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Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

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Viability of small seeds found in feces of the Central American tapir on Barro Colorado Island, Panama
Capece, P.I. ; Aliaga-Rossel, E. ; Jansen, P.A. - \ 2013
Integrative Zoology 8 (2013)1. - ISSN 1749-4877 - p. 57 - 62.
bairds tapir - french-guiana - rain-forest - habitat use - costa-rica - dispersal - diet - ecology - brazil - conservation
Tapirs are known as effective dispersers of large-seeded tree species, but their role in dispersing small-seeded plant species has yet to be established. Tapir feces have been reported to contain large numbers of small seeds, but whether these are viable has rarely been evaluated. We determined the abundance and viability of small seeds in feces of Central American tapir (Tapirus bairdii) on Barro Colorado Island, Panama. A total of 72 fecal samples were collected opportunistically from 4 tapir latrine sites. Seeds were manually extracted from feces and classified by size. Seed viability was estimated by opening each seed and examining for the presence of at least 1 intact firm white endosperm. In total, we obtained 8166 seeds of at least 16 plant species. Small-seeded species dominated, with 96% of all seeds found measuring
A taxonomic survey of Guatteria section Mecocarpus including the genera Guatteriopsis and Guatteriella p.p. (Annonaceae).
Maas, P.J.M. ; Westra, L.I.T. - \ 2011
Blumea 56 (2011)2. - ISSN 0006-5196 - p. 113 - 145.
french-guiana - america - guyana - trees - genus
This paper deals with a group of species of the Neotropical genus Guatteria (Annonaceae) which are characterized by leaves with tiny warts (verruculae) on both surfaces and by elongate and short-stipitate monocarps (i.e., the length of the monocarp body surpassing the length of the stipe). These species were placed by Fries in Guatteria sect. Mecocarpus (Fries 1939) (the name derives from Ancient Greek µ¿¿¿¿ = Poppy and ¿a¿p¿¿ = fruit: fruit resembling that of Papaver species). All occur in South America, none having been found elsewhere so far. Although there is much doubt nowadays about the taxonomic significance of Fries's sections, we maintain sect. Mecocarpus at present for convenience's sake. Additionally, the former genus Guatteriopsis, united with Guatteria a short time ago (Erkens & Maas 2008b), is now also included in sect. Mecocarpus. The same applies to one of the two species attributed to Guatteriella (also merged with Guatteria by Erkens & Maas 2008b), namely Guatteriella tomentosa R.E.Fr. (not Guatteria tomentosa Rusby) which is put into synonymy with Guatteria trichocarpa Erkens & Maas. One new species is described, namely Guatteria griseifolia Maas & Westra. The two species complexes of G. guianensis and G. decurrens are now treated each as a single polymorphic species. The present study falls within the framework of a planned monograph of the whole genus Guatteria.
An updated index to genera, species, and infraspecific taxa of Neotropical Annonaceae
Maas, P.J.M. ; Westra, L.I.T. ; Rainer, H. ; Lobao, A.Q. ; Erkens, R.H.J. - \ 2011
Nordic Journal of Botany 29 (2011)3. - ISSN 0107-055X - p. 257 - 356.
central-american republics - guatteria annonaceae - miscellaneous notes - french-guiana - pseudoxandra annonaceae - undescribed plants - south-america - rain-forest - revision - genus
Annonaceae form the most diverse family within the Magnoliales. In 1990 an Index to generic names of Annonaceae was published and in 1994 an Index to Neotropical species of Annonaceae was compiled. Especially the latter proved an immensely useful tool for Neotropical botanists. Here, we present an updated Index of all valid names in Neotropical Annonaceae on the genus and species level. It also includes nomina nuda and orthographic variants. Reference and year of first publication, synonymy, and typification are mentioned. Several new combinations are made. In addition, some lectotypifications are proposed. A supplementary list is added of all Neotropical type collections
Climate is a stronger driver of tree and forest growth rates than soil and disturbance
Toledo, M. ; Poorter, L. ; Peña-Claros, M. ; Alarcón, A. ; Balcázar, J. ; Leaño, C. ; Licona, J.C. ; Llanque, O. ; Vroomans, V. ; Zuidema, P. ; Bongers, F. - \ 2011
Journal of Ecology 99 (2011)1. - ISSN 0022-0477 - p. 254 - 264.
