1. There is growing interest in understanding the functional outcomes of species
interactions in ecological networks. For many mutualistic networks, including pollination
and seed dispersal networks, interactions are generally sampled by recording
animal foraging visits to plants. However, these visits may not reflect
actual pollination or seed dispersal events, despite these typically being the ecological
processes of interest.
2. Frugivorous animals can act as seed dispersers, by swallowing entire fruits and
dispersing their seeds, or as pulp peckers or seed predators, by pecking fruits to
consume pieces of pulp or seeds. These processes have opposing consequences
for plant reproductive success. Therefore, equating visitation with seed dispersal
could lead to biased inferences about the ecology, evolution and conservation of
seed dispersal mutualisms.
3. Here, we use natural history information on the functional outcomes of pairwise
bird–plant interactions to examine changes in the structure of seven European
plant–frugivore visitation networks after non-mutualistic interactions (pulp pecking
and seed predation) have been removed. Following existing knowledge of the
contrasting structures of mutualistic and antagonistic networks, we hypothesized
a number of changes following interaction removal, such as increased nestedness
and lower specialization.
4. Non-mutualistic interactions with pulp peckers and seed predators occurred in all
seven networks, accounting for 21%–48% of all interactions and 6%–24% of total
interaction frequency. When non-mutualistic interactions were removed, there
were significant increases in network-level metrics such as connectance and nestedness,
while robustness decreased. These changes were generally small, homogenous
and driven by decreases in network size. Conversely, changes in species-level metrics were more variable and sometimes large, with significant decreases in
plant degree, interaction frequency, specialization and resilience to animal extinctions
and significant increases in frugivore species strength.
5. Visitation data can overestimate the actual frequency of seed dispersal services in
plant–frugivore networks. We show here that incorporating natural history information
on the functions of species interactions can bring us closer to understanding
the processes and functions operating in ecological communities. Our categorical
approach lays the foundation for future work quantifying functional interaction outcomes
along a mutualism–antagonism continuum, as documented in other frugivore
faunas., Peer reviewed

Juvenile animals generally disperse from their birthplace to their future breeding territories. In fragmented landscapes, habitat-specialist species must disperse through the anthropogenic matrix where remnant habitats are embedded. Here, we test the hypothesis that dispersing juvenile frugivores leave a footprint in the form of seed deposition through the matrix of fragmented landscapes. We focused on the Sardinian warbler ( Sylvia melanocephala), a resident frugivorous passerine. We used data from field sampling of bird-dispersed seeds in the forest and matrix of a fragmented landscape, subsequent disperser identification through DNA-barcoding analysis, and data from a national bird-ringing programme. Seed dispersal by Sardinian warblers was confined to the forest most of the year, but warblers contributed a peak of seed-dispersal events in the matrix between July and October, mainly attributable to dispersing juveniles. Our study uniquely connects animal and plant dispersal, demonstrating that juveniles of habitat-specialist frugivores can provide mobile-link functions transiently, but in a seasonally predictable way., Spanish MINECO (CGL2017-82847-P) and Junta de Andalucía Excellence Projects (RNM–5731) awarded to P.J., Severo Ochoa Award for Centres of Excellence in R + D + I (SEV-2012-0262) and a postdoctoral fellowship from the Severo Ochoa Program awarded to J.P.G.-V. (SEV-2012-0262). While writing this paper, J.P.G.-V. was funded by a Spanish ‘Ramon y Cajal’ fellowship (RYC-2017-22095).

