The astonishing diversity of floral form in angiosperm plants is driven in large part by preferences of pollinators for various floral traits, including learned preferences. Remarkably, almost all of a vast literature on learning and memory in pollinators relates to nectar as a reward, even though bees and many flies, beetles, and butterflies must collect pollen. In this study, we asked if bees formed preferences for plant species from which pollen had been collected successfully. Using absolute conditioning, we gave pollen foraging bees experience with plant species that offered only pollen rewards. Naive bees generally showed modest preferences, whereas experienced bees adopted strong preferences for those species over alternative species not previously experienced. Learned preferences were retained for at least 24 h, consistent with preferences learned with nectar rewards. These experience-mediated changes in preference raised the possibility that bees formed associations between particular floral features and pollen rewards. We therefore asked if learned preferences required that bees successfully collect pollen. Using differential conditioning, we determined that learned preferences were strongly influenced by receipt of a pollen reward. In a final experiment, we characterized the importance of 2 floral features, the corolla and the anther, in the expression of learned preferences. Although experience altered responses to both floral parts, responses to anthers were influenced more strongly. We discuss recent evidence in the literature for associative learning with pollen rewards and propose that learned preferences in the context of pollen collection have played an important role in floral display evolution.

<p> Many floral characters have can affect plant fitness by altering the frequency or efficiency of pollinator visits. More frequent pollinator visitation may lead to larger pollen loads and greater outcrossing rates, which in tern may lead to greater numbers of offspring, with higher genetic variability and less inbreeding depression. Mating systems may moderate the strength of natural selection on traits that attract pollinators through its effects on inbreeding depression, and the ability to self-pollinate autogamously. Natural selection is expected to be stronger in largely outcrossing systems where inbreeding depression is high, but reduced in largely selfing systems where deleterious alleles have been purged.</p> <p> Here I investigate the role of floral display height in attracting pollinators, and its consequences for plant fitness in two closely related monocarpic herbs (Hesperis matronalis and Alliaria petiolata) with different mating systems. Though others have looked at height as a potential trait attracting pollinators, no one has yet clearly separated the effects of floral display height from that of plant size. I experimentally altered plant height independently of plant size by placing potted plants into either elevated or non-elevated treatments and observed pollinator foraging behaviour and reproduction.</p> <p> Pollinators preferred taller floral displays in the predominant outcrosser Hesperis matronalis. Elevated plants produced more seeds than control plants although their seeds were smaller, reflecting a strong seed size-number trade-off. Path analysis showed seed number was affected directly by plant height, presumably though greater pollinator visitation, and indirectly by plant mass through increased fruit number.</p> <p> In Alliaria petiolata, a predominant self-pollinating species, pollinators visited taller displays in field observations and experimentally elevated plants had significantly greater seed per fruit. Experimentally outcrossed and self-pollinated plants showed no difference in seed production, but offspring quality was significantly higher in outcrossed plants for early traits. Measures of maternal fitness increased significantly with both maternal and seed mass. For individual seeds, seed mass was the most important factor in seed fitness, where larger seeds germinated sooner, more frequently, and had higher survivorship than smaller seeds, regardless of pollination treatment. Competition strongly affected all seedling traits, with increased density having a significant negative effect on seedling mass, total leaf area, and maximum leaf length; and, a positive effect on hypocotyl length and petiole length. Seedling mass at harvest was not significantly affected by elevation treatment, seed mass, or maternal mass, however, this may have been due to lower competition brought about by low germination and survival; thus, competition did not accentuate the effect of maternal size or elevation treatment on seedling. Taken together, the results of these two studies suggest the importance of height, in attracting pollinators, independent of size in both species. The consequences of pollinator attraction were highly significant in the predominant outcrosser Hesperis matronalis, while maternal size and seed size played more important roles in the fitness of the predominant selfer Alliaria petiolata.</p> / Thesis / Master of Science (MSc)