tropical rain-forest - long-term plots - diameter increment - amazonian forests - french-guiana - phosphorus fertilization - silvicultural treatments - nutrient limitation - neotropical forest - carbon dynamics
1. Essential resources such as water, nutrients and light vary over space and time and plant growth rates are expected to vary accordingly. We examined the effects of climate, soil and logging disturbances on diameter growth rates at the tree and stand level, using 165 1-ha permanent sample plots distributed across Bolivian tropical lowland forests. 2. We predicted that growth rates would be higher in humid than in dry forests, higher in nutrient-rich than nutrient-poor forests and higher in logged than non-logged forests. 3. Across the 165 plots we found positive basal area increases at the stand level, which agree with the generally reported biomass increases in tropical forests. 4. Multiple regression analysis demonstrated that climate variables, in particular water availability, were the strongest drivers of tree growth. More rainfall, a shorter and less intense dry period and higher temperatures led to higher tree growth rates. 5. Tree growth increased modestly with soil fertility and basal area growth was greatest at intermediate soil fertility. Surprisingly, tree growth showed little or no relationship with total soil nitrogen or plant available soil phosphorus. 6. Growth rates increased in logged plots just after logging, but this effect disappeared after 6 years. 7. Synthesis. Climate is the strongest driver of spatial variation in tree growth, and climate change may therefore have large consequences for forest productivity and carbon sequestration. The negative impact of decreased rainfall and increased rainfall seasonality on tree growth might be partly offset by the positive impact of increased temperature in these forests.
New species of Annonaceae from the Neotropics and miscellaneaous notes
Maas, P.J.M. ; Westra, L.I.T. - \ 2010
Blumea 55 (2010)3. - ISSN 0006-5196 - p. 259 - 275.
guatteria annonaceae - french-guiana - pseudoxandra annonaceae - genus - america - guyana - trees
In this paper six new Neotropical species in four genera are described, viz. Annona oxapampae, Duguetia vaupesana, Guatteria castilloi, G. pachyphylla, G. sanctae-crucis and Pseudoxandra xylopiifolia. Furthermore additional data on four poorly known species of Guatteria (G. denudata, G. glauca, G. modesta and G. terminalis) are added.
Two new species of Guatteria (Annonaceae) from the Atlantic Forest of Brazil.
Lobao, A.Q. ; Maas, P.J.M. ; Mello-Silva, R. de - \ 2010
Blumea 55 (2010)2. - ISSN 0006-5196 - p. 120 - 122.
french-guiana - america - guyana - trees - genus
Guatteria emarginata and G. stenocarpa, two new species from the Atlantic Forest in Espírito Santo and Bahia, Brazil, are presented here. Guatteria emarginata is characterized by narrowly obovate, verruculose leaves, densely covered with cinereous hairs on the lower side and an emarginate apex. Guatteria stenocarpa is remarkable among the Atlantic Forest species of the genus for its narrowly ellipsoid to cylindric monocarps of 22-25 mm long.
