COMPORTAMENTO PILHADOR DO BEIJA-FLOR CHIFRE-DE-OURO (Heliactin bilophus) (AVES: TROCHILIDAE) EM DUAS ESPÉCIES DE PLANTAS DOS GÊNEROS Amphilophium KUNTH (BIGNONIACEAE) E Sinningia Nees (GESNERIACEAE)

The Horned Sungem Hummingbird (Heliactin bilophus) is a typical savannah hummingbird inhabiting opened phytophysiognomies in areas of Cerrado, Caatinga, highlands and plains with low vegetation.  There are few studies about its feeding habits and little known about its behavior patterns. Here we report the bird feed behavior on two plant species Amphilophium elongatum and Sinningia sp. Trough illegitimate visits to the floral nectary, H. bilophus obtained food acting as a nectar robber. This foraging strategy included new sources of food for the hummingbird and could represent negative effects to the related plant species.Keywords: bird-flower interactions; food resources; floral visitor.O beija-flor chifre-de-ouro (Heliactin bilophus) é uma espécie tipicamente savânica que habita fitofisionomias abertas em áreas de Cerrado, Caatinga, regiões serranas e chapadas com vegetação baixa.  Existem poucos estudos sobre sua alimentação e pouco se sabe sobre seus padrões comportamentais. Aqui relatamos o comportamento alimentar da ave em duas espécies vegetais Amphilophium elongatum e Sinningia sp. Através de visitas ilegítimas ao nectário floral, H. bilophus obteve alimento atuando como pilhador. Esta estratégia de forrageamento inclui novas fontes alimentares para H. bilophus e pode representar efeitos negativos para as espécies vegetais relacionadas.Palavras-chave: interação ave-flor, recurso alimentar, visitante floral

Bee-Plant Interactions in Coffee Agroecosystems: Management and Matrix Effects on Mutualistic and Antagonistic Relationships

Given the rapid pace of anthropogenic environmental change, understanding how such change influences biotic interactions and ecosystem functions is a key challenge for ecologists. My dissertation addresses this challenge by examining how land management practices in coffee agroecosystems affect multiple interactions between stingless bees and the plants upon which they feed, and explores the effects of the resulting restructuring of plant-bee interactions on the interacting species. To do this, I focus on two overarching questions: 1) How do farm management practices and landscape context affect stingless bee foraging patterns in coffee agroecosystems, and how do these foraging patterns in turn influence coffee pollination? 2) How is nectar robbing by stingless bees influenced by agricultural land use, what are the underlying drivers of land use-mediated changes to nectar robbing behavior, and to what extent does this behavior lead to adaptive pollen limitation in the plant firespike (Odontonema cuspidatum) by constraining floral display size? In Chapter 1, I introduce a framework for understanding the multiple pathways by which anthropogenic environmental change can influence the frequency, outcome, or consequences of interspecific interactions without changing species composition. In Chapter 2, I evaluate how the management of weedy herbaceous vegetation and canopy trees shaped the way coffee (Coffea arabica) interacts with neighboring plants for both pollination and abiotic resources. Co-flowering plants that share pollinators can interact with one another simultaneously for both pollination and abiotic resources, yet few studies have considered the joint effects of both interaction types on plant reproduction or yield. In this study, I tackle this problem by examining coffee and non-coffee pollen deposition, pollen tube formation, initial fruit set, and final fruit set in coffee plants with different background floral environments, using structural equation models. I find that coffee competes with neighbors for pollination, but that this has little effect on yield because the crop is not pollen-limited. Interactions with neighbors for abiotic resources have a stronger effect, and I find evidence for both competition (with weeds and co-flowering canopy trees) and facilitation (with non-co-flowering canopy trees). In Chapters 3-5, I examine nectar robbery (extracting nectar from a flower via an opening other than the corolla mouth) by stingless bees of firespike. In Chapter 3, I show that habitat-based heterogeneity in the intensity of nectar robbery is due to changes in floral traits and associated bee preferences, with plants growing in coffee fields producing more and more nectar-rich flowers and therefore experiencing more nectar robbery than plants growing in forest fragments. In Chapter 4, I use a reciprocal-translocation experiment to show that light availability drives differences in both floral traits and nectar-robbing behavior, and that light environment exerts clonal transgenerational effects on floral traits. In Chapter 5, I develop a novel conceptual framework to explain strong pollen limitation in firespike: conflicting selection on floral traits by pollinators and floral antagonists (nectar robbers). I develop this framework using data from field surveys and a field experiment, and explore its potential generality as a mechanism of pollen limitation. Finally, in Chapter 6, I situate the studies presenting in Chapters 2-5 in the context of the framework developed in Chapter 1, using them to highlight directions for future work.PHDEcology and Evolutionary BiologyUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/170017/1/gmfitch_1.pd

EDITOR'S CHOICE: REVIEW: Trait matching of flower visitors and crops predicts fruit set better than trait diversity

