Clusia blattophila sp. nov. (Clusiaceae) from an inselberg in French Guiana

Clusia blattophila (Clusiaceae) is described as a new species. It is distinguished from related species in C. sect. Oedematopus by e.g. the relatively large and reflexed petals and from other Clusia spp. by having fewer (6–16) stamens and only four petals. Unique traits are the almost sessile inflorescence and the presence of a secretory pit at the floral apex in staminate flowers. The species grows epilithically and is known only from the Nouragues inselberg, a massive granite outcrop in eastern French Guiana. The name refers to its cockroach pollinators.     

Genetic structure of the saxicole Pitcairnia geyskesii (Bromeliaceae) on inselbergs in French Guiana

South American inselbergs constitute singular and fragmented habitats in the tropical rain forest. Pitcairnia geyskesii is restricted to these habitats and exhibits both sexual and asexual reproduction. The genetic structure of populations on three inselbergs in French Guiana is examined by analysis of ten isozyme loci. All analyzed populations show high levels of genetic variation. On average, 63.3% of loci per population were polymorphic, with a mean number of 2.21 alleles per polymorphic locus, and mean observed and expected heterozygosities of 0.185 and 0.183, respectively. The analyses of genetic variability displayed at different levels (inselbergs, subpopulations, and mats) give different but complementary information. A significant multilocus disequilibrium was detected in one subpopulation, whereas none was observed within the whole populations sampled on the three inselbergs. Tests on spatial genetic structure indicate a patchy distribution of genotypes on two inselbergs. The data give some insights on the reproductive behavior of P. geyskesii. (1) Efficient sexual reproduction leads to seed recruitment at the level of the inselberg. (2) Both clonality and seed recruitment occur within mats. (3) Vegetative spread by fragmentation is involved in the establishment of new mats. There is substantial differentiation (F(ST) = 0.322) and low gene flow among inselbergs (Nm = 0.234). High genetic diversity within inselbergs appears as a consequence of the association of genet longevity induced by clonal replication and recruitment of new genets produced by sexual reproduction.     

Successional patterns on tropical inselbergs: A case study on the Nouragues inselberg (French Guiana)

A number of plant communities have been described on tropical inselbergs, known as hot spots of plant and animal biodiversity. However, few studies tried to question what drives seral processes in these harsh environments, submitted to natural hazards (violent storms, intense runoff and lightning strikes) which may destroy the vegetation cover and its accumulated organic matter. We analysed quantitative data from the granitic Nouragues inselberg (French Guiana) in order to discern how successional processes featured their variety. We showed that the transition from herbaceous carpets (bromeliaceous mats and grassy meadows) to woody vegetation (shrub thickets) was not conditioned by slope, but was truly successional. We also showed that there was a cycle of change in shrub thickets, reinitiated by the destruction of scrub vegetation by fire (lightnings), wood-destroying fungi and termites.     

Antimicrobial compounds of fungi vectored by Clusia spp. (Clusiaceae) pollinating bees

The production of antimicrobial compounds by fungi associated with Clusia spp. pollinating bees (Trigona sp., Trigonini) was investigated in order to approach natural mechanisms of microbial density control within nest environment. By using a bioassay-guided approach based on bioautography and minimal inhibitory concentration (MIC), known alpha,beta-dehydrocurvularin and curvularin were isolated from Curvularia eragrostidis (CCT 5634) and Curvularia pallescens (CCT 5654), and known cochlioquinone A and isocochlioquinone A were isolated from Drechslera dematioidea (CCT 5631).     

