Poricidal Anthers Research Articles

The importance of plant diversity in maintaining the pollinator bee, Eulaema nigrita (Hymenoptera: Apidae) in sweet passion fruit fields

The euglossine bee Eulaema nigrita plays an important role for the pollination of native and economically important plants, such as the sweet passion-fruit Passiflora alata. E. nigrita uniquely collects the nectar from the flowers of P. alata, nevertheless, it needs to visit other plants to collect pollen, nectar and other resources for its survival. There are two methods to identify the species of plants used by bees in their diet: by direct observation of the bees in the flowers, and through identification of pollen grains present in brood cells, feces, or in the bees' body. In order to identify the other plants that E. nigrita visits, we analyzed samples of pollen grains removed from the bee's body in the course of the flowering period of P. alata. Among our results, the flora visited by E. nigrita comprised 40 species from 32 genera and 19 families, some of them used as a pollen source or just nectar. In spite of being a polyletic species, E. nigrita exhibited preference for some plant species with poricidal anthers. P. alata which has high sugar concentration nectar was the main source of nectar for this bee in the studied area. Nonetheless, the pollinic analysis indicated that others nectariferous plant species are necessary to keep the populations of E. nigrita. Studies such as this one are important since they indicate supplementary pollen-nectar sources which must be used for the conservation of the populations of E. nigrita in crops neighbouring areas. In the absence of pollinators, growers are forced to pay for hand pollination, which increases production costs; keeping pollinators in cultivated areas is still more feasible to ensure sweet passion fruit production.

Floral Anatomy of Xyrids (Poales): Contributions to Their Reproductive Biology, Taxonomy, and Phylogeny

Xyridaceae, Eriocaulaceae, and Mayacaceae form the xyrid clade, which is weakly supported in Poales. The floral anatomy of xyrid species was studied, to contribute to the understanding of the relationships within the group. Both Eriocaulaceae and Xyridaceae have petals with elongated epidermal cells with straight walls, epipetalous stamens, staminodes, anthers with longitudinal dehiscence, an endothecium with band-like thickenings, and a style vascularized by the dorsal carpellary bundles; these characteristics thus corroborate the close relationship of these groups indicated by phylogenetic analyses. Mayacaceae is distinguished by the presence of papillose epidermal cells in the petals, a reduced inner whorl of stamens, poricidal anthers, an endothecium lacking thickenings, a style and stigma vascularized by the dorsal and ventral carpellary bundles, and the presence of an obturator in the ovary wall. A reduction in the inner whorl of fertile stamens also occurs in Juncaceae and Cyperaceae, linking Mayacaceae to the cyperids. The stylar appendages of Orectanthe (Xyridaceae) have been shown to be nectariferous and anatomically similar to those of Abolboda, differentiating these two genera from Xyris (Xyridoideae) and confirming their placement in Abolbodoideae. Stylar appendages also occur in Eriocaulaceae, with the same function, position, and vascularization, and are therefore homologous structures, reinforcing the phylogenetic proximity between Eriocaulaceae and Xyridaceae.

Biologia floral e visitantes de Gaylussacia brasiliensis (Spr.) Meissner (Ericaceae) - uma espécie com anteras poricidas polinizada por beija-flores

A biologia floral de Gaylussacia brasiliensis (Spr.) Meissner (Ericaceae) foi estudada na borda de uma mata de galeria na reserva ecológica do Clube de Caça e Pesca Itororó de Uberlândia, Minas Gerais. G. brasiliensis é um arbusto que pode alcançar de 0,3 a 3,0 m de altura e ocorre de forma isolada ou agregada. Apresenta floração contínua e possui inflorescências racemosas, axilares com flores pendentes. As flores são hermafroditas, vermelhas, de corola urceolada, apresentam antese diurna e ausência odor. O néctar apresentou volume de cerca de 3,0 μL e concentração de açúcares por volta de 13%. G. brasiliensis é autocompatível, não apresenta autopolinização espontânea e nem apomixia. Os polinizadores foram os beijaflores: Chlorostlibon lucidus (Shaw), Amazilia fimbirata (Gmelin), Hylocharis chrysura (Shaw) (Throchilinae) e Phaethornis pretrei (Lesson & DeLattre) (Phaethornithinae). G. brasiliensis apresenta anteras poricidas com poros amplos e os beija-flores, quando adejam com o bico inserido nas flores em busca de néctar, fornecem a vibração necessária para a liberação dos grãos de pólen. Apesar de apresentar volume e concentração de açúcar no néctar relativamente pequenos, os agrupamentos de indivíduos com muitas flores parecem atrair beija-flores com comportamento territorial.

