© The Authors 2015. Oceanic archipelagos are threatened by the introduction of alien species which can severely disrupt the structure, function and stability of native communities. Here we investigated the pollination interactions in the two most disturbed Galápagos Islands, comparing the three main habitats and the two seasons, and assessing the impacts of alien plant invasions on network structure.We found that the pollination network structure was rather consistent between the two islands, but differed across habitats and seasons. Overall, the arid zone had the largest networks and highest species generalization levels whereas either the transition between habitats or the humid habitat showed lower values. Our data suggest that alien plants integrate easily into the communities, but with low impact on overall network structure, except for an increase in network selectiveness. The humid zone showed the highest nestedness and the lowest modularity, which might be explained by the low species diversity and the higher incidence of alien plants in this habitat. Both pollinators and plants were alsomore generalized in the hot season, when networks showed to bemore nested. Alien species (both plants and pollinators) represented a high fraction (~56 %) of the total number of interactions in the networks. It is thus likely that, in spite of the overall weak effect we found of alien plant invasion on pollination network structure, these introduced species influence the reproductive success of native ones, and by doing so, they affect the functioning of the community. This certainly deserves further investigation., This research is part of a larger project funded by BBVA Foundation and is also framed within project CGL-2013-44386-P financed by the Spanish Government. R.H. was supported by the Portuguese grant FCT-IF/00441/2013, and by the Marie Curie action FP7-2012-CIG-321794, Peer Reviewed

Coextinction models are useful to understand community robustness to species loss and resilience
to disturbances. We simulated pollinator extinctions in pollination networks by using a hybrid model
that combined a recently developed stochastic coextinction model (SCM) for plant extinctions and
a topological model (TCM) for animal extinctions. Our model accounted for variation in interaction
strengths and included empirical estimates of plant dependence on pollinators to set seeds. The
stochastic nature of such model allowed us determining plant survival to single (and multiple) extinction
events, and identifying which pollinators (keystone species) were more likely to trigger secondary
extinctions. Consistently across three different pollinator removal sequences, plant robustness was
lower than in a pure TCM, and plant survival was more determined by dependence on the mutualism
than by interaction strength. As expected, highly connected and dependent plants were the most
sensitive to pollinator loss and collapsed faster in extinction cascades. We predict that the relationship
between dependence and plant connectivity is crucial to determine network robustness to interaction
loss. Finally, we showed that honeybees and several beetles were keystone species in our communities.
This information is of great value to foresee consequences of pollinator losses facing current global
change and to identify target species for effective conservation., This study was performed within project CGL2013-44386-P financed to AT by the Spanish Ministry of Economy and Competitiveness., Peer reviewed

Coextinction models are useful to understand community robustness to species loss and resilience to disturbances. We simulated pollinator extinctions in pollination networks by using a hybrid model that combined a recently developed stochastic coextinction model (SCM) for plant extinctions and a topological model (TCM) for animal extinctions. Our model accounted for variation in interaction strengths and included empirical estimates of plant dependence on pollinators to set seeds. The stochastic nature of such model allowed us determining plant survival to single (and multiple) extinction events, and identifying which pollinators (keystone species) were more likely to trigger secondary extinctions. Consistently across three different pollinator removal sequences, plant robustness was lower than in a pure TCM, and plant survival was more determined by dependence on the mutualism than by interaction strength. As expected, highly connected and dependent plants were the most sensitive to pollinator loss and collapsed faster in extinction cascades. We predict that the relationship between dependence and plant connectivity is crucial to determine network robustness to interaction loss. Finally, we showed that honeybees and several beetles were keystone species in our communities. This information is of great value to foresee consequences of pollinator losses facing current global change and to identify target species for effective conservation., This study was performed within project CGL2013-44386-P financed to AT by the Spanish Ministry of Economy and Competitiveness and project SPASIMM (FIS2016-80067-P AEI/FEDER, UE) to VME by Agencia Estatal de Investigación (AEI, Spain) and Fondo Europeo de Desarrollo Regional (FEDER)., Peer reviewed

