ABSTRACT Distyly is a floral polymorphism with reciprocal placement of male and female structures, heteromorphic self-incompatibility, and other ancillary traits. However, breeding system breakdowns and loss of polymorphism are common. Here we traced the diversification of breeding strategies in the type genera of tribes Palicoureeae and Psychotrieae and discussed the evolution of distyly in a phylogenetic framework. We used literature and field information for breeding systems transitions in 46 species of Palicourea and Psychotria. Beyond distyly, we found four additional breeding systems, including monomorphism with herkogamy, homostyly (without herkogamy), monoecy and dioecy. Breeding transitions arose independently and were mostly derived from distyly. Only two species presented monomorphism as an intermediate state into gender specialization. It was not possible to evaluate the origin and evolutionary pathways for distyly in Psychotria and Palicourea as a whole, since distyly seems to be ancestral to their diversification. Breeding transitions in Psychotria and Palicourea appeared to be phylogenetically and biogeographically independent and occurred mostly in islands or isolated forest fragments, with distinct divergence times. Breeding transitions were not related to changes in ploidy. We propose that evolution of breeding transitions in Psychotria and Palicourea represent phylogenetically independent strategies to reproductive assurance in isolated or disturbed habitats.

Resumo Diferentes citótipos na mesma espécie têm sido associados a mudanças na reprodução das plantas, da sexualidade à apomixia, e podem explicar o isolamento entre populações e espécies. Os híbridos resultantes de cruzamentos de interploidia podem contribuir para o entendimento de como essas populações e espécies podem ter se originado e evoluído. A morfometria estomática e as análises de citometria de fluxo foram realizadas para plântulas de diferentes populações de Eriotheca estevesiae, E. gracilipes e E. pubescens, espécies arbóreas dos Cerrados do Brasil Central. Polinizações cruzadas controladas entre indivíduos de citótipos distintos de E. gracilipes (2n = 2x = 92 e 2n = 6x = 276) e entre citótipos sexuais de E. gracilipes (2n = 2x = 92) e E. pubescens (2n = 4x = 184 ) foram realizadas. Apenas uma semente viável foi obtida a partir de cruzamentos interploidias de E. gracilipes. A hibridização entre citótipos sexuais não produziu frutos. As análises do tamanho do genoma indicaram que aparentemente não havia híbridos naturais ou população de ploidia mista entre as plântulas analisadas. O tamanho dos estômatos das plântulas era consistente com os citótipos e o nível de ploidia supostos; e quando comparados com os estômatos do híbrido de interploidia viável de E. gracilipes, indicou um nível de ploidia intermediário, tetraplóide. Embora os dados tenham confirmado a possibilidade de hibridização interploidia, os citótipos pareceram relativamente estáveis e a hibridização interploidia natural parece ser menos comum em árvores Eriotheca.

Abstract Hybridization and changes in ploidy have been associated with shifts from sexuality to apomixis, and may explain isolation among populations and species. Hybrids resulting from interploidy crosses may contribute to a broader understanding of how these populations and species have originated and evolved. Stomatal morphometrics and flow cytometry analyses were carried out for seedlings from different populations of Eriotheca estevesiae, E. gracilipes and E. pubescens, a group of closely related tree species in the Central Brazilian Cerrados. Controlled cross-pollinations between individuals of different cytotypes of E. gracilipes (2n = 2x = 92 and 2n = 6x = 276) and between sexual cytotypes of E. gracilipes (2n = 2x = 92) and E. pubescens (2n = 4x = 184) were performed. Only one viable seed was obtained from interploidy crosses of E. gracilipes. The hybridization between sexual cytotypes did not produce fruits. Genome size analyses indicated that there were apparently no natural hybrids or mixed ploidy populations among the seedlings analyzed. Seedlings stomatal size was consistent with previously reported cytotypes and ploidy levels; and when compared with the stomata of the viable interploidy hybrid of E. gracilipes, indicated a tetraploid, intermediate ploidy level. Although the data suggest the possibility of interploidy hybridization, cytotypes appeared relatively stable and natural interploidy hybridization seems to be uncommon among Eriotheca trees.