Potential pollinators of Comolia ovalifolia DC Triana (Melastomataceae) and Chamaecrista ramosa (Vog.) H.S. Irwin and Barneby var. ramosa (Leguminosae-Caesalpinioideae), in restinga, Bahia, Brazil

Comolia ovalifolia DC Triana (Melastomataceae) and Chamaecrista ramosa (Vog.) H.S. Irwin and Barneby var. ramosa (Leguminosae-Caesalpinioideae) are tropical plant species found in restinga (herbaceous-shrubby, sandy costal ecosystems). They have flowers with poricidal anthers and are pollinated by bees. The study sought to analyse potential pollinators of both plants during visits to their flowers in a restinga area in Bahia. The flowering displayed by both species was considered continuous and long duration, constantly providing pollen to floral visitors. C. ovalifolia was visited by 17 species of bees and C. ramosa by 16 species, predominantly from the Apidae family (with a similarity index of 74%). The behavior displayed by these visiting bees was of vibrating anthers. The small-sized Euglossa sp. Latreille, 1802 and Florilegus similis Urban, 1970 bees played less of a role as pollinators, since they rarely touched the flower stigma during harvests and were thus considered opportunist visitors or casual pollinators. Centris decolorata Lepetier, 1841 (= C. leprieuri) and Xylocopa subcyanea Perez, 1901 are large bees and were considered efficient pollinators of C. ovalifolia and C. ramosa because of the higher frequency and constancy of their visits, and their favourable behaviour and size for pollen transfer between flowers, which guarantees the survival of these native restinga plant species.

Crab spiders (Araneae: Thomisidae) in flowering plants in a Brazilian "Cerrado" ecosystem

Although crab spiders are common in flowering plants, their relations with plant species and its floral traits have been poorly known in the Neotropics. Observations regarding plant habits, floral visitors and also floral characteristics such as anthesis, odour, shape, colour and floral resources were recorded in flowering plant species of an area of "Cerrado" on a 2 km long trail. Misumenops argenteus and Misumenops pallens accounted for 62.86% of the spiders captured on 22 flowering plant species. The plants Senna rugosa (Fabaceae), Styrax ferrugineus (Styracaceae) and Banisteriopsis campestris (Malpighiaceae), hosted, each one, about 10 to 17% of the total spiders collected and these plants had diurnal anthesis, bee-attractive flower colours such as yellow (S. rugosa), white (S. ferrugineus), and pink (B. campestris), poricidal anthers as well as being visited by bees which evidenced bee-pollination syndrome. This study is the first survey regarding crab spiders and their associations with plant species of the "Cerrado".

Further Range Extension of Xylocopa micans Lepeletier (Hymenoptera: Apidae)

