The temporal dynamics of resource use by frugivorous birds: a network approach

Ecological network patterns are influenced by diverse processes that operate at different temporal rates. Here we analyzed whether the coupled effect of local abundance variation, seasonally phenotypic plastic responses, and species evolutionary adaptations might act in concert to shape network patterns. We studied the temporal variation in three interaction properties of bird species (number of interactions per species, interaction strength, and interaction asymmetry) in a temporal sequence of 28 plant frugivore interaction networks spanning two years in a Mediterranean shrubland community. Three main hypotheses dealing with the temporal variation of network properties were tested, examining the effects of abundance, switching behavior between alternative food resources, and morphological traits in determining consumer interaction patterns. Our results demonstrate that temporal variation in consumer interaction patterns is explained by short-term variation in resource and bird abundances and seasonal dietary switches between alternative resources (fleshy fruits and insects). Moreover, differences in beak morphology are associated with differences in switching behavior between resources, suggesting an important role of foraging adaptations in determining network patterns. We argue that beak shape adaptations might determine generalist and specialist feeding behaviors and thus the positions of consumer species within the network. Finally, we provide a preliminary framework to interpret phylogenetic signal in plant animal networks. Indeed, we show that the strength of the phylogenetic signal in networks depends on the relative importance of abundance, behavioral, and morphological variables. We show that these variables strongly differ in their phylogenetic signal. Consequently, we suggest that moderate and significant phylogenetic effects should be commonly observed in networks of species interactions. Read More: http://www.esajournals.org/doi/abs/10.1890/07-1939.

Self-organization, scaling and collapse in a coupled automaton model of foragers and vegetation resources with seed dispersal

We introduce a model of traveling agents ({\it e.g.} frugivorous animals) who feed on randomly located vegetation patches and disperse their seeds, thus modifying the spatial distribution of resources in the long term. It is assumed that the survival probability of a seed increases with the distance to the parent patch and decreases with the size of the colonized patch. In turn, the foraging agents use a deterministic strategy with memory, that makes them visit the largest possible patches accessible within minimal travelling distances. The combination of these interactions produce complex spatio-temporal patterns. If the patches have a small initial size, the vegetation total mass (biomass) increases with time and reaches a maximum corresponding to a self-organized critical state with power-law distributed patch sizes and L\'evy-like movement patterns for the foragers. However, this state collapses as the biomass sharply decreases to reach a noisy stationary regime characterized by corrections to scaling. In systems with low plant competition, the efficiency of the foraging rules leads to the formation of heterogeneous vegetation patterns with $1/f^{\alpha}$ frequency spectra, and contributes, rather counter-intuitively, to lower the biomass levels.Comment: 11 pages, 5 figure

Parasitoid and ant interactions of some Iberian butterflies (Insecta: Lepidoptera)

As a result of recent field studies in the Iberian Peninsula, interactions between 17 parasitoid taxa and 17 butterfly species, and 9 species of Lycaenidae and 15 species of Formicidae are detailed and discussed. Several of these, which are presented quantitatively, are otherwise unrecorded in the literature, while others confirm previous records. Attention is drawn to the need for the deposition of voucher material and both carefully and prolonged quantitative recording in order to understand and conserve these vulnerable aspects of biodiversit

Dispersal of the monarch butterfly (Danaus plexippus) over southern Spain from its breeding grounds