Orientador: Elza Maria Guimarães Santos / Resumo: A limitação de pólen é um dos fatores que mais afeta a produção de frutos e sementes de muitas populações naturais. Cerca de 60% das angiospermas apresentam baixo sucesso reprodutivo decorrente da transferência ineficiente dos grãos de pólen pelos polinizadores. Assim, o objetivo geral desse estudo foi avaliar diversos aspectos ligados à limitação de pólen em Zeyheria montana (Bignoniaceae), uma espécie ornitófila e autoincompatível. Ao longo do período de florescimento, com ampla variação do anúncio floral, nós avaliamos o efeito do padrão de forrageamento dos polinizadores dentro e entre plantas sobre o sucesso reprodutivo das mesmas. Avaliamos também as estratégias de forrageamento empregadas por cada espécie de polinizador e o efeito do roubo de néctar sobre a produção de frutos. Além disso, estimamos o tamanho do genoma das plantas com a finalidade de avaliar se havia variações intrapopulacional no nível de ploidia que pudessem estar associadas ao baixo sucesso reprodutivo. Em geral, nós demonstramos que a baixa qualidade do pólen transferido pelos polinizadores é o principal fator limitante do sucesso reprodutivo de Z. montana. Esse efeito ocorre principalmente no pico do florescimento, quando o anúncio floral é mais intenso, e os polinizadores tendem visitar um maior número de flores sequenciais dentro da mesma planta transferindo pólen incompatível. Além disso, o padrão de movimento entre plantas também não se mostrou eficiente, visto que os polinizadores frequentemen... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Pollen limitation is one of the factors that most affects the fruits and seeds production of many natural populations. Around 60% of angiosperms have low reproductive success due to inefficient pollen grains transfer among flowers by pollinators. Thus, the general goal of this study was to evaluate several aspects related to pollen limitation in Zeyheria montana (Bignoniaceae), an ornithophilous and self-incompatible species. Throughout the flowering period, with wide variation in floral display, we evaluated the effect of the pollinators’ foraging pattern within and between plants on their reproductive success. We also evaluated the foraging strategies employed by each pollinator species and the effect of nectar robbing on fruit production. In addition, we estimated the plants’ genome size in order to evaluate whether there were intrapopulation variations in the ploidy level that could be associated with the low reproductive success. In general, we demonstrated that the low pollen quality transferred by pollinators is the main limiting factor of the reproductive success. This effect occurs mainly at the flowering peak, when the floral display is more intense, and pollinators tend to visit a larger number of sequential flowers within the plant transferring incompatible pollen. In addition, the movement pattern between plants also was not efficient, since pollinators often visited nearby plants that possibly were more related. Although some hummingbirds species alternate their... (Complete abstract click electronic access below) / Doutor

Orientador: Elza Guimarães / Resumo: Nessa tese estudamos duas espécies melitófilas de Bignoniaceae, Jacaranda caroba e J. decurrens, que coocorrem em formações savânicas de cerrado e que se mostraram modelos interessantes para explorarmos aspectos ecológicos e evolutivos relacionados à sua reprodução sexual, tendo em vista que apresentam uma complexa rede de interações com mutualistas e antagonistas. A sobreposição geográfica dessas duas espécies nos permitiu avaliar padrões de coexistência relacionados à dinâmica de florescimento, bem como seu anúncio floral relacionado à atração de visitantes florais mutualistas e antagonistas. Além disso, essa interação com mutualistas e antagonistas possibilitou averiguar o impacto da atuação de antagonistas que roubam néctar sobre a polinização de ambas as espécies e como os danos realizados por abelhas roubadoras de néctar interferem na sinalização visual e química aos polinizadores. Também avaliamos a exploração de néctar por diferentes grupos funcionais de visitantes florais de J. caroba e J. decurrens. Por fim, considerando que o sucesso reprodutivo está diretamente relacionado com a eficiência da polinização investigamos o sistema reprodutivo dessas duas espécies e o efeito da qualidade do pólen transferido entre flores associado ao comportamento dos polinizadores durante o forrageamento, buscando compreender os fatores intrínsecos relacionados à seleção mecanismos de autoincompatibilidade nas populações naturais amostradas. / Abstract: In this dissertation we studied two mellithiphilous Bignoniaceae species, Jacaranda caroba and J. decurrens, that co-occur in savanic cerrado formations. This is an interesting model to explore ecological and evolutionary aspects related to their sexual reproduction taking into account that