Anti-bacterial function in the sexually dimorphic pollinator rewards of Clusia grandiflora (Clusiaceae)

Many species of the dioecious, neo-tropical plant genus Clusia secrete a viscous, hydrophobic resin from glandular tissues in both male and female flowers. This substance is readily gathered by meliponine and euglossine bees for whom it most often serves as the sole pollinator reward. Bees use Clusia resin as a nest-building material. As such, resin clearly serves an indispensable mechanical function. However, resins with antimicrobial properties may also serve to reduce the risk of pathogenesis in the nest. If resin-gathering apids benefit from antimicrobial properties in nesting materials and are able to discern these characteristics in the forage they gather, one might predict that the resin reward presented in Clusia could have evolved under selection for both mechanical and antimicrobial properties. In dioecious species, where females and males each present a resin reward, selection regimes may differ between the sexes with the result that resin form and function diverge. We investigated both the form and function of the male and female pollinator reward resins of Clusia grandiflora. Using thin-layer chromatography (TLC), we compared the chemical compositions of floral resins from five widely separated populations of this species growing in southeastern Venezuela. We found that male and female resins exhibited a marked chemical dimorphism, with females having two major TLC-resolvable fractions and males having seven. This dimorphism was stable: there were no component differences between populations in either sex. Using a disk-diffusion technique, we surveyed the same resins for antimicrobial activity using assay microorganisms isolated from eusocial meliponine bees. Both male and female Clusia grandiflora resins had pronounced but relatively directed antimicrobial activity: both were toxic to 10 of 11 Gram-positive bacteria, 7 of 15 Gram-negative or variably-staining bacteria, 0 of 3 yeasts, and 0 of 3 filamentous fungi. Again with the disk-diffusion technique, we performed more detailed tests of resin bioactivity using two Gram-positive honeybee associates, Paenibacillus larvae and P. alvei, as model pathogens. Both male and female C. grandiflora resins were highly toxic to these honeybee pathogens. Female resin, however, produced zones of inhibition with more than twice the mean diameter of those produced by the male resin. This divergence in form and function of the C. grandiflora pollinator reward resins could be in response to different selective regimes as mediated by the pollinating insects. Received: 19 October 1998 / Accepted: 9 February 1999     

Two polyisoprenylated benzophenones from the trunk latex of Clusia grandiflora (Clusiaceae)

The polyisoprenylated benzophenones, chamones I and II, were isolated from the trunk latex of Clusia grandiflora (Clusiaceae) growing in southeastern Venezuela. A third benzophenone, nemorosone II, was isolated from the pollinator reward resin of the female flowers of the same plant. Chamone I and nemorosone II are structurally similar, differing only in the degree of prenylation. Bioassays of chamone I and nemorosone II using the honeybee pathogens, Paenibacillus larvae and Paenibacillus alvei, demonstrate that both have potent antibacterial activity, and that their structural differences affect both their bactericidal efficacies and their aqueous mobilities.     

Developmental plasticity and biomechanics of treelets and lianas in Manihot aff. quinquepartita (Euphorbiaceae): a branch-angle climber of French Guiana

Background and Aims

Most tropical lianas have specialized organs of attachment such as twining stems, hooks or tendrils but some do not. Many climbers also have an early self-supporting phase of growth and in some species this can produce treelet-sized individuals. This study focuses on how a liana can climb without specialized attachment organs and how biomechanical properties of the stem are modulated between self-supporting treelets and canopy-climbing lianas.

Methods

Biomechanics and stem development were investigated in self-supporting to climbing individuals of Manihot aff. quinquepartita (Euphorbiaceae) from tropical rain forest at Saül, central French Guiana. Bending tests were carried out close to the site of growth. Mechanical properties, including Young''s elastic modulus, were observed with reference to habit type and changes in stem anatomy during development.

Key Results

This liana species can show a remarkably long phase of self-supporting growth as treelets with stiff, juvenile wood characterizing the branches and main stem. During the early phase of climbing, stiff but unstable stem segments are loosely held in a vertical position to host plants via petiole bases. The stiffest stems – those having the highest values of Young''s modulus measured in bending – belonged to young, leaning and climbing stems. Only when climbing stems are securely anchored into the surrounding vegetation by a system of wide-angled branches, does the plant develop highly flexible stem properties. As in many specialized lianas, the change in stiffness is linked to the development of wood with numerous large vessels and thin-walled fibres.