Dispersión de la mariposa monarca (Danaus plexippus) en el sur de España desde las zonas de apareamiento Durante el período comprendido entre los años 2000 y 2016, se detectaron mariposas monarca en 127 lugares fuera de las zonas costeras donde se reproducen habitualmente en el sur de la península ibérica. Estos datos se obtuvieron en verano e invierno, coincidiendo con la máxima abundancia de individuos y la mayor proporción de sitios ocupados en sus zonas de reproducción cercanas al estrecho de Gibraltar. Los individuos que se dispersan no tienen ninguna posibilidad de establecer nuevas colonias en estos sitios porque las plantas en las que ponen los huevos no crecen en las localidades en las que fueron detectados. Sin embargo, estos movimientos de dispersión podrían ser la causa de la colonización de plantas alimentarias que crecen en otras zonas de la península ibérica y en otros países del Mediterráneo.From 2000–2016, monarch butterflies were detected at 127 locations away from their usual coastal breeding areas in the south of the Iberian peninsula. These findings were recorded in the summer–autumn period, coinciding with the highest abundance of individuals and the highest proportion of patches occupied in their reproduction areas near the Strait of Gibraltar. These dispersing individuals have no chance of successfully establishing new colonies at these sites because the food plants for egg laying do not grow in the localities where they were detected. However, these dispersive movements could be the source of their successful colonisation on food plants growing in other areas of the Iberian peninsula and in other Mediterranean countries.Dispersión de la mariposa monarca (Danaus plexippus) en el sur de España desde las zonas de apareamiento Durante el período comprendido entre los años 2000 y 2016, se detectaron mariposas monarca en 127 lugares fuera de las zonas costeras donde se reproducen habitualmente en el sur de la península ibérica. Estos datos se obtuvieron en verano e invierno, coincidiendo con la máxima abundancia de individuos y la mayor proporción de sitios ocupados en sus zonas de reproducción cercanas al estrecho de Gibraltar. Los individuos que se dispersan no tienen ninguna posibilidad de establecer nuevas colonias en estos sitios porque las plantas en las que ponen los huevos no crecen en las localidades en las que fueron detectados. Sin embargo, estos movimientos de dispersión podrían ser la causa de la colonización de plantas alimentarias que crecen en otras zonas de la península ibérica y en otros países del Mediterráneo

Gomphocarpus R. Br. (Apocynaceae sufma. Asclepiadoideae) en Andalucía Occidental

Se da a conocer la presencia en Andalucía Occidental de Gomphocarpus physocarpus E. Mey., un neófi to originario del E y S de África. Se comenta la fenología de la fl oración y fructifi cación, así como la capacidad de dispersión de las plantas en las poblaciones naturalizadas, y se comparan con las de G. fruticosus (L.) T.W. Aiton, también presente en el territorio. Se discute el carácter invasor de las tres especies de Asclepiadaceae citadas en el texto.In this article the neophyte Gomphocarpus physocarpus E.Mey., widely distributed in SE Africa, is fi rst cited in western Andalucía (southern Spain). The flowering and fruit ripening phenology and dispersal potential of plants in different naturalized populations are described and compared with that of G. fruticosus (L.) T.W. Aiton also present in this territory. The invasive potential of the three Asclepiadaceae species here considered is also discussed.Fundación MIGRE

El derecho a disfrutar de un medio ambiente adecuado: elementos para su articulación expansiva

El presente estudio nace de la amable invitación de los Profesores Ballesteros y Bellver Capella. Constituye un intento de síntesis y de revisión de anteriores trabajos. La construcción del derecho a disfrutar de un medio ambiente adecuado como derecho subjetivo es posible en nuestro ordenamiento jurídico. Esta construcción, apenas hoy esbozada, posee un indudable potencial expansivo en sus consecuencias, y, pese a no estar exenta de problemas, puede ser un producto exportable a otros ordenamientos nacionales (aunque también a una posible Constitución de la Unión Europea y, exagerando el optimismo, a una Constitución planetaria en el seno de una paz perpetua renovada)

Frugivore species maintain their structural role in the trophic and spatial networks of seed dispersal interactions

1. Trophic relationships have inherent spatial dimensions associated with the sites where species interactions, or their delayed effects, occur. Trophic networks among interacting species may thus be coupled with spatial networks linking species and habitats whereby animals connect patches across the landscape thanks to their high mobility. This trophic and spatial duality is especially inherent in processes like seed dispersal by animals, where frugivores consume fruit species and deposit seeds across habitats. 2. We analysed the frugivore–plant interactions and seed deposition patterns of a diverse assemblage of frugivores in a heterogeneous landscape in order to determine whether the roles of frugivores in network topology are correlated across trophic and spatial networks of seed dispersal. 3. We recorded fruit consumption and seed deposition by birds and mammals during 2 years in the Cantabrian Range (N Spain). We then constructed two networks of trophic (i.e. frugivore–plant) and spatial (i.e. frugivore–seed deposition habitat) interactions and estimated the contributions of each frugivore species to the network structure in terms of nestedness, modularity and complementary specialization. We tested whether the structural role of frugivore species was correlated across the trophic and spatial networks, and evaluated the influence of each frugivore abundance and body mass in that relationship. 4. Both the trophic and the spatial networks were modular and specialized. Trophic modules matched medium-sized birds with fleshy-fruited trees, and small bird and mammals with small-fruit trees and shrubs. Spatial modules associated birds with woody canopies, and mammals with open habitats. Frugivore species maintained their structural role across the trophic and spatial networks of seed dispersal, even after accounting for frugivore abundance and body mass. 5. The modularity found in our system points to complementarity between birds and mammals in the seed dispersal process, a fact that may trigger landscape-scale secondary succession. Our results open up the possibility of predicting the consumption pattern of a diverse frugivore community, and its ecological consequences, from the uneven distribution of fleshy-fruit resources in the landscape

