THE CONSEQUENCES OF DIOECY FOR SEED DISPERSAL: MODELING THE SEED-SHADOW HANDICAP

Abstract:The spatial distribution of adult trees is typically not expected to reflect the spatial patterns of primary seed dispersal, due to many factors influencing post-dispersal modification of the seed shadow, such as seed predation, secondary seed dispersal and density-dependent survival. Here, we test the hypothesis that spatial distributions of primary seed shadows and adult trees are concordant by analysing the spatial distributions of adult Genipa americana trees and the seed shadow produced by its key primary disperser, the capuchin monkey (Cebus capucinus) in a tropical dry forest in Costa Rica. We mapped the dispersal of G. americana seeds by the capuchins during focal animal follows (mean = 463 min, n = 50) of all adults in one free-ranging group over two early wet seasons (May–July, 2005 and 2006). We mapped the locations of all G. americana trees within a 60-ha plot that lay within the home range of the capuchin group. We conducted multiple spatial point pattern analyses comparing degrees of clustering of capuchin defecations and G. americana trees. We found that adult tree distributions and primary dispersal patterns are similarly aggregated at multiple spatial scales, despite the modification of the primary dispersal patterns and long dispersal distances.

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Two-stage dispersal of Guarea glabra and G. kunthiana (Meliaceae) in Monteverde, Costa Rica

Journal of Tropical Ecology ◽

10.1017/s0266467499000966 ◽

1999 ◽

Vol 15 (4) ◽

pp. 481-496 ◽

Cited By ~ 40

Author(s):

Daniel G. Wenny

Keyword(s):

Costa Rica ◽

Seed Dispersal ◽

Seed Predation ◽

Soil Surface ◽

Vegetation Density ◽

Seed Shadow ◽

Secondary Dispersal ◽

Germination Success ◽

Tayassu Tajacu ◽

Para Determinar

Seed dispersal of Guarea glabra and G. kunthiana (Meliaceae) in Monteverde, Costa Rica was studied to determine how seed predation and secondary dispersal affect the distribution of seeds available for recruitment. The arillate seeds are consumed mainly by birds that regurgitate or defecate the seeds intact. After dispersal, 45.6% of G. glabra and 26.6% of G. kunthiana seeds were buried 1–3 cm in the soil, presumably by scatterhoarding rodents such as agoutis (Dasyprocta punctata). G. glabra seeds that were not cached were eaten mostly by beetles, and 33.7% of the seeds remained cached after 12 wk. The cached G. glabra seeds did not germinate, however, perhaps as a result of experimental procedures used to mark the seeds. In greenhouse experiments, G. glabra seeds buried to mimic scatterhoarding had higher germination success than seeds on the soil surface. G. kunthiana seeds not cached were eaten by peccaries (Tayassu tajacu) and other seed predators (60%) or were inviable (10%). Only nine (7.5%) viable G. kunthiana seeds remained in caches after 12 wk. Secondary dispersal resulted in a rearrangement of the seed shadow. G. glabra seeds were moved to sites with less leaf litter and lower vegetation density, while G. kunthiana seeds were moved farther from conspecific trees and closer to fallen logs during secondary dispersal. Considering the high rates of seed predation in the field for both species, the germination advantages for G. glabra in the greenhouse, and the shifts in microhabitat during scatterhoarding, it is likely that secondary dispersal by scatterhoarding rodents is an important stage in Guarea recruitment.RESUMEN. Dispersión de semillas de Guarea glabra y G. kunthiana (Meliaceae) en Monteverde, Costa Rica fureon examinadas para determinar como la predación de semillas y dispersión secundaria afectan la distribución de semillas disponibles para recrutamiento. Las semillas ariladas son consumidas principalmente por aves que regurgitan o defecan la semilla intacta. Luego de dispersión, 30–45% de las semillas fueron enterradas 1–3 cm en el suelo, posiblemente por roedores que disperan y acumulan como al agouti (Dasyprocta puncaata). Semillas de G. kunthiana que no fueron escondidas fueron comidas por pécaris (Tayassu tajacu) y otros predadores de semillas (60%) o no fueron viables (10%). Solo neuve (7.5%) semillas viables de G. kunthiana permanecieron en los escondites luego de 12 semanas. En contraste, semillas de G. glabra que no fueron escondidas fueron comidas mayormente por escarabajos que por pécaris, y 33.7% de las semillas permanecieron escondidas luego de 12 semanas. Las semillas esconditas de G. glabra enterradas para imitar dispersión y acumulión tuvieron una germinación mayor que semillas en la superficie del suelo. Dispersión secundaria resulto en un rearreglo de la sombra de semillas. Las dos especies experimentaron un leve aumento neto en la distancia promedio de conspecificos en frutos luego de dispersión y acumulación. Semillas de G. kunthiana fueron movidas cerca de troncos caidos durante dispersión secundaria, mientras semillas de G. glabra fueron movidas a lugares con menos lecho de hojas y baja densidad de vegetación. Considerando la alta proporción de predación de semillas en el campo para ambas especies, la ventaja de germinación de G. glabra en el invernáculo, y el cambio en micrambiente durante dispersión y acumulación, es posible que dispersión secundaria por roedores que dispersan y acumulan es importante in etapas de recrutamiento en Guarea.

