Search

Many endangered plants are susceptible to pollination failure due to their rareness. We studied the threatened Chilean tree Legrandia concinna (Myrtaceae) with melittophilous pollen-only flowers and the pollen loads of Manuelia postica and asked: Do bees guarantee fruit set? What is the role of the endangered plant as a pollen source for M. postica? Only bees of the relictual endemic Manuelia postica and introduced Bombus terrestris and honeybees visited the flowers. Overall flower visitation was very low and so was fruit set. Exotic B. terrestris was the only effective pollinator. The small native M. postica scarcely contributed to pollination and mainly used pollen of L. concinna to rear offspring in the resource-poor Nothofagus forest: pollen of 19 flowers was sufficient to feed a single larvae. Reintroduction of trees of L. concinna as a measure of species protection would also benefit the maintenance of native populations of M. postica. We assume that the introduced bumblebees displaced native Bombus dahlbomii as pollinators of this red list tree species.

The global pollination crisis is not only produced by loss of pollinators but also by their homogenization, both processes caused by humans. This crisis impacts the persistence of many native plants species worldwide. In this document we analyze the ecological impacts that warrant the prohibition of new income of commercial bumblebee, Bombus terrestris to Chile. This species is highly invasive, it has been banned in other countries, but in Chile its entry is allowed since 1997. Thousands of colonies and fertilized queens entered the country every year and expand throughout the rest of South America. We give eleven reasons to stop B. terrestris entry to Chile and start controlling it. We justify these reasons based on work done both in the country and outside of it. At the same time, through the conclusions, we mentioned what should be the steps to followed regarding the prohibition B. terrestris entry to Chile.

Bumble bees (Bombus spp.) are considered one of the most important pollinators of native, non-native, and domesticated plants. Pathogens and parasites, such as the tracheal mite Locustacarus buchneri (Podapolipidae), are harmful to bumble bees. We developed primers based on the mitochondrial CO1 gene for the specific detection of L. buchneri directly from samples of native Bombus dahlbomii and non-native B. terrestris and B. ruderatus. PCR products amplified and sequenced for these primers shared 100 % identity among themselves and around 99–100 % identity with other sequences of L. buchneri reported in Belgium, the Netherlands, and Japan. Bombus terrestris was the most infected species (41 %), followed by B. ruderatus (31 %) and B. dahlbomii (23 %). This is the first report involving L. buchneri in native and non-native bumble bees in Chile. Our described PCR-based detection offers a feasible, specific, and rapid method for the screening of L. buchneri in any bumble bee species.

RESUMEN La crisis mundial de polinización no solo es producida por la pérdida de polinizadores, sino también por su homogeneización, ambos procesos causados por el ser humano. En este documento analizamos los impactos ecológicos que justifican la prohibición de nuevos ingresos del abejorro comercial Bombus terrestris a Chile. Esta especie es altamente invasiva y ha sido prohibida en otros países, pero en Chile se permite su ingreso desde 1997. Miles de colonias y reinas fertilizadas ingresan al país cada año y se expanden por el resto de Sudamérica. En este artículo entregamos once razones para detener los ingresos de B. terrestris a Chile y comenzar a controlarlo. Justificamos estas razones en base al trabajo realizado tanto en el país como fuera de él. Al mismo tiempo, a través de las conclusiones, mencionamos cuáles deberían ser los pasos a seguir respecto a la prohibición de ingreso de B. terrestris a Chile.

Resumen: Se informa sobre la ausencia del abejorro Bombus dahlbomii Guérin-Méneville en Punta Arenas (Región de Magallanes, Chile) durante la primavera y verano (2017-2018). El análisis del estado actual de la flora y vegetación, en adición con el registro climático y teoría de la ventana temporal no son elementos suficientes para explicar la ausencia de este ápido. Se proporcionan los antecedentes históricos para completar su ficha nomenclatural y establecer un posible estatus de no continuidad de su existencia específica. Se hipotetiza que este abejorro, por razones desconocidas, estaría iniciando su período de extinción.

