In this thesis, I combined field observations and lab experiments to explore the ecological significance of floral signals in a North American wildflower, Penstemon digitalis. More specifically, to determine the potential mechanisms driving selection on floral scent, I studied how scent mediates interactions with pollinators and antagonists by (1) observing spatiotemporal variation in scent emission (2), floral volatile ability to suppress microbes (3) the honest advertisement of nectar, and (4) if scent could aid pollinator learning by reinforcing visual signals. Scent sampling of flower development, flower tissues, rewards and inflorescence day/night emission, revealed a complexity in floral scent composition and emission that could reflect several ecological functions. The floral bouquet of P. digitalis was strongest when flowers opened, primarily emitted from flower nectaries and was strongest during the day when pollinators are most active, suggesting a role in plant-pollinator interactions. Because linalool was one of the few floral compounds found in nectar where microbe growth can degrade the pollinator reward, I studied its role in plant-microbe interactions. Bacteria strains isolated from floral and vegetative tissues were exposed to varying concentrations of nectar volatiles: linalool and methyl nicotinate. Linalool inhibited bacteria growth rate from all tissue origins whereas methyl nicotinate had little effect, suggesting that microbes could drive selection on linalool emission strength.    To determine the extent that linalool could honestly signal nectar availability, linalool-nectar associations were measured for inflorescences and flowers. Linalool predicted inflorescence nectar availability but not flower, exposing a limit to its honesty. Pollinator Bombus impatiens could use linalool as a foraging signal at varying concentrations, suggesting linalool could be learned and used to choose the most rewarding plants.    Measurement and comparison of signal-reward associations for both olfactory and visual signals/cues of P. digitalis displays found display size and linalool honest indicators of nectar. Lab behaviour experiments showed multiple signals correlated with reward could increase bumblebee foraging efficiency and promote learning, providing an explanation for why floral displays are complex and consist of multiple signals.    Together my results show that an integrated approach is required to understand the mechanisms driving the evolution of the floral phenotype.

In this study poplar trees have been examined under different stress conditions. Apart from the detailed descriptions above two main conclusions might be drawn: i) A small plant like Arabidopsis thaliana is highly susceptible to stress situations that might become life-threatening compared to a tree that has extremely more biomass at its disposal. Such an organism might be able to compensate severe stress much longer than a smaller one. It seems therefore reasonable that a crop like Arabidopsis reacts earlier and faster to a massive threat. ii) In poplar both tested stress responses seemed to be regulated by hormones. The reactions to abiotic salt stress are mainly controlled by ABA, which also has a strong impact upon cold and drought stress situations. The term commonly used for ABA is “stress hormone” and is at least applicable to all abiotic stresses. In case of herbivory (biotic stress), jasmonic acid appears to be the key-player that coordinates the defence mechanism underlying extrafloral nectary and nectar production. Thus the presented work has gained a few more insights into the complex network of general stress induced processes of poplar trees. Future studies will help to understand the particular role of the intriguing indirect defence system of the extrafloral nectaries in more detail. / In dieser Arbeit wurden Pappelbäume unter verschiedenen Stressbedingungen untersucht. Zusammenfassend und zusätzlich zu den obigen Beschreibungen lassen sich zwei Schlussfolgerungen ziehen: i.) Eine kleine Pflanze wie Arabidopsis ist viel empfindlicher für Stresssituationen, die möglicherweise lebensbedrohlich werden könnten, im Gegensatz zu einem Baum mit wesentlich grösserer Biomasse . Solch ein Organismus kann schwerwiegendem Stress viel länger kompensieren als ein kleinerer Organismus. Es erscheint daher sinnvoll, dass eine Pflanze wie Arabidopsis viel früher und schneller auf eine massive Bedrohung reagiert. ii.) In Pappeln scheinen beide untersuchten Arten von Stressreaktion durch Hormone reguliert zu werden. Die Reaktionen auf abiotischen Salzstress werden hauptsächlich durch ABA kontrolliert, welches auch einen starken Einfluss auf Kälte- und Trockenstressszenarien hat. Üblicherweise wird für ABA der Ausdruck "Stress-Hormon" verwendet, was zumindest für abiotischen Stress zutreffend ist. Im Fall von Herbivorie (biotischer Stress) scheint Jasmonsäure die Schlüsselrolle zu spielen, die die Abwehrmechanismen koordiniert, die den extrafloralen Nektarien und der Nektarproduktion zu Grunde liegt. Demzufolge hat die vorliegende Arbeit ein paar neue Einsichten in das komplexe Netzwerk der Stress-induzierten Prozesse der Pappel ermöglicht. Zukünftige Studien werden dazu beitragen die besondere Rolle des faszinierendem indirektem Abwehrmechanismus der extrafloralen Nektarien en detail zu verstehen.