Conclusions

Some angiosperms can develop highly effective climbing behaviour and specialized flexible stems without highly specialized organs of attachment. This is linked to a high degree of developmental plasticity in early stages of growth. Young individuals in either open or closed marginal forest conditions can grow as substantial treelets or as leaning/climbing plants, depending on the availability of host supports. The species of liana studied differs both in terms of development and biomechanics from many other lianas that climb via twining, tendrils or other specialized attachment organs.Key words: Biomechanics, bending, developmental plasticity, French Guiana, liana, Manihot aff. quinquepartita (Euphorbiaceae), treelet, branch angle climber, Young''s modulus     

A new Thismia (Burmanniaceae) from French Guiana

Thismia saülensis is described and illustrated.     

Beetle pollination of Philodendron solimoesense (Araceae) in French Guiana

The pollination of Philodendron solimoesense (subgenus Meconostigma) was studied in four populations of French Guiana. Flowering is asynchronous within each population during July, and the flowering cycle is a 2-d process. Numerous insects visit Philodendron inflorescences, but the main pollinator seems to be Cyclocephala colasi (Scarabaeidae, Dynastinae). The pollination process displays aspects typical of beetle pollination: the production of heat and of a strong odor, the presence of a food reward (stigmatic secretion and sterile male flowers), and the presence of a copulation chamber. Flower heat production is important (ca. 11 degrees C above the ambient air) and may help to volatilize the fragrance. Attraction and choice-test experiments showed that C. colasi is not likely to depend on chemical information (such as pheromone) to localize conspecifics but may rely instead on stimuli produced by the inflorescences in order to meet mating partners.     

Genetic structure of the xerophilous bromeliad Pitcairnia geyskesii on inselbergs in French Guiana – a test of the forest refuge hypothesis

Inselbergs are isolated granitic rock outcrops that provide distinctive ecological conditions. In northern South America they rise above the surrounding rainforest. Among inselberg specialists, Pitcairnia geyskesii (Bromeliaceae) is restricted to these habitats in French Guiana. We studied populations from 12 inselbergs using 7 microsatellite loci to give a "reverse image" of the reduction-expansion of the rainforest in the context of the refuge hypothesis. Our analyses showed that populations are fragmented with dispersal occurring only over very short distances. Genetic diversity was higher in northern French Guiana, whereas specific alleles were observed in the south. The results point to the occurrence of a dry corridor in the north, as hypothesized by Tardy (1998) based on charcoal analyses, whereas de Granville's (1982) hypothesis of a unique past refuge is not confirmed. Moreover, our data suggests the importance of Oyapock River as a pathway for range expansion, arguing against the potential role of the Inini-Camopi Mountains as a physical barrier. Finally, in spite of a strongly argued scenario in favour of a north-to-south migration history, a clear genetic isolation of P. geyskesii populations living on inselbergs of the Mitaraka archipelago suggests a distinct ancestry of the most southern populations.     

Aspects of reproductive ecology of Clusia valerioi Standl. and Clusia peninsulae Hammel (sp. nov.), two Central American species of Clusiaceae with resin flowers

Clusia valerioi Standl. and C. peninsulae Hammel, sp. nov. (formally established in the Appendix), two Central American species of Clusiaceae offering resin as a floral reward, were studied in the Piedras Blancas National Park, SW Costa Rica. Basic data on phenology, flower structure, course of anthesis, flower visitors, flower visitation and pollination processes, fruit development and seed dispersal are communicated. Resin collection and pollen release are reported and documented in greater detail. The significance of stingless bees for pollination is confirmed, but honeybees were also observed to visit the flowers and to collect resin. The seeds of C. valerioi, exhibiting a clearly ornithochorous character syndrome, were observed to be eaten and dispersed by four species of the tanager family (Thraupidae) and one species of finch (Fringillidae). Ants were also observed to carry away the seeds.     

A new species of Bactris (Palmae) from French Guiana

A new species,Bactris nancibaensis, from French Guiana, is described and illustrated.     

