Endozoochory is an important form of seed dispersal and as such plays a fundamental role in plant population and community ecology. This is especially true in the Subtropical Thicket biome where many plant species are adapted for endozoochory. Endozoochorous seed dispersal is carried out by a wide range of thicket fauna, but changes in the faunal assemblage associated with transformed thicket threatens to disrupt the process of endozoochorous seed dispersal and in turn the regeneration dynamics of thicket plants. Outside of conservation areas, indigenous seed dispersers are often replaced by domestic species, such as goats, which are hypothesized to differ in their seed dispersal efficiencies. The dispersal efficiencies of important thicket seed dispersers that occur in transformed and untransformed thicket were therefore investigated. The influence of gut morphologyphysiology on seed gut passage time, seed mortality and germination in animal species representing different digestive models was measured, as well as the role of black-backed jackal in thicket plant seed dispersal. Black-backed jackal were found to disperse the seeds of few thicket plant species and are therefore not considered important thicket seed dispersers under the climatic conditions prevailing during the study. The average gut passage time of seeds was found to differ significantly between birds and mammals, but not between elephants (hindgut fermentor), goats (ruminant) and pigs (omnivore, foregut fermentor) as was expected considering the differences in their digestive morphology. A significantly shorter gut passage of large seeds compared with small seeds was observed in goats, due to the regurgitation of larger seeds. Seed regurgitation in ruminants may prove to be an important factor contributing to their quality as seed dispersers in transformed thicket. The mortality of seeds was significantly higher in goats than in elephants, probably due to the efficient digestion associated with ruminants. The effect of gut passage on seed germination was not consistent and varied between animal species and across different thicket plant species. It was concluded that seed dispersers that occur in transformed and untransformed thicket differ in their seed dispersal efficiency due, in part, to differences in the nature of their digestive tracts. This has important implications for the process of seed dispersal in thicket, and the rehabilitation of degraded thicket vegetation.

Managing cattle to disseminate seeds of desirable plants, or alternatively, to restrict weed seed contamination on rangelands is of interest to managers. Four experiments were conducted to determine effects of ruminant digestion on germination of ingested seeds. A number of plant species representing a variety of seed size and seed coat hardness were subjected to in vitro digestion. Experiment one was conducted to determine effect of varying lengths of digestion time on seed germination. Seed germination varied by plant species in response to length of digestion. Germination of large soft-coated seeds, such as bluebunch wheatgrass (Agropyron spicatum (Pursh) Scribn. & Smith Goldar) and basin wildrye (Elymus cinereus Scribn & Merril Magnar), was reduced to 0%. Smaller grass seeds, such as Sherman big bluegrass (Poa secunda Presl. Sherman), survived but germination declined following 24-hour, 48-hour, and 72-hour digestion. Experiment two examined effect of different stages of ruminant digestion on seed germination. The combination of Stage I (rumen-simulated digestion) and Stage II (abomasal-simulated digestion) resulted in greatest seed mortality. Two water treatments were included to evaluate the effects of high temperatures (39��C), moisture uptake, and lack of oxygen. Water + O��� and Water + CO��� reduced germination, however not as much as Stage I and Stage II treatments. The third experiment determined effects of diet quality on seed germination. Seeds digested in rumen fluid collected from steers fed a 72% corn concentrate diet resulted in 0% germination for all species. Grass seed germination was low for seeds digested in rumen fluid collected from steers fed a forage diet. Whitetop (Cardaria draba (L.) Hand.) germination was 24% and 28% for 35-hour and 59-hour roughage treatment, respectively, and germination was 0% for 35-hour and 59-hour concentrate treatments. Germination of water-only treatments for most species was reduced in comparison to the control treatment, but was greater than remaining treatments. Experiment four evaluated germination of seeds exposed to in situ versus in vitro digestion. In situ digestion resulted in lower seed germination than in vitro digestion for all species examined. Large, soft grass seeds may not be suitable candidates for reseeding rangelands. However, it is important for managers to recognize that cattle may distribute viable weed seeds in feces. Confining cattle or supplementing with high concentrate diets may help prevent spread of weedy species. / Graduation date: 1997

published_or_final_version / abstract / Ecology and Biodiversity / Doctoral / Doctor of Philosophy

published_or_final_version / Biological Sciences / Master / Master of Philosophy

Germination of seeds of desert annual plants is reduced where there are high densities of annual seedlings. This is interpreted as a response by seeds to avoid a severe biotic environment in which growth rate and fecundity are likely to be reduced by larger established competitors. This density-dependent germination response is due primarily to reduced germination of small-seeded annuals where densities of large-seeded annuals are high. Because of this germination response, and because of competition at the plant stage, large-seeded annuals could, in the absence of significant levels of predation by seed-eating rodents, dominate the annual plant community to a much greater extent than is commonly observed. By reducing densities of large-seeded annuals, rodents allow densities of small-seeded annuals to increase and thus exert a positive indirect effect on granivorous ants. Seed-eating rodents and a parasitic fungus both prey on Erodium cicutarium, a dominant annual plant. These two unrelated predators significantly influence each other's densities by their use of a common prey species. Dispersal of desert annual seeds that successfully germinate is apparently not as widespread as is suggested by observations that some desert annual seeds are redistributed throughout the year by wind and water. Removal of plants during seed set significantly reduced densities of seedlings on sample plots the next year.

