Shrub vegetation on tropical granitic inselbergs in French Guiana

Abstract. In French Guiana, inselbergs in the form of granite outcrops rise abruptly from the surrounding rain forest. They constitute isolated islands of a special type of vegetation restricted to this peculiar substrate. Shrub granitic vegetation, organized in thickets on open exposed rocks of inselbergs, are described using the Braun‐Blanquet method combined with Correspondence Analysis. This phytosociological study revealed only one particular shrub community on each inselberg, including predominantly evergreen and sclerophyllous shrubs, especially microphanerophytes, belonging to the Clusiaceae, Myrtaceae and Bombacaceae. These outcrop communities exhibit species endemic to the Guianas region and also species rare in French Guiana. Affinities with flora of other inselbergs and vegetation types in South America are examined and discussed. Reasons for observed floristic and structural changes in each community are also discussed.     

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.     

Characterization of polymorphic microsatellite markers for Microcyclus ulei,causal agent of South American leaf blight of rubber trees

South American leaf blight caused by the ascomycete Microcyclus ulei is the most harmful disease of the rubber tree in Latin America and a potential threat to Asiatic and African natural rubber production. Until now, the variability of this fungus was assessed through observation of pathogenicity of isolates on a range of rubber tree clones with known resistance reactions. The present study describes the process used to design 11 microsatellite markers and evaluates their usefulness in detecting genetic polymorphism. Nine of these markers were polymorphic among six isolates from Brazil (with two to three alleles per locus) and five markers were polymorphic among four isolates from French Guiana (with two to four alleles per locus).     

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.     

A newly identified locus controls complete resistance to Microcyclus ulei in the Fx2784 rubber clone

Using cultivars which are genetically resistant to South American leaf blight (SALB) caused by the fungus Microcyclus ulei is the only way to plant rubber trees in disease-affected areas. Numerous field observations led to the hypothesis that the resistance of the cultivar Fx2784 to SALB is likely to be monogenic. In this study, we investigated this hypothesis by examining the distribution of the trait in a cross between the resistant cultivar and a susceptible one. The individuals resulting from this cross were planted in field trials in French Guiana and Brazil. The resistance of all the trees was assessed by field observations. Bulk segregant analysis (BSA) using microsatellite markers was performed in French Guiana to determine which markers were genetically linked to resistance, and the results were validated by field observations in Brazil. In both locations, a 1:1 segregation of the resistance trait was observed, thus reinforcing the monogenic hypothesis. BSA showed tight linkage between resistance and the microsatellite markers located in linkage group 2 in the Hevea genome and enabled to pinpoint the resistance locus. The location was confirmed by observations on the trees planted in Brazil. This result should facilitate the use of Fx2784 resistance in future breeding programs for SALB resistance. This is the third major locus conferring resistance to SALB identified in rubber tree (Hevea spp.). These three loci are genetically independent, a favorable situation for genetic improvement of SALB resistance.     

Epilithic plant communities on inselbergs in French Guiana

Abstract. Tropical inselbergs are isolated elevations with a special type of vegetation and surrounded by rain forest. The paper describes, using the field methods of Braun-Blanquet, combined with numerical analysis (clustering, Correspondence Analysis), plant communities on French Guianan inselbergs. Six new associations are described: Portulacetum sedifolii, Furcraeetum foetidae, Ananasetum annassoidis, Stylosanthetum guianensis, Axonopetum ramosi and (endemic to the Guianan inselbergs) Pepinietum geyskesii – with three subassociations. The six vegetation units reflect different combinations of environmental factors such as local relief, insolation, water availability and soil depth. All syntaxa show a low species diversity. Species of Cyperaceae, Poaceae, Lentibulariaceae and Bromeliaceae are predominant, whereas families typical of other South American inselbergs (Velloziaceae and Cactaceae), are missing or scarce. Similarities between vegetation units of South American and African inselbergs are emphasized.     

Development and characterization of microsatellite markers for a monoecious Ficus species,Ficus insipida,and cross‐species amplification among different sections of Ficus

The animal‐mediated pollination and seed‐dispersal mutualisms of Ficus species give them key roles in tropical ecosystems, but may make them vulnerable to habitat fragmentation. The development of highly polymorphic markers is needed to analyse their genetic diversity and investigate the effects of fragmentation on gene flow. Of thirteen microsatellite loci isolated from Ficus insipida, a monoecious species in French Guiana, eleven were polymorphic (two to six alleles each). High levels of variation were found among loci; expected heterozygosities ranged from 0.151 to 0.715. All markers revealed a broad cross‐species affinity when tested in 23 other Ficus species.     