Four new species of Calathea (Marantaceae) from French Guiana

Four new species are described: Calathea erecta, C. dilabens, C. granvillei , and C. squarrosa , based on material from French Guiana. Calathea erecta and C. granvillei are known also from the central Amazon Basin. Calathea squarrosa probably also occurs in Surinam. Calathea dilabens is presently known only from French Guiana, but probably occurs in adjacent Brazil and Surinam. A tentative key is provided to the species of Calathea known to occur in French Guiana.     

A new species of Ocotea (Lauraceae) from French Guiana

A new species ofOcotea,O. diffusa van der Werff, is described and illustrated based on recent collections from French Guiana and adjacent Brazil.     

A new species of Asterogyne (Palmae) from French Guiana

Asterogyne guianensis, a new species from French Guiana, is described and illustrated. The differences between this and the morphologically similarA. spicata are given. A map and discussion of distribution is given for all five species of the genus. Studies on the Flora of the Guianas number 28.     

Pollination of Cyphomandra endopogon var. endopogon (Solanaceae) by Eufriesea spp. (Euglossini) in French Guiana

The pollination systems of two closely related genera.Cyphomandra andSolanum, differ in rewards offered and pollinator activity. I suggest that the anther differences which define these two genera have evolved in response to the different pollination systems. Male euglossine bees of the genusEufriesea were observed to pollinate the flowers ofCyphomandra endopogon var.endopogon while gathering aromatic compounds from the anther connectives. Samples of the compound collected from the flowers and the bees were tentatively identified as ocimene, a terpene.     

Positional Behavior of Black Spider Monkeys (Ateles paniscus) in French Guiana

Spider monkeys (Ateles) frequently use suspensory locomotion and postures, and their postcranial morphology suggests convergence with extant hominoids in canopy and food utilization. Previous studies of positional behavior in Ateles, have produced variable rates in the use of different positional activities. I investigated the positional behavior of black spider monkeys (Ateles paniscus) in a wet rain forest in French Guiana, and assessed differences in the rates of use of positional modes across studies. I also discuss the significance of suspensory activities in forest utilization. In French Guiana, Ateles confined travel and feeding locomotion on small and medium-sized moderately inclined supports in the main canopy. Tail-arm brachiation and clamber were their main traveling modes, while clamber was the dominant feeding locomotor mode. Small horizontal supports were predominant during their feeding. Suspensory postures accounted for more than half of feeding bouts, with tail-hang and tail-hind limb(s) hang being the dominant postures. Feeding occurred largely in tree crown peripheries with the prehensile tail anchored frequently above the monkey. They usually collected food items below or at the same level as the body. There is no difference among the postures they used to acquire and eat young leaves and fruit. My results agree with reports on the positional behavior of different species of spider monkeys at other sites. Despite the use of different methods, the same species exhibited more or less similar profiles in similar forests. Interspecific differences could be associated with morphological differences. Moreover, intraspecific differences could be attributed to forest structure. The findings suggest that the major part of biological information is independent of methods used in the several studies. Suspensory behavior facilitates the exploitation of the forest canopy by shortening traveling pathways between and within trees, by enabling faster travel for the better exploitation of patchy food sources and by providing access to food in the flexible terminal twigs.     

Diet of the red howler monkey (Alouatta seniculus) in French Guiana

We report the feeding behavior and food preferences of a troop of red howler monkeys (Alouatta seniculus) over two annual cycles in primary tropical rain forest in French Guiana. The monkeys used 195 plant species from 47 families as food. Major food categories were young leaves (54%), mature fruits (21.5%), and flowers (12.6%). Other food categories included old leaves, immature fruits, termitarium soil, bark, and moss. The monkeys were less selective than other howler groups, since 19 plant species contributed 1% to their diet and accounted for only 35.7% of their total diet. The Sapotaceae was the most frequently eaten plant family and represented >10% of the total diet.     

Two new species of Eugenia (Myrtaceae) from Central French Guiana

Eugenia argyrophylla andE. morii from Saül in Central French Guiana are described and illustrated.