Linkage Rules for Plant–Pollinator Networks: Trait Complementarity or Exploitation Barriers?

9 pages.-- Final full-text version of the paper also available at: http://dx.doi.org/10.1371/journal.pbio.0050031.Recent attempts to examine the biological processes responsible for the general characteristics of mutualistic networks focus on two types of explanations: nonmatching biological attributes of species that prevent the occurrence of certain interactions ("forbidden links"), arising from trait complementarity in mutualist networks (as compared to barriers to exploitation in antagonistic ones), and random interactions among individuals that are proportional to their abundances in the observed community ("neutrality hypothesis"). We explored the consequences that simple linkage rules based on the first two hypotheses (complementarity of traits versus barriers to exploitation) had on the topology of plant–pollination networks. Independent of the linkage rules used, the inclusion of a small set of traits (two to four) sufficed to account for the complex topological patterns observed in real-world networks. Optimal performance was achieved by a "mixed model" that combined rules that link plants and pollinators whose trait ranges overlap ("complementarity models") and rules that link pollinators to flowers whose traits are below a pollinator-specific barrier value ("barrier models"). Deterrence of floral parasites (barrier model) is therefore at least as important as increasing pollination efficiency (complementarity model) in the evolutionary shaping of plant–pollinator networks.Funding by the Spanish Ministry of Science and Technology (project INVASRED, REN2003–06962) is acknowledged.Peer reviewe

Effects of begging on growth rates of nestling chicks

We investigated whether an increase in begging levels delays growth of chicks. In experiment 1, we hand-reared nine pairs of ring dove squabs, divided into a control and a begging group. All squabs received similar amounts of food, but those in the begging group had to beg for a prolonged period in order to be fed, while squabs in the control group received food without begging. Squabs stopped responding to the treatment after 10 days and, at that time, there was no effect of induced begging on their body mass. In experiment 2, we hand-reared 27 pairs of magpie chicks for 3 days. The design of experiment 2 was similar to that of experiment 1. Daily food intake and begging affected growth rates. On average, chicks in the begging group grew 0.8 g/day less than control chicks, which represents a decrease of 8.15% in growth rate. Because growth is usually positively associated with expected fitness, this demonstrates that begging is a costly behavior, an assumption routinely made in models of begging behavior.Peer Reviewe

How foraging behaviour and resource partitioning can drive the evolution of flowers and the structure of pollination networks

11 páginas, 1 figura. --. Artículo bajo licencia Creative Commons Attribution.Many flowers are visited by a large array of pollinators, often belonging to different taxonomic groups, and many pollinator species visit a wide array of flowers with different morphologies. This observation has led pollination ecologists to question the role played by pollinators in flower diversification and the extent to which floral similarities reflect convergent evolution to specific pollinator assemblages rather than other factors, such as phylogenetic constraints. In this paper, we review several ecological and evolutionary models that help to explain how pollinators can play a key role in floral evolution despite heterogeneities in plant-pollinator interactions. Our basic tenant is that, in animal pollinated species, the trajectory of pollen grains is determined by the foraging strategy of pollinators. Starting from a first approximation based on optimal foraging theory, ecological models related to the principles behind the ideal free distribution can be used to predict differences in floral and pollinator traits that will lead to resource partitioning. Building upon these results, evolutionary models based on game theory can be used to predict changes in traits of flowers and pollinators. These models show that pollinators can drive the evolution of floral divergence in the presence of behavioural noise and temporal variability in the composition of pollinator ensembles.Este trabajo ha sido financiado por el Ministerio de Ciencia e Innovación de España / FEDER (proyecto CGL2007-63223/BOS) y la Junta de Andalucía / FEDER (proyecto RNM-340).Peer reviewe

Interacciones entre arañas cangrego y polinizadores : estrategias de caza de las arañas cangrejo y estrategias antidepredatorias de los polinizadores

Beca I3P predoctoral del CSIC (I3P-BPD2005), Proyecto Ministerio de Ciencia e Innovación/FEDER (CGL2007-63223/BOS), Proyecto CSIC (PIE 2006 3 OI 073)Peer reviewe