ABSTRACT
Synzoochory is the dispersal of seeds by seed-caching animals. The animal partner in this interaction plays a dual role, acting both as seed disperser and seed predator. We propose that this duality gives to synzoochory two distinctive features that have crucial ecological and evolutionary consequences. First, because plants attract animals that have not only positive (seed dispersal) but also negative (seed predation) impacts on their fitness, the evolution of adaptations to synzoochory is strongly constrained. Consequently, it is not easy to identify traits that define a synzoochorous dispersal syndrome. The absence of clear adaptations entails the extra difficulty of identifying synzoochorous plants by relying on dispersal traits, limiting our ability to explore the full geographic, taxonomic and phylogenetic extent of synzoochory. Second, the positive and negative outcomes of interactions with synzoochorous animals are expressed simultaneously. Consequently, synzoochorous interactions are not exclusively mutualistic or antagonistic, but are located at some point along a mutualism-antagonism continuum. What makes synzoochory interesting and unique is that the position of each partner along the continuum can be evaluated for every plant—animal interaction, and thus the continuum can be precisely described by assessing the relative frequency of positive and negative interaction events in each pairwise interaction. Herein we explore these two main features of synzoochory with a comprehensive quantitative survey of published studies on synzoochory. Synzoochory has been recorded for at least 1339 plant species differing in life forms, from annual and short-lived herbs to long-lived trees, belonging to 641 genera and 157 families widely distributed across the globe and across the seed plant phylogeny. Over 30 animal families belonging to five disparate taxonomic groups (rodents, marsupials, birds, insects, and land crabs) potentially act as synzoochorous dispersers. Although synzoochory appears to be fundamentally a secondary dispersal mode, many abundant and dominant trees are primarily synzoochorous. In addition, we found evidence of the existence of diplosynzoochory (caching animals acting both as primary and secondary dispersers of the same individual seed), mostly in nut-bearing trees. Finally, we found that synzoochorous interactions are widely spread across the mutualism—antagonism continuum. Nevertheless, there were some differences among disperser species and functional groups. Corvids and some rodents (cricetids, nesomyids, sciurids) were located in the positive-effects region of the continuum and presumably behave mostly as dispersers, whereas land crabs and insects were located in the negative-effects extreme and behave mostly as seed predators. Our review demonstrates that synzoochory is not an anecdotal ecological interaction. Rather, it is pivotal to the functioning of many ecosystems where the natural regeneration of keystone plant species depends on the activity of granivorous animals that play a dual role. This distinctive interaction should not be ignored if we wish to have an accurate understanding of the functioning of natural systems., J.M.G. and P.J. were supported by CYTED program (Red Temática 418RT0555). E.W.S. is supported by the Ecology Center and the Utah Agricultural Experiment Station (UAES), Utah State University. P.J. is supported by grant CGL2017‐82847‐P from the Spanish Ministry of Science, Innovation, and Universities (AEI).

The partition of the ecological niche can enhance the coexistence of predators
due to differences in how they exploit three main resources: food, space, and
time, the latter being an axis that often remains unexplored.
2. We studied niche segregation in a Mediterranean mesocarnivore community
composed by Vulpes vulpes, Genetta genetta, Meles meles, and Herpestes ichneumon,
addressing simultaneously different niche axes: the temporal, trophic, and
spatial axes.
3. We assessed temporal segregation between mesopredators and prey and between
potential competitors, using camera trap data between 2018 and 2020 in
a Mediterranean landscape in Southern Spain. We deployed camera traps in 35
stations in three sites with varying vegetation cover within Doñana National Park.
We further examined the spatial overlap in activity centers and trophic preferences
between potential competitors using diet information from studies performed
in the study area.
4. We found an overall temporal segregation between trophic generalist species,
with species showing higher temporal overlap differing in their trophic preferences
and/or showing limited spatial overlap. Furthermore, we observed an overall
high overlap between the activity patterns of predators and their major prey
in the area (the common genet vs. small mammals and the red fox vs. European
rabbit).
5. Our study suggests that coexistence of the different species that compose the
mesocarnivore assemblage in Mediterranean landscapes can be facilitated by subtle
differences along the three main niche axes, with temporal segregation being
a most pronounced mechanism. Our findings reinforce the idea that the coexistence
mechanisms underlying community structure are multidimensional, Peer reviewed

[Methods] Data include two different datasets (each one separated in a different file): 1) Bird abundance data; 2) Bird trapping data using mist nets. Data were collected in Hato Ratón, in Doñana’s Natural Area, close to Villamanrique de la Condesa, Sevilla province, southern Spain (37° 10’ 26.4” N, 6° 20’ 17.4” W, 11 m a.s.l.). Sampling was carried on in two time periods: 1981-1983 and 2019-2021.

Bird abundance was estimated using 1-km linear transects to calculate the kilometric abundance index. These were conducted 2-5 times per month (40 censuses in total). For each individual that was seen or heard, we recorded its species and the time it was seen. Bird censusing started one hour after sunrise and was carried out when weather conditions were not extreme (in absence of rain or strong wind). Data on censed birds include a total of 0 species.

Bird ringing data comes from birds captured by mist nets deployed weekly during 1981-1983 (6-10 nets per survey day, average 10-25 mist-net m/h) and fortnightly in 2019-2021 (12-20 nets per survey day, average 25-50 m/h). Data on trapped birds include a total of 32 species.

[Usage Notes] Medata information:

File: censuses80s_20s.txt

Including abundance censuses carried on in 1981-1983 and 2019-2021-

Variable names: yeargroup (study period, either 1981-1983 or 2019-2021), Date (Year/Month/Day), year, months, Transect, species, count (number of individuals), distance (transect length), ikas (relative abundance, individuals/km).