Development and characterization of microsatellite markers for the endangered northern riffleshell mussel Epioblasma torulosa rangiana (Bivalvia: Unionidae)

Primers for six polymorphic microsatellite loci were developed for the endangered northern riffleshell Epioblasma torulosa rangiana from the Sydenham River, Ontario, Canada. These loci along with an additional nine microsatellite loci, developed from other unionoid species, available in the literature, were tested and characterized on individuals from two populations in the Allegheny River; one population in French Creek, PA, USA, and one population from the Sydenham River. Allelic diversity ranged from two to 28 alleles per locus and averaged 13.7 per locus. These primers are being used in a rangewide study on the conservation genetics of remaining extant populations of the northern riffleshell.     

Polymorphic microsatellite DNA loci identified in the common frog (Rana temporaria,Amphibia, Ranidae)

We developed seven microsatellite loci in the common frog, Rana temporaria. There were between 2 and 27 alleles per locus and the expected heterozygosities ranged from 0.28 to 0.96 in a sample of frogs collected in the French Alps. Adding these seven markers to the 15 previously available microsatellite loci for this species should facilitate studies of genetic structure of Rana temporaria populations at a fine geographical scale.     

A survey of adult anophelines in French Guiana: enhanced descriptions of species distribution and biting responses

In French Guiana, Anopheles darlingi is considered the main malaria vector. However, several reports have hypothesized the implication of other anopheline species in malaria transmission for the territory. Data on the ecology of these other potential vectors is rare or even unexplored in French Guiana. The aim of this study was to describe the biting habits of several anopheline species in multiple localities in French Guiana. Six sampling sites yielded 1,083 anopheline adults. Results indicated the presence of An. darlingi in all study locations and it was the only species to be collected inside villages. Other anophelines collected included An. aquasalis, An. braziliensis, An. intermedius, An. mediopunctatus, An. nuneztovari, An. oswaldoi, and An. triannulatus, all of which were associated with open areas and forests. The environment and time, at which biting behavior was recorded, varied for each species. It was noted that An. oswaldoi showed a daytime rhythm in open areas. This study is the first to report on the biting habits of a range of anophelines in French Guiana that may play a role in malaria transmission. This information is vital to fully describe the risk of malaria transmission and thereby design appropriate vector control measures and malaria prevention programs.     

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.     

Characterization of 16 microsatellite loci for a common coral reef fish,the fierce shrimpgoby Ctenogobiops feroculus

We developed 16 pairs of primers for microsatellite loci of the fierce shrimpgoby, Ctenogobiops feroculus. Analysis of 35–40 gobies per locus from five islands in French Polynesia indicated that allele frequency varied from two to 30 per locus, while observed heterozygosity ranged between 0.05 and 0.98. These microsatellites should provide insight into patterns of dispersal and connectivity among populations of this common coral reef fish.     

Systematic review of Atractus schach (Serpentes: Dipsadidae) species complex from the Guiana Shield with description of three new species

The Guiana Shield harbours one of the best preserved and largest extents of tropical forest on Earth and an immense biodiversity. The herpetofauna of this region remains poorly known. The species-rich snake genus Atractus contains ～140 species, many with complicated taxonomic histories, including A. schach. Examination of specimens in museums and newly collected material from French Guiana has allowed the illustration of hemipenial morphology for the first time and an expanded diagnosis. Concatenated molecular phylogenetic (mitochondrial and nuclear genes) and phenotypic (morphometrics, external and hemipenial morphology) analyses confirm non-monophyly of the A. flammigerus group and indicate that A. schach is a species complex with three new species described here. The geographic distribution of A. schach sensu stricto is restricted to Guiana, Surinam, and French Guiana north of Tumucumaque massif. Populations tentatively assigned to A. schach from the east from French Guiana in the Roura lowlands to Almeirim, and from central Amazonia between the Negro and Trombetas rivers in Brazil are also recognized as new species. Our results suggest that populations from south of the Amazon River are not conspecific with those from the Guiana Shield.

http://www.zoobank.org/urn:lsid:zoobank.org:pub:A7AE40BC-4716-4302-B3BE-1F43600B0A72     

Isolation and characterization of microsatellite markers in the tropical tree species Dicorynia guianensis (Caesalpinaceae)

Dicorynia guianensis is a canopy tree endemic to French Guyana and the first to be exploited as timber wood. To investigate levels of diversity and dynamics of gene flow in a 40‐ha study plot, highly polymorphic microsatellite markers were developed. An enriched microsatellite library was constructed and seven microsatellite primer pairs were developed. Total genomic DNA was extracted and amplified from cambium tissue from 172 adult individuals. The level of genetic diversity was found to be low. A large heterozygote deficiency was found at one locus. This was resolved by redesigning the primer set.     

