Epizoochorous dispersal by barbs, hooks, and spines in a lowland moist forest in central French Guiana

An analysis of the flowering plant flora of a lowland moist forest in central French Guiana reveals 25 species with adaptations for epizoochorous dispersal by barbs, hooks, or spines (stick-tights). This represents 1.5% of the flowering plant flora. Stick-tights are represented among the monocotyledons of the flora of central French Guiana by five species of Poaceae. The Fabaceae and Asteraceae, each with six species with stick-tight dispersal, are the richest families of flowering plants in terms of stick-tight dispersal in central French Guiana. This region possesses numerous potential mammal and bird dispersal agents, therefore it is a puzzle why stick-tight dispersal, especially among species of the canopy, is not more frequent.     

Seed dispersal by red howling monkeys (Alouatta seniculus) in the tropical rain forest of French Guiana

A 2-year field study of the frugivorous diet of a howling monkey troop, in a tropical rain forest in French Guiana, shows that they disperse by endozoochory ≥95% of plant species from which they eat ripe fruit. Passage through the digestive tract of howlers does not significantly modify the germination success of most plant species samples. Their low digestion rate (X = 20 hr 40 min) is the ultimate cause of a bimodal defecation rhythm that results in the concentration of 60% of defecations being deposited under sleeping sites. The distance of seed dispersal can reach more than 550 m from parent trees,with a mean of 260 m. Although howling monkeys consume fruits differing in morphological characteristics, they are particularly able to disseminate seeds of species whose fruits have a hard and indehiscent external coat or large seeds or both. In French Guiana, they may be especially important dispersers of the Sapotaceae with fruits that simultaneously present both characteristics.     

Guarea michel-moddei (meliaceae), a new species from central French Guiana

Guarea michel-moddei, a new species from central French Guiana is described and illustrated. It differs from the morphologically similarG. cristata of western Amazonia by its unbranched habit; shorter, less dense indumentum of the young parts, leaves, and inflorescence; bullate leaves, shorter inflorescence, shorter pubescence on the corolla; and smaller corolla and staminal tube.     

Seasonality of reproduction in the three largest terrestrial rodents of French Guiana forest

We investigated the main life history of the three largest terrestrial rodents of French Guiana forest: the acouchy (Myoprocta exilis), the agouti (Dasyprocta leporina) and the paca (Agouti paca), using data collected during several years. There were noticeable differences among the species in sexual maturation and degree of seasonality in reproduction. Percentage of pregnant females, births and juveniles, and body weight of juveniles decreased progressively from the acouchy, through the agouti to the paca. The acouchy was by far the most seasonal: no births occur in the period August–October, 56% of births were encountered in November–January; consequently, young form an unique cohort in the population. The agouti was also seasonal, but to a lesser degree. Newborns appeared in every period of the year in paca, without any formation of cohort of young. These differences tended to be linked to the seasonal importance of fruits in diets, the most aseasonal species having the most diversified diet during the poor fruit season.

Zusammenfassung

Jahreszeitliche Fortpflanzung von den drei größten terrestrischen Nagern im Regenwald von Französisch GuayanaDie Untersuchungen beziehen sich auf die wichtigsten Merkmale der Lebenszyklen der drei größten terrestrischen Nager, Acouchi, Aguti und Tieflandpaka, im Regenwald von Französisch Guayana, unter Verwendung von über mehrere Jahre währenden Beobachtungen, die beachtenswerte Unterschiede in bezug auf Geschlechtsreife und Fortpflanzung aufzeigen. Fortpflanzung und Populationsstruktur, wie Prozentsatz trächtiger Weibchen, Geburten, Auftreten von Jungen sowie deren Körpergewicht verringern sich kontinuierlich von Acouchis über Agutis hin zu Tieflandpakas. Während Acouchis die bei weitem am stärksten ausgeprägte jahreszeitlich gebundene Fortpflanzung mit 56% der Geburten in den Monaten November bis Januar zeigen, konnten von August bis Oktober keine Geburten beobachtet werden. Demzufolge treten die Jungen in der Population als eine einheitliche Altersklasse auf. Eine periodische Fortpflanzung zeigen auch Agutis, wenn auch weniger ausgeprägt, wohingegen bei Tieflandpakas über das gesamte Jahr hinweg Junge geboren werden, ohne jegliche Bildung von einer Altersklasse. Diese Unterschiede scheinen an die jahreszeitlich bedingte Produktion von für die Ernährung wichtigen Früchten gebunden zu sein, wobei die am wenigsten periodische Art in der früchtearmen Zeit das breiteste Nahrungsspektrum aufweist.     