File: ringing80s_20s.txt

Including bird ringing data carried on in 1981-1983 and 2019-2021-

Variable names: Date (Year/Month/Day), Species, Tarsus length (mm), Weight (g), residuals (Weight ~ tarsus residuals), Fat_rescaled (fat value after rescaling, from 0 to 8), fat_cat (Fat category: low or medium-high fat content), Migratory_type (Resident, Summer, Wintering, or Migrant), Trophic_type (combinations of Herbivore, Frugivore, Insectivore, Granivore, Carnivore, Omnivore, and Necrophage), Functional type (NF, PC, SP, SD, PC/SP/SD, PC/SP). NF = Non Frugivore; PC = Pulp Consumer; SP = Seed Predator; SD = Seed Disperser., 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 13% decrease of the wintering and seed-disperser species, respectively. Seasonal abundance peaks were advanced for at least one month in 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 fruiting plants and hence less food availability for the avian community., Horizon 2020 Framework Programme, Award: 798269. Consejería de Economía, Conocimiento, Empresas y Universidad, Junta de Andalucía, Award: P18-HO-4814. Agencia Estatal de Investigación, Award: CGL 2017-82847., Peer reviewed

Special Issue: Fruits, animals and seed dispersal: timely advances on a key mutualism., 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 fruiting plants and hence less food availability for the avian community., This project has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement no. 798269 and partially funded from the project CGL 2017-82847 from the Spanish Ministry of Science and Innovation (PJ) and the project BiodivINTERACTOME (P18-HO-4814) from the Junta de Andalucia. AB-L was funded by a Juan de la Cierva-Incorporación grant (IJCI-2017-31419) from the Spanish Ministry of Science and Innovation., Peer reviewed

Under current global change context, climate change is driving substantial phenological mismatches between plant species and the organisms that rely on them. Given that frugivorous birds are fundamental for forest regeneration, and most of them are migrant species, identifying the effect of global change over them must be a priority. In this study we have analysed changes in the composition, morphometry, and physical condition in an avian community at long- (40 years) and short time (seasonal) spans. Our findings indicate a profound transformation at practically every level of analysis. In 40 years, the avian community shows a 66% and 13% decrease of the wintering and seed-disperser species, respectively. Seasonal abundance peaks were advanced in 13 out of 15 species. In addition, we have found a significant 1.5% increase in the morphometric measurements of certain species, supporting findings in previous studies, and also a remarkable general decrease of body condition. Our results point towards land use changes and climate change as the main causes. If this influence continues to rise, biodiversity will likely be irreversibly altered, damaging crucial ecosystem functions such as animal-mediated seed dispersal and forest regeneration in particular., This TFM has benefited from the TEMPNET project, funded by a Marie-Sklodowska Curie Fellowship (798269 - TEMPNET - H2020-MSCA-IF-2017) by the European Commission to IM, and in part with funding from project CGL 2017-82847 from Spanish Ministry of Science and Innovation (PJ)., No

[Methods] Using a sample of Atlantic rainforest avian frugivores we analyze fruit effectiveness as a nutritional food resource for seed dispersing birds, i.e., Resource-Provisioning Effectiveness (RPE), an overlooked aspect of seed dispersal effectiveness. We found ample variation in RPE among plant species, given not just variation in fruit design and nutrient content but also in fruit availability, accessibility and other features that determine how rewarding a fruit resource is for the frugivore. Yet fruit species show consistent RPE values despite highly variable outcomes of interactions with different avian frugivores.

The rationale for our study includes four steps: 1) selecting a representative sample of frugivore species illustrating both the full range of body mass and phylogenetic diversity of the Brazilian Southeastern Atlantic forest frugivores; 2) compiling a literature dataset on fruit foraging and usage data for these frugivore species; 3) analyze variation in RPE across selected plant species by building effectiveness landscapes from the frugivore’s perspective; and 4) experimentally assess RPE subcomponents (i.e. fruit pulp digestibility) that refine the estimates of RPE variation among plant species.

To estimate the RPE for fruit species consumed by each frugivore species we have defined its two components: the rate at which the fruits are ingested/handled by the animal (feeding rate) as the quantity component, and the energy gained from eating the fruit (fruit energy) as the quality component. The feeding rate is calculated by multiplying the bird visitation frequency to the plant by the number of fruits consumed in each visit; from a frugivore perspective these subcomponents of RPE-quantity illustrate potential encounter rates with the fruit resource (visitation) and potential handling/ingestion rates once the fruits are encountered (fruits/visit). Fruit-pulp energy yield is assessed using the specific energy (KJ/g) multiplied by the fruit pulp dry mass. Since the nutrient proportional contents of the fruit pulp are calculated based on its dry mass, we use this value as the profitable fruit mass per fruit (Herrera 1981). Specific energy was quantified using the following energy conversion factors for fruits (FAO, 2002): 14.1 KJ/g for proteins, 35 KJ/g for lipids and 15.1 KJ/g for carbohydrates. Ultimately, by multiplying the two components we obtained the total effect value for each specific interaction (RPE; Schupp, 1993; Schupp, Jordano, & Gómez, 2017):

