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Seed Diversity (seed + diversity)

Distribution by Scientific Domains

Life Sciences	80%

Selected Abstracts

Influence of temporal fluctuations in seed abundance on the diet of harvester ants (Pogonomyrmex spp.) in the central Monte desert, Argentina

AUSTRAL ECOLOGY, Issue 8 2009
GABRIELA I. PIRK
Abstract Harvester ants usually go through temporal fluctuations in environmental seed abundance and composition which could influence their behaviour and ecology. The aim of this study was to evaluate how these fluctuations influence the diet of Pogonomyrmex rastratus, P. pronotalis and P. inermis (Hymenoptera, Formicidae) in the central Monte desert during three consecutive growing seasons. Although seeds were the main item in the diet, these ants turned more generalist when seed abundance of the most consumed species (grasses Aristida spp., Trichloris crinita, Pappophorum spp., Digitaria californica and Stipa ichu) was low. Accordingly, diversity of items in the diet decreased with seed abundance in a logarithmical fashion, showing higher foraging efficiency for seeds at higher seed abundance. Seed diversity, however, was not related to seed abundance as ants always included several species in their diet, with alternating prevalence. The proportion of the most consumed species increased logarithmically in the diet of P. rastratus and P. pronotalis along with their abundance in the environment probably as a consequence of diet switching (from forb and shrub seeds to grass seeds) and by an increase in foraging efficiency at higher seed densities. In contrast, foraging activity of P. inermis was very low at low seed abundance and its diet included only the five grasses. Among the most consumed species, proportion in the diet was not associated with relative abundance in the environment. Aristida spp., Pappophorum spp. and D. californica were overall highly selected. However, the flexibility in the diet of P. pronotalis and P. rastratus and the low foraging activity of P. inermis during periods of low resource abundance could attenuate potential top-down effects in the central Monte desert. This study shows that bottom-up effects are important in ant-seed interactions and should be considered when predicting and evaluating ants' effects on seed resources. [source]

Frugivory and Seed Dispersal by the Lowland Tapir Tapirus terrestris in the Peruvian Amazon

BIOTROPICA, Issue 2 2010
Mathias W. Tobler
ABSTRACT The lowland tapir Tapirus terrestris is the largest herbivore in the Neotropics and feeds on a large quantity of fruits, often ingesting the seeds and defecating them intact. Seed dispersal by the lowland tapir in the southwestern Amazon was studied by examining seeds from 135 dung samples collected between 2005 and 2007. Seeds of a total of 122 plant species were identified, representing 68 genera and 33 families. The species accumulation curve showed that more species can be expected with further sampling. Many species (45%) were only encountered once, and only 10 percent of all species were found in >10 samples, indicating that the lowland tapir is an opportunistic forager. Seed diversity showed a clear seasonal pattern and was highly correlated with fruit availability. Seed diameter ranged from <1 to 25 mm with 81 percent <10 mm diam. The size distribution of seeds found in lowland tapir dung generally followed that of seeds found in the forest, but had a lower proportion of seeds in the smallest size class (<2.5 mm) and a larger proportion found in the largest size class (20,25 mm). The diversity of seeds encountered in dung of the lowland tapir in this study was much higher than in previous studies. We conclude that the lowland tapir is a potential disperser for a large number of plant species, including many that previously have been thought to be dispersed only by large primates. Abstract in Spanish is available at http://www.blackwell-synergy.com/loi/btp. [source]

The Role of Research Institutions in Seed,related Disaster Relief: Seeds of Hope Experiences in Rwanda