Resumo A heterostilia é um polimorfismo floral geneticamente controlado onde populações de plantas apresentam dois ou três morfos com peças reprodutivas em alturas recíprocas entre os morfos. Em populações naturais, espera-se encontrar uma razão igual entre os morfos (isopletia). O objetivo do estudo foi caracterizar o sistema reprodutivo, a biologia floral, as características heterostílicas, incluindo reciprocidade das peças reprodutivas, fenologia e polinização em Palicourea crocea, uma espécie arbustiva do sub bosque de formações florestais do Cerrado. Para tal foram medidas estruturas florais, realizados cruzamentos controlados, observados os visitantes florais, além de acompanhamento fenológico. Palicourea crocea é uma espécie distílica típica, autoincompatível, com altos índices de hercogamia recíproca entre os morfos. Polinizada preferencialmente por beija-flores, além de mariposas e abelhas. Houve formação maior de frutos em polinização cruzada intermorfo (> 50%) e menor formação em polinização intramorfo (< 20%) e autopolinização (< 13%). Esses dados foram confirmados pelo não crescimento de tubos polínicos em pistilos autopolinizados e polinizados de forma intramorfo. A floração é anual, e ocorre entre os meses de novembro e fevereiro, com pico de floração em dezembro e janeiro. Os dados reprodutivos avaliados se mostram similares a outras espécies de Rubiaceae do sub bosque de ambientes florestais do Cerrado.

Abstract The heterostyly is a floral polimorphysm genetically controlled where populations of plants present two or three morphs with reproductive structures in reciprocal heights among the morphs. In natural populations, a balanced ratio between morphs (isoplethy) is expected. The objective of the study was to characterize the breeding system, the floral biology, the characteristics of heterostyly, including reciprocity of reproductive parts, the phenology and pollination in Palicourea crocea, a shrub species of the understory of forest formations of Cerrado. For such measures were floral structures, held controlled crossings, observed flower visitors, in addition to phenological monitoring. Palicourea crocea is proved to be a typical distylous species, self-incompatible, with high levels of reciprocal herkogamy between the morphs. Preferentially pollinated by hummingbirds, followed by moths and bees. There was a higher fruit formation in cross-pollination intermorph (> 50%) and lower fruit formation intramorph pollination (< 20%), and self-pollination (< 13%). These data were confirmed by the not growth of pollen tubes in self-pollination and pollinated intramorph pistils. Flowering is annual and occurs between the months of November and February, with peak flowering in December and January. Reproductive data evaluated to show similar to other species of Rubiaceae of the understory of forest formations of Cerrado.

ABSTRACT In diploid late-acting self-incompatible (LSI) species of Bignoniaceae, self-pollinated pistils show a marked delay in ovule penetration by pollen tubes, followed by delayed, but otherwise normal, initial stages of endosperm development and subsequent pistil abscission. Most polyploid species of Bignoniaceae are apomictic and set selfed fruits with viable polyembryonic seeds carrying adventitious embryos. Handroanthus serratifolius is a polyploid species with sporophytic apomictic individuals that produce polyembryonic seeds after either self- or cross-pollination, and other LSI individuals that produce exclusively monoembryionic seeds. Our aim was to determine whether self-sterility events in the latter are similar to those observed in other diploid LSI species of Bignoniaceae. No conspicuous differences in the progress of ovule penetration, fertilization and early stages of endosperm development were observed between selfed and crossed pistils, which contrasts with the marked delay observed in these events after self-pollination in diploid LSI species of the family. Adventitious embryo precursor cells (AEPs) were observed in some ovules, but they apparently do not develop into embryos. We believe that the AEPs in these plants represent a ‘potential’ for sporophytic apomixis, which would explain the similar behaviour of post-pollination events in selfed vs. crossed pistils despite their inability to set fruits after selfing.

ABSTRACT The relationship between plants and frugivorous animals is modulated by morphological and nutritional characteristics of fruits, as well as their seasonal availability across habitats. We evaluated fruiting phenology, fruit morphology and nutritional characteristics of 35 abundant plant species from 15 families associated with frugivorous birds from distinct habitats in the Cerrado (savanna, forest, and palm swamp). For a subset of 16 plant species, we also evaluated the overlap in interactions with frugivorous birds using data from the literature. Open-habitat plants had their fruiting peak during the rainy season, while fruiting of forest species was evenly distributed across the year. Plants of the same family exhibited similar fruit morphology and nutritional characteristics. Most plants had fruits with more sugars than lipids, while all species with higher lipid content were from savanna habitats and produced fruits during the rainy season, the peak reproductive season for birds. Assemblages of frugivorous birds exhibited considerable overlap, irrespective of habitat or fruiting season of plants. The complementarity found among habitats, considering seasonal availability and nutritional profile of fruits for frugivorous birds, is relevant for community maintenance and regeneration. Therefore, this landscape level complexity should always be considered in conservation and restoration policies for the Cerrado.