There are seven species in the genus Xylocopa Latreille that occur in North America north of Mexico, and only two of these are known to occur in the Eastern United States: Xylocopa virginica L. and X. micans Lepeletier. While the range of X. virginica extends through much of the Eastern United States, the distribution of X. micans is concentrated along the coastal areas to the far south and east. Until 2010, X. micans had only been recorded in Alabama, Florida, Georgia, Louisiana, Mississippi, North Carolina, South Carolina and Texas (Hurd, 1955). In 2006 and 2007, four specimens of X. micans were collected in southwestern Arkansas, representing the first records of X. micans in Arkansas, about 250 km northwest of its historical range (Warriner, 2010). Additionally, we report here that two males of X. micans were netted on May 10, 2010 north of Biscoe in Prairie County, AR (34.845000uN, 91.415833uW). This location is approximately 50 km northeast of the first specimens found in Arkansas three years prior. The specimens were determined with the keys of Hurd (1955) and Mitchell (1962). The voucher specimens have been deposited at the University of Arkansas’ Arthropod Museum, Department of Entomology in Fayetteville, Arkansas, USA. This is a new locality record for X. micans in the state of Arkansas and supports Warriner’s (2010) suggestion that this represents an extension of its historically recorded range, rather than an incidental introduction. Xylocopa micans is a member of the Neotropical subgenus Schoenherria Lepeletier, and its range may be restricted to warmer climates. In the Lower Rio Grande Valley, Porter (1981) found that X. micans was only collected in the warmer months from spring through summer, while other Xylocopa species were collected year round. The presence of X. micans in Prairie County, Arkansas may reflect a climate-driven northward range expansion as predicted by climate change and already evidenced by the range shifts of species such as the nymphalid Euphydryas editha (Boisduval) (Parmesan, 1996). Conversely, the specimens found in Prairie County, Arkansas may be human-mediated introductions and not representative of a natural expansion. The site at which they were collected is located along Interstate 40, which connects to the southwestern locations via Interstate 30. It is possible that these individuals were transported from their native range to Arkansas and have spread by means of highway traffic. Xylocopa species, including X. micans, nest in dead wood, and may inadvertently be transported long distances in shipments of lumber or other wood products. This was shown to be the case for Xylocopa brasilianorum L. which arrived in San Francisco in a balsa wood shipment from Hawaii (Hurd, 1955). Further sampling of bees in Arkansas may help determine how X. micans arrived in and spread throughout Arkansas. Large bees, such as Bombus and Xylocopa species, have the ability to sonicate the anthers of flowers with poricidal dehiscence, such as Solanum species (King and Buchmann, 2003). Due to this somewhat unique capacity, large bees such as Xylocopa micans are of particular interest as pollinators of many plant species with poricidal anthers. Out of 153 bee visitors, X. micans and two species of Melissodes were shown to be the only effective pollinators of Chamaecrista keyensis Pennell (Fabaceae), the big pine partridge pea, which is listed as an endangered species in the state of Florida (Liu and Koptur, 2003). Clearly, the role of X. micans as generalist pollinator with special abilities can be an important factor in plant communities. If the distribution of X. micans is changing, either as the result of climate change or through anthropogenic introductions, there may be additional ecological repercussions.

Molecular systematics and morphological character evolution of the Condamineeae (Rubiaceae)

The Condamineeae have in previous molecular studies been shown to be part of an early-divergent clade within the subfamily Ixoroideae, together with the tribes Calycophylleae, and Hippotideae, and genera of the former Cinchoneae and Rondeletieae. Generic relationships within this clade have, however, remained largely unresolved. • In this study, the systematics of the Condamineeae was further examined by phylogenetic reconstruction of six cpDNA regions and one nrDNA region using parsimony and Bayesian Markov chain Monte Carlo inference. Morphological character evolution within the tribe was assessed by ancestral state reconstruction using likelihood optimization of characters onto Bayesian trees. • Calycophylleae appears polyphyletic. "Hippotideae" is monophyletic but nested within the Condamineeae. The phylogenetic hypotheses presented support a resurrection of the genera Holtonia, Schizocalyx, and Semaphyllanthe. Furthermore, Bathysa is found to be polyphyletic, Tresanthera is found nested within Rustia, and the taxonomically disputed genus Dialypetalanthus is here shown to be sister to a Bothriospora-Wittmackanthus clade. Morphological ancestral state reconstructions indicate that protogyny have evolved at least two times within the tribe and that indehiscent fruits, loculicidal fruit dehiscence, and intrapetiolar stipules have evolved independently several times. The occurrence of calycophylls (leaf-like calyx lobes), poricidal anthers, and winged seeds also appear homoplastic within the tribe. • A diagnosis and delimitation of the tribe Condamineeae is presented, with taxonomic proposals to synonymize Tresanthera and to transfer several species of Bathysa as well as Phitopis to a resurrected Schizocalyx.