RPE[g energy assimilated] = [no fruits consumed/obs time (h)] × [g energy accumulated/fruit consumed] (1)

Note that the RPE estimate for a given fruit species is specific for its interaction with a frugivore, so we used the average RPE values of a given fruit of all the frugivore species it provides food to, to characterize its overall or total effectiveness (RPET):

RPET= sum(RPEi)/N (2)

where, for a given focal fruit species, N is the number of pairwise interactions with RPE data available, and RPEi is the RPE value for a specific pairwise interaction i. Thus, RPET is fruit species-specific, while each pairwise interaction has a specific RPE value (RPEi) depending on the identity of the specific frugivore partner.

Data collection

RPE Quantity component

Most of the data used to calculate the quantitative component have been obtained from available bibliographic sources. Data compilation comes from a total of 51 studies and four databases for frugivore-plant interactions from the Brazilian Atlantic Forest (see Data Sources section for a list of data sources used and Supp. Mat. Fig. S1 for a map of study locations). Variables collected from the bibliography were: number of visits, observation time and number of fruits consumed per visit. To reduce bias we divided the total number of visits to the plants by observation time to control for the different duration of each study. The fruit mass ingested per visit was positively correlated with frugivore body mass (Pearson’s correlation r = 0.588, p < 0.001, n = 541 distinct pairwise interactions; Supp. Mat. Fig. S2). Fruit mass-body mass correlation allowed the estimation of the number of fruits consumed per visit for avian species with no data on fruit consumption rates available; this was done for special cases when avian species had limited number of records in most studies (n = 7 fruit species for Aburria jacutinga, n = 2 fruit species for Penelope obscura, n = 3 fruit species for Procnias nudicollis).

We have referred to a fruit as all the dispersing and consequently ingested units (i.e. diaspora). Diaspora and fruit are often the same thing; however, in some cases such as Cabralea canjerana or Virola spp., an aril (i.e. a fleshy covering in some seeds) acts as a diaspore, being smaller than the actual fruit. Therefore, when the diaspore was actually different from the fruit, the energy in the qualitative component has been measured accordingly. In other cases frugivores may peck pieces and ingest just a part of the whole fruit or infructescence (e.g. catkins of Cecropia spp. or syconia from Ficus spp.). For those large infructescences that birds do not consume whole, we used the number of pecks and assessed the percentage of a single fruit actually consumed, corresponding to a given number of pecks and the beak size of the frugivore. Data on each species’ gape size and fruit length (obtained from Bello et al., 2017 and Galetti et al., 2013) allowed us to estimate the total number of pecks needed to consume an infructescence (Supp. Mat. Table S1).

RPE Quality component

All fruit pulp dry masses and nutrient proportions were obtained from available databases (Pizo, 2017 unpublished; Jordano 1995, 2007; Bello et al., 2017). In a few cases, pulp dry mass values were missing; these were estimated using additional species-specific data such as pulp fresh mass or water proportion (6 species records imputed in this way; see Supp. Mat. Table S2). However, when species-specific data were unavailable, we estimated the specific values by averaging the data available for congeneric species. This type of data imputation was done for a few cases and only when essential to retain a given species in the dataset (9 species records were imputed this way; see Supp. Mat. Table S3).

When calculating specific energy, we preferably used the non-structural carbohydrate content for the carbohydrate value; however, when this information was not available total carbohydrate content or total sugar content was used (see Suppl. Mat. Table S4).

Due to the diverse origin of nutritional data, variation in the techniques and devices used for their analyses is likely. This variation in methods together with the use of different carbohydrate content variables have limitations when comparing energetic values among fruits. We therefore want to highlight these possible limitations and advise to take results cautiously. While the quality component gives us an approximate idea of the nutritional value of each fruit it does not offer a detailed ranking.

A total of 315 different fruit species were reported to be eaten by the frugivore species considered in this study, of which 36 fruits had enough data to calculate the quantity and quality component.