ABSTRACT Pollination research in Brazil virtually started with Fritz Muller, whose insights supported Darwin's evolutionary theory. Pollination systems of Brazilian plants were studied mainly by travelling researchers until early last century when native or resident geneticists began to use floral biology information to deal with crop acclimatization and breeding, later applying similar experiments and techniques to investigate native plants. Bee geneticists studied common pollinators of crops, such as coffee and Citrus, and even the introduction of feral African honeybees, despite their associated problems, stimulated pollination research. Geneticists attracted Dobzhansky to Brazil, where his research on tree distribution in the Brazilian Amazon represented a turning point for tropical pollination research by prompting the discovery of long-distance pollinating bees, thus bringing pollination back to mainstream evolutionary research. Tropical pollination studies stimulated the emergence of research groups in the Amazon and São Paulo states. In 1998, a seminal conference held in São Paulo called for the need to conserve pollinators and pollination systems. Subsequent research has been integrated under the Brazilian Pollinators Initiative, with research groups established throughout the country. A revived International Pollination Course, a National Pollination Symposium, and cooperative efforts to tackle complex interaction networks may direct future pollination research in Brazil.

Resumo Espécies distílicas possuem populações com dois morfos florais. O morfo longistilo possui flores com pistilos longos e estames curtos e o morfo brevistilo, pistilos curtos e estames longos. Normalmente, os morfos apresentam um sistema heteromórfico de incompatibilidade e os morfos estão em uma razão de 1:1 (isopletia) nas populações. Diferentes variações podem ser encontradas em espécies distílicas, como a presença de autocompatibilidade, anisopletia e variações no nível de reciprocidade entre anteras e estigmas dos dois morfos. O objetivo desse trabalho foi investigar a ocorrência das características distílicas em duas espécies de Rubiaceae. Para isso, a razão dos morfos, a hercogamia recíproca, o sistema de incompatibilidade e os visitantes florais de Psychotria deflexa e Declieuxia fruticosa foram estudados. Ambas as espécies apresentaram os dois morfos em proporção semelhante, altos valores de reciprocidade entre a altura dos verticilos sexuais dos morfos florais e apenas insetos como visitantes florais. O morfo brevistilo das duas espécies apresentou autoincompatibilidade parcial. Dentro de Rubiaceae, mesmo em grupos filogenéticos distintos, o relaxamento ou quebra da distilia parece ocorrer em padrões similares e comumente tal variação é mais comum no morfo longistilo. Para as espécies estudadas, mesmo com a pseudocompatibilidade do morfo brevistilo, as populações apresentaram proporção igual dos morfos, indicando que fatores como a alta hercogamia recíproca e, possivelmente, o serviço de polinização podem promover a manutenção da isopletia característica da distilia.

Abstract Distylous species have populations with two floral morphs. The pin morph has long pistils and short stamens while the thrum morph presents short pistils and long stamens. Usually heterostylous plants present a diallelic system of incompatibility and morphs occur in a 1:1 ratio (isoplethy) in the populations. Different forms of variations occur in distylous species, such as the presence of self-compatibility, anisoplethy and variation in the reciprocity level between anthers and stigmas of the two floral morphs. The aim of this study was to investigate the occurrence of the distylous characteristics in two Rubiaceae species. For this purpose, morph ratio, reciprocal herkogamy, incompatibility system and flower visitors of Psychotria deflexa and Declieuxia fruticosa were studied. Both species have the two floral morphs in equal ratio, high reciprocity values for height of the reproductive whorls of the floral morphs and were visited only by insects. However, the thrum morph on both species presented partial self-incompatibility. Within the Rubiaceae, even in distinct phylogenetic groups, weakening or breakdown of distyly seems to occur in similar patterns, but deviations in the incompatibility system have been mostly recorded for the pin morph of distylous species. In the studied species the populations had equal morph ratio despite the pseudocompatibility of the thrum morph, which indicates that factors such as high reciprocal herkogamy and possibly efficient pollination services could promote the maintenance of distyly in these species.