The ongoing biodiversity crisis entails the concomitant loss of species and the ecological services they provide. Global defaunation, and particularly the loss of frugivores, may negatively affect the seed dispersal of fleshy-fruited plant species, with predictable stronger impacts in simplified communities such as those on oceanic islands. However, logistical difficulties have hindered the experimental and theoretical need to disentangle the roles of species identity, richness (i.e. number of species) and abundance. Consequently, studies to date have focused exclusively on the loss of species richness leaving us largely ignorant regarding how species identity and abundance affect the loss of ecosystem functions. Here, we applied a network approach to disentangle the effects of disperser abundance, richness and identity on the seed dispersal service provided by frugivores to the Galapagos plant community. We found that both abundance and richness of the dispersers significantly affect the function of seed dispersal and that richness becomes increasingly important as disperser abundance declines. Extinction simulations revealed that the order of species loss has profound implications to the plant community. On the one hand, abundant generalist dispersers like the Galapagos lizards, can mitigate the loss of specialized dispersers. On the other hand, specific threats affecting key dispersers can lead to the rapid collapse of the community-level dispersal services. Our results suggest that the identity of the disperser species lost can have a large effect on the number of plant species dispersed, and generalist species are essential to the persistence of the community dispersal service. Both abundance and species richness of seed dispersers are key and synergistic drivers of the number of plant species dispersed. Consequently, the coupled negative effect of population declines and species extinctions in frugivore assemblages may lead to an accelerated loss of the seed dispersal function. plain language summary is available for this article., We also thank the European Union Marie Curie Action (FP7‐PEOPLE‐2012‐CIG‐ 321794), the Portuguese Foundation for Science and Technology (IF/00441/2013). This study is framed within a biodiversity project in the Galapagos Islands, partially financed by BBVA Foundation (Spain) and the projects CGL2012‐C02‐01 and CGL2013‐44386‐P funded by Ministerio de Economía y Competitividad (Spain)., Peer Reviewed

[Premise of the Study] The characteristic scarcity of insects on remote oceanic islands has driven nonflower-specialized vertebrates to broaden their trophic niches and explore floral resources. From our previous studies in the Galápagos, we know that native insectivorous and frugivorous birds visit a wide range of entomophilous flowers and can also act as effective pollinators. Here, we tested whether opportunistic Galápagos birds show any preference for specific floral traits, and if so, this preference differs from that of insects, [Methods] Sixteen floral morphology and nectar traits of 26 native species were studied, as well as the frequency with which they are visited by birds and insects. Nonmetric multidimensional scaling (NMDS) was used to evaluate the distribution of flower traits values along two main dimensions and measure the similarity between the plants visited mostly by birds versus those by insects, [Key Results] NMDS of floral traits resulted in two species groups: (1) bell-shaped, white flowers with wider corollas at nectary level and higher nectar volume, associated with high bird visitation rates; and (2) bowl and tubular-shaped flowers with narrower corollas at nectary level and lower nectar volume, associated with high insect visitation rates, [Conclusions] Despite the divergence in floral trait preferences between opportunistic Galápagos birds and insects, bird-visited flowers display mixed traits not fitting the classical ornithophilous syndrome. This finding is compatible with the existence of a transitional or bet-hedging phenotype between insect and bird visitors and underscores the importance of coevolution and floral diversification in nonspecialized plant–visitor interactions., This research is framed within projects CGL2013-44386-P, CGL2015-67865-P, and CGL2017-88122-P funded by the Ministerio de Economía y Competitividad (MINECO), Spain., Peer Reviewed

Oceanic island ecosystems favour the appearance of novel interactions as a consequence of their depauperate and disharmonic flora and fauna. We investigated Echium simplex, endemic to the Anaga Biosphere Reserve in NE Tenerife, Canary Islands, belongs to the Canarian bird–flower element. Along two flowering seasons, we studied the breeding system of E. simplex, identified the floral visitors and compared the pollination effectiveness of different animal guilds (insects versus vertebrates) by means of selective exclosures. E. simplex is self-compatible but selfing significantly reduced fruit set. The flowers were visited by five bird species (mostly Phylloscopus canariensis and Serinus canarius, but also Cyanistes teneriffae, Sylvia atricapilla and Sylvia melanocephala), a lizard species (Gallotia galloti) and over a hundred insect species (mainly hymenopterans and coleopterans). Flying insects increased fruit set whereas small flower dwellers (mostly beetles) decreased both fruit and seed set. Vertebrates had a negligible effect on reproductive success. We conclude that although the floral resources provided by E. simplex may be important to some vertebrate species, these do not appear to contribute to increase fitness of the plant, which was more dependent upon flying insects for fruit and seed set. We additionally found that plant reproductive structures are heavily damaged by feral goats, which threaten the maintenance of this Canarian endemic species., The study was funded by a predoctoral fellowship to Julia Jaca from the Ministerio de Educación, Cultura y Deporte [FPU13/05880] and framed within a project financed by Ministerio de Economía, Industria y Competitividad [CGL2013‐44386‐P] to Anna Traveset., Peer Reviewed