[Usage Notes] Please visit the GitHub repository for this dataset to find updates and additional information: https://github.com/PJordano-Lab/MS_JEcol_Resource-provisioning-effectiveness., 1. Mutualistic interactions between frugivorous birds and fleshy fruited plants are key processes for both natural plant regeneration and the maintenance of birds relying on fruit resources. However, seed dispersal effectiveness (SDE) has been frequently studied only from the plant’s perspective, i.e. the contribution of animals to plant fitness. 2. Using a sample of Atlantic rainforest avian frugivores, this study presents a first comparative, empirical study of fruit effectiveness as a nutritional food resource for seed dispersing birds through the use of Resource-Provisioning Effectiveness (RPE) models. RPE is the product of the amount of fruits a frugivore can consume (quantity component) and the quality of the ingesta in terms of energy and nutrients obtained (quality component). 3. Our results show wide variation in Resource-Provisioning Effectiveness among fleshy-fruited plant species. Energy-rich fruits consistently show a smaller quantity component, while energetically-poor fruits are consistently the most consumed, with fruit species spanning a gradient from these two extremes. 4. The specific RPEi resulting from a pairwise fruit-frugivore interaction is positively correlated to the total RPE (RPET) that a given fruit species has for the whole frugivore assemblage. RPE therefore appears to be a characteristic feature of the fruit species, rather than of the specific frugivore partner. 5. Only the fruit’s specific energy content showed a significant phylogenetic signal, suggesting potential constraints for free covariation between RPE and SDE of fruits and frugivores. 6. Synthesis: We analyze variation in the effectiveness of fleshy fruit food provisioning to avian frugivores by explicitly redefining Resource-Provisioning Effectiveness within the Seed Dispersal Effectiveness framework. We found ample variation in RPE among plant species, showing differences in both quantity and quality components of fruit resources rewards for the frugivores. Our findings help unravel how seed-dispersing birds may discriminate among alternative fruit resources and to understand the configuration of mutual dependencies among mutualistic partners., Agencia Estatal de Investigación, Award: CGL2017-82847-P. Fundación La Caixa, Award: LCF/BQ/ES18/11670007. Consejería de Economía, Innovación, Ciencia y Empleo, Junta de Andalucía, Award: RNM–5731., Peer reviewed

Ecological interactions are one of the main forces that sustain Earth’s biodiversity. A major challenge for studies of ecology and evolution is to determine how these interactions affect the fitness of species when we expand from studying isolated, pairwise interactions to include networks of interacting species1,2,3,4. In networks, chains of effects caused by a range of species have an indirect effect on other species they do not interact with directly, potentially affecting the fitness outcomes of a variety of ecological interactions (such as mutualism)5,6,7. Here we apply analytical techniques and numerical simulations to 186 empirical mutualistic networks and show how both direct and indirect effects alter the fitness of species coevolving in these networks. Although the fitness of species usually increased with the number of mutualistic partners, most of the fitness variation across species was driven by indirect effects. We found that these indirect effects prevent coevolving species from adapting to their mutualistic partners and to other sources of selection pressure in the environment, thereby decreasing their fitness. Such decreases are distributed in a predictable way within networks: peripheral species receive more indirect effects and experience higher reductions in fitness than central species. This topological effect was also evident when we analysed an empirical study of an invasion of pollination networks by honeybees. As honeybees became integrated as a central species within networks, they increased the contribution of indirect effects on several other species, reducing their fitness. Our study shows how and why indirect effects can govern the adaptive landscape of species-rich mutualistic assemblages., This study was financed in part by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior – Brasil (CAPES), finance code 001. L.G.C. is funded by a São Paulo Research Foundation PhD scholarship (FAPESP; grants 2019/22146-3 and 2022/07939-0). P.R.G. is funded by Brazil’s Council for Scientific and Technological Development (CNPq; grant 307134/2017-2), FAPESP (grant 2018/14809-0) and the Royal Society (CHL/R1/180156). A.P.A.A. was supported by CAPES, finance code 001, and FAPESP (grant 2016/14277-2). M.M.P. is funded by FAPESP (grant 2019/25478-7) and CNPq (grant 313059/2022-5). M.A.M.A. is funded by FAPESP (grant 2021/14335-0-ICTP‐SAIFR), and by CNPq (grant 301082/2019‐7). A.V. is supported by the Spanish Ministry of Science, Innovation, and Universities (PGC2018-099772-B-100). P.J. is funded by the Spanish Ministry of Science, Innovation, and Universities (CGL2017-82847-P), LifeWatch ERIC-SUMHAL (LIFEWATCH-2019-09-CSIC-13)/FEDER-EU funding), and the VI and VII Research Funding Program from the Universidad de Sevilla (2021/00000826). J.B. is supported by the Swiss National Science Foundation (grant 310030_197201). We thank R. Cogni, M. A. R. Mello, C. R. Montoya and M. C. Vidal for comments on previous versions of this manuscript., Peer reviewed

Memoria presentada por Elena Quintero Borrero para optar al Título de Doctora por la Universidad de Sevilla., [EN] Studying interactions among species and their multiple forms and outcomes has become a central question of ecological research. Mutualisms have changed the way ecologists understand the functioning of ecosystems. Generalised mutualistic networks, especially among free-living species, have been observed to include highly heterogeneous assemblages, in which most species establish few interactions while a minority of species establish a wide range of interactions. These highly connected species are referred to as super-generalists. They are characterised for connecting otherwise isolated groups of interacting species or modules and for providing stronger cohesion to ecological networks. Their characteristics make them fundamental for local biodiversity and the structure and stability of interactions.