Demographic limitation processes

20 páginas, 2 figuras, 1 tabla, 3 cuadros.-- Editor: Valladares, F.[ES]: Procesos de limitación demográfica. Este capítulo ofrece una revisión de los factores que afectan a la regeneración natural de la vegetación, considerando la serie de etapas demográficas que determinan la dinámica demográfica de una pobla- ción. Son muy escasos los estudios disponibles que analizan toda la serie de eventos concatenados entre la producción de flores y frutos y el establecimiento exitoso de una planta adulta reproductiva. También son escasos los trabajos que permiten establecer los efectos aplazados que tienen las interacciones con animales a lo largo del ciclo de regeneración. La aproximación que proponemos cuantifica las pérdidas de propágulos en cada etapa demográfica e identifica “cuellos de botella” del reclutamiento que pue- den colapsar la regeneración natural de una especie. Revisamos una serie de casos de estudio que ilustran diversos procesos de limitación demográfica. El uso de técnicas explícitamente demográficas es fundamental para comprender la evolución de las especies forestales Mediterráneas y para diseñar actuaciones de preservación de sus poblaciones y de su extraordinaria diversidad.[EN]: We review the main factors influencing recruitment limitation in Mediterranean woody species by considering the sequential stages that determine the demographic cycle. Very few studies examine the whole set of demographic stages, from flower production to the successful establishment of adult reproductive plants, and their influence on recruitment. There are also few studies exploring the delayed effects of animal interactions throughout the regeneration cycle, but the information on stage-specific effects is more detailed. We propose an approach that quantifies the propagule losses at each sequential demographic stage and identifies demographic bottlenecks that might collapse population growth. We review a series of case studies illustrating different limitation processes. The use of explicit demographic techniques is central to understand the evolution of Mediterranean woody species and to design sound, ecologically-based, conservation plans to preserve their extraordinary diversity.Juan Arroyo agradece la financiación otorgada a los proyectos 4474-91 (National Geographic Society), PB 91-0894, PB95-0551, 1FD97-0743-CO3-03, PB98-1144, BOS200307924-CO2-01 (MECD, MCyT). Los trabajos de Pedro Jordano han sido financiados con proyectos MECD y MCyT (1FD97-0743-CO3-01, PB 96-0857, BOS2000-1366-C02-01 y REN2003-00273), así como la Junta de Andalucía (PAI). Juan Luis García-Castaño estuvo financiado durante su período pre-doctoral con una beca FPU, AP96-27318040. El trabajo de Fernando Pulido ha sido parcialmente financiado por una beca FPI de la Junta de Extremadura y los proyectos regional IPR-0A050 y estatal BOS2002- 12222-E del Ministerio de Ciencia y Tecnología. Los trabajos de Patricio García-Fayos han sido financiados con proyectos MCyT (1FD97-0551), de la Generalitat Valenciana (02-046) y de la Institució Alfons el Magnánim (02-046)Peer reviewe

Cascading Dynamics in Modular Networks

In this paper we study a simple cascading process in a structured heterogeneous population, namely, a network composed of two loosely coupled communities. We demonstrate that under certain conditions the cascading dynamics in such a network has a two--tiered structure that characterizes activity spreading at different rates in the communities. We study the dynamics of the model using both simulations and an analytical approach based on annealed approximation, and obtain good agreement between the two. Our results suggest that network modularity might have implications in various applications, such as epidemiology and viral marketing.Comment: 5 pages, 4 figure