Islands harbor a considerable portion of global biodiversity and endemic biota, and also are the recipients of the largest proportional numbers of alien invaders. Such invaders may jeopardize the performance of native species, through either their direct or indirect effects. In this study, we investigated the reproductive ecology of the endemic scrambling perennial herb Canarina canariensis in remnants of the former thermosclerophyllous woodland of Tenerife (Canary Islands), assessing how two widespread alien invasive species, the honeybee (Apis mellifera) and the black rat (Rattus rattus), affect its reproductive success. Apis mellifera visits its flowers whereas the black rat consumes both its flowers and fruits. Here, we compared the pollination effectiveness of different animal guilds (vertebrates vs insects) by means of selective exclosures and determined the level of floral herbivory. Three bird species (Phylloscopus canariensis, Cyanistes teneriffae and Sylvia melanocephala), a lizard (Gallotia galloti) and two insects (A. mellifera and the butterfly Gonepteryx cleobule) were the main flower visitors. Phylloscopus canariensis was the most frequent visitor in the early flowering season whereas A. mellifera predominated in the flowers during mid and late flowering periods. Birds increased fruit set, whilst lizards and insects had a negligible effect. Rats consumed about 10% of the flowers and reduced fruit set to one third. Besides contributing little to plant reproduction, A. mellifera might interfere with bird pollination by depleting flowers of nectar. We conclude that both alien species can threaten C. canariensis reproduction and hence population sustainability in the thermosclerophyllous vegetation. Apis mellifera, in particular, may become especially detrimental if apiculture keeps expanding, or if this bee becomes active earlier in the season due to global warming., Julia Jaca was funded by a predoctoral fellowship from the Ministerio de Educación, Cultura y Deporte [FPU13/05880] and by the unemployment benefit from the Ministerio de Trabajo, Migraciones y Seguridad Social; and the study was framed within a project financed by the Ministerio de Economía, Industria y Competitividad [CGL2013-44386-P], granted to Anna Traveset., Peer Reviewed

A double mutualism (DM) occurs when two interacting species benefit each other in two different functions, e.g. when an animal species acts both as pollinator and seed disperser of the same plant. Besides the double benefit, a DM also imposes a larger risk to both functions if the performance of one partner declines. We conducted the first global review of DMs involving pollinators and seed dispersers, aiming to: 1) assess their prevalence across ecosystems and biogeographical regions; 2) identify the main plant and animal taxa, and their traits, implicated in DMs; and 3) evaluate the conservation status of double mutualist species. We compiled published and unpublished DM records using specific search terms, noting the species involved, their conservation status and geographic location, as well as the type of study (species vs community-level) in which the DM was detected. We identified 302 DM cases involving 207 plant and 92 animal species from 16 mainland and 17 island areas. Most records come from tropical regions and islands. Animals included birds (62%), mammals (22%), and reptiles (16%), mostly opportunist species; only 18% were nectarivores. Plants were mainly fleshy-fruited shrub or tree species (59%) with actinomorphic flowers that were visited by several or many pollinator species (87%). Most (56%) DMs were detected in community-level studies. DMs are mostly prevalent in ecosystems with limited food resources and mutualist partners, and with high generalization levels. Nearly 30% of the species involved in DMs are threatened according to IUCN criteria, 68% of which are found on islands. The high prevalence of DM on islands paired with the threat status of island species suggest that the loss of a double mutualists and its cascading consequences may have a severe impact on community composition and functioning of fragile island ecosystems., This work is framed within project CGL2013‐44386‐P and FF is funded by a PhD fellowship (BES‐2014‐068207), both financed by the Spanish Government.

[Premise] Opportunistic nectar‐feeders may act as effective pollinators; nonetheless, we still lack information on whether these opportunistic species differ in their pollination effectiveness from specialized nectarivorous vertebrates and insects. Many nectar specialists have coevolved with the plants on which they feed; therefore, we would expect higher pollination effectiveness in specialists than in opportunistic feeders. Here, we assessed quantity and quality components of pollination effectiveness in specialist and opportunistic vertebrate nectarivores and insects, focusing on three plants from the Seychelles: Thespesia populnea, Polyscias crassa, and Syzygium wrightii., [Methods] We determined the quantity component (QNC) of pollination effectiveness with pollinator observations, and the quality component (QLC) by measuring fruit and seed set resulting from single visits by each pollinator. To detect potential negative effects of invasive ants on native plant‐pollinator interactions, we classified pollinator visits (quantity component) as disturbed (>6 ants/30 min) vs. undisturbed., [Results] All focal plants were visited by insects, and vertebrate specialist and opportunist nectarivores, yet their pollination effectiveness differed. Flying insects were the most effective pollinators of T. populnea. The other two plants were most effectively pollinated by vertebrates; i.e., sunbirds (nectar specialists) in S. wrightii and Phelsuma geckos (nectar opportunists) in P. crassa, despite marked variation in QNC and QLC. Ant presence was associated with lower pollinator visitation rate in P. crassa and S. wrightii., [Conclusions] Our study highlights the importance of all pollinator guilds, including opportunist nectarivorous vertebrates as pollinators of island plants, and the vulnerability of such interactions to disruption by nonnative species., This work was part of projects CGL2013‐44386‐P and CGL2017‐88122‐P awarded to A. T. and financed by the Spanish Government. F. F. was funded by the Spanish Government with a Ph.D. fellowship (BES‐2014‐ 068207). C. N. K.‐B. was supported by funding from the German Research Foundation (DFG; KA 3349/2‐1 and KA 3349/3‐1).