they present a complex network of interactions with mutualists and antagonists. These species‟ geographical overlap allowed us to evaluate patterns of coexistence related to the flowering dynamics, as well as its floral display related to the attraction of mutualists and antagonists‟ floral visitors. Besides, their interactions with mutualists and antagonists allowed us to evaluate the impact of nectar-robbing antagonists on both species and how damage by nectar-robber bees interferes with visual and chemical signaling to pollinators. We also evaluated the nectar exploitation by different functional groups of J. caroba and J. decurrens floral visitors. Finally, considering that these species‟ reproductive success and the effect of pollinator behavior during foraging on the quality of the pollen that is transferred among flowers. Considering that species‟ reproductive success is directly related to the pollination efficiency, we investigated the reproductive system of these two species and the effect of the quality of the pollen transferred between flowers associated to the pollinators‟ behavior during the foraging, trying to understand the intrinsic factors related to mechanisms of self-in... (Complete abstract click electronic access below) / Doutor

A disponibilidade e distribuição espaço-temporal do néctar nos diferentes tipos vegetacionais está relacionada a diversos fatores. Em espécies nectaríferas, o néctar é o recurso principal disponibilizado aos visitantes florais e sua produção pode determinar o sucesso no fluxo de pólen entre indivíduos na população. Nesse estudo, os objetivos foram: (i) avaliar se o display floral e seus caracteres morfológicos estão associados à produção do néctar; (ii) verificar se a distribuição do néctar é concentrada ou uniformemente distribuída ao longo do ano e; (iii) como a produção do néctar atua na atração dos visitantes florais e na deposição intra e interespecífica de pólen no estigma em espécies de plantas nectaríferas. O estudo foi feito em vegetação de cerrado na Estação Ecológica de Jataí (EEJ), localizada em Luís Antônio, São Paulo. Na EEJ, nós demarcamos duas transeções de 500 m por 10 m de cada lado. As transeções foram percorridas quinzenalmente no período de agosto de 2013 a julho de 2014 e para cada espécie de planta nectarífera em floração, nós contamos o número de indivíduos e de flores produzidas/indivíduo (display floral). Nós encontramos que há interação significativa entre o tamanho e a forma da flor na produção do néctar (F = 40,48, p < 0,0001). Nós observamos que quanto maior o número médio de óvulos de uma dada espécie, maior a produção média de néctar por flor (Rs = 0,58; p < 0,05). Encontramos que a razão pólen intraespecífico/pólen total depositado no estigma das flores foi influenciada negativamente pela abundância das abelhas (t= -3,930; p= 0,005). Nós observamos um nível intermediário de especialização (H2 = 0,412) quando analisamos a interação entre as espécies nectaríferas e as abelhas visitantes por meio de observação direta e mais especializado quando analisamos a interação por meio dos grãos de pólen depositados no corpo das abelhas (H2 = 0,62). Nós encontramos uma interação altamente especializada quando avaliamos os grãos de pólen depositados nos estigmas (H2 = 0,943). Nós corroboramos as nossas hipóteses de que a produção e distribuição do néctar na comunidade estão associadas ao número de flores disponíveis e à morfologia floral das espécies nectaríferas e que as plantas que produzem mais flores e um maior volume de néctar, apresentaram mais óvulos e atraem um maior número de abelhas visitantes e consequentemente apresentam uma maior deposição polínica nos estigmas / The availability and the spatial and temporal distribution of nectar in different types of vegetation are related to several factors. In nectariferous species, nectar is the main resource available to floral visitors and its production can determine a successful pollen flow between individuals in the population. The present study aimed to: (i) assess whether the floral display and its morphological traits are associated with nectar production; (ii) verify whether the distribution of nectar is concentrated or evenly distributed throughout the year and; (iii) analyze the influence of nectar production in attracting floral visitors and on intra and interspecific deposition of pollen on the stigma in nectariferous plant species. The study was conducted in cerrado in the Jataí Ecological Station (EEJ), located in Luís Antônio, São Paulo State. Inside the EEJ, two transects measuring 500 m x 10 m were delimited. The transects were run every two weeks from August 2013 to July 2014 and the number of individuals and flowers produced/individual (floral display) were counted for each species of nectariferous plant at flowering. There was a significant interaction between the size and shape of the flower for nectar production (F = 40.48, p < 0.0001). The higher the average number of ovules of a given species, the greater the average production of nectar