RESUMO
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.
Assuntos
Lagartos/fisiologia , Plantas/classificação , Polinização/fisiologia , Distribuição Animal , Animais , Ecossistema , EquadorRESUMO
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.
Assuntos
Aves , Flores/anatomia & histologia , Magnoliopsida , Animais , Equador , InsetosRESUMO
The role of the most common land iguana (Conolophus subcristatus) in the Galápagos Islands as an effective seed disperser is explored in this study. A total of 5705 seeds of 32 plant species were identified from 160 scats, 4545 of which (80%) appeared visually undamaged. Germination trials of 849 seeds from 29 species revealed that at least 10 species remained viable after passing through the iguana's gut, although only a small proportion of those seeds (4%) germinated. In any case, we argue that C. subcristatus exerts an important role on the 7 Galapagos islands where it occurs because of its abundance and capacity to ingest and disperse seeds at long distances. Our results strongly suggest that the Galápagos C. subcristatus plays an important role as a seed disperser of not only of native species but also some introduced plants in the Galápagos Islands.
Assuntos
Germinação , Iguanas/fisiologia , Dispersão de Sementes , Sementes/fisiologia , Animais , Equador , FezesRESUMO
Owing to food scarcity and to the high densities that vertebrates often reach on islands, typical insect- and seed-eaters widen their feeding niche and interact with a greater fraction of species than their mainland counterparts. This phenomenon, coined here 'interaction release', has been previously reported for single species but never for an entire community. During 4 years, we gathered data on bird-flower visitation on 12 Galápagos islands. We show that all sampled land birds exploit floral resources and act as potential pollinators across the entire archipelago, in all major habitats and all year round. Although species and link composition varies among islands, strong interaction release takes place on all islands, making their bird-flower network highly generalized. Interaction release is crucial to the survival of native birds but simultaneously threatens the unique biodiversity of this archipelago, as the birds also visit invading plants, likely facilitating their integration into pristine native communities.
Assuntos
Aves/fisiologia , Flores/fisiologia , Dispersão Vegetal/fisiologia , Polinização/fisiologia , Animais , Biodiversidade , Comportamento Competitivo/fisiologia , Equador , Comportamento Alimentar/fisiologia , Cadeia Alimentar , Insetos/fisiologia , Espécies Introduzidas/tendências , PlantasRESUMO
Colonization across the Galápagos Islands by the carpenter bee (Xylocopa darwini) was reconstructed based on distribution of mitochondrial haplotypes (cytochrome oxidase II (COII) sequences) and haplotype lineages. A total of 12 haplotypes were found in 118 individuals of X. darwini. Distributional, phylogenetic and phylogeographic analyses suggest early colonization of most islands followed by historical isolation in two main groups: eastern and central-western islands. Evidence of recurrent inter-island colonization of haplotypes is largely lacking, despite strong flight capability and ecological amplitude of the species. Recent palaeogeographic data suggest that several of the current islands were connected in the past and thus the isolation pattern may have been even more pronounced. A contrast analysis was also carried out on 10 animal groups of the Galápagos Islands, and on haplotype colonization of seven animal and plant species from several oceanic archipelagos (the Galápagos, Azores, Canary Islands). New colonization metrics on the number of potential vs. inferred colonization events revealed that the Galápagos carpenter bee shows one of the most significant examples of geographic isolation.
Assuntos
Abelhas/genética , Animais , Abelhas/classificação , DNA Mitocondrial/análise , Ecologia , Equador , Variação Genética , Haplótipos , Filogenia , Filogeografia , Análise de Sequência de DNARESUMO
The unique biodiversity of most oceanic archipelagos is currently threatened by the introduction of alien species that can displace native biota, disrupt native ecological interactions, and profoundly affect community structure and stability. We investigated the threat of aliens on pollination networks in the species-rich lowlands of five Galápagos Islands. Twenty per cent of all species (60 plants and 220 pollinators) in the pooled network were aliens, being involved in 38 per cent of the interactions. Most aliens were insects, especially dipterans (36%), hymenopterans (30%) and lepidopterans (14%). These alien insects had more links than either endemic pollinators or non-endemic natives, some even acting as island hubs. Aliens linked mostly to generalized species, increasing nestedness and thus network stability. Moreover, they infiltrated all seven connected modules (determined by geographical and phylogenetic constraints) of the overall network, representing around 30 per cent of species in two of them. An astonishingly high proportion (38%) of connectors, which enhance network cohesiveness, was also alien. Results indicate that the structure of these emergent novel communities might become more resistant to certain type of disturbances (e.g. species loss), while being more vulnerable to others (e.g. spread of a disease). Such notable changes in network structure as invasions progress are expected to have important consequences for native biodiversity maintenance.
