Strongly unbalanced gender attractiveness in a dioecious mass flowering tropical tree pollinated by stingless bees.

In dioecious, bee-pollinated tree species, male and female flowers offer different resources. It is unclear how this unbalanced quantity and quality of floral resources affects flower visits and pollen transfer to female flowers. We asked, what characteristics of flowering and dynamics of resource production by trees favour flights of bees between male and female trees. We quantified the floral resources produced by individual flowers and entire trees of Myracrodruon urundeuva (Anacardiaceae), measured pollen flow to female flowers, fruit set of naturally pollinated flowers and determined the effective pollinators. Crown volume of male trees was four-fold, flower number 15-fold and nectar volume 60 times higher than in female trees. While ~70% of male flowers opened in the morning, ~70% of female flowers opened in the afternoon. Fruit set was 27%. Stingless bee species were the main pollinators, while honeybees were common only on male flowers. Strongly unbalanced production of floral resources, high potential lifespan of female flowers and anticipated opening of male flowers favour pollinator movement and pollen deposition on female flowers, albeit low (0.003% of pollen that reached stigmas), but sufficient to produce thousands of fruits per tree. Besides being an astonishing pollen and nectar source for numerous social bee species, only a few of them were effective pollinators. Our quantitative approach to floral resource production of each gender provides new insights, such as the proportion of resources allocated to each gender and the corresponding behaviour of flower visitors, for understanding the reproductive strategy of dioecious tropical mass-flowering trees.

Specialised protagonists in a plant-pollinator interaction: the pollination of Blumenbachia insignis (Loasaceae).

Analyses of resource presentation, floral morphology and pollinator behaviour are essential for understanding specialised plant-pollinator systems. We investigated whether foraging by individual bee pollinators fits the floral morphology and functioning of Blumenbachia insignis, whose flowers are characterised by a nectar scale-staminode complex and pollen release by thigmonastic stamen movements. We described pollen and nectar presentation, analysed the breeding system and the foraging strategy of bee pollinators. We determined the nectar production pattern and documented variations in the longevity of floral phases and stigmatic pollen loads of pollinator-visited and unvisited flowers. Bicolletes indigoticus (Colletidae) was the sole pollinator with females revisiting flowers in staminate and pistillate phases at short intervals, guaranteeing cross-pollen flow. Nectar stored in the nectar scale-staminode complex had a high sugar concentration and was produced continuously in minute amounts (~0.09 µl·h-1 ). Pushing the scales outward, bees took up nectar, triggering stamen movements and accelerating pollen presentation. Experimental simulation of this nectar uptake increased the number of moved stamens per hour by a factor of four. Flowers visited by pollinators received six-fold more pollen on the stigma than unvisited flowers, had shortened staminate and pistillate phases and increased fruit and seed set. Flower handling and foraging by Bicolletes indigoticus were consonant with the complex flower morphology and functioning of Blumenbachia insignis. Continuous nectar production in minute quantities but at high sugar concentration influences the pollen foraging of the bees. Partitioning of resources lead to absolute flower fidelity and stereotyped foraging behaviour by the sole effective oligolectic bee pollinator.

Heteranthery as a solution to the demand for pollen as food and for pollination - Legitimate flower visitors reject flowers without feeding anthers.

Heteranthery, the presence of feeding and pollinating anthers in the same flower, seems to mediate the evolutionary dilemma for plants to protect their gametes and yet provide food for pollinators. This study aims to elucidate the role of heteranthery in the buzz-pollinated Senna reniformis. The fecundity of pollen from long-, medium- and short-sized anthers was determined by hand cross-pollination experiments, and the quantity, size, ornamentation and viability of pollen of different anthers were compared. Rates of flower rejection by bees were measured in anther removal experiments to assess the preferences of flower visitors for feeding or pollinating anthers. Large bees, which were the effective pollinators of self-incompatible S. reniformis, avoided flowers without short feeding anthers, but not those without medium or long anthers. Illegitimate small and medium-sized bees were unresponsive to anther exclusion experiments. Long anthers deposited pollen on the back and short anthers on the venter of large bees. Pollen from long anthers had higher in vitro viability and higher fruit and seed set after cross-pollination than pollen from other sized anthers. Short anthers produce feeding pollen to effective pollinators and long anthers are related to pollination of S. reniformis. Bee behaviour and size was found to directly influence the role of anthers in the 'division of labour'. Only large bee pollinators that carry the pollinating pollen from long anthers in 'safe sites' associated short anthers with the presence of food. In the absence of these larger bee pollinators, the role of heteranthery in S. reniformis would be strongly compromised and its function would be lost.

