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Despite it is widely accepted that intrapopulation variation is fundamental to ecological and evolutionary processes, this level of information has only recently been included into network analysis of species/population interactions. When done, it has revealed non-random patterns in the distribution of trophic resources. Nestedness in resource use among individuals is the most recurrent observed pattern, often accompanied by an absence of modularity, but no previous studies examine bipartite modularity. We use network analysis to describe the diet composition of the Balearic endemic lizard Podarcis lilfordi in 2 islets at population and individual levels, based on the occurrence of food items in fecal samples. Our objectives are to 1) compare niche structure at both levels, 2) characterize niche partition using nestedness and modularity, and 3) assess how size, sex, season, and spatial location influence niche structure. At population-level niche width was wide, but narrow at the level of the individual. Both islet networks were nested, indicating similar ranking of the food preferences among individuals, but also modular, which was partially explained by seasonality. Sex and body size did not notably affect diet composition. Large niche overlap and therefore possibly relaxed competition were observed among females in one of the islets and during spring on both islets. Likewise, higher modularity in autumn suggests that higher competition could lead to specialization in both populations, because resources are usually scarce in this season. The absence of spatial location influence on niche might respond to fine-grained spatio-temporally distribution of food resources. Behavioral traits, not included in this study, could also influence resource partitioning.

[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, [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, [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- compat

Many Mediterranean beaches accumulate wrack of Posidonia oceanica L. leaves and rhizomes, creating an ecotone between marine and terrestrial systems that provides essential ecosystem services (e.g. shoreline protection, nutrient supply to adjacent dune systems). However, little is still known about the diversity of macrofauna that lives in this wrack and how its community structure varies in space and time. In this study, we assessed the variation in macrofauna composition on three Mallorcan beaches (Balearic Islands, Western Mediterranean Sea) characterized by different geomorphological features. For an entire year, we seasonally sampled P. oceanica wrack on each beach and identified the animal species living in them. We found up to 20 different species belonging to four functional groups: (A) detritivores/fungivores/scavengers, (B) phytophagous, (C) secondary consumers, and (D) tertiary consumers. Species composition and diversity indices showed strong differences among beaches associated with wrack dynamism. Both variables revealed also a significant temporal variation, with highest individual abundance in summer and lowest in winter. Detritivores were the most abundant group, and their contribution to community structure represented over 75% through the study period. Springtails, in particular, contributed the most (45%) to spatial and temporal changes in community structure, followed by the oligochaete Enchytraeus sp. (12.6%) and the sand hopper Talitrus saltator (4.6%). Our study builds towards a more robust understanding of these marine-terrestrial ecotones, demonstrating the existence of complex and dynamic macrofauna communities which can provide more ecological information about the food webs of these ecosystems and the services they provide.

All organisms are ultimately dependent on a large diversity of consumptive and non-consumptive interactions established with other organisms, forming an intricate web of interdependencies. In 1992, when 1700 concerned scientists issued the first “World Scientists' Warning to Humanity”, our understanding of such interaction networks was still in its infancy. By simultaneously considering the species (nodes) and the links that glue them together into functional communities, the study of modern food webs – or more generally ecological networks – has brought us closer to a predictive community ecology. Scientists have now observed, manipulated, and modelled the assembly and the collapse of food webs under various global change stressors and identified common patterns. Most stressors, such as increasing temperature, biological invasions, biodiversity loss, habitat fragmentation, over-exploitation, have been shown to simplify food webs by concentrating energy flow along fewer pathways, threatening long-term community persistence. More worryingly, it has been shown that communities can abruptly change from highly diverse to simplified stable states with little or no warning. Altogether, evidence shows that apart from the challenge of tackling climate change and hampering the extinction of threatened species, we need urgent action to tackle large-scale biological change and specifically to protect food webs, as we are under the risk of pushing entire ecosystems outside their safe zones. At the same time, we need to gain a better understanding of the global-scale synergies and trade-offs between climate change and biological change. Here we highlight the most pressing challenges for the conservation of natural food webs and recent advances that might help us addressing such challenges.

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 intraspec

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.

This letter to the editor describes the surge of “photo-friendly” stacks of stones as an emerging tourism-associated threat to rock-dwelling biodiversity.