published_or_final_version / abstract / toc / Ecology and Biodiversity / Master / Master of Philosophy

Resumo: Este trabalho teve como objetivos verificar como variam a chuva de sementes e o estabelecimento de plântulas entre ambientes colonizados (B) e não colonizados (SB) pelo bambu Guadua tagoara na floresta Atlântica do Parque Estadual Carlos Botelho, Sete Barras - SP. Foram utilizados 40 coletores e 40 parcelas de 1m2 em cada ambiente com monitoramento mensal no período de um ano. SB apresentou 38,71% mais sementes que B, maior riqueza, menor diversidade e equidade. Os ambientes mostraram uma alta similaridade no número de espécies de sementes em comum e com abundâncias semelhantes. SB apresentou maior média de sementes/mês e maior média de sementes/espécie. A densidade absoluta de sementes por coletor não variou entre ambientes, entretanto variou entre meses. Em relação às plântulas, B apresentou maior abundância, maior densidade, maior riqueza, maior dominância de Euterpe edulis, entretanto menor diversidade e equidade que SB. Os dois ambientes se apresentaram com baixa similaridade na composição e na abundância de plântulas por espécie. Em B houve maior média de plântulas/mês enquanto a média de plântulas/espécie foi semelhante entre ambientes. A densidade absoluta de plântulas de E. edulis variou entre meses e ambientes, com maior número em B. Para as demais espécies a diferença se deu entre ambientes e meses, porém maior número em SB. Quando analisadas todas as plântulas em conjunto houve diferença entre meses e ambientes. Maior média de plântulas emergiram e morreram no ambiente com bambu a cada mês. A taxa de sobrevivência variou segundo o tipo de ambiente e ao longo do ano. Nos dois ambientes E. edulis foi a única espécie que não apresentou qualquer tipo de limitação demográfica... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: This project aim to evaluate how the seed rain and the seedling establishment varied between environments with (B) and without (WB) the bamboo Guadua tagoara in the Atlantic forest of Carlos Botelho State Park, Sete Barras - SP. Forty traps and forty plots of 1m2 were placed within each patch type during one year of monthly monitoring. We recorded higher richness and more seeds in WB than in B, nonetheless, diversity and equitability were lower. Both environments showed high similarity in composition and abundance of seeds per specie. The average of seeds per month and seeds per specie was higher in WB. Also, the absolute density of seeds per trap varied predictable in time but there was not difference between B and WB. In respect to seedlings, B environment showed higher abundance, density, richness and dominance of Euterpe edulis, although diversity and equitability were lower than in WB. We found low similarity between B and WB environments in seedlings composition and abundance per specie. The average of seedlings per month was higher in B while the average of seedlings per specie was similar. The absolute density of E. edulis and other species seedlings varied in time in both environments, showing more seedlings density of the former in B and more seedlings density of the later in WB. When all species were analyzed together, seedling density was different between environments and months. The average of seedlings that emerged and died was higher in B environment. The survival rate varied between environments and in time. We found that E. edulis was the only specie that did not show any demographic limitations between environments. Seed rain did not vary between environments in relation to the specie composition as much as in the seed quantity... (Complete abstract, click electronic access below) / Orientador: Marco Aurélio Pizo Ferreira / Coorientador: Ricardo Ribeiro Rodrigues / Banca: Sergius Gandolfi / Banca: Mauro Galetti Rodrigues / Mestre

No study has been done in the western United States concerning dispersal of dwarf mistletoe by mammals. At the outset of the study it was determined that the red squirrel, the yellow pine chipmunk (Eutamias amoenus), the northern flying squirrel, and the bushy-tailed wood rat (Neotaoma cinerea), were all potential vectors of seeds. The red squirrel was chosen as the main object of study because it is diurnal and is closely associated with ponderosa pine (Pinus ponderosa), a heavily infected species. The study was undertaken to determine whether small mammals play a significant role in transporting mistletoe seeds to uninfected areas. Understanding their role can be helpful both in further understanding of the biology of dwarf mistletoe and in evaluating current control practices.

This research examined the influence of hydrochory (seed dispersal via water), anemochory (seed dispersal via wind), and zoochory (seed dispersal by animals) on the re-establishment of the important floodplain vegetation communities of the Kissimmee River floodplain. Fifty-eight seed species were identified from 19,849 and 43, 894 seeds trapped in hydrochory traps in sites north and south of Oak Creek, respectively. Seeds trapped by anemochory were measurable but were found to be far less important than hydrochory, while results showed no evidence of zoochory .... A number of interafting factors, e.g. hydrology, lack of remnants, seed phenology, etc. are limiting the dispersal of broadleaf marsh species north of Oak Creek, delaying range, expansion, and further community restoration. / by Garren Mezza. / Thesis (M.S.)--Florida Atlantic University, 2012. / Includes bibliography. / Mode of access: World Wide Web. / System requirements: Adobe Reader.

published_or_final_version / abstract / Ecology and Biodiversity / Doctoral / Doctor of Philosophy