Comparative Anatomy and Morphology of Nectar-producing Melastomataceae

Most neotropical Melastomataceae have bee-pollinated flowers with poricidal anthers. However, nectar rewards are known to be produced in about 80 species in eight genera from four different tribes. These nectar-producing species are pollinated by both vertebrates and invertebrates. The floral morphology and anatomy of 14 species was studied in six genera of nectar-producing Melastomataceae (Blakea, Brachyotum, Charianthus, Huilaea, Meriania and Miconia). Anatomical methods included scanning electron microscopy, and serial sections of paraffin-embedded flowers. All vertebrate-pollinated melastome flowers have petals that do not open completely at anthesis, thus forming a pseudo-tubular corolla, while closely related species that are bee pollinated have rotate or reflexed corollas. In most species, nectar secretion is related to stomatal or epidermal nectaries and not filament slits as previously reported. Moreover, the nectar is probably supplied by large vascular bundles near the release area. Blakea and Huilaea have nectary stomata located upon the dorsal anther connective appendages. Brachyotum also has nectary stomata on the anther connectives, but these are distributed lengthwise along most of the connective. Meriania may release nectar through the anther connective, but has additional nectary stomata on the inner walls of the hypanthium. Miconia has nectary stomata on the ovary apex. Charianthus nectaries were not found, but there is circumstantial evidence that nectar release occurs through the epidermis at the apex of the ovary and the lower portions of the inner wall of the hypanthium. Nectar release in Melastomataceae is apparently related to nectary stomata and not filament slits. The presence of nectary stomata on stamens and on ovary apices in different lineages suggests that the acquisition of nectaries is a derived condition. Nectary location also supports a derived condition, because location is strongly consistent within each genus, but differs between genera.

Polinização por vibração e sistema reprodutivo de duas espécies de Sauvagesia L. (Ochnaceae)

Reproductive phenology, floral biology, pollination, and breeding system of Sauvagesia erecta L. and S. sprengelii A. St.-Hil. were studied, respectively, in a remnant of Atlantic forest, located at the Parque Estadual Dois Irmaos, Recife, and in open areas, Goiana, both in Pernambuco state, northeastern Brazil. The species have pollen flowers with poricidal anthers and a staminodial envelope, which surrounds the stamens and the gynoecium, creating an apical pore to pollen release. The pattern of flowering of both species is continual. The species are self-compatible, autogamic and do not set apomictic fruits. Exclusively bees, mainly of the families Apidae and Halictidae, visited the flowers of both species. Bees of the genus Paratetrapedia visited only S. erecta flowers. Bombus brevivillus Franklin, Florilegus similis Urban, Xylocopa muscaria Fabricius were observed visiting only S. sprengelii flowers. Nevertheless, Augochloropsis species visited flowers of both species. Buzz pollination mechanism takes place with all these bee species acting as effective pollinators, excepting for one species of Paratetrapedia, which is a pollen thief. According to the pollinators' behaviour, the staminodial envelope has a function on the buzz pollination process, which characterizes a mechanism of transference of function, already mentioned to the family.

Abelhas (Apoidea) visitantes de flores de Comolia ovalifolia DC Triana (Melastomataceae) em uma área de restinga na Bahia

As flores de Comolia ovalifolia apresentam anteras poricidas e seu polen serve como fonte proteica a um grupo especifico de abelhas, capaz de extrair o polen das anteras atraves de vibracao. O florescimento de C. ovalifolia e a atividade das abelhas mais frequentes foram observadas de janeiro a dezembro/2001. Os picos de florescimento de C. ovalifolia ocorreram nos meses de marco/2001 e entre setembro e novembro/2001. As flores de C. ovalifolia foram visitadas por 16 especies de abelhas, sendo as mais frequentes Centris leprieuri (Spinola), Xylocopa subcyanea Perez, Centris sp., Euglossa sp. e Florilegus similis Urban. Entre elas, C. leprieuri destacou-se com 89% das visitas e sua atividade forrageira anual coincidiu com a floracao de C. ovalifolia. Alem disso, essa abelha apresentou tamanho adequado e comportamento eficiente na coleta e transferencia de polen para o estigma, sendo considerada polinizador legitimo dessas flores.