per flower (Rs = 0.58; p < 0.05). Also, the ratio intraspecific pollen/total pollen deposited on the stigma of flowers was negatively affected by the abundance of bees (t= -3.930; p= 0.005). An intermediate level of specialization (H2 = 0.412) was found when analyzing the interaction between nectariferous species and visiting bees through direct observation and a more specialized level when analyzing the interaction by means of pollen grains deposited on the body of bees (H2= 0.62). In turn, considering the pollen grains deposited on stigmas, a highly specialized interaction was recorded (H2= 0.943). Our following hypotheses were confirmed: the production and distribution of nectar in the community are associated with the number of available flowers and with floral morphology of the nectariferous species and plants producing more flowers and a greater volume of nectar present more ovules and attract a higher number of visiting bees and thus show a greater deposition of pollen on stigmas

<p>In this thesis, I combined comparative and experimental approaches to examine selection on reproductive traits, and population differentiation in the insect-pollinated, outcrossing, perennial herb <i>Arabidopsis lyrata</i>. More specifically, I (1) determined whether selection on flowering phenology and floral display can be attributed to interactions with pollinators and herbivores, (2) examined whether population differentiation in flowering phenology and floral display is correlated with current selection on these traits, and (3) tested for local adaptation from contrasting environments in Europe.</p><p>A field experiment conducted in a Swedish population demonstrated, that interactions with pollinators may markedly affect selection on both floral display and phenology of flowering. In an alpine population in Norway, grazing damage to inflorescences strongly influenced selection on floral display. The results suggest that variation in the abundance of pollinators and herbivores should contribute to spatio-temporal variation in selection on flowering phenology and floral display in <i>A. lyrata</i>. </p><p>A common-garden experiment showed that flowering phenology and floral display vary among Scandinavian populations of <i>A. lyrata</i>. For some traits patterns of population differentiation were consistent with differences in the direction and strength of phenotypic selection determined in comparisons (a) between an alpine population in Norway and a coastal population in Sweden, and (b) among coastal populations in Sweden. This suggests that current selection contributes to the maintenance of genetic differentiation in these traits.</p><p>Adaptive differentiation among populations was examined in a reciprocal transplant experiment that included populations from three contrasting environments, alpine Norway, coastal Sweden and lowland, continental Germany. The experiment provided evidence for local adaptation, and indicated that populations have diverged in traits affecting plant establishment and early growth.</p>

In this thesis, I combined comparative and experimental approaches to examine selection on reproductive traits, and population differentiation in the insect-pollinated, outcrossing, perennial herb Arabidopsis lyrata. More specifically, I (1) determined whether selection on flowering phenology and floral display can be attributed to interactions with pollinators and herbivores, (2) examined whether population differentiation in flowering phenology and floral display is correlated with current selection on these traits, and (3) tested for local adaptation from contrasting environments in Europe. A field experiment conducted in a Swedish population demonstrated, that interactions with pollinators may markedly affect selection on both floral display and phenology of flowering. In an alpine population in Norway, grazing damage to inflorescences strongly influenced selection on floral display. The results suggest that variation in the abundance of pollinators and herbivores should contribute to spatio-temporal variation in selection on flowering phenology and floral display in A. lyrata. A common-garden experiment showed that flowering phenology and floral display vary among Scandinavian populations of A. lyrata. For some traits patterns of population differentiation were consistent with differences in the direction and strength of phenotypic selection determined in comparisons (a) between an alpine population in Norway and a coastal population in Sweden, and (b) among coastal populations in Sweden. This suggests that current selection contributes to the maintenance of genetic differentiation in these traits. Adaptive differentiation among populations was examined in a reciprocal transplant experiment that included populations from three contrasting environments, alpine Norway, coastal Sweden and lowland, continental Germany. The experiment provided evidence for local adaptation, and indicated that populations have diverged in traits affecting plant establishment and early growth.