Implications of CO2 pooling on d13C of ecosystem respiration and leaves in Amazonian forest
Araujo, A.C. de; Ometto, J.P.H.B. ; Dolman, A.J. ; Kruijt, B. ; Waterloo, M.J. ; Ehleringer, J.R. - \ 2008
Biogeosciences 5 (2008)3. - ISSN 1726-4170 - p. 779 - 795.
carbon-isotope discrimination - rain-forest - tropical forest - water availability - natural-abundance - deciduous forest - cycle research - use efficiency - boreal forest - french-guiana
The carbon isotope of a leaf (d13Cleaf) is generally more negative in riparian zones than in areas with low soil moisture content or rainfall input. In Central Amazonia, the small-scale topography is composed of plateaus and valleys, with plateaus generally having a lower soil moisture status than the valley edges in the dry season. Yet in the dry season, the nocturnal accumulation of CO2 is higher in the valleys than on the plateaus. Samples of sunlit leaves and atmospheric air were collected along a topographical gradient in the dry season to test whether the d13Cleaf of sunlit leaves and the carbon isotope ratio of ecosystem respired CO2 (d13CReco) may be more negative in the valley than those on the plateau. The d13Cleaf was significantly more negative in the valley than on the plateau. Factors considered to be driving the observed variability in d13Cleaf were: leaf nitrogen concentration, leaf mass per unit area (LMA), soil moisture availability, more negative carbon isotope ratio of atmospheric CO2 (d13Ca) in the valleys during daytime hours, and leaf discrimination (¿leaf). The observed pattern of d13Cleaf might suggest that water-use efficiency (WUE) is higher on the plateaus than in the valleys. However, there was no full supporting evidence for this because it remains unclear how much of the difference in d13Cleaf was driven by physiology or &delta13Ca. The d13CReco was more negative in the valleys than on the plateaus on some nights, whereas in others it was not. It is likely that lateral drainage of CO2 enriched in 13C from upslope areas might have happened when the nights were less stable. Biotic factors such as soil CO2 efflux (Rsoil) and the responses of plants to environmental variables such as vapor pressure deficit (D) may also play a role. The preferential pooling of CO2 in the low-lying areas of this landscape may confound the interpretation of d13Cleaf and d13CReco.
Serum Chemistry concentrations of captive Woolly Monkeys (Lagothrix Lagotricha)
Ange-van Heugten, K.D. ; Verstegen, M.W.A. ; Ferket, P. ; Stoskopf, M. ; Heugten, E. van - \ 2008
Zoo Biology 27 (2008)3. - ISSN 0733-3188 - p. 188 - 199.
french-guiana - world monkeys - vitamin-d - hypertension - carotenoids - adaptations - phosphorus - ferritin - primate - calcium
Woolly monkeys (Lagothrix sp.) are threatened species and numerous zoos have failed to sustain successful populations. The most common causes of death in captive woolly monkeys are related to pregnancy and hypertension. The objective of this retrospective study was to evaluate serum concentrations of a large number of captive woolly monkeys to establish baseline means and compare these concentrations with their closest related species to determine potential abnormalities. Serum analyses from 30 woolly monkeys housed at two institutions (Apenheul, The Netherlands and The Louisville Zoo, KY, USA) over 12yr were collected. The statistical model included gender, age group (young, 0-4 yr of age; middle, 5-9 yr; and old, 10 + yr), and zoological institution. All panel result means were similar to previously reported concentrations for howler (Alouatta sp.) and spider monkeys (Ateles sp.) with the possible exception of alanine aminotransferase and gamma-glutamyl-transferase being higher, whereas creatinine and phosphorus were lower. The serum glucose mean of 6.7 mmol/L is above the baseline range for humans and spider monkeys. Alkaline phosphatase (ALP), alanine aminotransferase, and sodium (Na) were higher in females and magnesium (Mg) was higher in males (P <0.05). ALP, Mg, and phosphorus were highest (P
Spatial contagiousness of canopy disturbance in tropical rain forest: An individual - tree-based test
Jansen, P.A. ; Meer, P.J. van der; Bongers, F. - \ 2008
Ecology 89 (2008)12. - ISSN 0012-9658 - p. 3490 - 3502.