Anther Dehiscence and Circumscription of Miconia sect. Hypoxanthus (Melastomataceae)

While most Melastomataceae have poricidal anthers, Miconia sect. Hypoxanthus (former sect. Chaenanthera) has anthers dehiscing by longitudinal pores, resembling rimose openings. Anther development of three species (Mironia pusilliflora and M. laticrenata from this section and M. cinnamomifolia from sect. Glossocentrum) studied through SEM and light microscopy showed that all have an epidermis with a thick and striate cuticle, except for the dehiscence area. This area is covered by a non-striate epidermis which is associated with the septum that lies between the two thecae. During dehiscence the septum holds the non-striate epidermis, which is torn at the margins of the dehiscence area. Since anther opening of all three species follows the same pattern, in terms of tissues and mechanisms, we conclude that the circumscription of Miconia sect. Hypoxanthus should comprise all species with stamens that dehisce along the septum, resulting in narrow openings that extend from the anther apex to the base (as in M. pusilliflora) or from the apex until half of the anther length (as in M. laticrenata). Miconia section Chaenopleura also has anthers opening by longitudinal slits, hut these expose four locules, instead of the two in Hypoxanthus.

FLORAL MANIPULATION BY LASIOGLOSSUM ZEPHYRUM (HYMENOPTERA: HALICTIDAE) ENSURES FIRST ACCESS TO FLORAL REWARDS BY INITIATING PREMATURE ANTHESIS OF XYRIS TENNESSEENSIS (XYRIDACEAE) FLOWERS

early bird gets the worm, is a cliche that often comes to mind when considering cases of exploitative competition in nature. In order to gain first access to pollen in flowers, some bees have been observed to chew holes in unopened flowers and poricidal anthers (Renner 1983; Young 1983; Hurd & Linsley 1963). Here we describe an interesting case of a bee, Lasioglossum zephyrum (Smith), manipulating a flower to open prematurely, thus ensuring first access to the floral rewards of Xyris tenneseensis Kral. Xyris tenneseensis is federally listed as endangered (U.S. Fish and Wildlife Service, 1994), and is only known from 14 extant populations. Our observations are restricted to a large population of X. tenneseensis located along the edge of a springfed pond in Fort McClellan, AL.Xyris tenneseensis is perennial, producing one flower (rarely two) per day from a cone-like inflorescence. The flower bud emerges from the inflorescence (Fig. la) approximately 45 minutes prior to natural anthesis. At this time a translucent membranaceous sepal sheaths the entire flower bud. As the bud continues to emerge, the flower petals exert outward pressure on the sheath-like sepal. This outward pressure on the sheath-like sepal causes it to slide up the flower bud and form an air-filled membranaceous atop the bud (Fig. 2b). Eventually the pressure exerted by the petals causes the sheath to fall off the flower, allowing the flower to open. The flower stays open for a few hours after which the corolla closes and falls off the inflorescence. Xyris tenneseensis flowers produce no nectar and anther dehiscence precedes anthesis. Previous studies indicate that the first visitor to a flower often gets a disproportionate amount of available floral resources (Harder 1990; Buchmann & Cane 1989). Due to the pre-anthesis presentation of pollen within the flowers of X. tenneseensis, the first floral visitor has access to all the floral rewards. Individuals of L. zephyrum (Fig. 2c) were seen to land on X. tenneseensis flower buds during the bubble stage (Fig. 2b). The bee would nip at the using its mandi-

Bees collecting pollen from flowers with poricidal anthers in a south Brazilian Araucaria forest: a community study

SUMMARYA community study of bees visiting flowers with poricidal anthers was made in the subtropical Araucaria forest region of Rio Grande do Sul, Brazil. Bees of 79 species, representing about 40% of the taxa occurring at the study site, were collected on 19 species of flowering plants with poricidal anthers of the families Melastomataceae and Solanaceae. The majority of flower visitors were able to buzz (sonicate) to release pollen. Buzzing is thought to be the only mode of pollen collection that results in pollination. No oligolectic bee-plant relation based on buzz pollination was detected. Most bees were not specialized to forage on plants with poricidal anthers. According to the abundance of visitors at specific flowers, three major groups of buzz pollinators could be distinguished; these were bumble bees, stingless bees of the genus Melipona and halictid bees. The pollen sources mainly exploited by them differ in flower structure, flowering syndrome and forest stratum. Therefore, the structure of the bee community seems to be closely related to the composition of the local vegetation. The extent to which bees of a species show preference for poricidal flowers, however, is more dependent on habitat than on plant taxa. The evolution of buzzing behaviour by female bees to maximize pollen harvest may have preceded the appearance of poricidal anthers and the syndrome of buzz pollination.