Assuntos
Biota , Insetos/fisiologia , Magnoliopsida/fisiologia , Polinização , Animais , Conservação dos Recursos Naturais , Clima Desértico , Equador , Espécies IntroduzidasRESUMO
Alien plants are a growing threat to the Galápagos unique biota. We evaluated the impact of alien plants on eight seed dispersal networks from two islands of the archipelago. Nearly 10 000 intact seeds from 58 species were recovered from the droppings of 18 bird and reptile dispersers. The most dispersed invaders were Lantana camara, Rubus niveus and Psidium guajava, the latter two likely benefiting from an asynchronous fruit production with most native plants, which facilitate their consumption and spread. Lava lizards dispersed the seeds of 27 species, being the most important dispersers, followed by small ground finch, two mockingbirds, the giant tortoise and two insectivorous birds. Most animals dispersed alien seeds, but these formed a relatively small proportion of the interactions. Nevertheless, the integration of aliens was higher in the island that has been invaded for longest, suggesting a time-lag between alien plant introductions and their impacts on seed dispersal networks. Alien plants become more specialized with advancing invasion, favouring more simplified plant and disperser communities. However, only habitat type significantly affected the overall network structure. Alien plants were dispersed via two pathways: dry-fruited plants were preferentially dispersed by finches, while fleshy fruited species were mostly dispersed by other birds and reptiles.
Assuntos
Aves/fisiologia , Cadeia Alimentar , Preferências Alimentares , Espécies Introduzidas , Répteis/fisiologia , Dispersão de Sementes , Animais , Dieta , Equador , Frutas/fisiologia , Modelos Lineares , Modelos Biológicos , Dinâmica Populacional , Estações do AnoRESUMO
The Galápagos are considered a model oceanic archipelago, with unique flora and fauna currently threatened by alien invasive species. Seed dispersal is an important ecosystem function with consequences for plant population dynamics and vegetation structure. Hence, understanding the seed dispersal abilities of the assemblages of frugivores will inform scientists and managers of the dynamics of plant invasions and improve management planning. Here we provide the first comprehensive review of published information on frugivory and animal seed dispersal in the Galápagos. We collected data from a variety of sources, including notes of the first naturalist expeditions, gray literature available only in Galápagos collections, and peer-reviewed journal articles. Plant-animal frugivorous interactions were retrieved from 43 studies and compiled into an interaction matrix describing 366 unique interactions. Most studies focused on fruit consumption as a driving force for natural selection, but seed fate was seldom considered. Although most (71%) of the interactions involved native plants, more than one-quarter (28%) involved introduced species. Interactions involving birds are considerably more common than those of reptiles and mammals, probably reflecting a research bias towards birds. Despite the historical importance of the archipelago as the laboratory for evolutionary and ecological research, understanding of its seed dispersal systems is limited. We end the review by suggesting 3 priority areas of research on frugivory and seed dispersal in the Galápagos: (i) target research to close knowledge gaps; (ii) the use of a network approach to frame seed dispersal at the community level; and (iii) evaluation of the effect of seed dispersal as a selective pressure acting upon plants and frugivores. Finally, the output of this research has to be properly delivered to the Galápagos National Park Services to help increase management effectiveness.
Assuntos
Comportamento Alimentar , Frutas , Dispersão de Sementes , Animais , Aves , Dieta , Equador , Espécies Introduzidas , Mamíferos , Dinâmica Populacional , RépteisRESUMO
DNA extraction methods for genotyping non-invasive samples have led to great advances in molecular research for ecological studies, and have been particularly useful for analyzing threatened species. However, scarce amounts of fragmented DNA and the presence of Taq polymerase inhibitors in non-invasive samples are potential problems for subsequent PCR amplifications. In this study we describe a novel technique for extracting DNA from alimentary tract cells found on external surfaces of feces and regurgitated seeds. The presence of contaminants and inhibitors is minimized and samples are preserved intact for use in other ecological research (e.g. trophic studies). The amplification efficiency and purity of the extracted DNA from feces were significantly higher than in commonly used extraction procedures. Moreover, DNA of two bird species was identified from seeds expelled by regurgitation. Therefore, this method may be suitable for future ecological studies of birds, and other vertebrate groups.
Assuntos
Columbidae/classificação , DNA Mitocondrial/isolamento & purificação , Fezes/química , Sementes/química , Animais , Columbidae/genética , Filtração/instrumentação , Genótipo , Reação em Cadeia da PolimeraseRESUMO
DNA extraction methods for genotyping non-invasive samples have led to great advances in molecular research for ecological studies, and have been particularly useful for analyzing threatened species. However, scarce amounts of fragmented DNA and the presence of Taq polymerase inhibitors in non-invasive samples are potential problems for subsequent PCR amplifications. In this study we describe a novel technique for extracting DNA from alimentary tract cells found on external surfaces of feces and regurgitated seeds. The presence of contaminants and inhibitors is minimized and samples are preserved intact for use in other ecological research (e.g. trophic studies). The amplification efficiency and purity of the extracted DNA from feces were significantly higher than in commonly used extraction procedures. Moreover, DNA of two bird species was identified from seeds expelled by regurgitation. Therefore, this method may be suitable for future ecological studies of birds, and other vertebrate groups.