Due to drastic changes in pollinators between native and invaded habitats, we might expect that pollinator-mediated selection on floral traits of alien plants differ from that in their native ranges. Here, through geometric morphometric tools and phenotypic selection analyses, we examined whether adaptation in flower shape and length occurred in Nicotiana glauca as a response to pollinator selection in contrasting pollination environments. We assessed populations of this plant species in the native range (South America), where plants depend on hummingbird pollination, and in two invaded areas, one where sunbirds act as pollinators (South Africa), and another where nectar feeding birds are absent and reproduction is entirely by autonomous self-pollination (Mallorca, Spain). Corolla length and shape varied significantly among pollination environments. Non-native sites were less variable and their range of variation fell within the native range of variation. Flower length in native populations and in a South African population matched the bill length of their respective pollinators. In contrast with the straight floral tubes in the native range, both non-native areas had significantly curved tubes. Curvature may improve the fit with the curved bills of sunbirds in South Africa (versus straight beaks of hummingbirds) and may enhance self-pollination in Mallorca, but this similarity between invaded areas may equally be due to drift and a shared colonization route. We found spatial variation in selection acting on corolla length but not on corolla shape. Overall, selection patterns were not consistent with floral trait variation. Although some results are consistent with both drift and selection, our study suggests that population divergence in flower shape and length is more likely the result of long-term diversifying pollinator-driven selection, which is difficult to detect by studying a single selection event., AAC, ANS, SBV and VP acknowledge the National Research Council of Argentina (CONICET) and the Universidad Nacional de Córdoba (UNC) as researchers. This work was supported by FONCyT (PICT 2015-3089; PICT-2011-0837) to ANS, the Department of Science and Technology of South Africa (438 75946) and the Spanish Ministry of Economy and Competitiveness (CGL2013-44386-P)., Peer reviewed

Special Issue: Animal‐plant interactions., Lizards have been reported as important pollinators on several oceanic islands. Here we evaluate the potential role of Galápagos lava lizards (Microlophus spp.) as pollinators across their radiation. Over 3 years, we sampled pollen transport by 9 lava lizard species on the 10 islands where they are present, including 7 single‐island endemics. Overall, only 25 of 296 individuals sampled (8.4%) transported pollen of 10 plant species, the most common being Prosopis juliflora, Exodeconus miersii, Sesuvium sp. and Cordia leucophlyctis. At least 8 of these plant species were native, and none were confirmed as introduced to the archipelago. Despite the low overall proportion of individuals carrying pollen, this was observed in 7 of the nine lizard species, and on 8 of the ten main islands (Española, Fernandina, Floreana, Isabela, Marchena, Pinta, Santa Cruz and Santiago), suggesting that this is a widespread interaction. The results reported here support the potential role of lava lizards as pollinators across their radiation, although they may represent a relatively modest contribution when compared with birds and insects. However, we cannot discard that lizards may be ecologically significant for particular plant species and ecosystems given the specific climatic condition and functional diversity of each island., This study is framed within the projects CGL2013-44386-P and CGL2015-67865-P funded by the Ministerio de Economía y Competitividad (Spain). We thank the Charles Darwin Foundation, especially Diana Flores and Patricia Jaramillo and the Galápagos National Park, especially Galo Quezada and Carlos Vera (research permit numbers: PC-46-14, PC-20-15, PC-22-16), for offering us information and logistic support.

Although most plants depend on different animals for pollination and seed dispersal, sometimes the same animal species provides both functions, being thus involved in what has been termed a ‘double mutualism’. Very little is known on the effectiveness of such species as both pollinators and seed dispersers, and even less on the intraspecific level differences at the contribution of an animal mutualist to plant fitness. In this study, we focused on the interaction between a Mediterranean shrub Cneorum tricoccon (Rutaceae) and the Balearic lizard Podarcis lilfordi (Lacertidae) in order to assess: 1) the role of this lizard as a legitimate pollinator of the plant (previously thought to be exclusively insect‐pollinated), and 2) the intraspecific variation in the use of flowers and fruits by lizard individuals, comparing males, females and juveniles. We further evaluated whether lizards show different fruit size selection depending on sex and age, with potential consequences for seed germination. Lizards visited more flowers and selected more hermaphrodite flowers than insects did, leading to relative increases in both fruit and seed set. Interestingly, female and juvenile lizards were the main flower visitors, whereas males were the main fruit consumers. Males selected the largest fruits (bearing the largest seeds) though this did not increase seed germination, which was only ca 15%. We concluded that P. lilfordi acts as a legitimate pollinator of C. tricoccon and, thus, confirm that this system constitutes a new case of double mutualism, especially common in island compared to mainland systems. Moreover, our findings show a large variation among conspecific individuals in their role as either pollinators or seed dispersers, with potential implications for plant reproductive success. Our study, therefore, highlights the importance of evaluating plant–animal interactions at the intraspecific level, and calls for more in‐depth studies on the consequences of such intraspecific variation., This work is framed within projects CGL2013‐44386‐P and CGL2017‐88122‐P, and FF is funded by a PhD fellowship (BES‐2014‐068207), all financed by the Spanish Government.