Resumen: Se informa sobre la ausencia del abejorro Bombus dahlbomii Guérin-Méneville en Punta Arenas (Región de Magallanes, Chile) durante la primavera y verano (2017-2018). El análisis del estado actual de la flora y vegetación, en adición con el registro climático y teoría de la ventana temporal no son elementos suficientes para explicar la ausencia de este ápido. Se proporcionan los antecedentes históricos para completar su ficha nomenclatural y establecer un posible estatus de no continuidad de su existencia específica. Se hipotetiza que este abejorro, por razones desconocidas, estaría iniciando su período de extinción. Abstract: The absence of the bumblebee Bombus dahlbomii Guérin-Méneville in Punta Arenas (Magallanes Region, Chile) during spring and summer (2017-2018) is reported. The analysis of current state of flora and vegetation, in addition to climatic record and theory of temporal window are not sufficient elements for explaining the absence of this apid. Historical bsckground is given to complete its nomenclatural card and to establish a possible status of no continuity of its specific existence. It is hypothesized that this bumblebee, for unknown reasons, should be beginning its extinction period.

Volcanic eruptions are large-scale natural disturbances, which can negatively affect insect fauna and the ecological interactions in which they are involved. The 2011 eruption of the volcanic complex Puyehue Cordon-Caulle (PCC) produced the deposition of 950 million tons of ash on Argentine Patagonia, creating an ash layer of varying thickness. Although experimental studies confirmed that PCC volcanic ash negatively affects survival and behavior in many insect taxa, including bees, the effects of ash deposition on the plant-pollinator interactions (PPI) of this group of insects in natural landscapes remained untested. We evaluated the effect of the gradient of increasing ash layer thickness (0-15cm) on: (1) number of wild bees visiting flowers and total bee richness in 16 raspberry fields after the eruption, (2) number of native ( Bombus dahlbomii) and invasive (B. terrestris and B. ruderatus) bumble bees foraging on wild flowers in 10 sites before and after the eruption, and (3) the proportion of "triggered" flowers (i.e. papilionaceous flowers visited for first time by large bees) in 32 populations of the invasive shrub scotch broom (Cytisus scoparius), before and after the eruption. With the increase of ash deposition, we found a consistent and significant decrease in (1) the number of wild bees and total bee richness visiting raspberry flowers; (2) the number of bumble bees, particularly B. terrestris, visiting wild flowers; and (3) the proportion of triggered flowers of scotch broom. Thus, volcanic eruptions can exert a detrimental effect on bee fauna and concomitant PPI, with a potential cascade effect on the pollination service to crops, the spread of invasive bumble bees, and the pollination success of invasive plants. (Keywords: Bombus terrestris, bumble bees, large scale disturbance, pollination, Puyehue Cordon-Caulle Volcano, raspberry, scotch broom)

Despite rising global concerns over the potential impacts of non-native bumble bee (Bombus spp) introductions on native species, large-scale and long-term assessments of the consequences of such introductions are lacking. Bombus ruderatus and Bombus terrestris were sequentially introduced into Chile and later entered Argentina's Patagonian region. A large-scale survey in Patagonia reveals that, in 5 years post-arrival, the highly invasive B terrestris has become the most abundant and widespread Bombus species, and its southward spread is concurrent with the geographic retraction of the only native species, Bombus dahlbomii. Furthermore, a 20-year survey of pollinators of the endemic herb Alstroemeria aurea in northern Patagonia indicates that B ruderatus and B terrestris have replaced B dahlbomii, formerly the most abundant pollinator. Although the decline's underlying mechanisms remain unknown, the potential roles of exploitative competition and pathogen co-introduction cannot be ruled out. Given that in...

La fragmentacion del habitat puede afectar el diseno morfologico de los insectos voladores de distintas maneras, a traves de cambios en los costos y beneficios de los patrones de dispersion. Como resultado, es probable que alas mas grandes puedan ser favorecidas cuando los recursos necesarios se encuentren dispersos a lo largo del paisaje fragmentado. En esta investigacion se puso a prueba esta prediccion en Bombus dahlbomii (Guerin), un polinizador nativo de Chile asociado al bosque Maulino fragmentado. Mediante trampas colgantes, se capturaron individuos en el bosque nativo continuo, en cuatro pequenos fragmentos y en dos plantaciones de Pinus radiata (matriz). A cada individuo colectado se le midio su tamano corporal (mm) y el largo de su primer y segundo par de alas (mm). En total, fueron capturados 280 individuos. El tamano corporal y el largo de ambos pares de alas fue mayor en los fragmentos y en la matriz, en comparacion con el bosque continuo. Ademas, se observo una relacion positiva y significativa entre la longitud de las alas y el tamano corporal en todos los habitats, sin embargo, la varianza explicada fue menor en el bosque continuo que en los fragmentos y la matriz. Estos resultados sugieren que la fragmentacion del bosque Maulino podria favorecer fenotipos con alas mas grandes, probablemente con mayores capacidades de vuelo para la busqueda de recursos escasos durante el forrajeo.