Neste estudo, avaliamos a distribuição espacial de recursos florais de Eriotheca gracilipes e suas conseqüências para a atividade de abelhas e florívoros no sucesso reprodutivo desta espécie de Cerrado. A distribuição de flores de Eriotheca gracilipes revelou que a disponibilidade destes recursos variou espacial e temporalmente. No ano em que a floração foi mais expressiva no cerrado, estas variações afetaram de modo distinto as abelhas grandes que visitam as flores de E. gracilipes à procura de néctar e pólen, quando estas abelhas responderam positivamente ao aumento na disponibilidade de flores, tanto na escala do indivíduo, como na escala da vizinhança. Independente da fase sexual das flores de E. gracilipes, a maior parte da variação na produção de energia do néctar é determinada pela variação entre flores e esta variação é determinada pela variação na produção de energia das flores na fase masculina. A maior produção de néctar na fase masculina das flores de Eriotheca gracilipes pode ser resultado de pressões seletivas distintas entre as funções sexuais. A incidência de florivoria em E. gracilipes diferiu entre os agentes e as fisionomias. As maiores taxas de sobrevivência das estruturas reprodutivas no cerrado e a correlação positiva entre o número de botões produzidos e o número de frutos formados nesta fisionomia reforçam a hipótese de que variações espaciais nas interações entre species, sejam elas mutualistas ou antagonistas, poderiam afetar diferentemente a reprodução sexuada de E. gracilipes, de acordo com as espécies antagonistas envolvidas. / In this study we evaluated the spatial distribution of Eriotheca gracilipes floral resources and its consequences for the bee foraging behavior, florivores and the reproductive output of this Cerrado species. Spatial and temporal variations were detected for Eriotheca gracilipes flower availability. At the cerrado physiognomy in 2005, this variation affected differently the large bees that visit E. gracilipes flowers, looking for pollen and nectar. Under this situation, we detected positive pollinator responses to the floral display of focal plants and also to its neighborhood. The greatest variation in energy production was explained by variation among flowers in male phase. The higher nectar production in male flowers indicated that distinct selective pressures might be occurring at each sexual function. The incidence of florivores reduced E. gracilipes flower availability and their action were different between agents and physionomies. Trigona spinipes had a major impact on buds and flowers of E. gracilipes at the campo cerrado. Our data indicate that spatial and temporal variation between plant-pollinator and plant-florivores occured even under low and almost homogeneous flower availability, affecting differently E. gracilipes reproductive success.

A heterogeneidade comum aos sistemas biológicos, sua influência na interação planta-polinizador e demografia de uma arvoreta tropical são os temas centrais desta tese. Utilizando uma abordagem hierárquica de estrutura de manchas de recursos florais: 1. caracterizamos a variação espaço-temporal na disponibilidade de recursos florais aos morcegos e beija-flores, polinizadores de Abutilon rufinerve. 2. avaliamos a existência de indícios de efeitos positivos ou negativos da densidade de A. rufinerve na atração de visitantes florais, em seu comportamento e possíveis conseqüências para a produção de sementes; e 3. discutimos a importância relativa da variação na produção de sementes para a demografia de A. rufinerve em diferentes condições ambientais caracterizadas por média e alta densidade de coespecíficos. A disponibilidade de recursos florais não diferiu entre dia e noite contrariando as expectativas de maior produção de néctar no período noturno em função de uma maior eficiência dos morcegos como polinizadores. As variações mais importantes na distribuição de recursos e na resposta dos visitantes florais foram observadas nas menores escalas. O aumento na densidade de recursos incrementou a visitação das flores por morcegos, porém diminuiu a visitação por beija-flores. A demografia de A. rufinerve indica que, atualmente e para esta população, os polinizadores parecem ter pouca influência em diferenças naaptidão dos indivíduos, e exercem pouca pressão seletiva sobre as plantas. Isto parece ocorrer devido à sobrevivência e crescimento das plântulas ser a etapa mais crítica do ciclo de vida desta população. No entanto é importante enfatizar que estes dados refletem um momento da população desta espécie vegetal, e que os processos evolutivos apresentam variação espaço-temporal, gerando os mosaicos geográficos. / Heterogeneity is a remarkable characteristic of biological systems. This thesis is about the influence of heterogeneity on plant-pollinator interaction and on demography of a tropical treelet Abutilon rufinerve. With an approach of hierarchical scales of patch structure we: 1. characterized the spatio-temporal variation on the availability of floral resources to bats and hummingbirds, the main pollinators of this species; 2. evaluated the occurrence of positive or negative density effects of A. rufinerve on pollinator attraction and seed production; and 3. elucidated the relative importance of variation in seed production to A. rufinerve\'s demography in different environmental conditions, characterized by medium and high conspecific density. The availability of resources did not differ between day and night, against our expectations of higher nectar production by night as a result of selective pressures made by bats, the most efficient pollinators. The greatest variation in floral resources and in the response of floral visitor was observed at fine spatial scales. Abutilon rufinerve\'s demography indicated that in this population, pollinators seem to pose no selective pressure on plants. Seed production has few effects on fitness because seedling survival and growth is the critical stage in life-cycle. However it is important to emphasize that this study reflects a short period of this population existence, and that evolutionary process vary spatio-temporaly creating geographic mosaics.