gap-phase regeneration - french-guiana - natural disturbance - species-richness - crown asymmetry - dynamics - growth - patterns - vegetation - temperate
Spatial contagiousness of canopy dynamics¿the tendency of canopy disturbances to occur nearby existing canopy openings due to an elevated risk of tree fall around gaps¿has been demonstrated in many temperate-zone forests, but only inferentially for tropical forests. Hypothesized mechanisms increasing the risk of tree fall around tropical forest gaps are (1) increased tree exposure to wind around gaps, (2) reduced stability of trees alongside gaps due to crown asymmetry, or (3) reduced tree health around gaps due to damage from prior disturbances. One hypothesized consequence of elevated disturbance levels around gaps would be that gap-edge zones offer relatively favorable prospects for seedling recruitment, growth, and survival. We tested whether disturbance levels are indeed elevated around natural canopy gaps in a neotropical rain forest in French Guiana, and more so as gaps are larger. We followed the fate of 5660 trees >10 cm stem diameter over five years across 12 ha of old-growth forest and analyzed the risk and magnitude of canopy disturbance events in relation to tree diameter and the proximity and size of natural canopy gaps. We found that the cumulative incidence of disturbance over the five-year survey was not significantly elevated around preexisting gaps, and only weakly related to gap size. Also, neither the risk nor the magnitude of canopy disturbances increased significantly with the proximity of gaps. Moreover, canopy disturbance risk around gaps was independent of gap size, while the magnitude of disturbance events around gaps was weakly related to gap size. Tree size was the major driver of disturbance risk as well as magnitude. We did find an elevated incidence of disturbance inside preexisting gaps, but this ¿repeat disturbance¿ was due to an elevated disturbance risk inside gaps, not around gaps. Overall, we found no strong evidence for canopy dynamics in this rain forest being spatially contagious. Our findings are consistent with the traditional view of tropical rain forests as mosaics of patches with predictable regeneration cycles.
Evidence for scatter-hoarding in a tropical peat swamp forest in Malaysia
Meer, P.J. van der; Kunne, P.L.B. ; Brunsting, A.M.H. ; Dibor, L. ; Jansen, P.A. - \ 2008
Journal of Tropical Forest Science 20 (2008)4. - ISSN 0128-1283 - p. 340 - 343.
mast-fruiting dipterocarpaceae - rain-forest - seed-dispersal - french-guiana - recruitment - predation - australia - rodents - tree
Above-ground biomass and productivity in a rain forest of eastern South America
Chave, J. ; Olivier, J. ; Bongers, F.J.J.M. ; Chatelet, P. ; Forget, P.M. ; Meer, P.J. van der; Norden, N. ; Riera, B. ; Charles-Dominique, P. - \ 2008
Journal of Tropical Ecology 24 (2008). - ISSN 0266-4674 - p. 355 - 366.
net primary production - wood specific-gravity - long-term plots - tropical forests - french-guiana - neotropical forest - live biomass - carbon - amazon - density
Abstract: The dynamics of tropical forest woody plants was studied at the Nouragues Field Station, central French Guiana. Stem density, basal area, above-ground biomass and above-ground net primary productivity, including the contribution of litterfall, were estimated from two large permanent census plots of 12 and 10 ha, established on contrasting soil types, and censused twice, first in 1992¿1994, then again in 2000¿2002. Mean stem density was 512 stems ha¿1 and basal area, 30m2 ha¿1. Stem mortality rate ranged between 1.51% and 2.06% y¿1. In both plots, stem density decreased over the study period. Using a correlation between wood density and wood hardness directly measured by a Pilodyn wood tester,we found that the mean wood densitywas 0.63 g cm¿3, 12% smaller than the mean of wood density estimated from the literature values for the species occurring in our plot. Above-ground biomass ranged from 356 to 398Mgha¿1 (oven-dry mass), and it increased over the census period. Leaf biomass was 6.47Mg ha¿1. Our total estimate of aboveground net primary productivity was 8.81 MgC ha¿1 y¿1 (in carbon units), not accounting for loss to herbivory, branchfalls, or biogenic volatile organic compounds, whichmay altogether account for an additional 1MgC ha¿1 y¿1. Coarse wood productivity (stem growth plus recruitment) contributed to 4.16 MgC ha¿1 y¿1. Litterfall contributed to 4.65MgC ha¿1 y¿1 with 3.16 MgC ha¿1 y¿1 due to leaves, 1.10 MgC ha¿1 y¿1 to twigs, and 0.39MgC ha¿1 y¿1 to fruits and flowers. The increase in above-ground biomass for both trees and lianas is consistentwith the hypothesis of a shift in the functioning of Amazonian rain forests driven by environmental changes, although alternative hypotheses such as a recovery from past disturbances cannot be ruled out at our site, as suggested by the observed decrease in stem density. Key Words: above-ground biomass, carbon, French Guiana, net primary productivity, tropical forest
Is farther seed dispersal better? Spatial patterns of offspring mortality in three rainforest tree species with different dispersal abilities.
