviation through water addition: increased first-year survival but not final survival (i.e. after two years). This suggests that extremely dry summers (i.e. the second summer in the experiment) can cancel out the positive effects of previous wetter summers. Therefore, an increase in the intensity and frequency of summer drought with climate change might cause a double negative impact on Quercus regeneration, due to a general reduction in survi

Understanding the processes of tree population recruitment and their limitations, is the scientific basis to assure the forest natural regeneration, and to improve techniques of restoration and afforestation. We present here preliminary results of a collaborative project (HETEROMED). The environmental heterogeneity of Mediterranean forests was related to natural patterns of seedling establishment. Factorial design experiments of seed addition were carried out and the resulting emergence and survival were related to the conditions of light and soil moisture. The fieldwork was carried out at two natural areas in South Spain: Sierra Nevada National Park (higher mountains on the Southeast) and Los Alcornocales Natural Park (lower mountains in Sierra del Aljibe range, on the southern tip of the Iberian Peninsula). The experiments were focussed in seven target species - Quercus suber, Quercus canariensis, Quercus ilex, Quercus pyrenaica, Pinus sylvestris, Acer granatense and Sorbus aria. In addition, a glasshouse factorial experiment investigated the differential response of the four Quercus species to the combined effects of shade and drought. In both field sites (Sierra Nevada and Sierra del Aljibe) seedling emergence differed among species, but was not significantly affected by habitat (light availability). In Sierra Nevada, seedling survival after dry summer was statistically different between tree species, habitat type and irrigation treatment. Summer drought was the main cause of seedling mortality. Survival was higher in deep shade habitats than in open stands. Irrigation boosted survival in open areas (full light) and under shrublands (medium shade), but had scant effect inside woodland stands (deep shade). In Sierra del Aljibe, there were significant differences in seedling survival of Quercus suber between habitat types. Most surviving seedlings after the dry summer were in habitats with medium shade (under tree canopy), rather than in full light (open areas) or