Digestive ecology of two omnivorous Canarian lizard species (Gallotia, Lacertidae)

Omnivorous endemic Canarian lacertids (Gallotia atlantica and G. galloti) do not present any specific digestive and physiological adaptations to herbivorous diet, compared to species and populations with a different degree of herbivory in the Canarian archipelago. The only charactristics that could be related to the type of diet were the number of cusps per tooth (between species) and the number of small stones contained in droppings (between species and populations). The rest of measured traits were correlated with lizard size and for this reason G. galloti has longer intestines, heavier stomachs and livers, more teeth and cusps, and longer gut passage. These data suggets that body size is a major determinant of the reliance on plant food (mainly flesh fruits) in these lizards and facilitates mutualistic interactions with fleshy-fruited plant species.We thank Luisa Hernández and Manuel Valido "Pololo" for assisting We thank Luisa Hernández and Manuel Valido "Pololo" for assisting us during the follow up of the GPT experiments. Félix Medina "Feluco" and Juan Carlos Sánchez captured some lizards and provided us with preserved specimens, respectively. Jaime Urioste gave us insects during the GPT experimental period, and the Servicio Electrónico de la Universidad de La Laguna assembled the control system of the climatic chamber. Pedro Jordano helped us to plan the experiments and encouraged in several ways at all stages of development of this study. Mario Díaz and specially Pedro Jordano, Francisco Bozinovic, Donald B. Miles, Raoul Van Damme and two anonymous referees improved and initial manuscript with useful comments. The control system used in the GPT experiments was supported by Dirección General de Universidades e Investigación del Gobierno de Canarias (grant 93/150).Peer reviewe

Ecología de la dispersión de semillas por los lagartos endémicos canarios (G: Gallotia, Lacertidae)

Bajo una perspectiva ecológica y evolutiva, muestrala importancia de los lagartos endémicos canarios(Gallotia spp.,Lacertidae) en dispersión de semillas de plantas vasculares en las Islas Canarias. El análisis de la saurocoria se ha desarrollado en tres niveles de aproximación que difieren en el grado de profundidad tratado, pero estrechamente relacionados entre sí: patrones de frugivoría en lagartos, interacciones ecológicas e interacciones evolutivas. En la primera se aportan datos sobre la variabilidad espacial (entre hábitats) y temporal (a lo largo de un ciclo anual) del componente frugívoro en la dieta de los lagartos (G. Galloti), las consecuencias del tratamiento digestivo sobre la viabilidad y germinación de las semillas, así como de los caracteres anatómicos y fisiológicos del tracto digestivo de los lagartos al comparar poblaciones(G. Galloti) y especies(G.galloti y G.atlantica) que difieren en la importancia que muestra el componente vegetal en su dieta. En la segunda parte se compara, de forma simultánea, la efectividad(cuantitativa y cualitativa) en la dispersión de semillas del Balo(Plocama pendula, Rubiacesae) llevada a cabo por dos grupos de vertebrados frugívoros: lagartos (G. Galloti) y aves (Sylvia spp.). Para ello y durante dos años de estudio, se analizó las diferentes fases en el proceso de dispersión de semillas. En la tercera parte se expone los resultados obtenidos al analizar la interacción de los lagartos canarios con los frutos de la Orijama(Neochamaelea pulverulenta, Cneoraceae) bajo una perspectiva evolutiva. En ésta se analiza al signo y magnitud del patrón de selección fenotípica realizado por los lagartos en relación al tamaño de las semillas dispersadas. El fin de ésta es sugerir y demostrar la existencia de un proceso de cambios en el tamaño de las semillas por un proceso de selección natural dirigido y modulado por los lagartos como agentes mutualista

Downsized mutualisms: Consequences of seed dispersers' body-size reduction for early plant recruitment

© 2014 Geobotanisches Institut ETH, Stiftung Ruebel. Extinction-driven, body-size reduction of seed dispersers (i.e. an ecological downsizing resulting from severe defaunation) can entail the loss of unique ecological functions, and impair plant regeneration. However, the manner in which the downsizing of mutualistic animals affects seed dispersal and plant recruitment remains understudied. Here, we took advantage of a natural experiment in the Canarian archipelago to document the consequences of lizards body-size reduction (. Gallotia, Lacertidae) on the recruitment of Neochamaelea pulverulenta (Rutaceae), which relies exclusively on these frugivores for seed dispersal. Subsequent to the arrival of humans (ca. 2000-2500 yr BP), the extinction of large-bodied lizards generated a gradient of increasing defaunation on the three islands inhabited by this plant. We hypothesized a significant reduction, and eventually collapse, of early seedling recruitment mirroring the defaunation intensity of the frugivores. We sampled 42 populations spanning the whole geographic range of the plant to examine the quantitative (age structure pattern) and qualitative components (proportion of seedlings growing outside the canopy, number of seedlings established outside the canopy relative to the number of adults - effective recruitment rate, and seedling vigour) of plant regeneration. Our results show that the age structure patterns did not differ among the three contrasted insular scenarios. However, we found significant reductions in seedling recruitment outside the canopy, effective recruitment rate, and delayed negative effects on seedling vigour in populations hosting small- to medium-sized lizard species. Thus, extirpation of large seed-dispersers did not cause substantial reductions in quantitative components of seed dispersal, but determined declines in qualitative aspects impairing dispersal effectiveness. Our study highlights the importance of examining all components of the dispersal and recruitment process to properly document the regeneration outcomes of plants in defaunated, downsized ecological scenarios.Peer Reviewe