Anatomical and chemical analyses of leaf secretory cavities of Rustia formosa (Rubiaceae)

Foliar secretory cavities, commonly called leaf pellucid glands, have been reported in many families of vascular plants. In the Rubiaceae, these structures have only been found in the sister genera Rustia and Tresanthera, which are also anomalous within the family because they have poricidal anthers, and in the distantly related Heterophyllaea. General leaf anatomy, with particular attention to secretory cavities, as well as the chemical analysis of the secreted substances of Rustia formosa, is presented here for the first time. The secretory structures have been found in the lamina between the palisade and spongy parenchymas and in the cortical region of the petiole. The chemical analysis showed that the essential oil secreted is a complex mixture of at least 75 components, mostly of sesquiterpenoid composition. Illustrations of the leaf anatomy, details of the secretory structures of Rustia formosa, a gas chromatogram, and a table of the principal components of the leaf essential oil are included.

The ecology of pollen limitation in buzz‐pollinated Rhexia virginica (Melastomataceae)

1 Pollen limitation of female fertility has often been documented in animal‐pollinated plants, but seldom have the ecological mechanisms responsible been investigated. We examined factors influencing pollen limitation in Rhexia virginica (Melastomataceae), a species in which pollen transfer depends on bumblebees capable of buzz pollination. Experimental studies were conducted in two populations at Lake Matchedash, southern Ontario, Canada, where the species occurs at the edge of its familial range. 2 Supplemental hand pollination of flowers increased their probability of fruit set compared with open‐pollinated control flowers by an average of 57.6%. Pollen limitation was assessed on a per flower basis because the median floral display size at Lake Matchedash was one flower. Pollen limitation was prevalent throughout the 3–4‐week blooming period in one population, whereas in the other it was only evident at the beginning of flowering, despite their close proximity. 3 Bumblebee visits (primarily Bombus impatiens) to R. virginica flowers were infrequent and variable in their occurrence. Visitation was recorded on 14 days during flowering. The median number of visits was 0.65 bees per hour; on 6 days there was virtually no bee activity, but on 2 days visitation rates were high. Variation in pollinator activity was apparently unrelated to local weather conditions. 4 Field experiments demonstrated that the poricidal anthers of R. virginica dispense pollen gradually, with only 10.2% of pollen removed from flowers during a single bumblebee visit. This level of pollen removal is lower than reported in other flowering plants. On average, 47.3% of pollen remained in anthers at the end of anthesis. 5 Investigation of the relation between pollen dispersal and pollen limitation demonstrated a significant negative correlation between the proportion of pollen removed from anthers on a given day and the intensity of pollen limitation. It appears that the pollen‐dispensing mechanism of R. virginica and infrequent visitation by bumblebees compromise pollen dispersal, causing pollen limitation in Ontario populations.

A New Species of Rustia (Rubiaceae, Rondeletieae) from Bilsa Biological Station, Esmeralda Province, Ecuador