A disponibilidade e distribuição espaço-temporal do néctar nos diferentes tipos vegetacionais está relacionada a diversos fatores. Em espécies nectaríferas, o néctar é o recurso principal disponibilizado aos visitantes florais e sua produção pode determinar o sucesso no fluxo de pólen entre indivíduos na população. Nesse estudo, os objetivos foram: (i) avaliar se o display floral e seus caracteres morfológicos estão associados à produção do néctar; (ii) verificar se a distribuição do néctar é concentrada ou uniformemente distribuída ao longo do ano e; (iii) como a produção do néctar atua na atração dos visitantes florais e na deposição intra e interespecífica de pólen no estigma em espécies de plantas nectaríferas. O estudo foi feito em vegetação de cerrado na Estação Ecológica de Jataí (EEJ), localizada em Luís Antônio, São Paulo. Na EEJ, nós demarcamos duas transeções de 500 m por 10 m de cada lado. As transeções foram percorridas quinzenalmente no período de agosto de 2013 a julho de 2014 e para cada espécie de planta nectarífera em floração, nós contamos o número de indivíduos e de flores produzidas/indivíduo (display floral). Nós encontramos que há interação significativa entre o tamanho e a forma da flor na produção do néctar (F = 40,48, p < 0,0001). Nós observamos que quanto maior o número médio de óvulos de uma dada espécie, maior a produção média de néctar por flor (Rs = 0,58; p < 0,05). Encontramos que a razão pólen intraespecífico/pólen total depositado no estigma das flores foi influenciada negativamente pela abundância das abelhas (t= -3,930; p= 0,005). Nós observamos um nível intermediário de especialização (H2 = 0,412) quando analisamos a interação entre as espécies nectaríferas e as abelhas visitantes por meio de observação direta e mais especializado quando analisamos a interação por meio dos grãos de pólen depositados no corpo das abelhas (H2 = 0,62). Nós encontramos uma interação altamente especializada quando avaliamos os grãos de pólen depositados nos estigmas (H2 = 0,943). Nós corroboramos as nossas hipóteses de que a produção e distribuição do néctar na comunidade estão associadas ao número de flores disponíveis e à morfologia floral das espécies nectaríferas e que as plantas que produzem mais flores e um maior volume de néctar, apresentaram mais óvulos e atraem um maior número de abelhas visitantes e consequentemente apresentam uma maior deposição polínica nos estigmas / The availability and the spatial and temporal distribution of nectar in different types of vegetation are related to several factors. In nectariferous species, nectar is the main resource available to floral visitors and its production can determine a successful pollen flow between individuals in the population. The present study aimed to: (i) assess whether the floral display and its morphological traits are associated with nectar production; (ii) verify whether the distribution of nectar is concentrated or evenly distributed throughout the year and; (iii) analyze the influence of nectar production in attracting floral visitors and on intra and interspecific deposition of pollen on the stigma in nectariferous plant species. The study was conducted in cerrado in the Jataí Ecological Station (EEJ), located in Luís Antônio, São Paulo State. Inside the EEJ, two transects measuring 500 m x 10 m were delimited. The transects were run every two weeks from August 2013 to July 2014 and the number of individuals and flowers produced/individual (floral display) were counted for each species of nectariferous plant at flowering. There was a significant interaction between the size and shape of the flower for nectar production (F = 40.48, p < 0.0001). The higher the average number of ovules of a given species, the greater the average production of nectar per flower (Rs = 0.58; p < 0.05). Also, the ratio intraspecific pollen/total pollen deposited on the stigma of flowers was negatively affected by the abundance of bees (t= -3.930; p= 0.005). An intermediate level of specialization (H2 = 0.412) was found when analyzing the interaction between nectariferous species and visiting bees through direct observation and a more specialized level when analyzing the interaction by means of pollen grains deposited on the body of bees (H2= 0.62). In turn, considering the pollen grains deposited on stigmas, a highly specialized interaction was recorded (H2= 0.943). Our following hypotheses were confirmed: the production and distribution of nectar in the community are associated with the number of available flowers and with floral morphology of the nectariferous species and plants producing more flowers and a greater volume of nectar present more ovules and attract a higher number of visiting bees and thus show a greater deposition of pollen on stigmas