Adaptation of flower and fruit colours to multiple, distinct 1 mutualists

Communication in plant–animal mutualisms frequently involves multiple perceivers. A fundamental uncertainty is whether and how species adapt to communicate with groups of mutualists having distinct sensory abilities. We quantified the colour conspicuousness of flowers and fruits originating from one European and two South American plant communities, using visual models of pollinators (bee and fly) and seed dispersers (bird, primate and marten). We show that flowers are more conspicuous than fruits to pollinators, and the reverse to seed dispersers. In addition, flowers are more conspicuous to pollinators than to seed dispersers and the reverse for fruits. Thus, despite marked differences in the visual systems of mutualists, flower and fruit colours have evolved to attract multiple, distinct mutualists but not unintended perceivers. We show that this adaptation is facilitated by a limited correlation between flower and fruit colours, and by the fact that colour signals as coded at the photoreceptor level are more similar within than between functional groups (pollinators and seed dispersers). Overall, these results provide the first quantitative demonstration that flower and fruit colours are adaptations allowing plants to communicate simultaneously with distinct groups of mutualists.Peer reviewe

Frugivory and Seed Dispersal by Lizards: A Global Review

Birds and mammals are the only vertebrates which receive comprehensive attention in studies of dispersal of fleshy-fruited plant species. However, recently the importance of fleshy fruit in the diet of lizards (order Squamata: suborder Sauria), and their role as seed dispersers have been recognized in a number of studies, especially in studies from arthropod-poor habitats, such as oceanic islands. Here, we revisit the evidence of fruit-eating lizards on a global scale in order to test if fruit consumption is more common on islands than expected by chance. We constructed a database of 470 lizard species (from a global count of 6,515 species), that have been reported to consume fleshy fruits. This set of lizards belong to 27 families with Scincidae (N = 78 species), Gekkonidae (69), and Dactyloidae (55) having more frugivorous species than other lizard families. We found that 62.4% of these lizards inhabit islands, whereas only one third (35.3%) of all lizard species inhabit islands. These values support the presence of an “insular phenomenon,” however; we also tested if this biogeographical pattern might be driven by body size and evolutionary history of lizards. Thus, we looked for any phylogenetic signals in the distributions of lizard body size, island-presence, and frugivory and calculated phylogenetically corrected correlations among the three variables on a global subset of 2,417 lizard species for which we had detailed phylogenetic information. Both lizard body size and island-presence were weakly influenced by phylogeny; whereas, frugivory was not. In addition, we found that (1) body size and frugivory were weakly positively correlated; (2) body size and island-presence were uncorrelated; and (3) island-presence and frugivory were strongly positively correlated. Thus, we conclude that the main driver of frugivory on islands is the specific island environment and not lizard body size per se. Islands are said to be poor in arthropods and predators, and this may force/allow island lizards to forage for additional food sources, such as fleshy fruits. We also suggest that modern lizards as well as their ancestors may potentially play an important role to many plants as seed dispersers. However, we do not known how tight the correlation is between frugivory and seed dispersal. Thus, lizards repeatedly inspire us to ask new ecological and evolutionary questions

The role of the brown bear Ursus arctos as a legitimate megafaunal seed disperser

Megafaunal frugivores can consume large amounts of fruits whose seeds may be dispersed over long distances, thus, affecting plant regeneration processes and ecosystem functioning. We investigated the role of brown bears (Ursus arctos) as legitimate megafaunal seed dispersers. We assessed the quantity component of seed dispersal by brown bears across its entire distribution based on information about both the relative frequency of occurrence and species composition of fleshy fruits in the diet of brown bears extracted from the literature. We assessed the quality component of seed dispersal based on germination experiments for 11 fleshy-fruited plant species common in temperate and boreal regions and frequently eaten by brown bears. Across its distribution, fleshy fruits, on average, represented 24% of the bear food items and 26% of the total volume consumed. Brown bears consumed seeds from at least 101 fleshy-fruited plant species belonging to 24 families and 42 genera, of which Rubus (Rosaceae) and Vaccinium (Ericaceae) were most commonly eaten. Brown bears inhabiting Mediterranean forests relied the most on fleshy fruits and consumed the largest number of species per study area. Seeds ingested by bears germinated at higher percentages than those from whole fruits, and at similar percentages than manually depulped seeds. We conclude that brown bears are legitimate seed dispersers as they consume large quantities of seeds that remain viable after gut passage. The decline of these megafaunal frugivores may compromise seed dispersal services and plant regeneration processes.This study was supported by the BearConnect project funded by the National Science Centre in Poland, (2016/22/Z/NZ8/00121) through the 2015–2016 BiodivERsA COFUND call for research proposals, with the national funders ANR/DLR-PT/UEFISCDI/NCN/RCN. Additional funding from the Polish Ministry of Science and Higher Education (project NN304-294037, NS), the National Science Centre in Poland (project DEC-2013/08/M/NZ9/00469, NS), the National Centre for Research and Development (GLOBE, POL-NOR/198352/85/2013, NS, JA) is also acknowledged.Peer reviewe

Body size in ecological networks

Body size determines a host of species traits that can affect the structure and dynamics of food webs, and other ecological networks, across multiple scales of organization. Measuring body size provides a relatively simple means of encapsulating and condensing a large amount of the biological information embedded within an ecological network. Recently, important advances have been made by incorporating body size into theoretical models that explore food web stability, the patterning of energy fluxes, and responses to perturbations. Because metabolic constraints underpin body-size scaling relationships, metabolic theory offers a potentially useful new framework within which to develop novel models to describe the structure and functioning of ecological networks and to assess the probable consequences of biodiversity change. © 2005 Elsevier Ltd. All rights reserved.Peer Reviewe

Anolis allisoni (Allison's Anole/Camaleón Azul). Nectar feeding.

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