Pollinator visitation patterns should affect pollination success and mating patterns in flowering species. In the orchid family, about one third of the species do not provide any reward for their pollinators. Pollination by deceit is typically associated with low fruit set but may increase the chance of cross-pollination since the pollinator should soon leave the individual plant when there is no reward in the flowers. This may be beneficial if self-fertilisation results in inbreeding depression. I studied the mating patterns of one rewarding and one deceptive orchid in two closely related genera by tracking the fate of stained pollinia. I also conducted controlled crosses to estimate inbreeding depression. The results show that the deceptive orchid Dactylorhiza lapponica has lower pollination success, but higher cross-pollination rate (ca. 90%) than the nectariferous orchid Gymnadenia conopsea (ca. 18% cross-pollination). The results further suggest that in G. conopsea, nocturnal visitors mediate higher geitonogamous pollination rate (ca. 100%) than diurnal visitors (ca. 60%). In both study species, fruits produced from cross-pollination were heavier than fruits produced from selfing. Inbreeding depression for fruit mass did not differ significantly between the two species (δ = 0.21 in D. lapponica and δ = 0.29 in G. conopsea). These data support the hypothesis that pollination by deceit can enhance cross-pollination. A literature study including several rewarding and non-rewarding orchid species indicated lower geitonogamy in the deceptive orchids, but the difference was not statistically significant.

Changed management of semi-natural grasslands is thought to be one important factor for explaining the decline of butterfly populations in Sweden and the rest of Europe. This study explores how vegetation height, variation in vegetation height and flower abundance can help predict the occurrence of butterfly species in semi-natural grasslands in southern Sweden. My study is based on data collected by a national environmental monitoring programme (NILS) during 2006-2010. Generalized linear models showed that all three explanatory variables significantly affected 26 of the 41 species of butterflies studied. The study also investigated preferences for three different systems for grouping species but did not find differences among groups. Several of the species would most likely benefit from variation in grazing pressure or rotational grazing as well as flower-rich grasslands. The results may also help when aiming management at the preservation of individual species.

The pollination biology of Impatiens sakeriana was studied in Northwest province, Cameroon. The most efficient way of reproduction was examined, futhermore nectar production was neasured and bird pollinators was observed.