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The effect of seed dispersal limitations on the spatial distribution of a gap species, seaside goldenrod (Solidago sempervirens)

Canadian Journal of Botany ◽

10.1139/b93-111 ◽

1993 ◽

Vol 71 (7) ◽

pp. 978-984 ◽

Cited By ~ 13

Author(s):

Philip C. Lee

Keyword(s):

Seed Dispersal ◽

Seed Storage ◽

Coastal Dunes ◽

Seed Rain ◽

Significant Drop ◽

Seed Shadow ◽

Ammophila Breviligulata ◽

Seed Sources ◽

Transition Areas ◽

Solidago Sempervirens

This study examined the seed ecology of seaside goldenrod, Solidago sempervirens L., a gap species, on coastal dunes dominated by American beachgrass, Ammophila breviligulata. A test was done to determine whether lower densities of S. sempervirens on undisturbed primary dune grasslands were due to limited seed dispersal or barriers to seedling establishment. Seed rain was greater within blowouts and transition areas than in immature and mature grasslands. Blowouts and transition areas produced prominent seed shadows and served as primary seed sources. Both seed shadow measurements and inflorescence removal experiments suggested that the majority of seeds fell to the ground within 10 m outside blowouts. Experiments involving the hand broadcasting of seeds increased densities of seedlings in undisturbed areas. Plots with hand-drilled seeds showed no differences in percent emergence between transition and undisturbed areas; however, both were significantly greater than blowouts. Persistent seed storage in the soil was probably negligible. Seed bank densities at 5 m depth did not accurately reflect temporal or spatial patterns of seed rain. Often very low densities or no seeds were found in collected samples within an area. Furthermore, emergence percentages of field-buried seeds showed a significant drop-off after a single year. Thus, this study concluded that lower densities of plants in undisturbed areas were, in part, due to lack of seed dispersal from blowouts. Key words: seed dispersal, gap species, patchy disturbances, dune ecology, grassland ecology.

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THE CONSEQUENCES OF DIOECY FOR SEED DISPERSAL: MODELING THE SEED-SHADOW HANDICAP

Evolution ◽

10.1554/0014-3820(2001)055[0880:tcodfs]2.0.co;2 ◽

2001 ◽

Vol 55 (5) ◽

pp. 880 ◽

Cited By ~ 79

Author(s):

Jana C. Heilbuth ◽

Katriina L. Ilves ◽

Sarah P. Otto

Keyword(s):

Seed Dispersal ◽

Seed Shadow

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Influence of gibbon ranging patterns on seed dispersal distance and deposition site in a Bornean forest

Journal of Tropical Ecology ◽

10.1017/s0266467407003999 ◽

2007 ◽

Vol 23 (3) ◽

pp. 269-275 ◽

Cited By ~ 36

Author(s):

Kim R. McConkey ◽

David J. Chivers

Keyword(s):

Home Range ◽

Seed Dispersal ◽

Time Of Day ◽

Dispersal Distance ◽

Ranging Patterns ◽

Seed Shadow ◽

Dipterocarp Forests ◽

Home Range Use ◽

Dispersal Distances ◽

Seed Shadows

Frugivores display daily and seasonal behavioural variation, yet the influence of this variability on subsequent seed shadows is rarely considered. We investigated the extent to which three aspects of gibbon (Hylobates muelleri × agilis) foraging and ranging behaviour (revisitation of favoured fruit sources, daily and monthly ranging patterns) influenced seed dispersal distances and deposition sites for two groups in dipterocarp forests at the Barito Ulu research site, Kalimantan, Indonesia. Dispersal distances and sites were estimated using gut retention times and ranging patterns collected over 12 mo. Gibbons dispersed few seeds (0.7%) under parent trees and most seeds (> 90%) were dispersed more than 100 m. Mean dispersal distances differed significantly between groups (339 m and 431 m) and across different months. Deposition site was only influenced by time of day, with all seeds swallowed in the first hour of activity being deposited under sleeping trees used that night. Both groups visited all 0.25-ha quadrats within their home range over the study period, indicating that gibbons potentially disperse seeds throughout their home range. Given the general uniformity of the gibbon seed shadow, the intensity of home range use and large seed dispersal distances, gibbons appear to be consistently effective seed dispersers and are probably one of the most important frugivores in Asian rain forests.