DISASTERS, Issue 4 2002
Robin A. Buruchara
The article describes the efforts of a coalition of agricultural research centres, Seeds of Hope (SOH) in the rebuilding of Rwanda, after the genocide and war of 1994. Research involvement in emergency relief and rehabilitation was unusual at the time and SOH had to forge its unique complementary role. Focusing on crop and variety development and conservation it: provided technical advice to relief agencies on seed procurement; used its baseline ken to assess the effects of war on seed diversity and seed security; made preparations to restore specific germplasm (which, fortunately, proved unnecessary) and spent substantial effort on rebuilding human resource capacity in research as well as basic scientific facilities. The involvement of SOH highlighted the critical, yet very different, roles for research during emergency versus rehabilitation periods and demonstrated the cost effectiveness of building in a diagnostic component , before massive seed or germplasm distributions are programmed. [source]

Factors Affecting the Small Mammal Community Inside and Outside Katavi National Park, Tanzania1

BIOTROPICA, Issue 2 2002
T. M. Caro
ABSTRACT Small mammal trapping showed that a minimum of 12 species live in and around Katavi National Park in western Tanzania. Species richness and abundance were greater outside the park than inside, extending results of an earlier study. Species richness and abundance were not significantly associated with vegetation cover or plant biomass but were negatively correlated with seed diversity, seed biomass, and possibly small carnivore abundance. Unfortunately, small mammal diets are unknown in this ecosystem and it can be argued that carnivores are unlikely to reduce species diversity, casting doubt on the importance of these variables. While the factors causing small mammals to fare poorly in this protected area are not yet understood, reduced food availability remains the best candidate. [source]

The Importance of Where to Dump the Refuse: Seed Banks and Fine Roots in Nests of the Leaf-Cutting Ants Atta cephalotes and A. colombica,

BIOTROPICA, Issue 1 2000
Alejandro G. Farji-Brener
ABSTRACT The location of the nutrient-rich organic refuse produced by a leaf-cutting ant colony varies among ant species. Atta cephalotes locate their organic refuse in subterranean chambers, whereas A. colombica place their organic refuse on the soil surface near the nest. We studied the effect of the absence or presence of external organic refuse on the abundance of fine roots and seed bank composition in the superficial horizons of ant nests. We sampled soils from ant nests or dumps and adjacent areas of 15 adult nests of A. cephalotes at La Selva (LS), Costa Rica, and of 15 of A. colombica nests on Barro Colorado Island (BCI), Panama. Soils from A. cephalotes nests did not differ from adjacent soils in abundance of fine-root and seed diversity. In contrast, organic refuse from A. colombica nests was less diverse in seed composition (due to the great abundance of Miconia argentea) and had a greater abundance of fine roots than adjacent areas. Thus the external location of the ant-nest organic refuse is potentially important in determining the different types of plant recolonization in abandoned or dead ant nests. The relative abundance of these Atta species may influence the structure and/or composition of tropical forests. RESUMEN En las hormigas cortadoras de hojas, la ubicación de los desechos orgánicos ricos en nutrientes producidos por el hongo que cultivan varía segun la especie. Mientras Atta cephalotesubica sus desechos orgánicos en cámaras subterráncas, A. colombicalos coloca sobre la superficie del suelo cerca del nido. Nosotros estudiamos el efecto de la presencia o ausencia de desechos orgánicos externos sobre la abundancia de raíces finas y la composición del banco de semillas en los suelos superficiales cerca de los hormigueros. Para ello sacamos muestras de basureros o suelo superficial en 15 nidos y areas adjacentes de A. cephalotesen La Selva (LS), Costa Rica, y en 15 nidos de A. colombica ubicados en Barro Colorado (BCI), Panamá. Los suelos de A. cephalotesno difirieron de los suelos adjacentes en abundancia de raíces finas ni en la diversidad de semillas. Por el contrario, los desechos orgánicos externos en nidos de A. colombicafueron menos diversos en composición de semillas (debido principalmente a la gran dominancia de Miconia argentea) y tuvieron una mayor concentración de raices finas que los suelos adyacentes. La ubicación de los desechos es poten-cialmente importance en determinar los diferentes tipos de plantas que pueden recolonizar los nidos abandonados o muertos. Por lo tanto, la abundancia relativa de estas especies de Atta pueden influir en la estructura y/composicion de los bosques tropicales. [source]