Colonization front of the understorey palm Astrocaryum sciophilum in a pristine rain forest of French Guiana

Aims Astrocaryum sciophilum (Miq.) Pulle (Arecaceae) is an understorey palm, endemic to north‐eastern South America with a patchy distribution. We tested the hypothesis that the spatial distribution of this palm species is not in equilibrium but is slowly colonizing the forest understorey. Location Inventories and seed dispersal studies were conducted in the undisturbed tropical forest close to the Nouragues research station, French Guiana. Additional data were collected in the entire territory of French Guiana. Methods We studied the demography of A. sciophilum on a 20‐ha plot located at the edge of its distribution. The age of the palms was estimated by postulating an exponentially decreasing abundance by age class. Direct seed dispersal experiments were also conducted, to estimate dispersal parameters. The seeds of A. sciophilum were dispersed only by rodents. This information was used to parameterize a forest growth simulator, to study the spatial spread of this species. Results Within the sampling plot, the density of A. sciophilum dropped sharply from about 500 individuals per hectare to zero. The maturation age was estimated to be 170 ± 70 years, and over 55 years with 95% confidence. Seed‐dispersal experiments yielded an average seed dispersal distance of 11 m and a maximum estimated dispersal distance of 125 m across a generational span of 55 years to maturity. Therefore, the maximal estimated colonization speed is 2.3 m/y. Conclusions Empirical results and numerical simulations suggest that the boundary of the A. sciophilum population is a colonization front, and that the range of this species is slowly expanding. The implications of this result in respect of palaeoenvironmental changes in this region are discussed.     

Effects of Dispersal Pattern and Mammalian Herbivores on Seedling Recruitment for Virola michelii (Myristicaceae) in French Guiana1

The effects of dispersal pattern (seeds in small clumps vs. seeds scattered in pairs) and distance to the nearest Carapa procera (Meliaceae; a tree that produces seeds preferred by terrestrial vertebrates) on survival of seeds and seedlings were examined for the animal–dispersed tree species Virola michelii (Myristicaceae) in a mature forest‘at Paracou, French Guiana, in 1992 and 1993. We assessed the putative role of ground–dwelling mammalian herbivores, rodents, and ungulates that filter the seed shadow, acting either as dispersers or predators and thus modifying the original pattern of seed dispersal made by frugivores. We measured the effects of simulated seed burial by rodents using marked seeds and quantified the effect of protecting seeds and seedlings from ground–dwelling vertebrates on seedling germination and survival with fence exclosures in 1992. Dispersal pattern had short–term but no long–term effects on the proportion of V. michelii seeds that survived one year later as seedlings. In the short term, within six weeks, clumped seeds survived better than scattered seeds in both years. Marked seeds that were removed from their site of dispersal were eaten; rodents only rarely buried seeds of V. michelii, and seed burial reduced seed and seedling survivorship. The combined effect of the factors year and Carapa proximity significantly affected seed survival within six weeks. Although six–week seed survival was greater in 1993 than in 1992, seedling establishment was lower in 1993 than in 1992 following a lower rainfall regime during the key period of seed germination (February). One–year seed and seedling survivorship was similar between treatments and years. Seed survival and seedling establishment in V. michelii was dependent on vertebrates in the short term and on climate in the long term. Overall, seed and seedling survivorship depended on a combination of these factors.     