Understanding the relationships between trait diversity, species diversity and ecosystem functioning is essential for sustainable management. For functions comprising two trophic levels, trait matching between interacting partners should also drive functioning. However, the predictive ability of trait diversity and matching is unclear for most functions, particularly for crop pollination, where interacting partners did not necessarily co-evolve. World-wide, we collected data on traits of flower visitors and crops, visitation rates to crop flowers per insect species and fruit set in 469 fields of 33 crop systems. Through hierarchical mixed-effects models, we tested whether flower visitor trait diversity and/or trait matching between flower visitors and crops improve the prediction of crop fruit set (functioning) beyond flower visitor species diversity and abundance. Flower visitor trait diversity was positively related to fruit set, but surprisingly did not explain more variation than flower visitor species diversity. The best prediction of fruit set was obtained by matching traits of flower visitors (body size and mouthpart length) and crops (nectar accessibility of flowers) in addition to flower visitor abundance, species richness and species evenness. Fruit set increased with species richness, and more so in assemblages with high evenness, indicating that additional species of flower visitors contribute more to crop pollination when species abundances are similar. Synthesis and applications. Despite contrasting floral traits for crops world-wide, only the abundance of a few pollinator species is commonly managed for greater yield. Our results suggest that the identification and enhancement of pollinator species with traits matching those of the focal crop, as well as the enhancement of pollinator richness and evenness, will increase crop yield beyond current practices. Furthermore, we show that field practitioners can predict and manage agroecosystems for pollination services based on knowledge of just a few traits that are known for a wide range of flower visitor species

Distasteful nectar deters floral robbery

Toxic nectar is an ecological paradox[1,2]. Plants divert substantial resources to produce nectar that attracts pollinators [3], but toxins in this reward could disrupt the mutualism and reduce plant fitness [4]. Alternatively, such compounds could protect nectar from robbers [2], provided they do not significantly alter pollinator visitation to the detriment of plant fitness [1,5–8]. Indeed, very few studies have investigated the role of plant toxins in nectar for defence against nectar robbers [4,9,10]. Here, we compared two Aconitum species (A. napellus and A. lycoctonum) that have flowers specialized for long-tongued bumblebee pollinators (Bombus hortorum) but are occasionally robbed by short-tongued bumblebees (B. terrestris) [6,11–13]. Pollinator visits to flowers were much more frequent than by robbers but visits correlated negatively with nectar alkaloid concentration and declined sharply between 200-380ppm. However, alkaloid concentrations of > 20ppm were deterrent to B. terrestris suggesting robbers were less tolerant of nectar alkaloids. Nectar of both plant species contained similar concentrations of carbohydrates and toxic alkaloids, but A. lycoctonum was more likely to secrete nectar in each flower and was also visited more frequently by pollinators and robbers.  We conclude that alkaloids in Aconitum sp. nectar affect rates of both pollinator visitation and robbery but may have co-evolved with nectar availability to maintain the fitness benefits of specialized plant-pollinator relationships. Chemical defence of nectar is, however, ultimately constrained by pollinator gustatory sensitivity

Pollinator Sharing in Specialized Bee Pollination Systems: a Test with the Synchronopatric Lip Flowers of Centrosema Benth (Fabaceae)

Bee-pollinated lip flowers of two synchronopatric species of Centrosema were used as models to examine the influence of specialized pollination systems on the ecological mechanisms of pollinator sharing. Regression analysis of bee abundances in the habitat on bee abundances on C. pubescens flowers was significant (r = 0.69; P = 0.001) and became very consistent and highly significant (r = 0.87; P = 0.00001) using a size threshold of bee pollinators longer than 15mm. These same relationships were not significant (P > 0.01), however, for C. brasilianum flowers. The structures of the two pollination systems also sustained the hypothesis of a size threshold for pollinators, although only the C. pubescens-bees interactions sustained the hypothesis of random interactions proportional to species abundances in the habitat. The flower visitor pools of the two plant species shared the same four main bee guilds: the pollinators Centridini, Xylocopa, and Euglossini and the primary nectar robber Oxaea. However, a significant divergence (P < 0.01) was detected between the two systems when the abundances and behaviors (pollinators or cheaters) of the main shared flower visitors were incorporated into the overall quantitative analysis (NMDS). The flowers size differences are not significant (P > 0.05) and could not explain these divergences. Particularly, the concentrations of the largest pollinators Eulaema and Xylocopa on C. pubescens flowers and the behavior shift of Centridini bees that act as legitimate pollinators in C. pubescens and as nectar robbers in C. brasilianum are better understood as functional foraging responses triggered by the synchronopatry and by nectar volume differences (P = 0.001) between both lip flowers. Paradoxically, the robbery activity of Centridini bees arises as a supply side effect of smaller nectar volume in C. brasilianum flowers

Foraging Oxaea flavescens bees as a function of the dynamics of abiotic factors and food resource availability from Styrax camporum flowers