Tesis Doctoral.-- Doctoral Programme of Plant Biology., [EN] Plant reproductive success depends on the effectiveness of the mutualistic interaction and the context in which it occurs. This thesis investigates and quantifies plant fitness with a particular group of animal mutualists, opportunistic vertebrates, in the context of oceanic islands. Compared to mainland systems, oceanic islands are generally characterized by simpler mutualistic networks, largely as a result of depauperate animal faunas. Because of this, plant species are likely to include new, even novel flower–pollinator and fruit-dispersal interactions after island colonization. In the Canary Islands, passerine birds and lacertid lizards are frequent floral visitors and fruit consumers of native flora, but their effectiveness and relative importance in reproductive success has remained almost unknown. In addition, islands are particularly vulnerable to alien species like rats, honeybees, and goats, which are all successful invaders in the Canary Islands. These interact with native plant species and their potential detrimental effects on plant fitness deserve our attention, in order to preserve this endemic flora. Our main goal was to gain further insights into the role of vertebrates in plant reproductive success in the archipelago, and the evolution of the bird pollination syndrome in the Macaronesian islands in general. For this, we selected the endemic plant species Echium simplex and Canarina canariensis, both interacting with native mutualists and alien antagonists. Chapters 1 and 2 assess the breeding system, identify nocturnal and diurnal flower visitors and compare the pollination effectiveness of different animal guilds (vertebrates vs. insects, and diurnal vs. nocturnal insects) along different inflorescence sections in Echium simplex. It is a self-compatible species, but its reproductive success is enhanced by animal pollinators. Bees and beetles were the most common insect visitors, while the African blue tit and the Canarian chiffchaff were the most prevalent vertebrates visiting flowers. Flying diurnal insects increased fruit set whereas small flower dwellers (mostly beetles) decreased both fruit and seed set; by contrast, vertebrates had a negligible effect on reproductive success. We additionally found that plant reproductive structures are heavily damaged by feral goats, which threaten the conservation of this Canarian endemic species. Chapter 3 studies the pollination of Canarina canariensis in remnants of the former thermosclerophyllous woodland, evaluating how two widespread alien invasive species, the honeybee and the black rat, affect its reproductive success. The Canarian chiffchaff was the most frequent visitor in the early flowering season, whereas the honeybee predominated in the flowers during mid and late flowering periods. Birds increased fruit set, whilst insects had a negligible effect. Besides contributing little to plant reproduction, honeybees might interfere with bird pollination by depleting flowers of nectar. Rats consumed about 10% of the flowers and reduced fruit set to one third. Both alien species can threaten C. canariensis reproduction and hence population sustainability in the thermosclerophyllous vegetation. Chapter 4 investigates the relative effectiveness of two vertebrate groups (birds and lizards) at different stages (pollination and seed dispersal) of the reproductive cycle of Canarina canariensis in the thermosclerophyllous habitat. We built three stochastic models (namely ‘pollination’, ‘dispersal’ and ‘pollination + dispersal’) that simulated seedling recruitment. The dispersal stage contributed more than the pollination stage through the recruitment process. Moreover, birds and lizards exhibited a functional complementarity, with birds contributing most in the pollination model and lizards in the dispersal model., [ES] El éxito reproductivo de las plantas depende de la eficacia de la interacción mutualista y del contexto en el que ocurre. Esta tesis investiga y cuantifica el “fitness” (éxito biológico) de la planta con un grupo particular de animales mutualistas, los vertebrados oportunistas, en un contexto particular, en islas oceánicas. Comparadas con los sistemas continentales, las islas oceánicas generalmente se caracterizan por redes mutualistas más simples, en gran medida como resultado de su fauna depauperada. A consecuencia de esto, las especies de plantas son proclives a incluir nuevas interacciones de flor-polinizador y fruto-dispersor después de su colonización. En las Islas Canarias, las aves paseriformes y los lagartos (F. Lacertidae) son visitantes florales y consumidores de frutos frecuentes de la flora nativa, pero su eficacia e importancia relativa en el éxito reproductivo es casi desconocida. Por otro lado, las islas son particularmente vulnerables a las especies exóticas. Ratas, abejas de la miel y cabras son invasores exitosos en las Canarias que interaccionan con especies nativas de plantas, muchas de ellas endémicas, y cuyos potenciales efectos perjudiciales en el “fitness” de las plantas merece nuestra atención con el fin de preservar esta flora endémica. Con el principal objetivo de aportar más conocimiento en el papel de los vertebrados en el éxito reproductivo de las plantas en el archipiélago canario, y en la evolución del síndrome de polinización por aves en las islas Macaronésicas, seleccionamos los endemismos Echium simplex y Canarina canariensis, ambos interaccionando con mutualistas nativos, y también con antagonistas exóticos. Los capítulos 1 y 2 evalúan el sistema reproductivo, identifican los visitantes florales diurnos y nocturnos, y comparan la eficacia de polinización de diferentes gremios de animales (vertebrados vs insectos, insectos diurnos vs insectos nocturnos) a lo largo de diferentes secciones de la inflorescencia de E. simplex. La planta es auto-compatible, pero su éxito reproductivo es claramente favorecido por animales polinizadores. Las abejas y los escarabajos fueron los insectos visitantes más comunes, mientras que el herrerillo y el mosquitero canarios fueron los vertebrados predominantes. Los insectos voladores diurnos aumentaron el cuajado de frutos, mientras que los pequeños habitantes de las flores (en su mayoría escarabajos) disminuyeron tanto el cuajado de frutos como de semillas; en cambio, los vertebrados tuvieron un efecto insignificante en el éxito reproductivo. Adicionalmente, encontramos que las estructuras reproductivas son considerablemente dañadas por cabras asilvestradas, lo cual amenaza la supervivencia de esta especie endémica canaria El capítulo 3 estudia la polinización de C. canariensis en fragmentos del antiguo bosque termoesclerófilo, evaluando cómo dos especies exóticas invasoras ampliamente distribuidas, la abeja de la miel y la rata, afectan a su éxito reproductivo. El mosquitero canario fue el visitante más frecuente al principio de la temporada de floración, mientras que la abeja de la miel predominó a mitad y al final de la misma. Las aves aumentaron el cuajado de frutos, mientras que los insectos tuvieron un efecto insignificante. Además de contribuir poco a la reproducción de la planta, la abeja de la miel podría interferir con la polinización por las aves al agotar el néctar de las flores. Las ratas consumieron alrededor del 10% de las flores y redujeron el cuajado de frutos a un tercio. Ambas especies exóticas pueden amenazar la reproducción de C. canariensis y, por tanto, el futuro de la sostenibilidad de la población en la vegetación termoesclerófila. El capítulo 4 investiga la eficacia relativa de diferentes gremios de vertebrados (aves vs lagartos) en dos etapas diferentes (polinización y dispersión de semillas) del ciclo reproductivo de C. canariensis en el hábitat termoesclerófilo. Construimos tres modelos estocásticos (específicamente, 'polinización', 'dispersión', y 'polinización + dispersión') que simulaban el reclutamiento de plántulas. La etapa de la dispersión contribuyó en mayor medida que la etapa de la polinización a lo largo del proceso de reclutamiento. Además, aves y lagartos mostraron una complementariedad funcional, contribuyendo más las aves en el modelo de polinización, mientras que los lagartos influyeron más en el modelo de dispersión., [CA] L'èxit reproductiu de les plantes depèn de l'efectivitat de la interacció mutualista i del context d'aquesta. Aquesta tesi investiga i quantifica la fitness de les plantes amb un determinat grup de mutualistes animals, els vertebrats oportunistes, dins d'un context en particular, les illes oceàniques. En comparació amb els sistemes peninsulars, les illes oceàniques generalment es caracteritzen per xarxes mutualistes més simples, degut en gran mesura a una fauna animal empobrida. Degut a això, és més probable que les espècies de plantes presentin noves interaccions flor–pol·linitzador i dispersió de fruits després de la colonització de l'illa. A les Illes Canàries, els aucells passeriformes i els sargantanes de la familia dels lacèrtids són visitants freqüents de les flors i consumidors de fruits de la flora nativa, però la seva efectivitat i la importància relativa del seu èxit reproductiu són encara desconeguts. D'altra banda, les illes són particularment vulnerables a les espècies alienes. A les Illes Canàries les rates, les abelles de la mel i les cabres són invasors d'èxit que interactuen amb les espècies natives de plantes i els seus efectes detrimentals a la fitness de les plantes mereix la nostra atenció per a preservar aquesta flora endèmica. Amb l'objectiu principal d'aportar una visió més profunda del paper dels vertebrats en l'èxit reproductiu de les plantes de l'arxipèlag, i de l'evolució del síndrome de l'aucell pol·linitzador a les illes Macaronèsiques, hem seleccionat les endèmiques Echium simplex i Canarina canariensis, de cara a la interacció d'ambdues amb els mutualistes natius i els antagonistes aliens. Els capítols 1 i 2 avaluen el sistema reproductiu d’Echium simplex, identificant els visitants nocturns i diürns de les flors i comparen l'efectivitat de la pol·linització dels diferents gremis d'animals (vertebrats vs insectes, i insectes diürns vs nocturns) juntament amb seccions d'inflorescència de la planta. Aquesta espècie és auto- compatible però el seu èxit reproductiu millora amb els pol·linitzadors animals. Les abelles i escarabats varen ser els visitants insectes més comuns, mentre que la mallerenga africana i el mosquiter canari foren els visitants de flors vertebrats més prevalents. Els insectes voladors diürns incrementaren el quallat del fruit, mentre que els habitants de les flors més petites (principalment escarabats) reduïren el quallat del fruit i de les llavors; en contraposició, els vertebrats tingueren un efecte negligible en l'èxit reproductiu. A més, es va confirmar que les cabres ferals fereixen les estructures reproductives de les plantes, la qual cosa amenaça el manteniment d'aquesta espècie endèmica canària El capítol 3 estudia la pol·linització de Canarina canariensis als vestigis del bosc termescleròfil, avaluant com dues espècies invasores alienes esteses, l'abella de mel i la rata negra, afecta al seu èxit reproductiu. El mosquiter canari va ser el visitant més freqüent al inici de l'estació de floració mentre que l'abella de mel va ser predominant durant els mitjans i darrers períodes de floració. Els aucells incrementaren el quallat del fruit mentre que els insectes tingueren un efecte negligible. A més de contribuir poc a la reproducció de les plantes, les abelles de la mel podrien interferir en la pol·linització dels aucells, buidant les flors del seu nèctar. Les rates consumiren devers el 10% de les flores i reduïren el quallat del fruit a una tercera part. Ambdues espècies alienes poden amenaçar la reproducció de C. canariensis i per tant el sosteniment de la població a la vegetació termoescleròfila. El capítol 4 investiga l'efectivitat relativa de grups vertebrats diferents (aucells and sargantanes) a dos nivells diferents (és a dir, pol·linització i dispersió de llavors) del cicle reproductiu de Canarina canariensis a l'hàbitat termoescleròfil. Hem construït tres models estocàstics (principalment els models de 'pol·linització', 'dispersió' i 'pol·linització + dispersió') que simularen el reclutament de plàntules. L'etapa de dispersió va contribuir més que l'etapa de pol·linització en el procés de reclutament. A més, els aucells i les sargantanes exhibiren una complementarietat funcional, amb els aucells contribuint més al model de pol·linització i les sargantanes al de dispersió., The study was funded by a predoctoral fellowship to Julia Jaca from the Ministerio de Educación,Cultura y Deporte [FPU13/05880] and framed within project financed by Ministerio de Economía, Industria y Competitividad [CGL2013-44386-P] to Anna Traveset., Peer reviewed