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.

[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.

1. One very conspicuous sign that warming is affecting the ecology of butterflies are the phenological advances occurring in many species. Moreover, rising temperatures are having a notable impact – both negative and positive – on population abundances. To date, patterns have generally been analysed at species level without taking into account possible differences between populations, which, when they are noted, are mostly attributed to large‐scale climate differences across a latitudinal gradient. 2. We use a long‐term database (18 years) of butterflies from five sites of the island of Menorca (Balearic Islands, Spain) to investigate how phenology and population dynamics have been affected by climate warming during the past two decades. 3. Both species' phenology and abundance respond differently to warming at a local scale depending on the season. Rising temperatures in spring give rise to greater advancement of the phenology, whereas warming affects population abundance negatively in summer. Additional variability of responses among sites suggests that habitats are involved in the modulation of the aforementioned seasonal effect. 4. We discuss how the effects of temperature could be partially offset in more inland habitats such as forests or deep ravines, especially the latter which represent particularly fresh and humid environments. The positive effect of temperature on ravine populations during the summer suggests that butterflies disperse across habitats as a response to rising temperatures during the season. This dispersal behaviour as a response to warming could be especially important in island ecosystems where the possibilities of modifying altitudinal or latitudinal distributions are often severely limited.

Pollination is thought to be under positive density‐dependence, destabilising plant coexistence by conferring fitness disadvantages to rare species. Such disadvantage is exacerbated by interspecific competition but can be mitigated by facilitation and intraspecific competition. However, pollinator scarcity should enhance intraspecific plant competition and impose disadvantage on common over rare species (negative density‐dependence, NDD). We assessed pollination proxies (visitation rate, pollen receipt, pollen tubes) in a generalised plant community and related them to conspecific and heterospecific density, expecting NDD and interspecific facilitation due to the natural pollinator scarcity. Contrary to usual expectations, all proxies indicated strong intraspecific competition for common plants. Moreover interspecific facilitation prevailed and was stronger for rare than for common plants. Both NDD and interspecific facilitation were modulated by specialisation, floral display and pollinator group. The combination of intraspecific competition and interspecific facilitation fosters plant coexistence, suggesting that pollination can be a niche axis maintaining plant diversity.

Understanding the response of ecological networks to perturbations and disruptive events is needed to anticipate the biodiversity loss and extinction cascades. Here, we study how network plasticity reshapes the topology of mutualistic networks in response to species loss. We analyze more than one hundred empirical mutualistic networks and considered random and targeted removal as mechanisms of species extinction. Network plasticity is modeled as either random rewiring, as the most parsimonious approach, or resource affinity-driven rewiring, as a proxy for encoding the phylogenetic similarity and functional redundancy among species. This redundancy should be positively correlated with the robustness of an ecosystem, as functions can be taken by other species once one of them is extinct. We show that effective modularity, i.e. the ability of an ecosystem to adapt or restructure, increases with increasing numbers of extinctions, and with decreasing the replacement probability. Importantly, modularity is mostly affected by the extinction rather than by rewiring mechanisms. These changes in community structure are reflected in the robustness and stability due to their positive correlation with modularity. Resource affinity-driven rewiring offers an increase of modularity, robustness, and stability which could be an evolutionary favored mechanism to prevent a cascade of co-extinctions.

Many vertebrate species act as both plant pollinators and seed-dispersers, thus interconnecting these processes, particularly on islands. Ecological multilayer networks are a powerful tool to explore interdependencies between processes; however, quantifying the links between species engaging in different types of interactions (i.e. inter-layer edges) remains a great challenge. Here, we empirically measured inter-layer edge weights by quantifying the role of individually marked birds as both pollinators and seed-dispersers of Galápagos plant species over an entire year. Although most species (80%) engaged in both functions, we show that only a small proportion of individuals actually linked the two processes, highlighting the need to further consider intra-specific variability in individuals' functional roles. Furthermore, we found a high variation among species in linking both processes, i.e. some species contribute more than others to the modular organization of the multilayer network. Small and abundant species are particularly important for the cohesion of pollinator seed-dispersal networks, demonstrating the interplay between species traits and neutral processes structuring natural communities.