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Flowering, seed dispersal, seed predation and seedling recruitment in two pyrogenic flowering resprouters

Australian Journal of Botany ◽

10.1071/bt02009 ◽

2002 ◽

Vol 50 (5) ◽

pp. 545 ◽

Cited By ~ 19

Author(s):

Andrew J. Denham ◽

Tony D. Auld

Keyword(s):

Seed Dispersal ◽

Seed Predation ◽

Seedling Recruitment ◽

Growth Conditions ◽

Fruit Production ◽

Seed Shadow ◽

South Eastern ◽

Seed Loss ◽

Eastern Australia ◽

South Eastern Australia

A few resprouting plants in fire-prone environments have no local seed bank (soil or canopy) when a fire occurs. These species rely on post-fire flowering and the production of non-dormant seeds to exploit favourable post-fire establishment and growth conditions. For two such pyrogenic flowering species (Doryanthes excelsa Correa and Telopea speciosissima (Smith) R.Br.), we examined the timing of seed release, patterns of fruit production, seed dispersal, seed predation and seedling establishment following a fire in the Sydney region of south-eastern Australia. Both species took some 19 months after the fire to flower and the first seeds were released 2 years after the fire. D. excelsa flowered and fruited only once after the fire. For T. speciosissima, plants also flowered at least once more in the subsequent 5 years, but produced seed in only the first three post-fire flowering years. Fruit production differed between species, with fruiting individuals of D. excelsa producing fewer infructescences, similar numbers of follicles, but many more seeds per follicle than fruiting individuals of T. speciosissima. Ultimately, D. excelsa produced approximately six times as many seeds per m2 and four times as many seeds per adult in one flowering season than T. speciosissima did after four flowering (three successful fruiting) seasons. Seeds were passively dispersed from fruits borne 3–4 m (D. excelsa) or 1–2 m (T. speciosissima) above the ground. Most seeds were found within 5 m (D. excelsa) or 3 m (T. speciosissima) of parent plants. The primary seed shadow of both species was a poor predictor of the distribution of seedlings, with more seedlings occurring further from the adults than expected from the distribution of seeds. Seed loss to predators was high in both species in exclusion experiments where mammals had access to clumps of seeds (77–88%). It was variable and generally lower (8–65%) in experiments where seeds were not locally clumped. However, for T. speciosissima, at one site, some 65% of seeds were lost to mammals and invertebrates in these latter experiments. At this site, these losses appeared to influence subsequent recruitment levels, as very low seedling densities were observed. For both species, germination of seedlings first occurred some 2.5–3 years after the passage of the fire. The percentage of seeds produced to seedlings successfully established was low in D. excelsa (2–3%) and more variable across sites and years in T. speciosissima (0–18%). Resultant post-fire seedling densities of D. excelsa (two sites) and T. speciosissima at one site were similar, but they were much lower at the T. speciosissima site that had high levels of seed predation. Both D. excelsa and T. speciosissima are amongst the slowest woody resprouting species to recruit seedlings after fire in south-eastern Australia and lag years behind species with soil or canopy seed banks.

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FRUGIVORIA E DISPERSÃO DE SEMENTES POR PEIXES

Scientific Magazine UAKARI ◽

10.31420/uakari.v1i1.2 ◽

2008 ◽

Vol 1 (1) ◽

pp. 7-18

Author(s):

Luciane Lopes de Souza

Keyword(s):

Sustainable Development ◽

Seed Dispersal ◽

Tropical Forests ◽

Natural Regeneration ◽

Main Species ◽

Fishing Gears ◽

Solimões River

Biotic or abiotic processes of seed dispersal are important for the maintenance of the diversity, and for the natural regeneration in tropical forests. Ichthyochory is one of the fundamental mechanisms for seed dispersal in flooded environments, as the igapó forests. A study on the ichthyochory of the igapós was conducted at Amanã Sustainable Development Reserve, in the middle Solimões river, from June 2002 to September 2004. Monthly samples of frugivorous fish were taken, with the main fishing gears used locally. Guts of 1,688 fish caught were examined. The main species were Myloplus rubripinnis (29.21%), Hemiodus immaculatus (18.96%),Colossoma macropom um (16.23%) and Mylossoma duriventre (16.05%). The diet was made of vegetables (fruits, leave and flowers), and animals (arthropods). 53.02% of all fish caught ingested fruits. The total number of intact seeds in the stomachs and intestines were 8,069 and 5,763 respectively. About 61.9% of the Brycon melanopterus (matrinchão), 46.34% of the Brycon amazonicus (mamuri) and 30.22% of M . rubripinnis (parum ) analysed had intact seeds in their guts. Seeds of Nectandra amazonum and Genipa spruceana ingested proved to be more viable than those non-ingested by fish. The high rates of frugivory, the presence of intact seeds in the guts of fish and the greater viability of ingested seeds all suggest that these animals are important seed dispersors in the igapó forests of Amanã Reserve.

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