Invasive plants displaying disparate pollination environments and abiotic conditions in native and non-native ranges provide ideal systems to test the role of different ecological factors driving flower colour variation. We quantified corolla reflectance of the ornithophilous South American Nicotiana glauca in native populations, where plants are pollinated by hummingbirds, and in populations from two invaded regions: South Africa, where plants are pollinated by sunbirds, and the Balearic island of Mallorca, where plants reproduce by selfing. Using visual modelling we examined how corolla reflectance could be perceived by floral visitors present in each region. Through Mantel tests we assessed a possible association between flower colour and different abiotic factors. Corolla reflectance variation (mainly along medium to long wavelengths, i.e. human green-yellow to red colours) was greater among studied regions than within them. Flower colour was more similar between South America and South Africa, which share birds as pollinators. Within invaded regions, corolla reflectance variation was lower in South Africa, where populations could not be distinguished from each other by sunbirds, than in Spain, where populations could be distinguished from each other by their occasional visitors. Differences in corolla colour among populations were partially associated with differences in temperature. Our findings suggest that shifts in flower colour of N. glauca across native and invaded ranges could be shaped by changes in both pollination environment and climatic factors. This is the first study on plant invasions considering visual perception of different pollinators and abiotic drivers of flower colour variation., This work was supported by the Agencia Nacional de Promoción Científica y Tecnológica (FONCYT PICT 2015-3089, PICT 2011-0837, PICT 2012-2763, and PICT 2019-3633), the National Research Foundation of South Africa (438 75946) and the Spanish Ministry of Economy and Competitiveness (CGL2013-44386-P). We acknowledge the Universidad Nacional de Córdoba and Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), both of which support the research facilities. MM, ANS, AAC and VP are staff researchers and AC, JVI and MED are fellowship holders from CONICET., Peer reviewed

