Pollen limitation in a narrow endemic plant: Geographical variation and driving factors

Fernández J.D., Bosch J., Nieto-Ariza B., Gómez J.M. (2012) Pollen limitation in a narrow endemic plant: Geographical variation and driving factors. Oecologia. 170: 421-431.
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Doi: 10.1007/s00442-012-2312-1

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Pollen limitation may have important consequences for the reproduction and abundance of plant species. It may be especially harmful to endangered and endemic plants with small populations. In this study, we quantify the effect of pollen limitation on seed production and seedling emergence in an endangered narrow endemic crucifer, Erysimum popovii. We conducted a pollen addition experiment across the entire geographic distribution of the species, and explored the effect of pollinator assemblage, plant population size and density, and other habitat variables on pollen limitation intensity in 13 populations. We supplemented flowers in 20 plants per population with allogamous pollen. To account for potential resource reallocation, we used two types of control untreated flowers: internal control flowers from the same individual as the supplemented flowers, and external control flowers from other individuals. Our results indicate that E. popovii is pollen-limited in most of the populations studied, but only through seed production, since pollen supplementation did not enhance seedling emergence. Beefly abundance was associated with among-population differences in pollen limitation intensity. Populations in which beeflies were more abundant were less pollen-limited. In contrast, the abundance of other flower visitors, such as large bees or butterflies, was not associated with pollen limitation. Annual rainfall and bare soil cover were associated with the intensity of pollen limitation across populations. © 2012 Springer-Verlag.

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Efecte de la gestió forestal sobre la comunitat d'abelles i vespes nidificants en cavitats pre-establertes i la seva fauna associada.

Barril-Graells H, Comas LL,  Rodrigo A,  Bosch J (2012) Efecte de la gestió forestal sobre la comunitat d'abelles i vespes nidificants en cavitats pre-establertes i la seva fauna associada. IX Jornades sobre recerca al parc Nacional d'Aigüestortes i Estany de Sant Maurici. Boi, 17-19 Octubre (Comunicació oral).

BVOCs in the plant-pollinator market and other applications of ecology to betytyerunderstand BVOC emissions in the environment.

Peñuelas J, Filella I, Farré G, Owen S, Primante C, Rodrigo A, Martín A, Bosch J, Seco R, Porcar A, Llusià J, Greenberg J, Harley P, Rapparini F, Estiarte M, Mejia-Chang M, Ogaya R, Ibañez J, Sardans J, Turnipseed A, Geron C, Duhl T, Facini O, Baraldi R, Rapparini F, Guenther A (2012) BVOCs in the plant-pollinator market and other applications of ecology to betytyerunderstand BVOC emissions in the environment. BVOCs Gordon Conference, Biogenic Hydrocarbons & the atmosphere. Reaching across scales: from molecule to the globe. Bates College, Maine. June 24-29. Key note invited speaker.

Drivers of compartmentalization in a Mediterranean pollination network

Martín González A.M., Allesina S., Rodrigo A., Bosch J. (2012) Drivers of compartmentalization in a Mediterranean pollination network. Oikos. 121: 2001-2013.
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Doi: 10.1111/j.1600-0706.2012.20279.x

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We study compartmentalization in a Mediterranean pollination network using three different analytical approaches: unipartite modularity (UM), bipartite modularity (BM) and the group model (GM). Our objectives are to compare compartments obtained with these three approaches and to explore the role of several species attributes related to pollination syndromes, species phenology, abundance and connectivity in structuring compartmentalization. BM could not identify compartments in our network. By contrast, UM revealed four modules composed of plants and pollinators, and GM four groups of plants and five of pollinators. Phenology had a major influence on compartmentalization, and compartments (both UM and GM) had distinct phenophases. Compartments were also strongly characterized by species degree (number of connections) and betweenness centrality. These two attributes were highly related to each other and to phenophase duration. Differences among compartments in abundance were only apparent with GM. We attribute this to the fact that abundance is strongly correlated with Degree, and the GM algorithm is particularly powerful at discriminating species based on degree. On the other hand, the role of pollination syndrome-related features in compartmentalization mostly emerged with UM. Only UM compartments differed in corolla length and pollen production. Both UM and GM compartments differed in their pollinator spectra. We found inconsistent reciprocity between plant attributes and pollinator spectra, thus it is difficult to conclude compartments follow clear-cut syndromes. Also, both UM and GM identified a compartment composed of pollinators with long activity periods that acted as connectors, linking all compartments providing cohesiveness to the network. © 2012 The Authors.

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Effects of body size and sociality on the anti-predator behaviour of foraging bees

Rodríguez-Gironés M.A., Bosch J. (2012) Effects of body size and sociality on the anti-predator behaviour of foraging bees. Oikos. 121: 1473-1482.
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Doi: 10.1111/j.1600-0706.2011.19473.x

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Pollinators, like most other animals, often face a tradeoff between increasing food uptake and minimising predation. An earlier model suggests that social bees should be more likely than solitary bees to adopt riskier foraging strategies in order to increase food uptake. In this paper, we extend this model by studying the effect of body size, in addition to sociality, on the predation-intake rate tradeoff. When, following standard practice, we express the foraging strategies in terms of mortality probability and net food uptake, we find that body size should have no effect on the foraging strategies of solitary bees. Social bees, on the other hand, should change their foraging preferences according to their size. Small social bees should tend to maximise food uptake, and large social bees to minimise mortality rate. Mortality, however, is the product of two terms: the probability of suffering an attack and the probability of succumbing to it. Noting that larger bees are less susceptible to succumb to a predation attempt than smaller bees, model predictions change when foraging strategies are expressed in terms of exposure to predators. Following this second approach, exposure to predators should increase monotonically with body size in solitary bees. In social bees it should reach a minimum for medium-sized bees. We conclude that both bee body size and sociality should be considered when studying the effect of predators on resource use. © 2011 The Authors.

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Duration of prepupal summer dormancy regulates synchronization of adult diapause with winter temperatures in bees of the genus Osmia

Sgolastra F., Kemp W.P., Maini S., Bosch J. (2012) Duration of prepupal summer dormancy regulates synchronization of adult diapause with winter temperatures in bees of the genus Osmia. Journal of Insect Physiology. 58: 924-933.
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Doi: 10.1016/j.jinsphys.2012.04.008

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Osmia (Osmia) bees are strictly univoltine and winter as diapausing adults. In these species, the timing of adult eclosion with the onset of wintering conditions is critical, because adults exposed to long pre-wintering periods show increased lipid loss and winter mortality. Populations from warm areas fly in February-March and are exposed to longer growth seasons than populations from colder areas, which fly in April-May. Given their inability to produce an extra generation, early-flying populations should develop more slowly than late-flying populations and thus avoid the negative consequences of long pre-wintering periods. In this study we compare the development under natural and laboratory conditions of phenologically-distinct populations in two Osmia species. Early-flying populations took ∼2. months longer to develop than late-flying populations. Differences between populations in larval and pupal period duration were very small, whereas the prepupal period was much longer in early-flying populations. In contrast to the larval and pupal stages, the prepupal stage showed a non-linear response to temperature, was strongly affected by thermoperiod, and exhibited minimum respiration rates. Coupled with other lines of evidence, these results suggest that the prepupal period in Osmia corresponds to a summer diapause, and its duration may be under local selection to synchronize adult eclosion with the onset of winter temperatures. We discuss the implications of our results relative to current expectations of global warming. © 2012 Elsevier Ltd.

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