Adesmia tristis Vogel é uma espécie endêmica com potencial forrageiro nos Campos de Altitude. Objetivou-se estudar a biologia floral e as interações com os polinizadores, a morfo-fenologia da planta, os componentes do rendimento de sementes e a dinâmica do néctar; avaliar as relações pólen/óvulo e semente/óvulo na espécie; analisar a morfo-anatomia das sementes; avaliar o tamanho e distribuição do banco de sementes do solo (BSS) e a interferência da acidez no mesmo. O estudo ocorreu entre dezembro 2007 a novembro 2011, no Pró-Mata/PUCRS (29°27'-29°35'S e 50°08'-50°15'W), São Francisco de Paula, RS. A área do estudo foi de 15 x 30 m subdividida em seis parcelas, três com corte e três sem corte (4,0 plantas/m2). Para os estudos nas flores fizeram-se marcações e ensacamento com tecido “voal”, com amostras aleatórias. O néctar foi recolhido em quatro horários diários durante a antese, com utilização de micropipeta e leitura através de refratômetro. Para os cortes e levantamento dos parâmetros do rendimento de sementes, foi utilizado um retângulo metálico com 0,5 m2. Para análise dos dados utilizou-se da estatística descritiva, índice de Morisita, regressões, teste t de Student e análise de variância. A antese durou dois dias, e os principais polinizadores foram das famílias Megachilidae e Andrenidae, com pico de visitação ao meio dia. Abelhas do gênero Megachile forrageiam no estrato envolvendo o dossel, as da família Andrenidae no estrato inferior. Na base do estandarte há uma bolsa armazenadora de néctar, que começa a ser secretado na pré-antese. A planta faz reabsorção de parte do néctar, tornando as flores do segundo dia mais atraentes aos polinizadores. O regime de corte promoveu maior produção de sementes. A razão pólen/óvulo acusou alogamia obrigatória. Constatou-se déficit de polinização. Adesmia tristis possui dormência tegumentar e a semente possui adaptações para as variações de umidade no ambiente, promovendo ressemeadura natural. Em áreas naturais a planta apresenta distribuição agregada e aleatória em campos manejados. A acidez do solo contribui com a germinação de sementes de A. tristis contidas no BSS. Após o período reprodutivo ocorre perdas de plantas-mãe. / Adesmia tristis Vogel is an endemic species with forage potential in the Campos de Altitude. The aim of this research was to study the floral biology and the interactions with pollinators, the plant’s morphophenology, the components of seed yield and dynamics nectar; assess relationships pollen/ovule and seed/ovule in the species; to analyze the seeds’ morphology and anatomy; evaluate the size and distribution of the soil seed bank (SSB) and the acidity interference in it. The study was conducted between December 2007 to November 2001, in Pró-Mata/PUCRS (29º 27’ – 29º 35’S and 50º 08’ – 50º 15’ W) in the town of São Fransisco de Paula, RS. The study area had 15 x30 m subdivided into six plots. Three with cut and three no cut (4.0 plants/m2). For studies on the flowers were made marks and bagging by “voal” textile, with random samples. The nectar was collected four times daily, during anthesis, using micropipette and reading through refractometer. For cuts and taking seed yield parameters, we used a metal rectangle with 0.5 m2. Data analysis used descriptive statistics, Morisita index, regression function, Student’s t test and variance analysis. Anthesis lasted two days, and the main pollinators belong to Megachilidae and Andrenidae families, with peak visitation at noon. The genus Megachile bees foraging in the canopy, the Andrenidae family foraging in the lower levels. On the banner basis there is storage bag nectar. The nectar starts to be secreted in the pre anthesis phase. The plant reabsorbs part of the nectar, making the second day life flowers more attractive to pollinators. The cutting regime caused greater seed production. The pollen/ovule ration accused obligatory allogamy. It was observed pollination deficit. Adesmia tristis has tegument dormancy and seed has adapted to variation of moisture in the environment and promoting natural replanting. In natural area the plant has aggregated distribution, but in managed field plays random distribution. The soil acidity aim in the seed germination of A. tristis SSB. After the reproductive period occurs loss of mother plants.