In this PhD thesis we aim to better comprehend the super-generalist strategy and the mutualistic interactions at the individual level. For this purpose, we use as a model organism Pistacia lentiscus L. (Anacardiaceae), a woody shrub species abundant in the Mediterranean Basin, together with the coterie of frugivorous animals that consume its fruits and disperse its seeds. In Chapter 1 we review sampling methods used to record frugivory interactions, assessing their strengths, caveats, and convenience in different contexts. We discuss different approaches for combining data gathered using different methodologies. In Chapter 2, we explore the effectiveness of the frugivory/seed-dispersal mutualism between individual plants of P. lentiscus and its avian frugivore assemblage, assessing the level of reciprocity in reward exchange and dependence asymmetry among partners. In Chapter 3 we investigate the delayed outcomes of animals’ fruit consumption in early seedling recruitment of P. lentiscus plants. Lastly, in Chapter 4 we analyse individual-based networks of different plant species and regions of the world, we compare their topology and structure with that of species-based networks, and explore the specialisation and interaction profile of individual plants within populations.

We highlight the significant advancements brought by emerging methods like camera traps and molecular tools, which allow recording interactions across large spatiotemporal scales and even tracking the movement of individual seeds by animals. We also show how data integration improves network completeness and representativity, and compare different data merging approaches for adjacency matrices. We document how the effectiveness of interactions established between P. lentiscus individual plants and their frugivores is mainly determined by fruit consumption frequency (the component with highest variation), leading to highly reciprocal exchange of services but still highly asymmetric dependence among partners. Despite being mostly determined by the number of fruits consumed, the dispersal service provided by birds is decoupled from microhabitat suitability: frugivores deposit a smaller number of seeds in the most suitable microhabitats. These results underscore the role of different frugivores in spatial recruitment of heterogeneous landscapes. Finally, we demonstrate that the structure of individualbased networks is very similar to that of species-based networks. Plant individuals presented similar interaction profiles irrespective of the species or regions their population belonged to. Within populations, plants present low to medium levels of specialisation, and few frugivore species contribute most interactions in all studied networks.

Overall, these results suggest that super-generalist species may evolve when they combine sets of traits that make them accessible and attractive to a diversified assemblage of frugivores. Numerical effects, such as abundant fruit crops, facilitate plenty of frugivory interactions, characterised in most cases by high reciprocity. In exchange for a fair nutritious reward, plants secure their recruitment thanks to a vast amount of seeds dispersed. Finally, our results indicate that the variation encountered in the way plant individuals structure their interactions is highly consistent across populations of generalised mutualisms worldwide.

Collectively, the four chapters in this thesis contribute to better understanding the origin and maintenance of super-generalist species within complex ecological networks, by focusing on the biological scale at which interactions actually occur in nature, that is, the individual scale., [ES] Estudiar las interacciones entre especies junto a sus múltiples formas y resultados se ha convertido en una cuestión central de la investigación en ecología. Los mutualismos han cambiado la forma en que los ecólogos entienden el funcionamiento de los ecosistemas. Se ha observado que las redes mutualistas generalizadas, especialmente entre especies de vida libre, incluyen conjuntos muy heterogéneos, en los que la mayoría de las especies establecen pocas interacciones, mientras que una minoría de especies establece una amplia variedad de interacciones. Estas especies altamente conectadas se denominan super-generalistas. Se caracterizan por conectar grupos de especies o módulos que de otro modo estarían aislados, y por proporcionar una mayor cohesión a las redes ecológicas. Sus características las convierten en especies fundamentales para la biodiversidad local así como para la estructura y estabilidad de las interacciones.

En esta tesis doctoral pretendemos comprender mejor la estrategia supergeneralista y las interacciones mutualistas a nivel individual. Para ello, utilizamos como organismo modelo Pistacia lentiscus L. (Anacardiaceae), una especie arbustiva leñosa abundantemente distribuida por la cuenca mediterránea, junto a los animales frugívoros que consumen sus frutos y dispersan sus semillas. En el Capítulo 1 se revisan los métodos de muestreo utilizados para registrar las interacciones de frugivoría, evaluando sus ventajas, inconvenientes y conveniencia en diferentes contextos; y se discuten diferentes enfoques para combinar los datos recogidos utilizando diferentes metodologías. En el Capítulo 2, exploramos la eficacia en el mutualismo frugivoría/semilla-dispersión entre plantas individuales de P. lentiscus y las aves frugívoras que consumen sus frutos, evaluando el nivel de reciprocidad en el intercambio de recompensas y la asimetría de dependencia entre los socios. En el Capítulo 3, investigamos los resultados aplazados del consumo de frutos por animales en plantas de P. lentiscus para el reclutamiento temprano de plántulas. Por último, en el Capítulo 4 analizamos redes basadas en individuos para diferentes especies de plantas y regiones del mundo, comparando su topología y estructura con la de redes basadas en especies, y exploramos la especialización y el perfil de interacción de plantas individuales dentro de sus poblaciones.