Jansen, P.A. ; Bongers, F.J.J.M. ; Meer, P.J. van der - \ 2008
Ecography 31 (2008)1. - ISSN 0906-7590 - p. 43 - 52.
vouacapoua-americana caesalpiniaceae - french-guiana - tropical forests - virola-surinamensis - recruitment - survival - distance - seedlings - gaps - dynamics
The paradigm that tropical trees with farther seed dispersal experience lower offspring mortality is currently based on within-species studies documenting higher survival of offspring located farther from conspecific adults and/or closer to light gaps. We determined whether the paradigm also holds among species by comparing spatial patterns of offspring mortality among three sympatric Neotropical rainforest tree species with the same seed dispersers but with different dispersal abilities. First, we assessed spatially non-random mortality for each species by measuring spatial shifts of the population recruitment curve (PRC) with respect to conspecific adults and light gaps across three early life stages: dispersed seeds, young seedlings and old seedlings. Then, we determined whether PRC shifts were greater for the species with short dispersal distances than for the species with greater dispersal distances. We found that the PRC shifted away from conspecific adults consistently across life stages, but we found no consistent PRC shifts towards gaps, suggesting that mortality was related more to the proximity of conspecifics than to absence of light gaps. PRC shifts away from adults were greatest in the species with the lowest dispersal ability, supporting the paradigm. Differential PRC shifts caused the spatial distribution of offspring to become almost independent with respect to adult trees and gaps in all three species, despite large differences in seed dispersal distance among these species. Our results provide direct empirical support for the paradigm that among tropical trees, species with farther seed dispersal are less impacted by spatially non-random mortality than are similar species with shorter dispersal distances. Thus, greater dispersal effectiveness merits extra investments of trees in seed dispersal ability, even at the cost of fecundity.
Hunting increases dispersal limitation in the tree Carapa procera, a nontimber forest product
Forget, P.M. ; Jansen, P.A. - \ 2007
Conservation Biology 21 (2007)1. - ISSN 0888-8892 - p. 106 - 113.
orange-rumped agouti - seed dispersal - tropical forest - french-guiana - rain-forest - bertholletia-excelsa - dasyprocta-leporina - amazonian forests - recruitment - fate
The sustainability of seed extraction from natural populations has been questioned recently. Increased recruitment failure under intense seed harvesting suggests that seed extraction intensifies source limitation. Nevertheless, areas where more seeds are collected tend to also have more intense hunting of seed-dispersing animals. We studied whether such hunting, by limiting disperser activity, could cause quantitative dispersal limitation, especially for large crops and for crops in years of high seed abundance. In each of four Carapa procera (Meliaceae) populations in French Guiana and Surinam, two with hunting and two without, we compared seed fate for individual trees varying in crop size in years of high and low population-level seed abundance. Carapa seeds are a nontimber forest product and depend on dispersal by scatter-hoarding rodents for survival and seedling establishment. Hunting negatively affected the proportion of seeds dispersed and caused greater numbers of seeds to germinate or be infested by moths below parent trees, where they would likely die. Hunting of seed-dispersing animals disproportionally affected large seed crops, but we found no additional effect of population-level seed abundance on dispersal rates. Consistently lower rates of seed dispersal, especially for large seed crops, may translate to lower levels of seedling recruitment under hunting. Our results therefore suggest that the subsistence hunting that usually accompanies seed collection is at the cost of seed dispersal and may contribute to recruitment failure of these nontimber forest products. Seed extraction from natural populations may affect seedling recruitment less if accompanied by measures adequately incorporating and protecting seed dispersers
Tropical rodents change rapidly germinating seeds into long-term food supplies
Jansen, P.A. ; Bongers, F.J.J.M. ; Prins, H.H.T. - \ 2006
Oikos 113 (2006)3. - ISSN 0030-1299 - p. 449 - 458.