Forest fragmentation produces sharp changes in the spatial configuration of remnant forest patches, which include the increasing influence of patch edges on the interior of forest patches (‘edge effects’). Human activities responsible for forest fragmentation tend also to change the internal characteristics of remnant patches, for example, through the creation of gaps by selective logging. While edges and gaps can be expected to cause comparable changes in the micro-environmental conditions of the forest, their effects on forest-dwelling species and their interactions are not necessarily comparable. This study compares the effect of forest edges and anthropogenic gaps on the reproductive success of a self-incompatible epiphytic plant (Mitraria coccinea), mediated by changes in its relationship with mutualists (pollinators) and antagonists (flower larcenists). Mitraria coccinea's flowers are pollinated by hummingbirds and robbed by the bumblebee Bombus dahlbomii. Edges and gaps had comparable positive effects on flower production and fruit set; however, nectar robbing was up to sevenfold higher in patches with numerous gaps and resulted in lower reproductive success (fruit set and total fruit crop). Forest fragmentation studies should therefore avoid treating forest remnants as homogeneous units (i.e. focusing exclusively on their characteristics and connectivity), without taking into account the internal heterogeneity caused by anthropogenic pressures (e.g. gaps and edge effects).

Resource preemption by alien organisms can contribute to their invasion success and the demise of functionally equivalent native species, particularly when opportunistic foraging by aliens results in more efficient exploitation. In forests of NW Patagonia, the only native bumble bee and major pollinator, Bombus dahlbomii, declined almost to extinction as the alien B. ruderatus increased in abundance since its first appearance about 17 years ago. To explore whether resource competition might have driven this displacement we studied the behav- ior and foraging efficiency of both bumble bees while they harvested nectar from flowers of Alstroemeria aurea, the main summer food resource in the forests of NW Patagonia. We compared the nectar content of flowers that bees selected, recently visited, and rejected with that of randomly-chosen neighboring flowers and assessed differences in visitation rates. The native bumble bee selects flowers with abundant nectar and mostly exploits nectar-rich flower patches by rejecting a higher proportion of flowers with little or no nectar. On the other hand, the alien bumble bee discriminated less with respect to sugar content per visited flower, but visited more flowers per minute. Workers of the native bumble bee harvested *70% more sugar per unit of time than those of the alien species in absolute terms, and a similar amount when sugar harvested was expressed as a percentage of body mass. In contrast to expectation, the opportu- nistic foraging of the alien bumblebee was not more efficient and therefore cannot explain the ecological extinction of the native species through exploitative competition. These findings suggest that the displace- ment of the native species by the alien may be driven by other factors, such as the associated introduction of novel diseases or parasites.

Bees naturally suffer from a broad range of parasites, including mites, protozoans, bacteria, fungi and viruses. Some appear to be host-specific, but most appear able to infect multiple bee species, and some are found in insects outside of the Hymenoptera. The host range, natural geographic range and virulence in different hosts are poorly understood for most bee parasites. It is of considerable concern that the anthropogenic movement of bees species for crop pollination purposes has led to the accidental introduction of bee parasites to countries and continents where they do not naturally occur, exposing native bees to parasites against which they may have little resistance. In at least one instance, that of the South American bumble bee Bombus dahlbomii, this has led to a catastrophic population collapse. The main bees that are moved by man are the western honeybee, Apis mellifera, and two species of bumble bee, the European Bombus terrestris and the North American Bombus impatiens. We propose a range of mitigation strategies that could greatly reduce the risk of further impacts of the commercial bee trade on global bee health, including stricter controls on international movement of bees and improved hygiene and parasite screening of colonies before and after shipping.