Genetic variation and geographical structure of five mouse-sized opossums (Marsupialia, Didelphidae) throughout the Guiana Region

Aim and location To study the patterns of genetic variation and geographical structure of five forest‐dwelling didelphid species distributed throughout the Guiana Region (Marmosops parvidens, M. pinheiroi, Monodelphis brevicaudata, Marmosa murina, Micoureus demerarae) and place the results for wide‐ranging species (M. murina, M. demerarae) in the broader geographical context of the rest of the taxon ranges based on published data. Methods Variation in the mitochondrial cytochrome b gene were analysed in order to assess intra‐specific sequence divergence as well as haplotypic and nucleotide diversity among populations. Relationships between haplotypes were inferred by cladistic (maximum parsimony) and probabilistic (maximum likelihood) approaches, allowing comparisons between tree topologies and patterns of populations geographical distribution. Results Phylogenetic analysis of the Guiana Region populations suggest the lack of common patterns of geographical structure among mouse‐sized opossums except for both Marmosops species. Marmosops parvidens and M. pinheiroi showed individuals from Surinam strongly related with those from Guyana, and haplotypes from French Guiana having a basal position. Concerning Micoureus demerarae, haplotypes from Venezuela were positioned as ancestral, in contrast with Monodelphis brevicaudata, whose French Guiana haplotypes were clustered in a basal position. No evidence of geographical structure was observed for Marmosa murina. Genetic variation within Guiana Region populations fluctuated between 1% for M. murina and 7% in the case of M. brevicaudata. Regarding the widely distributed species, phylogeographical structure at the scale of the Amazon Basin suggests that Guiana Region populations are the sister group of south‐eastern Amazonian and Atlantic Forest populations, thus resulting in an eastern clade well separated from the western Amazonian regions. Main conclusions Monophyly of mouse‐sized opossums haplotypes over the Guiana Region confirms the presence of a well‐differentiated zoogeographical area relative to other Amazonia bioregions. Low genetic diversity among Guiana Region samples suggests a relatively recent origin of populations dating from later Miocene and Pleistocene periods. Moreover, nucleotide and haplotypic diversity values suggest an evolutionary scenario of rapid population growth and dispersal over the Guiana territory, from an ancestral population with small effective size. Dispersal events – rather than vicariance – seem to be responsible for the present genetic and phylogeographical patterns observed in the Guiana Region.     

Reproductive strategies and population structure in Leishmania: substantial amount of sex in Leishmania Viannia guyanensis

Leishmania species of the subgenus Viannia and especially Leishmania Viannia guyanensis are responsible for a large proportion of New World leishmaniasis cases. Since a recent publication on Leishmania Viannia braziliensis, the debate on the mode of reproduction of Leishmania parasites has been reopened. A predominant endogamic reproductive mode (mating with relatives), together with strong Wahlund effects (sampling of strains from heterogeneous subpopulations), was indeed evidenced. To determine whether this hypothesis can be generalized to other Leishmania Viannia species, we performed a population genetic study on 153 human strains of L. (V.) guyanensis from French Guiana based on 12 microsatellite loci. The results revealed important homozygosity and very modest linkage disequilibrium, which is in agreement with a high level of sexual recombination and substantial endogamy. These results also revealed a significant isolation by distance with relatively small neighbourhoods and hence substantial viscosity of Leishmania populations in French Guiana. These results are of epidemiological relevance and suggest a major role for natural hosts and/or vectors in parasite strain diffusion across the country as compared to human hosts.     

Aedes aegypti survival and dengue transmission patterns in French Guiana.

Field survival of Aedes aegypti females is a key parameter for estimating the dengue transmission potential of a mosquito population. The objectives of this study were to explore the dynamics of these survival rates at different times of the year in French Guiana and to analyze the results from the perspective of dengue patterns. The mosquitoes were captured, marked, released, and recaptured during four consecutive days in six houses every month, for three to 24 months, from January 1997 to December 1998. Laboratory experiments showed no effects on female survival but some effect on the survival of males. Females' daily survival in the field varied from 0.525 to 1 but was mostly between 0.8 and 0.95 during the entire year, with a mean value of 0.913. The field survival of Ae. aegypti females in French Guiana was thus in agreement with the likely transmission of dengue and the dengue endemic patterns throughout the year. On the other hand, heavy rainfalls during this time were less favorable to Ae. aegypti survival, which may explain part of the El Ni?o effect on dengue epidemics in French Guiana. The methods and results on Ae. aegypti survival will be implemented in a global dengue surveillance network in French Guiana.     

Herpetomonas dedonderi N. Sp. (Sarcomastigophora,Trypanosomatidae) from Haemagogus janthinomys Dyar, 1921 (Diptera,Culicidae)1

ABSTRACT. A new species of Herpetomonas was isolated from the intestinal tract of a mosquito, Haemagogus janthinomys, in French Guiana (South America). Ultrastructure, growth in various culture media, and morphological changes are presented. The name, Herpetomonas dedonderi, is proposed for this new species of lower trypanosomatid.     

Characterization of polymorphic microsatellite loci in the terrestrial isopod Porcellionides pruinosus

We developed a set of six polymorphic microsatellite loci for the woodlouse, Porcellionides pruinosus. We screened 43 individuals from three French populations and found that locus‐specific allelic diversity ranges from 3 to 17 alleles (mean = 9.8) and observed heterozygosity ranges from 0.51 to 0.89 (mean = 0.77). These are the first microsatellites loci reported from the woodlouse.