We provide an overview of the current state of knowledge of island frugivory and seed dispersal and identify knowledge gaps that are important for fundamental research on—and applied conservation of—island ecosystems. We conducted a systematic literature search of frugivory and seed dispersal on islands, omitting large, continental islands. This revealed a total of 448 studies, most (75%) published during the last two decades, especially after 2010. Nearly 65% of them were focused on eight archipelagos. There is a paucity of studies in Pacific archipelagos near Asia and Australia, and in the Indian Ocean. Data on island frugivory and seed dispersal are diverse but highly uneven in geographic and conceptual coverage. Despite their limited biodiversity, islands are essential reservoirs of endemic plants and animals and their interactions. Due to the simplicity of insular ecosystems, we can assess the importance of seed dispersal theory and mechanisms at species and community levels. These include the ecological and biogeographical meaning and prevalence of non-standard mechanisms of seed dispersal on islands; the seed dispersal effectiveness and the relative roles of different frugivore guilds (birds and reptiles being the most important); and patterns of community organization and their drivers as revealed by interaction networks. Island systems are characterized by the extinction of many natives and endemics, and high rates of species introductions. Therefore, understanding how these losses and additions alter seed dispersal processes has been a prevailing goal of island studies and an essential foundation for the effective restoration and conservation of islands., MN, AT and RH were partially funded by the Ministerio de Economía y Competitividad (Spain), projects: CGL2013-44386-P, CGL67865-P, CGL2017-88122-P and PID2022-137906NB-I00), funded by Ministerio de Ciencia, Innovación y Universidades (Spain). PJB was partially funded by the New Zealand Ministry for Business, Innovation and Employment’s Strategic Science Investment Fund. JHH was funded by Carlsberg grant no. CF19-0695., Peer reviewed