In this thesis, I combined comparative and experimental approaches to examine selection on reproductive traits and population differentiation in the insect-pollinated, self-incompatible, perennial herb Primula farinosa. More specifically, I (1) determined whether the effects of floral display and interactions with pollinators and seed predators, and plant reproductive success were frequency-dependent and affected by surrounding vegetation context, (2) examined the consequences of intermittent drought years on population dynamics using numerical simulations based on demographic data collected over seven years, (3) analyzed among-population differentiation in flowering phenology and reproductive allocation, and its relationship to soil-depth at the site of origin. A field experiment suggested that conspicuous plants facilitate inconspicuous plants in terms of pollinator attraction, and that the facilitation effect is contingent on the height of the surrounding vegetation. Further experiments revealed that both mutualistic and antagonistic interactions can result in frequency-dependent selection on floral display. Among inconspicuous plants, both fruit initiation, and damage from seed predators increased with the proportion of the conspicuous morph. The relative strength of these effects, and therefore their net outcome on the relationship between morph ratio and seed production varied among years. I combined information on vital rates and their relation to environmental conditions in simulations to predict future population viability in changing environments. Simulated stochastic population growth rate decreased with increasing frequency of drought years. Reproductive allocation varied significantly among populations both in the field and in a common-garden experiment, but was correlated with soil depth at the site of origin only in the field. The results suggest that among-population variation in reproductive effort in the field mainly reflects plastic responses to environmental conditions, and that this plasticity may be adaptive. The common-garden experiment suggested that the study populations have diverged genetically in flowering time.

<p>In this thesis, I combined comparative and experimental approaches to examine selection on reproductive traits and population differentiation in the insect-pollinated, self-incompatible, perennial herb <i>Primula farinosa</i>. More specifically, I (1) determined whether the effects of floral display and interactions with pollinators and seed predators, and plant reproductive success were frequency-dependent and affected by surrounding vegetation context, (2) examined the consequences of intermittent drought years on population dynamics using numerical simulations based on demographic data collected over seven years, (3) analyzed among-population differentiation in flowering phenology and reproductive allocation, and its relationship to soil-depth at the site of origin. </p><p>A field experiment suggested that conspicuous plants facilitate inconspicuous plants in terms of pollinator attraction, and that the facilitation effect is contingent on the height of the surrounding vegetation. Further experiments revealed that both mutualistic and antagonistic interactions can result in frequency-dependent selection on floral display. Among inconspicuous plants, both fruit initiation, and damage from seed predators increased with the proportion of the conspicuous morph. The relative strength of these effects, and therefore their net outcome on the relationship between morph ratio and seed production varied among years. </p><p>I combined information on vital rates and their relation to environmental conditions in simulations to predict future population viability in changing environments. Simulated stochastic population growth rate decreased with increasing frequency of drought years. </p><p>Reproductive allocation varied significantly among populations both in the field and in a common-garden experiment, but was correlated with soil depth at the site of origin only in the field. The results suggest that among-population variation in reproductive effort in the field mainly reflects plastic responses to environmental conditions, and that this plasticity may be adaptive. The common-garden experiment suggested that the study populations have diverged genetically in flowering time.</p>