ABSTRACT Flowers of species of Senna are very morphologically diverse, however, nothing has been reported regarding variation in the presence of a unicarpellate gynoecium, which is characteristic of the group. This study reports the occurrence of a bicarpellate gynoecium in two enantiostylous species of Senna in an area of dry forest (Caatinga) in NE Brazil. Observations of floral morphology and estimates of the proportions of floral morphs in the populations were performed. The species produce three floral types: left (L), right (R) and bicarpellate (B). The proportion of these floral morphs were similar in the populations of Senna macranthera var. micans, but the number of B flowers in populations of S. trachypus was lower than that recorded for L and R flowers. The occurrence of this morphological variation may be related to enhancing pollen capture in both species; in S. trachypus, this variation may also be related to reducing florivory by caterpillars that were observed eating sexual elements of the flowers.

Os ambientes abertos de Cerrado têm sido considerados ambientes marginais ou complementares para beija-flores, apesar do registro de considerável número de espécies deste grupo de visitantes florais. Estes utilizam uma variedade de plantas, incluindo aquelas sem características ornitófilas. O objetivo do trabalho foi investigar a flora utilizada por beija-flores como recurso alimentar em três áreas de Cerrado, distantes entre si de ca. 20 a 150 km. Em cada área foram demarcados, em cerrado s.s., dois transectos de 1 ha cada, que foram percorridos quinzenalmente para identificação das espécies utilizadas pelos beija-flores, os quais também foram identificados. A riqueza de espécies de plantas encontrada (26) foi maior que a registrada em outros estudos na mesma região, porém foi menor que na maioria dos ambientes florestais. Destas espécies, apenas nove (34%) apresentaram síndrome de ornitofilia. Foram registradas nove espécies de beija-flores (Trochilidae) nas três áreas. Apesar da grande diversidade beta descrita para plantas no Cerrado, a similaridade de espécies utilizadas pelos beija-flores foi alta entre os transectos das três áreas estudadas, independente de serem plantas tipicamente ornitófilas ou não. Havia plantas oferecendo recursos florais para os beija-flores durante praticamente todo o ano. O grande número de espécies não ornitófilas utilizadas por estas aves corrobora a ideia de que, em ambientes de Cerrado, as espécies vegetais que oferecem néctar parecem ser mais importantes para os beija-flores que vice-versa.

The open savanna areas of the Cerrado region in Central Brazil have been considered as marginal or complementary habitats for hummingbirds, despite the considerable number of hummingbirds recorded. These birds use a variety of plants without ornithophilous caracteristcs. The objective of the study was to investigate the flora used by hummingbirds as food resource in three Cerrado areas 20 to 150 km apart. In each of these cerrado s.s. areas, two transects of 1 ha each were walked fortnightly to identify the plant species used by hummingbirds, which were also identified. The number of plant species recorded (26) was higher than that observed for other studies in the same region but was lower than that recorded for forest habitats. Only nine plants (34%) showed a truly ornithophilous syndrome. There were nine hummingbird species (Trochilidae) in the three areas. Although the Cerrado flora has been characterized by its high β-diversity, the hummingbird plants among transects and areas were very similar. Despite being truly ornithophilous or not, there were plants offering nectar to hummingbirds year round. The indiscriminate use of non-ornithophilous species corroborates the idea that, in Cerrado habitats, nectariferous plants seem to be more important to hummingbirds than vice-versa.

The ability of plants to generate fertile offspring is influenced by morpho-physiological and ecological factors. Hence, reproductive success is directly linked to factors affecting quantity and quality of their progeny. In the Cerrado (savanna) of Brazil, the Vochysiaceae is a widely distributed and ecologically important family. Factors affecting pre-dispersal seed predation and abortion were studied for populations of Callisthene fasciculata, C. major, Qualea multiflora and Q. parviflora. To characterize differences between genera, as well as among species, study areas, and individuals, we quantified pre-dispersal seed predation and abortion. Differences of seed abortion among the species were related to intrinsic reproductive features and not to area or other factors. In contrast, seed predation varied not only among species but also among areas and among individuals. Only C. fasciculata showed no seed predation. In Qualea species, insect predators were found inside the seeds; whereas predators of Callisthene species were outside seeds. In both genera, seed abortion correlated negatively with area size, as did pre-dispersal seed predation, which suggest seed abortion may be a counter-measure to avoid predation. Although seed abortion and predation reduced the progenies of the studied species, seed production did not differ from other Cerrado species.