Two common species dominate the species-rich Euglossine bee fauna of an Atlantic Rainforest remnant in Pernambuco, Brazil.

Nowadays, the northern part of the Atlantic Rainforest of Brazil is largely destroyed and forest remnants rarely exceed 100 ha. In a 118 ha forest fragment within a state nature reserve of Pernambuco (Reserva Ecológica Gurjaú), we surveyed the orchid bee fauna (Apidae, Euglossini) using eight different scent baits to attract males. Once a month during one year, the bees were actively collected with entomological nets, from November 2002 to October 2003 by two collectors. We collected 2,908 orchid bee males belonging to 23 species, one of the highest richness values of the Northern Atlantic Rainforest. Bees of only two species, Euglossa carolina (50%) and Eulaema nigrita (25%), which occurred throughout the year, accounted for three quarter of the collected individuals. Both species are typical for open or disturbed areas. Rainforest remnants like those of Gurjaú within the predominant sugar cane monocultures in the coastal plains of the northern Atlantic Rainforest play an important role in orchid bee conservation and maintenance of biodiversity.

Two common species dominate the species-rich Euglossine bee fauna of an Atlantic Rainforest remnant in Pernambuco, Brazil / Duas espécies comuns dominam a rica fauna de Euglossini em um remanscente de Floresta Atlântica em Pernambuco, Brasil

Abstract Nowadays, the northern part of the Atlantic Rainforest of Brazil is largely destroyed and forest remnants rarely exceed 100 ha. In a 118 ha forest fragment within a state nature reserve of Pernambuco (Reserva Ecológica Gurjaú), we surveyed the orchid bee fauna (Apidae, Euglossini) using eight different scent baits to attract males. Once a month during one year, the bees were actively collected with entomological nets, from November 2002 to October 2003 by two collectors. We collected 2,908 orchid bee males belonging to 23 species, one of the highest richness values of the Northern Atlantic Rainforest. Bees of only two species, Euglossa carolina (50%) and Eulaema nigrita (25%), which occurred throughout the year, accounted for three quarter of the collected individuals. Both species are typical for open or disturbed areas. Rainforest remnants like those of Gurjaú within the predominant sugar cane monocultures in the coastal plains of the northern Atlantic Rainforest play an important role in orchid bee conservation and maintenance of biodiversity.

Resumo Atualmente, a porção norte da Floresta Atlântica brasileira está drasticamente destruída e os remanescentes florestais raramente excedem 100 hectares. Com uso de iscas odoríferas atrativas aos machos, amostramos a fauna de abelhas-das-orquídeas (Hymenoptera: Apidae: Euglossini) em um fragmento florestal de 118 ha na Reserva Ecológica de Gurjaú, Pernambuco. As abelhas foram ativamente coletadas com redes entomológicas por dois coletores, uma vez por mês, de novembro de 2002 a outubro de 2003. Coletamos 2908 machos de Euglossini pertencentes a 23 espécies, um dos mais altos valores de riqueza registrados para a Floresta Atlântica nordestina. Três quartos das abelhas coletadas pertenceram a apenas duas espécies, Euglossa carolina (50%) and Eulaema nigrita (25%), típicas de áreas abertas e perturbadas e ativas ao longo de todo ano. Remanescentes de floresta como os de Gurjaú, em meio às monoculturas de cana-de-açúcar, podem desempenhar um importante papel na conservação das abelhas-das-orquídeas em ambientes fragmentados como os da Mata Atlântica do nordeste do Brasil.

Two common species dominate the species-rich Euglossine bee fauna of an Atlantic Rainforest remnant in Pernambuco, Brazil

Abstract Nowadays, the northern part of the Atlantic Rainforest of Brazil is largely destroyed and forest remnants rarely exceed 100 ha. In a 118 ha forest fragment within a state nature reserve of Pernambuco (Reserva Ecológica Gurjaú), we surveyed the orchid bee fauna (Apidae, Euglossini) using eight different scent baits to attract males. Once a month during one year, the bees were actively collected with entomological nets, from November 2002 to October 2003 by two collectors. We collected 2,908 orchid bee males belonging to 23 species, one of the highest richness values of the Northern Atlantic Rainforest. Bees of only two species, Euglossa carolina (50%) and Eulaema nigrita (25%), which occurred throughout the year, accounted for three quarter of the collected individuals. Both species are typical for open or disturbed areas. Rainforest remnants like those of Gurjaú within the predominant sugar cane monocultures in the coastal plains of the northern Atlantic Rainforest play an important role in orchid bee conservation and maintenance of biodiversity.