orange-rumped agouti - french-guiana - rain-forest - dasyprocta-leporina - tamias-amoenus - dispersal - ecology - perishability - herbivory - seedlings
Seed-hoarding vertebrates may survive yearly periods of food scarcity by storing seeds during the preceding fruiting season. It is poorly understood why rodents creating long-term reserves, especially those in the tropics, incorporate seeds from plant species that germinate rapidly and hence seem unsuitable for long-term storage. We carried out a series of experiments to understand why red acouchies (Myoprocta exilis) scatter-hoard Carapa procera (Meliaceae) seeds, which lack dormancy and germinate rapidly. Hypotheses tested were: (1) even germinated seeds are still significant long-term energy reserves for acouchies, (2) acouchies use the seeds only as short-term supplies, and (3) acouchies manipulate the seeds to slow down germination. The first two hypotheses were not supported; seed reserves were rapidly depleted during experimental planting, and acouchies did use seeds for long-term storage. We did find support for the third hypothesis. Acouchies intervened in germination by removing the protruding radicle and epicotyl after which they re-cached seeds. Pruning stopped further seedling development, yet the pruned seeds did not decay. The cotyledons apparently stayed alive and physiologically active as "zombie seeds" that only formed undifferentiated calli. Pruned seeds were suitable for long-term storage, with negligible loss of endosperm over time. Pruning was most effective after sprouting of the epicotyl, and germinating seeds were most susceptible to pruning during two weeks upon emergence. Acouchies actively managed their food supplies and must continuously survey for germinating seeds to timely intervene in seed reserve depletion, within the brief period of seedling emergence. We suggest that the trees use the rodents to achieve seed dispersal, and gain from imperfect intervention in germination by the rodents. Because scatter-hoarding rodents and large-seeded plant species with similar germination co-occur in tropical forests world-wide, it is plausible that the phenomenon of seed pruning to preserve seeds is more general than currently appreciated
Photosynthetic acclimation to light changes in tropical monsoon forest woody species differing in adult stature
Cai, Z.Q. ; Rijkers, A.J.M. ; Bongers, F.J.J.M. - \ 2005
Tree Physiology 25 (2005)8. - ISSN 0829-318X - p. 1023 - 1031.