Bombus terrestris Linnaeus is an invasive bumblebee in Argentina. Since its first record in March 2006, B. terrestris has rapidly become the most widespread species in the southern Argentina’s Patagonia. The explosion of B. terrestris populations has been associated with the rapid decline of the unique native species B. dahlbomii, Guérin-Méneville. However, B. terrestris had never been yet reported farther south than the 50° parallel. We report for the first time the presence of B. terrestris at the southern end of continental Patagonia and discuss its meaning with regards on potential consequences for B. dahlbomii populations. Fil: Benoit Geslin, Mathias Yanin. Universidad Nacional de Río Negro; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Morales, Carolina Laura. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina

Colletia ulicina , an endemic species from the central region of Chile, displays red, tubular, scented, nectariferous flowers at the tip of its branches. Observations at two sites during two consecutive years indicate that the hummingbird Sephanoides sephaniodes (Trochilidae) visits the flowers on a regular basis. Captured hummingbirds had C. ulicina pollen loads on body parts matching the location of anthers and stigmas. The C. ulicina–S. sephaniodes interaction is well established (hummingbird visits were frequent, systematical, and occurred at different sites) although it lacks specificity ( S. sephaniodes is a generalist hummingbird and C. ulicina has another, seasonally important pollinator, the even more generalist bumblebee Bombus dahlbomii ). To the best of our knowledge this is the first documented report on bird pollination in the Rhamnaceae.

We studied the pollination and reproductive success in continuous and fragmented populations of Lapageria rosea, a self-compatible plant endemic to temperate forests of Chile. Pollinator abundance, visitation rates, flower abundance, nectar volume and concentration, pollen germination and fruit and seed production, were compared between continuous forest of 145 ha and four forest fragments of 6, 3, 3, and 1 ha respectively, surrounded by mature pine plantations of Pinus radiata. Flower abundance was lower in three out of four forest fragments relative to continuous forest. Nectar volume and sugar concentration did not differ between flowers in the two habitats. Pollinators of L. rosea, the hummingbird Sephanoides sephaniodes and bumblebee Bombus dahlbomii were less abundant and visited flowers of L. rosea at lower rates in fragments than in continuous forest. In addition, in vitro rates of pollen germination were lower for flowers in forest fragments. The number of seeds per fruit was also lower in forest fragments. We suggest that fragmentation affects the reproductive success of L. rosea, lowering the total numbers of seeds produced and possibly compromising long term persistence of fragmented populations.

Since its introduction in Chile, the European Bombus terrestris L. (Hymenoptera: Apidae) has progressively reduced the abundance of the native Patagonian bumblebee, Bombus dahlbomii Guérin. Because an important cause of successful invasion of a species may depend on a potentially advantageous phenotype, we studied morphologies related to flight performance (flight muscle ratio (FMR), wing loading (WL), excess power index (EPI, which integrates FMR and WL) and wing aspect ratio (AR)) in the queens of the two species. Previous empirical studies showed that greater FMR, AR and EPI, and lower WL increase flight performance. In the Patagonian Chilean fjord where the study was carried out, B. dahlbomii was 40% heavier than B. terrestris, a difference theoretically allowing the queens of the native species to take off with heavier loads, despite the fact that the two species have virtually identical FMRs. However, FMR negatively depended on body mass at the intra-specific level. The total wing area was 35% greater in B. dahlbomii, but the difference in forewing length was only of 16%. Once taken into account the effect of body size, WL, was significantly lower in B. terrestris. AR increased with body mass and did not differ between species. EPI was weakly but significantly higher in B. terrestris. Experiments formally linking such parameters with flight performance may help to explain the observed quick and wide spread of this alien species in Patagonia in the last few years., CP was also granted by a postdoctoral contract (Program JAE-Doc Junta para la Ampliación de Estudios funded by the Spanish Research Council (CSIC) and the ESF.

Most non-autogamous orchids rely on either a single, or on a small number of pollinators to set fruit. The nectar-rewarding orchid Brachystele unilateralis and the nectarless and deceit-pollinated Chloraea virescens are restricted to the Southern Andes, where a single native and endemic bumblebee (Bombus dahlbomii) occured until the introduction of honeybees and highly invasive European bumblebees. Here, we describe the floral features, breeding system, pollinator activity and fruiting success of these orchid species. Both are self-compatible but pollinator-dependent, i.e., unable to set fruit and seed in the absence of pollinators. Field observations revealed that most of their current reproductive success is due to the introduced Bombus terrestris, Bombus ruderatus and Apis mellifera bees. The only native pollinator recorded was B. dahlbomii, but this bee was rarely observed due to its steady decline since the introduction of the alien Bombus species. The observed natural fruiting success per inflorescence in both studied species proved to be remarkably high by orchid standards: 83% and 66%, respectively. These results suggest that sexual reproduction in these orchids is not necessarily threatened by the decline of their native pollinator since pollination is successfully achieved by introduced bees. This provides a plausible better outlook for these and other regional, bumblebee-pollinated orchids and raises caution on eventual conservation policies involving the management of these introduced bee species. To our knowledge, this is the first report of native orchid pollinators being effectively replaced by invasive bumblebees and, furthermore, the first description of the pollination biology of a species of Brachystele. Fil: Sanguinetti, Agustin. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Biodiversidad y Biología Experimental y Aplicada. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Biodiversidad y Biología Experimental y Aplicada; Argentina Fil: Singer, Rodrigo Bustos. Universidade Federal do Rio Grande do Sul; Brasil