Destacamos los importantes avances que han supuesto métodos emergentes como las cámaras trampa y técnicas moleculares, que permiten registrar interacciones a una amplia escala espacio-temporal e incluso rastrear el movimiento de semillas individuales por parte de animales. También mostramos cómo la integración de datos mejora la completitud y representatividad de las redes ecológicas, y comparamos distintos métodos de combinación de datos para matrices de adyacencia. A continuación, documentamos cómo la eficacia de las interacciones establecidas entre plantas individuales y sus frugívoros viene determinada principalmente por la frecuencia de consumo de frutos (el componente con mayor variación), lo que conduce a un intercambio de servicios altamente recíproco, pero manteniendo una dependencia altamente asimétrica entre los socios. A pesar de estar determinado principalmente por el número de frutos consumidos, el servicio de dispersión proporcionado por las aves está desvinculado de la idoneidad del microhábitat: los frugívoros depositan un menor número de semillas en los microhábitats más adecuados. Estos resultados resaltan el papel que los distintos frugívoros tienen en el reclutamiento en paisajes heterogéneos. Por último, demostramos que la estructura de las redes basadas en individuos es muy similar a la de las redes basadas en especies. Las plantas individuales presentaron perfiles de interacción similares independientemente de la especie o región a la que perteneciera su población. Dentro de las poblaciones, las plantas presentan niveles de especialización medio-bajos, y unas pocas especies de frugívoros contribuyen a la mayoría de las interacciones en todos las redes estudiadas.

Estos resultados sugieren que las especies super-generalistas pueden evolucionar cuando combinan conjuntos de rasgos que las hacen accesibles y atractivas para un conjunto diversificado de frugívoros. Efectos numéricos como la alta abundancia de frutos facilitan gran cantidad interacciones frugívoras, caracterizadas en la mayoría de los casos por una elevada reciprocidad. A cambio de la recompensa nutritiva que provee la pulpa de los frutos, las plantas aseguran su reclutamiento gracias a una gran cantidad de semillas dispersadas. Por último, nuestros resultados indican que la variación encontrada en la forma en que las plantas individuales estructuran sus interacciones es muy consistente en las poblaciones de mutualismos generalizados de todo el mundo.

En conjunto, los cuatro capítulos de esta tesis contribuyen a comprender mejor el origen y la persistencia de especies super-generalistas dentro de redes ecológicas complejas, centrándose en la escala biológica a la que se producen realmente las interacciones en la naturaleza, es decir, la escala individual., This thesis received financial support from “la Caixa” Foundation fellowship for Doctoral studies at Spanish Universities or Research Centres (ID 100010434) with code LCF/BQ/DE18/11670007, as well as by the projects CGL2017-82847-P and PID2022-136812NB-I00 from Agencia Estatal de Investigación, Ministerio de Ciencia e Innovación and project PAIDI_2020-P20_00736 from Consejería de Economía, Conocimiento, Empresas y Universidad, Junta de Andalucía. In addition, this thesis received support by a Fulbright fellowship for pre-doctoral research abroad, co-funded by Junta de Andalucia and by project LIFEWATCH-2019-09-CSIC-13 funded by European Fund for Regional Development (FEDER-EU)., Peer reviewed

Special Issue:Fruits, animals and seed dispersal: timely advances on a key mutualism., Recording species interactions is one of the main challenges in ecological studies. Frugivory has received much attention for decades as a model for mutualisms among free-living species, and a variety of methods have been designed and developed for sampling and monitoring plant–frugivore interactions. The diversity of techniques poses an important challenge when comparing, combining or replicating results from different sources with different methodologies. With the emergence of modern techniques, such as molecular analysis or multimedia remote recorders, issues when combining data from different sources have become especially relevant. We provide an overview of all the techniques used for monitoring endozoochorous primary seed dispersal, focusing on a critical appraisal of the advantages and limitations, as well as the context-dependency nature, of the different methods. We propose five data merging approaches potentially useful to combine frugivory interactions data from different methodologies. Additionally, we provide two case studies where we combine empirical data from plant–animal interactions in Mediterranean shrublands using different methodologies. Data merging resulted in a net increase in the number of distinct pairwise interactions recorded and compensated biases inherent to different methods, resulting in a more robust estimation of network topological descriptors. These case studies clarify the context-dependent character of the merging approaches, highlighting the value of collecting detailed information on the sampling effort in terms of reliable results and reproducibility. Finally, we discuss the trends with different methodological approaches used in the last decades and future perspectives in this field., Our work was funded by project by CGL2017-82847-P from the Agencia Estatal de Investigación, Spain. During their respective PhD projects, EQ is being supported by ‘La Caixa' Foundation grant ID LCF/BQ/DE18/11670007, and JI by FPI grant PRE2018-085916 from the Spanish Ministry of Science and Innovation., Peer reviewed