Resumo Atualmente, a porção norte da Floresta Atlântica brasileira está drasticamente destruída e os remanescentes florestais raramente excedem 100 hectares. Com uso de iscas odoríferas atrativas aos machos, amostramos a fauna de abelhas-das-orquídeas (Hymenoptera: Apidae: Euglossini) em um fragmento florestal de 118 ha na Reserva Ecológica de Gurjaú, Pernambuco. As abelhas foram ativamente coletadas com redes entomológicas por dois coletores, uma vez por mês, de novembro de 2002 a outubro de 2003. Coletamos 2908 machos de Euglossini pertencentes a 23 espécies, um dos mais altos valores de riqueza registrados para a Floresta Atlântica nordestina. Três quartos das abelhas coletadas pertenceram a apenas duas espécies, Euglossa carolina (50%) and Eulaema nigrita (25%), típicas de áreas abertas e perturbadas e ativas ao longo de todo ano. Remanescentes de floresta como os de Gurjaú, em meio às monoculturas de cana-de-açúcar, podem desempenhar um importante papel na conservação das abelhas-das-orquídeas em ambientes fragmentados como os da Mata Atlântica do nordeste do Brasil.

Assessment of pollen reward and pollen availability in Solanum stramoniifolium and Solanum paniculatum for buzz-pollinating carpenter bees.

The two widespread tropical Solanum species S. paniculatum and S. stramoniifolium are highly dependent on the visits of large bees that pollinate the flowers while buzzing them. Both Solanum species do not offer nectar reward; the rewarding of bees is thus solely dependent on the availability of pollen. Flower visitors are unable to visually assess the amount of pollen, because the pollen is hidden in poricidal anthers. In this study we ask whether and how the amount of pollen determines the attractiveness of flowers for bees. The number of pollen grains in anthers of S. stramoniifolium was seven times higher than in S. paniculatum. By contrast, the handling time per five flowers for carpenter bees visiting S. paniculatum was 3.5 times shorter than of those visiting S. stramoniifolium. As a result foraging carpenter bees collected a similar number of pollen grains per unit time on flowers of both species. Experimental manipulation of pollen availability by gluing the anther pores showed that the carpenter bees were unable to detect the availability of pollen by means of chemical cues before landing and without buzzing. Our study shows that the efficiency of pollen collecting on S. paniculatum is based on large inflorescences with short between-flower search times and short handling time of individual flowers, whereas that of S. stramoniifolium relies on a large amount of pollen per flower. Interestingly, large carpenter bees are able to adjust their foraging behaviour to drastically different strategies of pollen reward in otherwise very similar plant species.

Pollination in Jacaranda rugosa (Bignoniaceae): euglossine pollinators, nectar robbers and low fruit set.

Nectar robbers access floral nectar in illegitimate flower visits without, in general, performing a pollination service. Nevertheless, their effect on fruit set can be indirectly positive if the nectar removal causes an incremental increase in the frequency of legitimate flower visits of effective pollinators, especially in obligate outcrossers. We studied pollination and the effect of nectar robbers on the reproductive fitness of Jacaranda rugosa, an endemic shrub of the National Park of Catimbau, in the Caatinga of Pernambuco, Brazil. Xenogamous J. rugosa flowers continuously produced nectar during the day at a rate of 1 mul.h(-1). Female and male Euglossa melanotricha were the main pollinators. Early morning flower visits substantially contributed to fruit set because stigmas with open lobes were almost absent in the afternoon. Ninety-nine per cent of the flowers showed damage caused by nectar robbers. Artificial addition of sugar water prolonged the duration of flower visits of legitimate flower visitors. Removal of nectar, simulating the impact of nectar robbers, resulted in shorter flower visits of euglossine bees. While flower visits of nectar-robbing carpenter bees (Xylocopa frontalis, X. grisescens, X. ordinaria) produced only a longitudinal slit in the corolla tube in the region of the nectar chamber, worker bees of Trigona spinipes damaged the gynoecium in 92% of the flowers. This explains the outstandingly low fruit set (1.5%) of J. rugosa in the National Park of Catimbau.

Do consecutive flower visits within a crown diminish fruit set in mass-flowering Hancornia speciosa (Apocynaceae)?

Hancornia speciosa is a self-incompatible, mass-flowering, sphingophilous fruit crop (mangaba) of northeast and central Brazil. The flowers have a precise pollination apparatus, which optimizes pollen transfer between flower and pollinator. While the pollination mechanism avoids self-pollination, mass-flowering promotes geitonogamy. During a flower visit, almost half of the exogenous pollen grains adhering to the proboscis are deposited on the stigma surface. A pollination experiment with a nylon thread simulating six consecutive flower visits within a crown revealed that only the first two flowers visited (positions 1 and 2) are highly likely to set fruit. Super-production of flowers, and consequently obligate low fruit set, seem to be part of the reproductive strategy of the obligate outcrossing plant, Hancornia speciosa.