1. The Palaearctic Bombus ruderatus (in 1982/1983) and Bombus terrestris (1998) have both been introduced into South America (Chile) for pollination purposes. We here report on the results of sampling campaigns in 2004, and 2010–2012 showing that both species have established and massively expanded their range. 2. Bombus terrestris, in particular, has spread by some 200 km/year and had reached the Atlantic coast in Argentina by the end of 2011. Both species, and especially B. terrestris, are infected by protozoan parasites that seem to spread along with the imported hosts and spillover to native species. 3. Genetic analyses by polymorphic microsatellite loci suggest that the host population of B. terrestris is genetically diverse, as expected from a large invading founder population, and structured through isolation by distance. Genetically, the populations of the trypanosomatid parasite, Crithidia bombi, sampled in 2004 are less diverse, and distinct from the ones sampled later. Current C. bombi populations are highly heterozygous and also structured through isolation by distance correlating with the genetic distances of B. terrestris, suggesting the latter’s expansion to be a main structuring factor for the parasite. 4. Remarkably, wherever B. terrestris spreads, the native Bombus dahlbomii disappears although the reasons remain unclear. Our ecological and genetic data suggest a major invasion event that is currently unfolding in southern South America with disastrous consequences for the native bumblebee species., Die Eidgenössische Technische Hochschule Zürich, University of Stirling, Centro de Estudios Parasitológicos y de Vectores, Facultad de Ciencias Naturales y Museo, Pontificia Universidad Católica de Valparaiso

1. Batesian mimicry has been repeatedly reported in syrphid flies (Diptera: Syrphidae), with noxious Hymenoptera identified as the models, including bumblebees (Hymenoptera: Aculeata). Despite the number of detailed studies of bumblebee mimics from the Holarctic, only minimal biological and ecological information is available for the same phenomenon in most other biogeographical regions. 2. Here, we analyse in detail a case of Batesian mimicry by the syrphid fly Aneriophora aureorufa Philippi towards the bumblebee Bombus dahlbomii Guerin from Patagonia, a relationship only briefly noted previously in taxonomic studies. A. aureorufa possesses strikingly similar red tawny colouration to the highly hairy body of its model, and somewhat resembles it also in size. Cluster analysis suggests that the mimicry is more pronounced towards larger rather than smaller bumblebee workers. 3. The mimicry is visually very good, but there was no evidence of a behavioural component. Foraging activity of both species seems to be largely restricted to the endemic plant Eucryphia cordifolia. The time spent on flowers was much higher in syrphid flies than in B. dahlbomii and other pollinators, and the time spent between flower visits largely overlapped between all the tested species. 4. The endemic distribution, the apparent plant specialisation, and the invasion of alien bumblebees, make B. dahlbomii and A. aureorufa potentially threatened in some parts of the austral American forests, a priority conservation area., Financial support was also in part provided by the research project funded by the Ministry of Science and Innovation (subprogram BOS) CGL-2010-15786.