Olfactory detection of dimethyl sulphide in a krill-eating Antarctic penguin

In response to zooplankton grazing, phytoplankton release dimethylsulphoniopropionate in the seawater, which is then catabolized to dimethyl sulphide (DMS) that is emitted to the air. This molecule therefore signals areas of high productivity in the oceans, and it can be used by predators for locating foraging areas. Detection of this compound has been described in several species of procelariiform seabirds and non-Antarctic fish-feeding penguins. However, there is no evidence of DMS detection by krill-feeding penguins. The mechanisms of krill detection by its predators are especially relevant in Antarctica, where trophic webs are mainly based on krill. We explored for the first time whether a krill-feeding penguin species, the chinstrap penguin Pygoscelis antarctica, is able to detect DMS. We examined whether chinstrap penguins could detect DMS by locating DMS or control recipients in pathways that penguins used when moving between the colony and the sea. We also analysed the attraction of nestling penguins to DMS in a T-shaped experimental enclosure. Our results showed that adult penguins are attracted to DMS on land. Nestling penguins also tended to be attracted to the scent of DMS. Further research is needed to examine whether chinstrap penguins use natural DMS concentrations as a foraging cue at sea.This study has 347 been funded by the Acción Complementaria project [CTM2009-08154-E] of the 348 Spanish Ministerio de Ciencia e Innovación.Peer Reviewe

Feeding experience and relative size modify the begging strategies of nestlings

The offspring of birds and mammals use a combination of movements and vocalizations, known as begging, to solicit food from their parents. A widespread interpretation of begging is that it constitutes an honest signal of offspring need. But we know that in the house sparrow (Passer domesticus) the intensity of begging calls reflects the past experience of offspring in addition to their need. Here we show that this result generalizes to other species. An experiment with hand-reared magpies (Pica pica) and great spotted cuckoos (Clamator glandarius) indicates that the begging strategies depend on the past experience of chicks and the composition of their brood. In asynchronous two-magpie broods, both chicks begged at the same intensity when the large chick obtained food more easily than its sibling, but the large chick begged at higher intensity when it was easier for the smaller chick to obtain food. Cuckoo chicks begged at higher intensity than magpies.Peer Reviewe

Implicaciones de la capacidad de movimiento en las arañas (Araneae) para la evolución adaptativa del tamaño y la forma según el sexo, hábitat y modo de vida

Peer reviewe

The effect of a flower-dwelling predator on a specialized pollination system

Plant species vary greatly in the number and diversity of floral visitors with which they interact. Even so, pollination ecologists have focused mainly on direct pairwise interactions (mutualists), overlooking indirect effects produced by different agents, such as floral larcenists and flower-dwelling predators. In our study area in Brazil, the pollen-flowers of Chamaecrista ramosa (Fabaceae) harbour Misumenops sp. (Thomisidae) spiders, a flower-dwelling predator with unknown signalling strategy. We measured the effect of Misumenops on the foraging behaviour of three bee species, one behaving as a pollen robber (Trigona spinipes) and two as pollinators (Xylocopa ordinaria and X. hirsutissima), and the consequences for plant fitness. The presence of Misumenops reduced the frequency of Trigona bee visits and increased the proportion of undamaged anthers, and thus pollen available to Xylocopa bees, which seemed unaffected by spider presence. However, spider presence (detectable by both Trigona and Xylocopa bees through achromatic and chromatic contrasts) had no effect on fruit and seed set when compared to flowers without spiders. Thus, the apparently antagonistic interaction between Trigona and flowers can represent a commensalism, modulated by differences between pollinators and larcenists regarding the window of foraging activity, as well as regarding foraging efficiency. The results also indicate that the quantitative impact of predators of floral visitor on plant fitness will be highly dependent on context in species with specialized pollination systems.FJT thanks the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) for the Postdoctoral grant (PNPD-1659767), and the Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro (FAPERJ) for the >Reverse-sandwich” PhD fellowship (E-26/101.249/2014) at the Graduate Program in Ecology of the Federal University of Rio de Janeiro (UFRJ). LF thanks the Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) for PQ grant. MARG thanks the Spanish Ministerio de Economía y Competitividad/Fondo Europeo de Desarrollo Regional - FEDER (grant number CGL2015-71396-P MINECO/FEDER)