Disteganthus lateralis (Bromeliaceae), a new combination for the flora of central French Guiana

The new combination,Disteganthus lateralis, is coined based onAechmea lateralis. An illustration for this species is provided.     

Genetic studies in French Guiana populations: Synthesis

Twelve blood group and protein systems from a total of 819 individuals from six tribal groups (Apalaí‐Wayana, Emerillon, Kaliña, Palikur Wayampi, and Wayana) living in French Guiana and Brazil were compared with each other and integrated with previous results from 17 other South Amerindian populations studied for the same genetic markers. Using correspondence analysis, map methodologies, and maximum linkage cluster analysis developed with the UPGMA method, we attempted to establish the genetic position of these tribes among South American Indians. Peripheral positions for the Emerillon and the Palikur were observed. Ethnohistorical data in French Guiana suggest that a strong founder effect for the former and endogamy for the latter could have generated the genetic differentiation of these two ethnic groups. However, when considered in a wider context, all French Guiana Natives cluster together in an intermediate position as compared with 17 other Amerindian groups studied for the comparison. Am J Phys Anthropol, 2007. © 2006 Wiley‐Liss, Inc.     

Specific epithets of the flowering plants of central French Guiana

The epithets of the flowering plants of central French Guiana are classified into derivation categories. Specific epithets of the flowering plants of central French Guiana refer mostly to shapes (274 species), persons (252), places (212), appearance (146), and size (140). These categories account for 55% of names given to the plants of this flora. The most prolific publishers of names for the flora of central French Guiana are Aublet and Linnaeus, who were respectively the authors of 177 and 110 of the names of species (15% of the total) found in the flora of central French Guiana. Although many of the species names, such as those relating to place and person, are easy to categorize, many others are open to different interpretations. Specific epithets with different orthographies derived from Guiana or Guyana are discussed. In addition, problems in the use of diacritical marks and inconsistencies with spacing between the abbreviations of given names and surnames of authors of plant names are noted.     

Two new species of Lauraceae from central French Guiana

Aiouea opaca andBeilschmiedia hexanthera, recently collected in central French Guiana, are described and illustrated.     

Coussarea granvillei (Rubiaceae, Coussareeae), a new species from French Guiana

Coussarea granvillei is newly described and illustrated from material collected in the environs of Mount Galbao, near Saül, French Guiana. This new species is compared toC. amapaensis, for which the morphological and distributional ranges are extended and briefly discussed, and toC. leptophragma andC. revoluta.     

Formation and closure of canopy gaps in the rain forest at Nouragues, French Guiana

Formation and closure of canopy gaps was monitored for three years in 12 ha of primary rain forest at Nouragues, French Guiana. At the first inventory, in April 1991, 74 openings in the canopy > 4 m² (sensu Brokaw 1982a) were located; 60 of these gaps were formed before January 1990. Between January 1990 and December 1993, 5 to 15 gaps were annually formed, opening 0.64–1.33% of the forest canopy each year. Of all gaps, 41% were created by a falling, snapped tree, 34% by a falling, uprooted tree, 22% by a falling branch, and 3% by a falling dead stem. A refined nearest neighbour analysis showed that gaps formed after January 1990 were clustered: uprooting of trees seemed to be related to shallow soils, and relatively many other trees fell when a tree uprooted, independent of the dbh of the uprooted tree. In 37 gaps, canopy openness in the gap centre (determined by hemispherical photographs) was monitored over three years. In 54% of the gaps, canopy openness increased in two successive years. It is reasoned that edges of especially large gaps may frequently be re-disturbed by falling trees or branches. Results suggest that gaps have closed after around 15 years. More data are needed to verify this.     