The worldwide spread of diseases is considered a major threat to biodiversity and a possible driver of the decline of pollinator populations, particularly when novel species or strains of parasites emerge. Previous studies have suggested that populations of introduced European honeybee (Apis mellifera) and bumblebee species (Bombus terrestris and Bombus ruderatus) in Argentina share the neogregarine parasite Apicystis bombi with the native bumblebee (Bombus dahlbomii). In this study we investigated whether A. bombi is acting as an emergent parasite in the non-native populations. Specifically, we asked whether A. bombi, recently identified in Argentina, was introduced by European, non-native bees. Using ITS1 and ITS2 to assess the parasite's intraspecific genetic variation in bees from Argentina and Europe, we found a largely unstructured parasite population, with only 15% of the genetic variation being explained by geographic location. The most abundant haplotype in Argentina (found in all 9 specimens of non-native species) was identical to the most abundant haplotype in Europe (found in 6 out of 8 specimens). Similarly, there was no evidence of structuring by host species, with this factor explaining only 17% of the genetic variation. Interestingly, parasites in native Bombus ephippiatus from Mexico were genetically distant from the Argentine and European samples, suggesting that sufficient variability does exist in the ITS region to identify continent-level genetic structure in the parasite. Thus, the data suggest that A. bombi from Argentina and Europe share a common, relatively recent origin. Although our data did not provide information on the direction of transfer, the absence of genetic structure across space and host species suggests that A. bombi may be acting as an emergent infectious disease across bee taxa and continents., Centro de Estudios Parasitológicos y de Vectores

Long-term studies of plant–pollinator interactions are almost nonexistent in the scientific literature. The objective of the present study was to determine changes and trends in the pollinator assemblage of ulmo (Eucryphia cordifolia; Cunoniaceae), a canopy-emergent tree found in Chilean temperate rainforests. We assessed the temporal variability of the pollinator assemblage and identified possible modulators of the observed temporal shifts. We sampled insect visitors to the flowers of 16 individual trees of E. cordifolia during 10 consecutive flowering seasons (2000–2009), recording a total of 137 pollinator species with a mean number of species per year of 44. Only three pollinator species (2.2 %) were recorded every year. Two bee species accounted for 50 % of all insect visits to flowers. One bee species, Bombus dahlbomii (native), was dominant in one season, whereas Apis mellifera (exotic) dominated during the next season. These interannual shifts in population abundances presented first-order dynamics that were characterized by oscillations with a period of 2 years. Changes in the abundances of the dominant pollinators, as well as differences in temperature and precipitation during insect emergence and flowering, led to a nested temporal structure of pollinator composition. Furthermore, the abundances of less common pollinators were sensitive to the abundance of the dominant bee species and to monthly maximum temperatures and the average precipitation during spring and summer. Based on our results and those from other studies, we predict a decline in the numbers of Bombus dahlbomii and nondominant native pollinators in response to new exotic arrivals.

The alteration and transformation of the areas surrounding native forests due to anthropogenic disturbance can result in differences near this newly created boundary, termed 'edge effects'. Our study describes the consequences of edge creation over two successive stages in the life cycle of a hemi-parasitic mistletoe (Tristerix corymbosus), which determine its reproductive success, in temperate austral forests. We assessed how flower production and pollinator visits change with distance to the nearest forest edge and how these changes affect fruit set, fruit and seed size, and fruit removal by seed dispersers. Edge effects were dominated by fruit removal, which increased with the distance to the edge, height in the canopy and fruit availability. As a result, plant reproduction (in terms of seeds produced and fruits removed, which putatively leads to higher seed dispersal) decreased strongly near to forest edges. In contrast, visitation rates of the main pollinator (the hummingbird) were unaffected by edges, and their strong effects on fruit set (including the alleviation of quality pollen limitation arising in the forest interior) might be mitigating the decrease in bumblebee visitation near to forest edges. Synthesis. Our study shows clearly how secondary and tertiary responses to forest edges acted in opposite directions (increasing or decreasing plant reproductive performance), highlighting the need to study several successive processes that impact upon plant fitness under disturbance. Preserving relatively large patches of old-growth forest with low perimeter/area ratios would be key to the habitat requirements of the main disperser and pollinator and thus for mistletoe reproductive performance. © 2013 The Authors. Journal of Ecology © 2013 British Ecological Society., Funding by the BBVA Foundation (project DOSEL) and the Basque Country Government (pre-doctoral fellowship for A.M.) made this study possible. A.R.L. received funding from the JAEDOC program of the Spanish Research Council (CSIC)