Aim: Mutualistic network parameters, such as modularity and nestedness, show non-random linkage patterns. Both increase network stability in different ways. Modularity hampers extinction cascades, whereas nestedness resists network disassembly. We explore these parameters in seed-dispersal networks in two archipelagos and the significance of life history, habitat, geography and phylogeny as drivers of linkage patterns and the applicability of modules as biogeographical entities.

Location: Canaries (Atlantic Ocean) and Galápagos (Pacific Ocean).

Methods: We compiled data on plant–seed disperser interactions from own observations and the literature, estimated network parameters describing interaction patterns (connectance, nestedness and modularity) and constructed a backbone phylogeny for the analyses.

Results: The Canarian network was highly nested but weakly modular, whereas the Galápagos network showed the opposite characteristics. Most key network species are native and have a favourable conservation status. Modularity in the Canaries is correlated with habitats (indirectly affected by altitude and orientation), whereas in the Galápagos it mainly reflects the functional roles of species.
Main conclusions: The divergent link patterns for the archipelagos imply that the highly nested Canarian network is stable against disassembly, whereas the modular Galápagos network may show strong resistance against extinction cascades. This difference may be driven by the specific evolutionary dynamics on the archipelagos.

1. The ongoing biodiversity crisis entails the concomitant loss of species and the ecological services they provide. Global defaunation, and particularly the loss of frugivores, may negatively affect the seed dispersal of fleshy-fruited plant species, with predictable stronger impacts in simplified communities such as those on oceanic islands. However, logistical difficulties have hindered the experimental and theoretical need to disentangle the roles of species identity, richness (i.e. number of species) and abundance. Consequently, studies to date have focused exclusively on the loss of species richness leaving us largely ignorant regarding how species identity and abundance affect the loss of ecosystem functions.

2. Here, we applied a network approach to disentangle the effects of disperser abundance, richness and identity on the seed dispersal service provided by frugivores to the Galapagos plant community.

3. We found that both abundance and richness of the dispersers significantly affect the function of seed dispersal and that richness becomes increasingly important as disperser abundance declines. Extinction simulations revealed that the order of species loss has profound implications to the plant community. On the one hand, abundant generalist dispersers like the Galapagos lizards, can mitigate the loss of specialized dispersers. On the other hand, specific threats affecting key dispersers can lead to the rapid collapse of the community-level dispersal services.

4. Our results suggest that the identity of the disperser species lost can have a large effect on the number of plant species dispersed, and generalist species are essential to the persistence of the community dispersal service. Both abundance and species richness of seed dispersers are key and synergistic drivers of the number of plant species dispersed. Consequently, the coupled negative effect of population declines and species extinctions in frugivore assemblages may lead to an accelerated loss of the seed dispersal function.

Seed dispersal and seedling recruitment are crucial phases in the life cycle of all spermatophyte plants. The net contribution of seed dispersers to plant establishment is known as seed dispersal effectiveness (SDE) and is defined as the product of a quantitative (number of seeds dispersed) and a qualitative (probability of recruitment) component. In Galapagos, we studied the direct contribution to SDE (number of seeds dispersed and effect on seedling emergence) provided by the five island groups of frugivores (giant tortoises, lizards, medium-sized passerine birds, small non-finch passerine birds, and finches) in the two main habitats in this archipelago: the lowland and the highland zones, and found 16 vertebrate species dispersing 58 plant species. Data on frequency of occurrence of seeds in droppings and number of seeds dispersed per unit area produced contrasting patterns of seed dispersal. Based on the former, giant tortoises and medium-sized passerines were the most important seed dispersers. However, based on the latter, small non-finch passerines were the most important dispersers, followed by finches and medium-sized passerines. The effect of disperser gut passage on seedling emergence varied greatly depending on both the disperser and the plant species. Although the contribution to SDE provided by different disperser guilds changed across plant species, medium-sized passerines (e.g., mockingbirds) provided a higher contribution to SDE than lava lizards in 10 out of 16 plant species analysed, whereas lava lizards provided a higher contribution to SDE than birds in five plant species. While both the quantitative and qualitative components addressed are important, our data suggests that the former is a better predictor of SDE in the Galapagos archipelago.