Fractionation of phosphate in sediments of four representative mangrove stages (French Guiana)

Phosphate was fractionated in Guianese mangrove sediments. Fe(OOH)P was extracted using a Ca-EDTA + Na-dithionite solution buffered at pH 8. CaCO₃P was extracted using Na₂-EDTA solution at pH 4.5. Next, Acid Soluble Organic Phosphate (ASOP) was extracted by H₂SO₄ 0.5 N. Finally, Residual Organic Phosphate (ROP) was digested with H₂SO₄ + H₂O₂. Four representative mangrove stages have been studied: sea edge pioneer mangroves, mature coastal mangroves, mixed riverine mangroves, and declining to dead mangroves. The sum of the P-fractions varied between 638 to 804 g g^-1 in pioneer and mixed mangroves respectively. In all the stages, the percentage of inorganic phosphate was larger than 50% of the total P. Fe(OOH)P varied between 221 (pioneer mangrove) to 426 g g^-1 (dead mangrove). CaCO₃P varied between 75 to 102 g g^-1 in mixed, dead or mature mangroves and attained 125 g g^-1 in pioneer mangrove. The sum of the concentrations of organic phosphate (ASOP + ROP) increased markedly from the dead mangrove (189 g g^-1) to the mixed mangrove (380 g g^-1). Guianese mangroves, are relatively rich in total phosphate, possibly because they are narrowly related to the 'Amazon dispersal system. Each mangrove stage can be characterised by a prevailing form of phosphate. The concentrations of these different forms were ascribed to the marked relations with the seawater which controls import or export of suspended matters and to the wave action which controls the resuspension of the sediments and subsequently exchange of phosphate between the suspended matter and the water column.     

Calathea maasiorum (Marantaceae), a new species from French Guiana and Surinam

Calathea maasiorum from French Guiana and Surinam is described as new. It belongs toCalathea sectionBreviscapus Bentham. The foliage is patterned with a light green band along the midrib above. This new species has previously been confused withC. cyclophora Baker from Amazonian Colombia, Brazil, Venezuela, and Guyana but it is distinguished fromC. cyclophora by the absence of bracteoles, the elliptic to obovate leaf blade, and shorter (1–2 cm long) bracts.     

Online database for mosquito (Diptera,Culicidae) occurrence records in French Guiana

A database providing information on mosquito specimens (Arthropoda: Diptera: Culicidae) collected in French Guiana is presented. Field collections were initiated in 2013 under the auspices of the CEnter for the study of Biodiversity in Amazonia (CEBA: http://www.labexceba.fr/en/). This study is part of an ongoing process aiming to understand the distribution of mosquitoes, including vector species, across French Guiana. Occurrences are recorded after each collecting trip in a database managed by the laboratory Evolution et Diversité Biologique (EDB), Toulouse, France. The dataset is updated monthly and is available online. Voucher specimens and their associated DNA are stored at the laboratory Ecologie des Forêts de Guyane (Ecofog), Kourou, French Guiana. The latest version of the dataset is accessible through EDB’s Integrated Publication Toolkit at http://130.120.204.55:8080/ipt/resource.do?r=mosquitoes_of_french_guiana or through the Global Biodiversity Information Facility data portal at http://www.gbif.org/dataset/5a8aa2ad-261c-4f61-a98e-26dd752fe1c5 It can also be viewed through the Guyanensis platform at http://guyanensis.ups-tlse.fr     

Stability of plant communities along a tropical inselberg ecotone in French Guiana (South America)