Polyploidization is common among angiosperms and might induce typically allogamous plants to become autogamous (self-compatible, relying on sexual self-fertilization) or apomictic (achieving asexual reproduction through seeds). This work aimed to determine whether neopolyploidy leads to the breakdown of the self-incompatibility system in the hexaploid non-apomictic species Handroanthus serratifolius (Vahl) S. Grose, through analyses of its floral biology, pollination biology and breeding system. Although anthesis lasted for three days, increasing the overall floral display, receptivity decreased as of the second day. Centridini and Euglossini bees were the main pollinators, and low nectar availability (1.95 ± 1.91 µl/flower) might have obliged them to visit multiple flowers. We observed low reproductive efficacy. That might be explained by self-sterility and by the great number of flowers per individual, which could increase the frequency of geitonogamy. Ovule penetration by the pollen tubes in self-pollinated pistils with posterior abscission indicated late-acting self-incompatibility in H. serratifolius, as observed in other diploid Bignoniaceae species, although inbreeding depression cannot be excluded. The self-sterility found in the monoembryonic, hexaploid individuals studied here contrasts with the results for other neopolyploid Handroanthus and Anemopaegma species, which are often autogamous and apomictic. Our results suggest that neopolyploidy is not the main factor leading to self-fertility in Handroanthus.

Alguns fatores podem influenciar a distribuição dos recursos florais e sistemas de polinização bióticos nos ecossistemas, como por exemplo, o clima, a altitude, a região geográfica, fragmentação de áreas naturais e as diferenças na composição florística na estratificação vertical. Este estudo teve por objetivo avaliar a distribuição dos sistemas de polinização bióticos na estratificação vertical em fragmentos de cerrado sentido restrito no Triângulo Mineiro. Não houve diferença significativa (χ²0,05,9 =14,17; p = 0,12) na riqueza florística geral entre os fragmentos, nem quando comparada em separado para cada estrato (arbóreo, arbustivo, herbáceo e liana), estando o estrato arbustivo mais bem representado. Da mesma forma, não houve diferenças significativas entre fragmentos quanto aos sistemas de polinização (χ²0,05,21 =13,80; p = 0,8778), sendo a polinização por abelhas mais comum, correspondendo ao menos 85% das espécies de plantas em cada fragmento. Em termos relativos, as plantas polinizadas por abelhas foram dominantes em todos os estratos, chegando a 100% das lianas e herbáceas em alguns fragmentos. Neste estudo, com base na composição florística e distribuição dos sistemas de polinização na estratificação vertical, podemos caracterizar um mosaico vertical no cerrado sentido restrito, que tem implicações na sustentabilidade das comunidades no cerrado, assim como os mosaicos horizontais de fitofisionomias.

Several factors can influence the distribution of floral resources and pollination systems in ecosystems, such as climate, altitude, geographic region, fragmentation of natural areas and differences in floristic composition along the vertical stratification. This study aimed to evaluate the distribution of the vertical stratification of biotic pollination systems in cerrado (sensu stricto) fragments in the Triângulo Mineiro. There was no significant difference (χ²0.05,9=14.17; P = 0.12) in total plant species richness among fragments, nor in the species richness of each layer (trees, shrubs, herbs and lianas) and the shrub layer was the best represented. Likewise, there was no significant difference between fragments for the systems of pollination (χ²0.05,21 =13.80; P = 0.8778). Pollination by bees was the most common, corresponding to 85% of species in each fragment. In relative terms, plants pollinated by bees were dominant in all strata, reaching 100% for the lianas in fragments 1, 3 and 4 and for the herbs in fragments 1 and 4. In this study, based on floristic composition and distribution of biotic pollination systems in the vertical stratification, we could define a vertical mosaic in the cerrado studied, which has implications for the sustainability of communities in the cerrado, as well as the horizontal mosaic of vegetation types.

