Secretory trichomes,a substitutive floral nectar source in Lundia A. DC. (Bignoniaceae), a genus lacking a functional disc

This is the first report of corolla-borne secretory trichomes that substitute in role for a non-functional disc in a species of the neotropical genus Lundia A. DC. (Bignoniaceae). The floral biology and flowering phenology of Lundia cordata were investigated at two remnants of tropical rainforest in northeastern Brazil. This species is a typically omithophilous liana, with reddish, tubular, scentless flowers. The flowers are resupinate, protandrous and last for 2 d. There is a vestigial non-functional perigynous disc and nectar is secreted by glandular trichomes distributed along the internal surface of the corolla. The nectar is stored at the base of the corolla tube, thus showing secondary nectar presentation. The nectariferous trichomes are multi-cellular, uniseriate, with a basal foot cell rooting in the epidermis, one neck cell, and a glandular head with 13 cells on average. Three species of hummingbirds (Amazilia fimbriata, Eupetomena macroura and Phaethornis pretrei) serve as pollinators. Phaethornis ruber, Xylocopa bees, wasps and diurnal moths are considered nectar thieves.     

Effects of nectar robbing on pollinator behavior and plant reproductive success of Pitcairnia angustifolia (Bromeliaceae)

Nectar robbers may have direct and indirect effects on plant reproductive success but the presence of nectar robbing is not proof of negative fitness effects. We combined census data and field experiments to disentangle the complex effects of nectar robbing on nectar production rates, pollinator behavior, pollen export, and female reproductive success of Pitcairnia angustifolia. Under natural conditions flowers were visited by four different animal species including a robber‐like pollinator and a secondary robber. Natural levels of nectar robbing ranged from 40 to 100%. Natural variation in nectar robbing was not associated with fruit set in any year whereas seed set was weakly positively associated for 1 year only. Artificial nectar robbing did not increase nectar production or concentration, did not affect the behavior of long‐billed hummingbirds, and when faced with artificially robbed flowers, these visitors behaved as secondary nectar robbers. The number of stigmas within a patch that received pollen dye analogs and the average distance traveled by these analogs were not significantly different between robbing treatments (robbed flowers versus unrobbed flowers), but the maximum distance traveled by these pollen analogs was higher when nectar robbing was not prevented. Overall, the proportion of robbed flowers on an inflorescence had a neutral effect to a weak positive effect on the reproduction of individual plants (i.e. positive association between nectar robbing and fruit set in 2002) even when it clearly changed the behavior of its most efficient pollinator potentially increasing the frequency of nectar robbing within a plant.     

First Record of a Pregnant Female of Dasyatis hypostigma, with Description of the Embryos

Synopsis  We report the first pregnant female of the recently described stingray, Dasyatis hypostigma Santos & Carvalho 2004, from southeastern Brazil. This report confirms the aplacental viviparous mode of reproduction with trophonemata of the species and gives a brief account of the embryos.     

Regulation of nectar collection in relation to honey storage levels by honey bees, Apis mellifera

Honey bees collect distinct nutrient sources in the form ofnectar (energy) and pollen (nitrogen). We investigated the effectof varying energy stores on nectar and pollen foraging. We foundno significant changes in nectar foraging in response to changesin honey storage levels within colonies. Individual foragersdid not vary activity rates or nectar load sizes in responseto changes in honey stores, and colonies did not increase nectarintake rates when honey stores within the hive were decreased.This result contrasts with pollen foraging behavior, which isextremely sensitive to colony state. Our data show that individualforaging decisions during nectar collection and colony regulationof nectar intake are distincdy different from pollen foraging.The behavior of honey bees illustrates that foraging strategy(and therefore foraging models) can incorporate multiple currencies,including both energy and protein intake.[Behav Ecol 7: 286–291(1996)]     

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 μl·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.     

紫花苜蓿的花蜜量和访花蜜蜂数量对种子产量的影响

对10个紫花苜蓿品种的花萼直径、花蜜量、访花蜜蜂数量和种子产量进行了研究,结果表明,紫花苜蓿的单位面积花蜜量与访花蜜蜂数量呈极显著正相关(r=0.93**),访花蜜蜂数量与种子产量呈显著正相关(r=0.87*);紫花苜蓿的花蜜量与花萼直径呈极显著正相关(r=0.99**);紫花苜蓿品种赛特(Sitel)和德宝(Derby)在兰州地区能获得高产、优质的种子。     

“Murrí” (Antioquia Department, Colombia): hotspot for neotropical blueberries (Ericaceae: Vaccinieae)

A taxonomic review of the Vaccinieae (Ericaceae) from the region known as Murrí (Antioquia Department, Colombia) is presented. This area has the highest generic and specific diversity of Vaccinieae known in the Neotropics, with 10 genera and 45 species.Cavendishia antioquiensis, C. viridiflora, Psammisia citrina, andP. mediobullata are newly described and illustrated.Cavendishia sessiliflora andSatyria latifolia are redescribed from complete collections. Pollination by hummingbirds in neotropical Vaccinieae is discussed and nectar content is reported for the first time for 26 species.

---

Resumen  Se presenta una revisión taxonómica de la tribu Vaccinieae (Ericaceae) de la región conocida como Murrí (Departamento de Antioquia, Colombia). Esta área tiene la diversidad más alta tanto en géneros como en especies de esta tribu conocidos en el Neotrópico, con 10 géneros y 45 especies. Aquí se describenCavendishia antioquiensis, C. viridiflora, Psammisia citrina, yP. mediobullata con sus respectivas ilustraciones. Se redescribenCavendishia sessiliflora ySatyria latifolia de colecciones completas. También se discute polinización de Vaccinieae por colibríes en el Neotrópico y se incluye el contenido de nectar registrado por primera vez para 26 especies.