Theoretical models indicate that the structure of plant–pollinator networks has important implications for the reproduction and survival of species. However, despite the growing information on the mechanisms underlying such a structure, it is still difficult to predict the functional consequences of species’ structural positions in these networks. From the plant perspective, species position and roles in pollination networks might be related to traits describing flower attractiveness, availability and dependence on pollinators. In turn, both network metrics and plant traits might influence plant species fitness. During two field seasons, we collected data from the 23 most abundant plant species in a rich coastal community, to evaluate the association between population and floral traits (floral abundance at population level and flowers per individual, flower shape and size, flowering length, nectar volume, pollinator dependence), species-level network metrics (linkage level, specialization –d′–, weighted closeness centrality, network roles related to modularity) and plant fitness (seeds/flower, seed weight). Flowering length, flower size, flower abundance and pollinator dependence were positively related to greater generalization, as measured by various indices. More abundant species and those with larger flowers showed higher linkage levels (i.e. higher number of pollinator species), whereas longer flowering periods were negatively related to d′ and positively related to closeness centrality and important roles in the network. Likewise, plants species more dependent on pollinators occupied more central positions in the network. Furthermore, centrality in the networks was significantly associated with plant fitness. Specifically, central species in the network produced more and heavier seeds than the others. However, other plant traits, such as flower size and pollinator dependence had additional direct effects on seed production. Synthesis. Our study highlights how

Nocturnal pollination plays an important role in sexual plant reproduction but has been overlooked, partially because of intrinsic difficulties in field experimentation. Even less attention has received the effect of within-inflorescence spatial position (distal or proximal) on nocturnal pollinators of columnar plants, despite numerous studies examining the relationship between such position and reproductive success. Woody endemic Echium simplex possesses large erect inflorescences bearing thousands of flowers which are visited by a wide array of diurnal and nocturnal animals. In this study, we identified nocturnal visitors and compared their pollination effectiveness with that of diurnal pollinators in different inflorescence sections by means of selective exclosures in NE Tenerife (Canary Islands). Nocturnal visitors included at least ten morphospecies of moths (such as Paradrina rebeli and Eupithecia sp.), two coleopteran species (mainly Alloxantha sp.), neuropterans (Chrysoperla carnea), dictyopterans (Phyllodromica brullei), dermapterans (Guanchia sp.) and julidans (Ommatoiulus moreletii). In general, plants excluded from pollinators set less fruits than open-pollination (control) plants which set fruits homogeneously across sections. Diurnally pollinated plants set more fruit in their upper parts whereas nocturnally pollinated plants set fruit in both upper and bottom sections. We conclude that although the frequency and diversity of diurnal pollinators is far higher than that of nocturnal pollinators, both exhibit different foraging behaviour that generates complementary effects on the reproductive success of E. simplex.

Introduced plants become decoupled from their usual pollinators and by relying on resident pollinator species or other reproductive strategies become established in new areas, spread and, eventually, invade. Here, using breeding system experiments, we studied the reproductive biology of the bird-pollinated South American species Nicotiana glauca across native and non-native areas, both inside and outside the range of flower-visiting birds. In the native range, where the species is visited by hummingbirds, open cross-pollinated flowers set as many seeds and almost as many fruits as open pollination controls, suggesting that pollinators make a major contribution to reproductive success. In South Africa, the flowers were pollinated by sunbirds which, although less efficiently, also contributed to N. glauca reproduction, replacing hummingbirds. In contrast, in Mallorca, where nectar feeding birds are absent, fruit production in open cross-pollinated flowers was near zero, and significantly lower than in open pollination controls, suggesting that reproduction is almost entirely by autonomous self-pollination. Hand-pollination experiments showed that the species is self-compatible throughout its range. Pollinator exclusion experiment showed that N. glauca relies on self-pollination only in pollinator poor areas, where plants have a much higher capacity for autonomous self-pollination than elsewhere. A reduction in anther-stigma distance does not seem to account the higher self-pollination capacity in the non-native environment without pollinators. Despite probable evolutionary adaptation, and flexibility in pollinator association and mating system, seed production in the introduced range was somewhat pollen limited, suggesting that the mismatch between N. glauca and its novel pollination environment might retard invasion.