Indirect interactions among species within ecological communities govern ecological and evolutionary processes as much as, or even more, than direct effects. In insect-pollinated plant communities, indirect interactions between plants can be mediated by shared pollinators, and may influence plant fitness, population growth and community structure. As individuals are the entities actually interacting in nature, rather than species, downscaling a hierarchical level (i.e. from species to individuals) is essential to understand the underlying processes promoting these indirect interactions. We combined empirical data on plant–pollinator interactions collected in Mediterranean shrublands with a novel modelling framework to assess how the patterns of heterospecific and conspecific pollinator sharing between plant individuals are generated and their fitness implications. We found that the effects of flowering synchrony on pollinator sharing among conspecific and heterospecific plant individuals outperformed those of spatial distance. Our results revealed that plant individuals that shared more pollinators with conspecifics were also involved in a higher pollinator sharing with heterospecifics. For most plant species, the sharing of pollinator species between heterospecific plant individuals produced positive mean fitness outcomes, as long as plants did not share many pollinator interactions, which had negative effects on their fitness. At the level of plant individuals, we found that specific combinations of conspecific and heterospecific pollinator sharing lead to distinct reproductive outcomes that placed each individual along a competition–facilitation continuum. Interestingly, most plant species included a higher proportion of individuals likely experiencing competition compared to those potentially involved in facilitation processes. Our contribution provides novel insights into the factors responsible for local-scale indirect interactions within communities and their individual-level functional consequences. Such intricate patterns of indirect interactions have far-reaching implications, as the transitions of plant individuals along competitive or facilitative processes mediated by shared mutualists may contribute significantly to the functioning and coexistence of ecological communities., BA-C received funding from the Ministry of Universities of the Spanish Government (Ref. FPU19_02552). BA-C and PJ were supported by grants CGL2017-82847-P and PID2022-136812NB-I00, funded by MCIN/AEI/10.13039/501100011033 and by the “European Union NextGenerationEU/PRTR”, grant P20_00736 from Junta de Andalucía, and a LifeWatch ERIC-SUMHAL project (LIFEWATCH-2019-09-CSIC-13), with FEDER-EU funding., Peer reviewed

Ecologists have long recognized that seed dispersal mutualisms trigger natural regeneration and range expansion of animal-dispersed trees. Yet we lack empirical studies addressing whether frugivore activity influences founder effects, which reduce genetic diversity at the colonization front of expanding populations. Here, we evaluate the contribution, from both demographic and genetic perspectives, of animal frugivores dispersing seeds across an expansion gradient. We used DNA barcoding for frugivores identification and highly polymorphic genetic markers (SSRs) for maternal analysis of juniper seeds to investigate how (1) stand maturity, (2) microhabitat types and (3) foraging patterns shape the distribution of the maternal progenies along this gradient. We expect both reduced seed rain density and low numbers of source trees contributing to the seed rain at the colonization front, with limited availability of local fruiting trees. We also anticipated that large-sized frugivore species would promote maternally rich seed rain due to their ability to mix seed progenies during digestive processing and move further distances across the landscape. Contrary to our expectations, we found that all identified frugivores produced dense and genetically diverse seed rains across the expansion gradient, even at the colonization front, characterized by scarce fruiting trees. Synthesis: Our findings shed light on the fundamental and applied implications of plant–frugivore interactions in shaping highly diverse second-growth forests. These results emphasize the necessity of preserving plant–animal mutualistic interactions to ensure the persistence and expansion of natural tree populations, particularly in formerly fragmented landscapes., Our work was funded by grants CGL2017-82847-P and PID2022-136812NB-I00, Spanish Ministry of Science and Innovation and grant SUMHAL, LIFEWATCH-2019-09-CSIC-13, POPE 2014–2020, MICINN through the European Regional Development Fund, as well as funding from the VI Plan Propio de Investigación of the Universidad de Sevilla (VI PPIT-US) (PJ). JI was supported by an FPI grant PRE2018-085916 from the Spanish Ministry of Science and Innovation. MJF was supported by Investigadores por México-CONAHCYT (grant number: 73215). CG was supported by the Research Application Support Programme (RHUL) and the Royal Society (Research Application Support Programme) RaSP., Peer reviewed