Caladium bicolor (Araceae) and Cyclocephala celata (Coleoptera, Dynastinae): a well-established pollination system in the Northern Atlantic rainforest of Pernambuco, Brazil.

Flowering, pollination ecology, and floral thermogenesis of Caladium bicolor were studied in the Atlantic Rainforest of Pernambuco, NE Brazil. Inflorescences of this species are adapted to the characteristic pollination syndrome performed by Cyclocephalini beetles. They bear nutritious rewards inside well-developed floral chambers and exhibit a thermogenic cycle which is synchronized to the activity period of visiting beetles. Heating intervals of the spadix were observed during consecutive evenings corresponding to the beginning of the female and male phases of anthesis. Highest temperatures were recorded during the longer-lasting female phase. An intense sweet odour was volatized on both evenings. Beetles of a single species, Cyclocephala celata, were attracted to odoriferous inflorescences of C. bicolor and are reported for the first time as Araceae visitors. All the inflorescences visited by C. celata developed into infructescences, whereas unvisited inflorescences showed no fruit development. Findings of previous studies in the Amazon basin of Surinam indicated that Cyclocephala rustica is a likely pollinator of C. bicolor. This leads to the assumption that locally abundant Cyclocephalini species are involved in the pollination of this species.

Chemical and mechanical changes during leaf expansion of four woody species of dry Restinga woodland.

Young leaves are preferential targets for herbivores, and plants have developed different strategies to protect them. This study aimed to evaluate different leaf attributes of presumed relevance in protection against herbivory in four woody species (Erythroxylum argentinum, Lithrea brasiliensis, Myrciaria cuspidata, and Myrsine umbellata), growing in a dry restinga woodland in southern Brazil. Evaluation of leaf parameters was made through single-point sampling of leaves (leaf mass per area and leaf contents of nitrogen, carbon, and pigments) at three developmental stages and through time-course sampling of expanding leaves (area and strength). Leaves of M. umbellata showed the highest leaf mass per area (LMA), the largest area, and the longest expansion period. On the other extreme, Myrc. cuspidata had the smallest LMA and leaf size, and the shortest expansion period. Similarly to L. brasiliensis, it displayed red young leaves. None of the species showed delayed-greening, which might be related to the high-irradiance growth conditions. Nitrogen contents reduced with leaf maturity and reached the highest values in the young leaves of E. argentinum and Myrc. cuspidata and the lowest in M. umbellata. Each species seems to present a different set of protective attributes during leaf expansion. Myrciaria cuspidata appears to rely mostly on chemical defences to protect its soft leaves, and anthocyanins might play this role at leaf youth, while M. umbellata seems to invest more on mechanical defences, even at early stages of leaf growth, as well as on a low allocation of nitrogen to the leaves. The other species display intermediate characteristics.

Identification and expression of the Escherichia coli fdhD and fdhE genes, which are involved in the formation of respiratory formate dehydrogenase.

The two closely linked fdhD and fdhE genes of Escherichia coli are required for the formation of active membrane-bound phenazine methosulfate-linked formate dehydrogenase (FDH-PMS). Both genes were isolated from a cosmid library. Restriction endonuclease analysis associated with Mu dII1734 insertion mutagenesis indicated that the two genes were separated by at least 4 kilobases and transcribed in opposite orientations. Initial experiments indicate that the region between the two genes seems not to be essential to FDH-PMS activity. fdhD and fdhE were expressed either in maxicells or from the T7 promoter-polymerase system. They were shown to encode proteins with approximate Mr 30,500 and 32,000, respectively. Both proteins appeared in the soluble fraction and were not recognized by an FDH-PMS-specific antiserum. Therefore, neither fdhD nor fdhE plays a structural role in the formation of FDH-PMS. Expression of a phi(fdhD-lacZ) operon fusion was decreased about threefold by aerobiosis but was indifferent to other effectors tested. It was unaffected by pfl, chlA, selA, and fnr mutations. Expression of a phi(fdhE-lacZ) operon fusion was slightly induced by nitrate. This induction, requiring the presence of functional chl and fnr alleles, was mediated via nitrate metabolism. Transcription of phi(fdhE-lacZ) fusion was fully dependent on wild-type sel alleles. This might suggest the participation of fdhE in the synthesis of the selenopolypeptide of FDH-PMS.