We examined the abiotic factors and co-specific competition for food resources that regulate the foraging activity of Oxaea flavescens bees on Styrax camporum flowers. Foraging records were gathered during 20 min. periods at the beginning of each hour between 05:00h and 18:00h during three nonconsecutive days. Pearson correlation and linear regression tests indicated that the foraging activity of O. flavescens was associated with abiotic factors during the day. O. flavescens represented 89.9% of the observed foraging visits to S. camporum flowers. On the first day of sampling, when environmental conditions were stressful, the foraging activity of O. flavescens was significantly negatively correlated with light intensity, wind speed, and temperature, and positively correlated with relative humidity. Under those conditions, optimal foraging was little affected by the availability of floral resources. On the second and third days, however, when environmental conditions were more favorable, the principal limiting factor of O. flavescens foraging activity was nectar depletion. The maximum peak of foraging under those conditions occurred before the abiotic conditions were fully favorable, however, as the eventual depletion of floral resources resulted in unfavorable cost/benefit implications for foraging during the otherwise most adequate daylight period

Community complexity of a pollination network: Analysis of plant-pollinator interactions in the eastern Ecuadorian cloud forest

Global declines in pollinators and temporal/spatial mismatches between plants and pollinators threaten the integrity of plant-pollinator networks. Ecological network analysis provides a powerful framework for understanding the dynamics of plant-pollinator networks and measures of community complexity that can help inform areas of priority in conservation. This study observed a plant-pollinator network in a secondary forest close to the Río Zuñac Reserve in the eastern Ecuadorian cloud forest to identify assemblages of plants and pollinators and evaluate measures of community complexity, including specialization and nestedness. Flowering plants were identified and observed along a 1.2 km transect, and floral visitors to these plants were identified to morphospecies. The network was observed for a total of 26.5 hours. High species richness of plants and potential pollinators were observed in the network, with low frequencies of interactions between mutualist partners. The network had a high value of network-level specialization and a low degree of nestedness, which imply that the network does not have the ability to robustly respond to perturbations. Animals tended to be more specialized than plants, highlighting the importance of floral diversity in maintaining animal pollinators. Of the most abundant animal taxa observed, the family Apidae had the highest level of generalization, marking it as an important group of pollinators at the network level. This study presents a baseline understanding of pollination networks in the Río Zuñac reserve and concludes that network interactions are relatively specialized. Understanding pollination networks, especially in under-studied Neotropical environments like the cloud forest, represent an important first step in creating ecosystem-level conservation priorities and supporting robustness in ecological networks. Caídas globales de polinizadores y desajustes espaciales o temporales entre plantas y polinizadores amenazan la integridad de las redes de polinización. El análisis de redes ecológicas provee un marco potente para entender las dinámicas de redes de polinización y las medidas de complejidad de las comunidades para informar áreas de prioridad en la conservación. Este estudio fue basado en la observación de una red de polinización en un bosque secundario cerca de la reserva Río Zuñac en el bosque nublado oriental del Ecuador para identificar ensamblajes de plantas y polinizadores y evaluar medidas de complejidad de la comunidad, incluyendo especialización y anidamiento. Las plantas con flores fueron identificadas y observadas a lo largo de un transecto de 1.2 km, y visitantes florales a estas plantas fueron identificados a nivel de morfoespecie. La red fue observada por un total de 26.5 horas. Se observó una alta riqueza de especies de plantas y polinizadores potenciales con frecuencias bajas de interacciones entre compañeros mutualistas. Había un valor alto de especialización al nivel de la red y un nivel bajo de anidamiento, lo cual indica que esta red no tiene la habilidad de responder robustamente a perturbaciones. Los animales tendieron a ser más especializados que plantas, destacando la importancia de una diversidad florística en el mantenimiento de polinizadores. De los taxones más abundantes de animales, la familia Apidae tuvo el nivel más alto de generalización, marcando la familia como un grupo importante de polinizadores a nivel de la red. Este estudio presenta un punto de referencia de las dinámicas de redes de polinización en la reserva Río Zuñac y concluye que las interacciones de la red son relativamente especializadas. Entender redes de polinización, especialmente en ambientes Neotropicales pocos estudiados como los bosques nublados, representa un importante primer paso para crear prioridades de conservación al nivel del ecosistema y apoyar la robustez en redes ecológicas

First record of the carpenter bee Xylocopa pubescens (Hymenoptera, Apidae) in the Canary Islands confirmed by DNA barcoding

Island ecosystems are particularly vulnerable to the introduction of exotic species that can have an impact on local fauna and flora. Here, the carpenter bee Xylocopa pubescens is reported in Gran Canaria (Canary Islands, Spain) for the first time. This species is native to North Africa and the Near East and shows a rapid dispersion across the city of Las Palmas de Gran Canaria, together with a single record in the southernmost tip of the island. Different hypotheses about its arrival to the island are discussed.P. De la Rúa is supported by Project 19908/GERM/2015 of Regional Excellence (Fundación Séneca).Peer reviewe