     

Nectar sugar composition in angiosperms from Chaco and Patagonia (Argentina): an animal visitor's matter?

 We relate nectar sugar composition with floral visitors in samples from two biogeographic regions from Argentina: Chaco (99 spp. from its southern region) and Patagonia (48 spp. from its central region), using our own data published in earlier papers. The variables to be compared were sugar ratio and sucrose percentage. Differences in the sugar composition were observed when comparing both regions. Bee- and butterfly-visited Patagonian species showed lower sucrose percentages and sugar ratios than Chaquean species; i.e., a convergence in sugar composition was not verified. Moth-visited species showed a wide range of sucrose proportions and sugar ratios in both regions with no significant differences between them. As the differences found in sugar ratio between Chaco and Patagonia, according to the predominant pollinator guilds, may have been influenced by the sample size, we searched for similarities in sugar ratios between plants with the same visitor type in a comparative way, comparing our data pooled together against data by Baker and Baker's (1983a). Our data do not agree with theirs, i.e., no trends can be drawn for bees, moths, and butterflies sugar preferences. The exceptions were the hummingbird-visited species that showed a similar pattern in both cases, i.e., there is a convergence among plants offering nectar with a predominance of sucrose. To evaluate whether closely related species within a family have similar nectar composition and flower visitors, regardless of their region, sugar proportions were compared in several families. Hexose nectars were predominant in Asteraceae, Fabaceae, Solanaceae, and Verbenaceae, while sucrose nectars prevailed in Bromeliaceae and Onagraceae. Nectar composition seems to be a more conservative trait than flower morphology. This may be a reason to explain the absence of a convergence in sugar composition between plants growing in different biogeographical regions that share the same animal visitor guilds. Received August 27, 2002; accepted December 17, 2002 Published online: June 2, 2003     

Dyssochroma viridiflorum (Solanaceae): a reproductively bat-dependent epiphyte from the Atlantic rainforest in Brazil

Few Neotropical plant species seem to depend on the same animal type both for pollination and seed dispersal, and the known instances refer mostly to birds as the agents in these two phases of a plant reproductive cycle. Dyssochroma viridiflorum (Solanaceae), an epiphyte endemic to the Atlantic rainforest in south-eastern Brazil, was found to be visited by phyllostomid bats for nectar as well as for fruits, with the pollination and seed dispersal of the plant ensured by these flying mammals. The greenish flowers open at night and are visited by the nectar-feeding bat Glossophaga soricina, whereas the yellowish-white fruits are consumed by two species of fruit-eating bats, Carollia perspicillata and Sturnira lilium. Only clinging visits, an uncommon behavioural pattern for glossophagine bats while feeding on flowers, were recorded. The small seeds of D. viridiflorum are swallowed along with the fruit pulp and later defecated on the bats' flying pathways. It is suggested that species of Dyssochroma and two other solanaceous bat-pollinated genera, Merinthopodium and Trianaea, form a derived and bat-dependent clade within the Juanulloeae.     

Phylogenetic analysis of interspecific variation in nectar of hummingbird-visited plants

We tested whether phylogeny, flower size and/or altitude were significant predictors of interspecific variation in nectar production of hummingbird-visited plants in an assembled database (289 species, in 22 orders, 56 families and 131 genera). Although the study is focused on hummingbird-pollinated plants (241 plant species), plants with different pollinator syndromes (48 species) are also included in the analyses. Nectar volume secreted in a given time period (usually 24 h) by a given flower, its sugar concentration and corolla length were compiled mainly from the literature. Altitude was also obtained from the original references. Sugar production was computed basically as the product of nectar secretion and sugar concentration, and expressed on a per 24-h basis. All nectar traits and corolla length (all log transformed), as well as altitude, showed statistically significant phylogenetic signal. Both nonphylogenetic and phylogenetically informed (independent contrasts) analyses indicated a highly significant positive correlation between corolla length and both nectar volume and sugar production. In addition, altitude (which is partially a surrogate for temperature) was significantly negatively correlated with both sugar concentration and production. Possible reasons for coadaptation of nectar production and sugar production with corolla length are discussed.     

荇菜成熟花蜜腺的形态及其泌蜜过程的超微结构研究

荇菜花蜜腺共五枚,黄色,肾形,着生子房基部。它们由分泌表皮和泌蜜组织组成,属结构蜜腺。成熟蜜腺的分泌表皮具明显的角质层和气孔,还具少量短期生活的分泌毛,分泌毛不具明显的角质层。泌蜜组织具较小的胞间隙,胞间连丝发达。成熟蜜腺细胞中不人有丰富的线粒体,内质网,还有大量的质体。     

Adaptive spatial biases in nectar deposition in the nests of honey bees

Honey bees store their large supply of honey at the top and, to a lesser extent, along the edges of their nests. Whether this pattern is the result of preferences for where nectar is deposited is unclear. Camazine, in a path breaking study of pattern formation, found evidence that workers deposit nectar at random, while Free and Williams in an earlier study found evidence that bees prefer to deposit nectar into particular types of comb. Here we reexamine this question. We tested three hypotheses, all of which posit that bees have adaptive biases which allow them to deposit nectar directly into the most useful locations. We found that bees have preferences for depositing nectar into cells at the top of the nest, into old vs. new comb, and into interior facing comb vs. comb facing the exterior environment. These preferences may ensure that nectar is placed directly into those regions where it will ultimately be stored. They may also result in an optimal pattern of comb usage with respect to brood rearing. This work, along with the results of previous studies, suggests that comb usage patterns may reflect competing selective pressures and be more complicated than previously thought. Received 17 May 2007; revised 15 June 2007; accepted 3 July 2007.