The arrival of exotic pollinators to new habitats may introduce new patterns of floral preference and foraging behavior that modify the structure of the resident plant–pollinator community. The aim of this paper is to examine the potential impact of the exotic bumblebee Bombus terrestris on the pollination service provided by the native pollinator assemblage of the herb Mimulus luteus. The study was performed in a high-elevation locality in the Chilean Andes during the summer seasons of 2010, 2011, and 2012. We recorded visitation rate, and the number of pollen grains transported on the body of B. terrestris and native pollinators and the pollen deposition on the stigmas of M. luteus. Pollinator effectiveness (pollen deposited × visitation rate) was compared among species. Results revealed that B. terrestris was an inefficient pollinator, due to the low amount of pollen delivered on stigmas and the low and intermittent visitation rate across years. The parallel inter-annual variation in the visitation rate of B. terrestris and the native bumblebee Bombus dahlbomii suggests that the integration of B. terrestris had no important consequences for the congeneric species. In general, B. terrestris accounted for a low proportion of the pollen transfer in M. luteus, reaching 4.6 % in 2010, absence of effect in 2011, and 0.01 % in 2012. These results suggest that in spite of being a quickly spreading species in Chile, B. terrestris is still in the initial phase of invasion in this area.

SUMMARYIt has been argued that trichromatic bees with photoreceptor spectral sensitivity peaks in the ultraviolet (UV), blue and green areas of the spectrum are blind to long wavelengths (red to humans). South American temperate forests (SATF) contain a large number of human red-looking flowers that are reported to be visited by the bumblebee Bombus dahlbomii. In the present study, B. dahlbomii's spectral sensitivity was measured through electroretinogram (ERG) recordings. No extended sensitivity to long wavelengths was found in B. dahlbomii. The spectral reflectance curves from eight plant species with red flowers were measured. The color loci occupied by these flowers in the bee color space was evaluated using the receptor noise-limited model. Four of the plant species have pure red flowers with low levels of chromatic contrast but high levels of negative L-receptor contrast. Finally, training experiments were performed in order to assess the role of achromatic cues in the detection and discrimination of red targets by B. dahlbomii. The results of the training experiments suggest that the bumblebee relies on achromatic contrast provided by the L-receptor to detect and discriminate red targets. These findings are discussed in the context of the evolutionary background under which the relationship between SATF species and their flower visitors may have evolved.

This study characterizes the structure of a plant-pollinator network in a temperate rain forest of ChiloeIsland, southern Chile, where woody species are strongly dependent on biotic pollinators, and analyzes its robustness to the loss of participating species. Degree distribution, nestedness, and expected species persistence were evaluated. In addition, we assessed the roles of predefined subsets of plants (classified by life forms) and pollinators (grouped by taxonomic orders) in the network's structure and dynamics. For this, we simulated the com- plete removal of each plant and pollinator subset and analyzed the resultant connectivity patterns, as well as the expected long-term species losses by running a stochastic model. Finally, we evaluated the sensitivity of the network structure to the loss of single species in order to identify potential targets for conservation. Our results show that the plant-pollinator network of this Chilean temperate rain forest exhibits a nested structure of interactions, with a degree distribution best described by a power law model. Model simulations revealed the importance of trees and hymenopterans as pivotal groups that maintain the core structure of the pollination network and guarantee overall species persistence. The hymenopterans Bombus dahlbomii and Diphaglossa gayi, the shrubs Tepualia stipularis and Ugni molinae, the vines Mitraria coccinea and Asteran- thera ovata, and the entire set of tree species exerted a disproportionately large influence on the preservation of network structure and should be considered as focal species for conservation programs given current threats from selective logging and habitat loss.

[Figure][1] Most bees don't bother visiting red flowers; red flowers are usually reserved for other pollinators such as hummingbirds. But no one explained this to Bombus dahlbomii bumblebees in Chile. According to Jaime Martinez-Harms from the Universidad de Chile, they are perfectly happy

The separation between staminate and pistillate phases in protandrous, long- lived hermaphroditic flowers results in a seasonal shift in sex ratio from a pure male to a pure female flower population. In theory, temporal sex ratio associated with dichogamy may affect pollination, promoting the evolution of sexual specialization in plants when pollinator visitation does not limit seed output. Alstroemeria aurea, a perennial herb native to the temperate forests of southern South America, bears strongly protandrous flowers. Over a three-year period, I assessed the influence of seasonal changes in flower sex ratio and pollinator abundance on the pollination dynamics of this plant species. Workers of Bombus dahlbomii accounted for >90% of all visits to A. aurea flowers and were the most efficient pollinators on a per-visit basis. As the season progressed, pollen loads carried by bumble bees decreased by almost one order of magnitude, and the amount of pollen deposited per visit decreased as well from >40 to