Adesmia tristis Vogel é uma espécie endêmica com potencial forrageiro nos Campos de Altitude. Objetivou-se estudar a biologia floral e as interações com os polinizadores, a morfo-fenologia da planta, os componentes do rendimento de sementes e a dinâmica do néctar; avaliar as relações pólen/óvulo e semente/óvulo na espécie; analisar a morfo-anatomia das sementes; avaliar o tamanho e distribuição do banco de sementes do solo (BSS) e a interferência da acidez no mesmo. O estudo ocorreu entre dezembro 2007 a novembro 2011, no Pró-Mata/PUCRS (29°27'-29°35'S e 50°08'-50°15'W), São Francisco de Paula, RS. A área do estudo foi de 15 x 30 m subdividida em seis parcelas, três com corte e três sem corte (4,0 plantas/m2). Para os estudos nas flores fizeram-se marcações e ensacamento com tecido “voal”, com amostras aleatórias. O néctar foi recolhido em quatro horários diários durante a antese, com utilização de micropipeta e leitura através de refratômetro. Para os cortes e levantamento dos parâmetros do rendimento de sementes, foi utilizado um retângulo metálico com 0,5 m2. Para análise dos dados utilizou-se da estatística descritiva, índice de Morisita, regressões, teste t de Student e análise de variância. A antese durou dois dias, e os principais polinizadores foram das famílias Megachilidae e Andrenidae, com pico de visitação ao meio dia. Abelhas do gênero Megachile forrageiam no estrato envolvendo o dossel, as da família Andrenidae no estrato inferior. Na base do estandarte há uma bolsa armazenadora de néctar, que começa a ser secretado na pré-antese. A planta faz reabsorção de parte do néctar, tornando as flores do segundo dia mais atraentes aos polinizadores. O regime de corte promoveu maior produção de sementes. A razão pólen/óvulo acusou alogamia obrigatória. Constatou-se déficit de polinização. Adesmia tristis possui dormência tegumentar e a semente possui adaptações para as variações de umidade no ambiente, promovendo ressemeadura natural. Em áreas naturais a planta apresenta distribuição agregada e aleatória em campos manejados. A acidez do solo contribui com a germinação de sementes de A. tristis contidas no BSS. Após o período reprodutivo ocorre perdas de plantas-mãe. / Adesmia tristis Vogel is an endemic species with forage potential in the Campos de Altitude. The aim of this research was to study the floral biology and the interactions with pollinators, the plant’s morphophenology, the components of seed yield and dynamics nectar; assess relationships pollen/ovule and seed/ovule in the species; to analyze the seeds’ morphology and anatomy; evaluate the size and distribution of the soil seed bank (SSB) and the acidity interference in it. The study was conducted between December 2007 to November 2001, in Pró-Mata/PUCRS (29º 27’ – 29º 35’S and 50º 08’ – 50º 15’ W) in the town of São Fransisco de Paula, RS. The study area had 15 x30 m subdivided into six plots. Three with cut and three no cut (4.0 plants/m2). For studies on the flowers were made marks and bagging by “voal” textile, with random samples. The nectar was collected four times daily, during anthesis, using micropipette and reading through refractometer. For cuts and taking seed yield parameters, we used a metal rectangle with 0.5 m2. Data analysis used descriptive statistics, Morisita index, regression function, Student’s t test and variance analysis. Anthesis lasted two days, and the main pollinators belong to Megachilidae and Andrenidae families, with peak visitation at noon. The genus Megachile bees foraging in the canopy, the Andrenidae family foraging in the lower levels. On the banner basis there is storage bag nectar. The nectar starts to be secreted in the pre anthesis phase. The plant reabsorbs part of the nectar, making the second day life flowers more attractive to pollinators. The cutting regime caused greater seed production. The pollen/ovule ration accused obligatory allogamy. It was observed pollination deficit. Adesmia tristis has tegument dormancy and seed has adapted to variation of moisture in the environment and promoting natural replanting. In natural area the plant has aggregated distribution, but in managed field plays random distribution. The soil acidity aim in the seed germination of A. tristis SSB. After the reproductive period occurs loss of mother plants.

Neste estudo, avaliamos a distribuição espacial de recursos florais de Eriotheca gracilipes e suas conseqüências para a atividade de abelhas e florívoros no sucesso reprodutivo desta espécie de Cerrado. A distribuição de flores de Eriotheca gracilipes revelou que a disponibilidade destes recursos variou espacial e temporalmente. No ano em que a floração foi mais expressiva no cerrado, estas variações afetaram de modo distinto as abelhas grandes que visitam as flores de E. gracilipes à procura de néctar e pólen, quando estas abelhas responderam positivamente ao aumento na disponibilidade de flores, tanto na escala do indivíduo, como na escala da vizinhança. Independente da fase sexual das flores de E. gracilipes, a maior parte da variação na produção de energia do néctar é determinada pela variação entre flores e esta variação é determinada pela variação na produção de energia das flores na fase masculina. A maior produção de néctar na fase masculina das flores de Eriotheca gracilipes pode ser resultado de pressões seletivas distintas entre as funções sexuais. A incidência de florivoria em E. gracilipes diferiu entre os agentes e as fisionomias. As maiores taxas de sobrevivência das estruturas reprodutivas no cerrado e a correlação positiva entre o número de botões produzidos e o número de frutos formados nesta fisionomia reforçam a hipótese de que variações espaciais nas interações entre species, sejam elas mutualistas ou antagonistas, poderiam afetar diferentemente a reprodução sexuada de E. gracilipes, de acordo com as espécies antagonistas envolvidas. / In this study we evaluated the spatial distribution of Eriotheca gracilipes floral resources and its consequences for the bee foraging behavior, florivores and the reproductive output of this Cerrado species. Spatial and temporal variations were detected for Eriotheca gracilipes flower availability. At the cerrado physiognomy in 2005, this variation affected differently the large bees that visit E. gracilipes flowers, looking for pollen and nectar. Under this situation, we detected positive pollinator responses to the floral display of focal plants and also to its neighborhood. The greatest variation in energy production was explained by variation among flowers in male phase. The higher nectar production in male flowers indicated that distinct selective pressures might be occurring at each sexual function. The incidence of florivores reduced E. gracilipes flower availability and their action were different between agents and physionomies. Trigona spinipes had a major impact on buds and flowers of E. gracilipes at the campo cerrado. Our data indicate that spatial and temporal variation between plant-pollinator and plant-florivores occured even under low and almost homogeneous flower availability, affecting differently E. gracilipes reproductive success.