We questioned whether and how plant communities vary in space and time along an inselberg-rainforest ecotone in relation to present-day warming and whether biotic and non-biotic factors could explain the observed patterns. The study took place on a granitic inselberg in the French Guianan (South America) rainforest (Nouragues Natural Reserve: 4°5′N, 52°41′W). In a diachronic study (1995–2005) embracing a severe El-Niño event in 1997, we analysed vegetation structure and composition along three transects subsuming whole environmental and topographical variations in the transition zone from shrub vegetation at the fringe of open-rock vegetation to tall-tree rainforest. Data were analysed by PCA. Major variations in species and trait distribution were described in the low forest, with two floristic types evidenced by first PCA component and verified by cluster analysis: one with floristic composition reminiscent of open-rock vegetation but with higher and continuous canopy, the other typical of the low forest. There is no clear-cut boundary between typical open-rock and low forest vegetation. Variation in species composition of typical low forest was evidenced by second PCA component, which displayed differences according to slope and altitude. Small (∼1.5 m), although significant, shifts in the spatial distribution of plant species pointed to possible slow encroachment of typical low forest vegetation in the absence of disturbance. However, the stability of species and trait distribution was remarkable within the 10-yr interval considered, despite an otherwise recorded decrease in species richness and recruitment. The boundary between typical low forest and open-rock-like vegetation coincided with the spatial limit of the mineral soil above granite. Despite demographic accidents due to severe El Niño events, plant communities at the fringe of a tropical inselberg are stable at short-time both in composition and spatial distribution. In the absence of strong disturbances such as wildfire and further erosion, soil availability for roots could be interpreted as an environmental constraint to the successional development of forest vegetation. Soil development might thus act as an ecological barrier to forest encroachment, which could only be alleviated by erosion recovery, as otherwise demonstrated.     

Drought effects on seedling survival in a tropical moist forest

The amount and seasonality of rainfall varies strongly in the tropics, and plant species abundance, distribution and diversity are correlated with rainfall. Drought periods leading to plant stress occur not only in dry forests, but also in moist and even wet forests. We quantified experimentally the effect of drought on survival of first year seedlings of 28 co-occurring tropical woody plant species in the understory of a tropical moist forest. The seedlings were transplanted to plots and subjected to a drought and an irrigation treatment for 22 weeks during the dry season. Drought effects on mortality and wilting behavior varied greatly among species, so that relative survival in the dry treatment ranged from 0% to about 100% of that in the irrigated treatment. Drought stress was the main factor in mortality, causing about 90% (median) of the total mortality observed in the dry treatment. In almost half of the species, the difference in survival between treatments was not significant even after 22 weeks, implying that many of the species are well adapted to drought in this forest. Relative drought survival was significantly higher in species associated with dry habitats than in those associated with wet habitats, and in species with higher abundance on the dry side of the Isthmus of Panama, than in those more abundant on the wet side. These data show that differential species survival in response to drought, combined with variation in soil moisture availability, may be important for species distribution at the local and regional scale in many tropical forests.     

Fine-scale genetic structure and gene dispersal inferences in 10 neotropical tree species

The extent of gene dispersal is a fundamental factor of the population and evolutionary dynamics of tropical tree species, but directly monitoring seed and pollen movement is a difficult task. However, indirect estimates of historical gene dispersal can be obtained from the fine-scale spatial genetic structure of populations at drift-dispersal equilibrium. Using an approach that is based on the slope of the regression of pairwise kinship coefficients on spatial distance and estimates of the effective population density, we compare indirect gene dispersal estimates of sympatric populations of 10 tropical tree species. We re-analysed 26 data sets consisting of mapped allozyme, SSR (simple sequence repeat), RAPD (random amplified polymorphic DNA) or AFLP (amplified fragment length polymorphism) genotypes from two rainforest sites in French Guiana. Gene dispersal estimates were obtained for at least one marker in each species, although the estimation procedure failed under insufficient marker polymorphism, limited sample size, or inappropriate sampling area. Estimates generally suffered low precision and were affected by assumptions regarding the effective population density. Averaging estimates over data sets, the extent of gene dispersal ranged from 150 m to 1200 m according to species. Smaller gene dispersal estimates were obtained in species with heavy diaspores, which are presumably not well dispersed, and in populations with high local adult density. We suggest that limited seed dispersal could indirectly limit effective pollen dispersal by creating higher local tree densities, thereby increasing the positive correlation between pollen and seed dispersal distances. We discuss the potential and limitations of our indirect estimation procedure and suggest guidelines for future studies.