A new species of Rustia from Ecuador (Esmeraldas Province), R. bilsana, is described and illustrated. The new species is represented by trees endemic to the cloud forests of northwestern Ecuador, and is easily recognizable by having floral buds pointed at the apex, capsules widely obovoid, inflorescences 16-26 cm long, and purple corollas. RESUMEN. Se describe e ilustra una nueva especie de Rustia del Ecuador (Provincia de Esmeraldas), R. bilsana. La nueva especie esti representada por grboles endamicos de los bosques nublados del Noroeste del Ecuador, y es fcilmente distinguible por sus botones florales agudos, cipsulas anchamente obovoides, inflorescencias 16-26 cm de largo y corolas color pdirpura. Rustia is a genus of approximately 14 species of shrubs and trees, ranging from Costa Rica to southern Brazil. This genus is unique in having terminally poricidal anthers and pellucid-punctate leaves. Its sister genus, Tresanthera, is represented by trees endemic to the coastal forests of Venezuela and Trinidad and Tobago; it also has pellucid-punctate leaves but has laterally poricidal anthers. A full monographic treatment of Rustia is given by Delprete (in press-1999), and an account of the species present in Ecuador has been prepared by Delprete (1998). Rustia and Tresanthera have traditionally been placed in the tribe Condamineeae, but this tribe has been shown to be paraphyletic (Delprete, 1996b), and both genera are included in the tentatively delimited tribe Rondeletieae (Delprete, 1996b). Ecuador has the highest number of species of Rustia (6 out of a total of 14), representing the center of diversity for this genus. The high degree of biodiversity in Ecuador is correlated with the varied vegetational zones present in the country, the adaptation of the species to certain ecological niches, and the latitude being near the equator. In the case of Rustia, one species (R. occidentalis (Bentham) Hemsley) is a shrub endemic to coastal swamps, two are trees found in the wet forests of the western slopes of the Andes (R. alba Delprete from Carci Province and R. bilsana Delprete described below, from Esmeralda Province) and the remaining three (R. schunkeana Delprete, R. viridflora Delprete, and R. rubra Standley ex D. Simpson) are trees occurring on the forested slopes of the Amazonian region. During routine identification of Rubiaceae from Ecuador, while I was still a doctoral student at the University of Texas at Austin in fall 1995, a specimen (Clark, Bass & Pitman 139) of Rustia caught my attention. It was collected at the Bilsa Biological Station, and it was clearly an undescribed species of this genus. Several other species of Rustia occurring in Ecuador have recently been described (Delprete, 1995, 1996a), and the taxonomic position of the genus has been analyzed (Delprete, 1996b). The only specimen (Clark et al. 139) known to me in fall 1995 had inflorescences with only a few old flowers and immature fruits. One year later, John Clark returned to the original site in order to provide complete herbarium specimens (Clark 2979), pickled flowers for morphological studies, and photographs (see Fig. 2). The new species is still known only from the Bilsa Biological Station. The Bilsa Biological Station is a nature preserve of approximately 2500 ha, with an altitudinal range from 300 to 800 m and is located in the Mache Mountains portion of the northwestern province of Esmeraldas. Bilsa was founded in 1994 by the Jatun Sacha Foundation in memory of the late biologists Al Gentry (botanist) and Ted Parker (ornithologist), who died in an airplane crash in the Ecuadorian mountains. This reserve represents one of the few remnant patches of premontane wet forest in northwestern South America, of which less than 1% remains. This premontane forest ecosystem is extremely endangered and quickly disappearing due to farming practices and indiscriminate logging. The Bilsa reserve houses a unique composition of flora and fauna, with elements related to both the coastal rainforest of Colombian Choc6 Province and Andean cloud forests, and many of i s species are rare or still unknown to science. The NovoN 8: 231-234. 1998. This content downloaded from 207.46.13.99 on Sun, 04 Jun 2017 17:46:04 UTC All use subject to http://about.jstor.org/terms

Relationships between floral organization, architecture, and pollination mode inDillenia (Dilleniaceae)

The flowers ofDillenia are highly elaborate pollen-flowers adapted to buzzpollination byXylocopa bees. Two major forms of floral architecture (revolver flowers and roundabout flowers) are associated with two different pollination modes. In the first (e.g.,D. suffruticosa), the pollination organs are connivent to a cone; the pollinator grasps the entire cone with its legs and buzzes it; it revolves around its axis and repeats the buzzing in different positions. In the second (e.g.,D. alata, D. philippinensis), the stylar branches are spreading and the stamens are arranged in two sets of two different forms and colourations. The inner set has fewer and longer stamens that are cryptic pollination stamens; those of the outer set are shorter but optically conspicuous feeding stamens. The pollinator squeezes itself under the stylar branches and handles only the outer set by grasping part of the set at a time; it moves tangentially around the flower with several buzzing-stops; when buzzing pollen is sprayed onto its side and back from the inner stamen set. Centrifugal polyandrous androecia are a constitutive feature of flowers inDilleniaceae. InDillenia the centrifugal initiation of stamens proceeds for an unusually long time and is still not finished when the gynoecium is completely closed (in contrast toTetracera). The differentiation of heteranthery seems to be functionally correlated with the extended centrifugal inception. The latest formed stamens are small and sterile in many species. Generic features ofDillenia flowers can be understood from the roundabout architecture: big size, increased number of carpels, syncarpy forming a firm pedestal and spreading firm stylar branches with small, concave stigmas at the end, stamens with short, stout filaments and much elongated poricidal anthers, heteranthery, recurved stamens of the inner set.