Cuphea melvilla é uma espécie peculiar dentro de um gênero majoritariamente melitófilo. Dois agrupamentos de indivíduos, em bordas das matas de galeria do Córrego do Panga, Uberlândia, MG, foram estudados com o objetivo de investigar o sistema de polinização e sistema de reprodução da espécie na região. O estudo foi realizado de janeiro a junho de 1999. Cuphea melvilla é uma espécie arbustiva com características morfológicas e eventos florais que confirmam sua adaptação à polinização por beija-flores. A floração foi longa, com início em Janeiro, em plena estação chuvosa, e término em Julho, no início da seca. O tubo floral formado pelo hipanto é calcarado na base, onde se acumula o néctar produzido por nectário localizado na base do ovário. As flores são marcadamente protândricas, mas flores em diferentes fases podem ser encontradas nos racemos. Os dados mostraram que a espécie é autocompatível e não apomítica, mas devido à dicogamia marcada, necessita polinização ativa para formar frutos. Phaethornis pretrei, Amazilia fimbriata, Thalurania furcata, Eupetomena macroura e Chlorostilbon lucidus (fêmea) foram as espécies de beija-flores observadas visitando e polinizando as flores de C. melvilla. Amazilia fimbriata e C. lucidus apresentaram ocasionalmente comportamento territorial, P. pretrei apresentou forrageamento em linhas de captura, e T. furcata e E. macroura apresentaram forrageamento do tipo oportunístico, visitando as populações estudadas esporadicamente. Amazilia fimbriata, C. lucidus e P. pretrei foram considerados os polinizadores mais importantes, dada a sua constância. As características morfológicas das flores de Cuphea melvilla relacionadas a adaptações aos beija-flores parecem ser derivadas no gênero, sendo que a polinização por beija-flores nas distintas seções indica adaptação convergente a este modo de polinização.

Cuphea melvilla is a peculiar species of a mostly melittophilous genus. Various aspects of the floral and reproductive biology of two groups of individuals, which occur on the edge of gallery forests on the Panga stream (in Uberlândia, southeastern Brazil), were studied. Observations were carried out during the flowering season of 1999. Cuphea melvilla is a shrub with floral features adapted to hummingbird pollination. It has a long flowering period, from January to July, but flowers the most during the rainy season. The flower tube of this species is of hypanthial origin, has a spur at the base, and accumulates nectar, which is produced by a nectary at the base of the ovary. The flowers were protandrous but different floral phases were present from the top to the bottom of the simple racemes. The species appears to be self-compatible but non-apomictic and needs active pollination to form fruits. Pheathornis pretrei, Amazilia fimbriata, Thalurania furcata, Eupetomena macroura and Chlorostilbon lucidus (female) were the hummingbird species observed visiting and pollinating the C. melvilla flowers. Amazilia fimbriata and C. lucidus showed occasional territorial behaviour in relation to the C. melvilla populations, whereas P. pretrei seemed to be trapliner. Thalurania furcata and E. macroura visited the studied populations sporadically. Amazilia fimbriata, C. lucidus and P. pretrei were considered the main pollinators for the studied populations due to their frequency. The flower features of Cuphea melvilla that are related to hummingbird pollination appear to be derived within the genus, and bird pollination, within different sections of the genus, indicate a convergent adaptation.

O espectro de visitantes florais associados a uma planta é frequentemente maior que o esperado pelo conceito tradicional de síndromes florais e o papel desses visitantes inesperados tem recebido mais atenção. Os beija-flores freqüentemente visitam flores com síndromes florais distintas, especialmente em alguns ecossistemas pobre em flores ornitófilas como o Cerrado. Investigamos aqui o efeito das visitas de beija-flores na reprodução de Styrax ferrugineus, uma espécie melitófila. As flores foram visitadas por diferentes grupos de insetos e as visitas por beija-flores foram frequentes, especialmente no início das manhãs quando a disponibilidade de néctar foi maior. Os parâmetros de néctar variaram consideravelmente durante a antese, provavelmente afetados pela variação da temperatura durante o dia. Experimentos de exclusão de beija-flores não mostraram efeito sobre a produção de frutos. A incapacidade dos beija-flores em esgotar todo néctar produzido pela planta e a existência de outro recurso floral (pólen) para o polinizador principal (grandes abelhas) são apontadas como razões possíveis para a ausência desse efeito. Embora não tenha sido observado efeito sobre a produção de frutos, o uso de flores não ornitófilas deve ser importante para os beija-flores que são consumidores especializados de néctar.