central new-england - rain-forest - chlorophyll fluorescence - shade tolerance - photosystem-ii - french-guiana - maples acer - canopy gaps - tree-fall - photoinhibition
We studied morphological and physiological leaf and whole-plant features of seedlings of six late-successional woody species common in the Xishuangbanna lowland rain forest in southwest China. Study species differed in adult stature and shade tolerance and included the shrubs Lasianthus attenuatus Jack and Lasianthus hookeri C.B. Clarke ex Hook. f.; the sub-canopy species Barringtonia macrostachya (Jack) Kurz and Linociera insignis C.B. Clarke; the canopy tree Pometia tomentosa (Blume) Teijsm. & Binn.; and the emergent species Shorea chinensis (Wang Hsie) H. Zhu. After 1 year of growth in low light (4.5% full sun), seedlings were transferred to high light (24.5% full sun) to investigate acclimation responses of existing leaves to forest gap opening and to determine whether seedling capacity for acclimation is a limiting factor in its natural regeneration. Leaves of the shrub species are shade-adapted, as indicated by their lowphotosynthetic capacity, efficiency in using sunflecks, low stomatal density, low Chl a/b ratio and high spongy/palisade mesophyll ratio. The shrub species utilized sunflecks efficiently because they had a short photosynthetic induction time and low induction loss. In all species, transfer of seedlings to high light resulted in a substantial initial reduction in the dark-adapted quantum yield of photosystem II (variable chlorophyll fluorescence/ maximum chlorophyll fluorescence; Fv /Fm) at midday. Predawn Fv /Fm of the taller species did not change greatly, but predawn Fv /Fm of the shrub species decreased significantly without complete recovery within 25 days of transfer to high light, indicating chronic photoinhibition and damage to the previously shade-adapted leaves. Maximum net photosynthetic rate and dark respiration of the four taller species increased considerably after transfer to high light, but not in the shrub species. Similar trends were observed for the number of newly formed leaves and relative height growth rate. We conclude that the shrubs L. hookeri and L. attenuatus have limited potential for developmental and physiological acclimation to high light, which explains their absence from forest gaps. Compared with the shrub species, the taller tree species, which are more likely to experience high light during their life span, showed a greater potential for light acclimation. Physiological differences among the four tree species were not consistent with differences in adult stature. Keywords: chlorophyll fluorescence, leaf anatomy, light acclimation, photosynthesis, photosynthetic induction
Seed mass and mast seeding enhance dispersal by a neotropical scatter-hoarding rodent
Jansen, P.A. ; Bongers, F.J.J.M. ; Hemerik, L. - \ 2004
Ecological Monographs 74 (2004)4. - ISSN 0012-9615 - p. 569 - 589.
orange-rumped agouti - rain-forest - evolutionary ecology - french-guiana - dasyprocta-leporina - tropical palm - size - model - nuts - tree
Many tree species that depend on scatter-hoarding animals for seed dispersal produce massive crops of large seeds at irregular intervals. Mast seeding and large seed size in these species have been explained as adaptations to increase animal dispersal and reduce predation. We studied how seed size and seed abundance simultaneously influenced seed dispersal and predation by scatter-hoarding rodents in the large-seeded rain forest tree Carapa procera (Meliaceae) in French Guiana. We individually tracked the fates of 3000 seeds, using remote video monitoring and thread-marking. Seed size was manipulated by broadly varying intraspecific seed mass, whereas effects of seed abundance were examined by tracking seeds in three seed-rich years and two seed-poor years. The hypotheses, that seed mass and seed abundance both enhance dispersal success and that seed abundance reinforces the effect of seed mass, were supported by the results. Most seeds were removed by the scatter-hoarding rodent red acouchy (Myoprocta acouchy) and subsequently were buried in scattered, single-seeded caches up to distances >100 m. Seeds that were not removed failed to establish seedlings. Seed removal was slower, pre-removal seed predation was greater, and seed dispersal was less far in seed-rich years than in seed-poor years, suggesting poorer dispersal under seed abundance. However, this was more than counterbalanced by a disproportionally greater survival of cached seeds in seed-rich years. The per capita probability of seed survival and seedling establishment was at least 4(1/2) times greater under seed abundance. Large seeds were removed faster, were more likely to be scatter-hoarded, and were dispersed farther away than smaller ones, resulting in a higher probability of seedling establishment for larger seeds. Size discrimination was greater under seed abundance, albeit only during seed removal. Overall, large seeds shed in rich years had the highest probability of seedling establishment. Hence, both larger seed size and greater seed abundance stimulate rodents to act more as dispersers and less as predators of seeds. We conclude that scatter-hoarding rodents can select for both large seed crops and large seeds, which may reinforce mast seeding.
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