Sonication Dispensing of Pollen from Solanum laciniatum Flowers

1. Sonication is a seemingly effective method for foraging insects to extract pollen rapidly from poricidal anthers. However, without a dispensing mechanism to limit the pollen extraction a single forager might be able to glean all of the pollen from a flower in a single visit. 2. The vibratory release mechanism of a buzz-pollinated flower species, Solanum laciniatum, and its relationship with time was investigated. 3. The sonication vibration magnitude required to eject pollen from the anthers increased with frequency ; vibrations at frequencies below 180 Hz were particularly effective owing to the low (124 Hz) natural frequency of the stamens and the good transmission of low-frequency vibration by the anthers. The natural frequency of stamens was low compared with the sonication frequencies of bumble-bees and did not change significantly when sonicated. 4. Large amounts of pollen (72 000 grains) were released in initial sonications, but this was a small percentage (18%) of the total available pollen ; pollen release continued in metered quantities over time. 5. The stamen vibration mode created centrifugal forces, which forced pollen out of the apical pores, and the gradual dehydration of the tapetal fluid remaining in lower regions of dehiscent poricidal anthers produced a timed release mechanism. 6. The frequency increase from the flight wing-beat frequency to the sonication buzz enables bumble-bees to generate high accelerations, which are able to release pollen from the anthers, using thoracic vibrations, which are limited by the maximum possible displacement of the indirect flight muscles.

Pollination, Foraging, and Nesting Ecology of the Leaf-Cutting Bee Megachile (Delomegachile) addenda (Hymenoptera: Megachilidae) on Cranberry Beds

The leaf-cutting bee Megachile addenda Cresson is an effective and potentially manageable pollinator of cultivated cranberries, Vaccinium macrocarpon Aiton. This facultatively gregarious, univoltine bee excavates shallow subterranean nests in the dikes and periodically flooded sand beds of commercial cranberries in southern New Jersey. Females provision 1-2 leaf-lined nest cells per day, each containing 3.9-5.4 million pollen tetrads (1992 and 1993 means, respectively) collected from a calculated minimum of 1,076 1,207 cranberry flowers. Using their middle and hind legs, pollen-foraging females repeatedly stroked the 8 poricidal anthers of a virgin cranberry flower, removing 71% of the pollen while leaving an average stigmatic load of 28 tetrads (0.6% of pollen harvested). An estimated 1,291-1,440 berries should result from the daily foraging activity of a female, calculated using either pollen or time as currencies. In weather favorable for bee activity, an estimated 1,114 nesting females per hectare of cranberry bed could suffice to produce a commercial fruit set. Management of M. addenda for cranberry pollination must include control of its cleptoparasite Coelioxys immaculata Cockerell, which can parasitize >90% of nest cells when abundant.

The Functional Significance of Poricidal Anthers and Buzz Pollination: Controlled Pollen Removal From Dodecatheon

Given the diminishing returns associated with animal pollination, floral mechanisms that restrict pollen removal by individual pollinators and encourage transport on many pollinators generally promote a plant's cumulative success in pollen dispersal. Effective mechanisms for dispensing pollen should allow facultative adjustment of removal in response to the prevailing frequency of visits to a plant. We investigated whether the poricidal anthers of Dodecatheon conjugens, a buzz-pollinated species, function as dispensing mechanisms by (a) comparing pollen removal in response to buzz frequencies that pollen-collecting bumble-bees (Bombus spp.) produce (≤ 400 Hz) with removal stimulated by higher frequencies and (b) comparing removal from flowers that waited different periods of time for their first visit