The spectrum of floral visitors associated with a particular plant is frequently larger than predicted by the traditional concept of floral syndromes and the role that unpredicted visitors play in plant reproduction deserves attention. Hummingbirds are frequently recorded visiting flowers with distinct floral syndromes, especially in some hummingbird flower poor ecosystem such as the Cerrado. In this study we investigated the effect of frequent hummingbird visits on the reproduction of melittophilous Styrax ferrugineus. The flowers were visited by many different insect groups and visits by hummingbirds were frequent, especially early in the morning when nectar availability was higher. Nectar parameters varied considerably during the flower life span, and was probably affected by the temperature variation during the day. Hummingbird exclusion experiments showed no effect in the fruit-set of the plant. The inability of hummingbirds to deplete all of the nectar produced in this mass-flowering plant, and the existence of another resource (pollen) for the primary pollinator (large bees), are possible reasons why there was no perceptible hindrance of plant reproduction by the hummingbirds. Although no effect in the fruit-set was observed, the use of non-ornithophilous flowers must be important for hummingbirds, which are specialized nectar consumers.

Dioicia é caracterizada pela separação completa das funções sexuais, na qual plantas apresentam indivíduos masculinos e femininos. Este sistema evoluiu muitas vezes entre as Angiospermas e está amplamente distribuído entre as distintas famílias. É visto como uma estratégia reprodutiva para reduzir a endogamia e otimizar a alocação diferencial de recursos entre as funções sexuais masculinas e femininas. Neea theifera é uma espécie comum no Cerrado, área de Savana Neotropical no Brasil, mas informações acerca de sua biologia reprodutiva são incompletas. Para investigar se as condições ambientais afetam espécies dióicas, foi estudada sua biologia floral, a razão sexual e distribuição espacial dos morfos ao longo de um gradiente de solo-altitude. A razão sexual da população não diferiu da razão esperada de 1:1. Porém, a abundância de flores estaminadas na população foi significativamente maior. Os indivíduos femininos foram maiores que os masculinos e o tamanho das plantas correlacionou-se negativamente com a altitude, apesar de não diferirem entre os morfos sexuais. A população não apresentou segregação espacial dos morfos sexuais e os indivíduos masculinos apresentam maturação sexual precoce em relação aos femininos. Flores estaminadas foram maiores que as pistiladas, além de apresentarem alta viabilidade polínica. Abelhas Meliponini, pequenas moscas e tripes foram os potenciais polinizadores, entretanto o sucesso de polinização foi muito baixo. A dioicia em N. theifera corrobora muitas características gerais desta estratégia reprodutiva, como hábito lenhoso, flores inconspícuas, polinização por pequenos insetos generalistas e alocação diferencial de recursos entre indivíduos masculinos e femininos. Porém, a reprodução nesta espécie é aparentemente afetada por limitação de polinizadores. Os resultados mostram que o gradiente de solo-altitude influencia o padrão de crescimento da espécie e pode ter um importante papel na biologia reprodutiva da planta, mas não afeta diretamente a dioicia.

Dioecy is characterized by a complete separation of sexual functions on male and female plants. It has evolved many times in flowering plants and is widespread among distinct Angiosperm families. It is viewed as a reproductive strategy to reduce endogamy, and to promote optimal resource allocation between male and female sexual functions. Neea theifera is a common species in Cerrado, neotropical savannas in Brazil, but information regarding its reproductive biology is still incomplete. In order to investigate how environmental conditions possibly affect this dioecious species, we studied its floral biology, sex ratio and spatial distribution of sexual morphs along a soil-altitudinal gradient. The sex ratio did not significantly deviate from the expected 1:1 ratio. However, flower abundance in the population was significantly biased towards staminate flowers. Female individuals were larger than male individuals and plant size was negatively correlated with altitude, but did not differ between sexual morphs. The population did not show spatial segregation of sexes and male individuals were sexually mature earlier than female ones. Staminate flowers were larger than pistillate flowers and presented high pollen viability. Meliponini bees, small flies and thrips were potential pollinators, but pollination success was very low. Dioecy in N. theifera corroborates many general features of this reproductive strategy, such as woody habit, inconspicuous flowers, pollination by small generalist insects and differential resource allocation between male and female plants. However, reproduction in this species seems to be impaired by pollinator limitation. The results showed that the soil-altitude gradient influenced the growth pattern of the species and may play an important role in its reproductive biology but did not affect dioecy directly.