Orobanche ramosa L. is an annual, parasitic weed present in the western Murray-Mallee region of South Australia. A quarantine zone was established to encompass all known infestations, and has been adjusted over time as new infestations have been discovered. The movement of fodder, machinery, grain and straw, horticultural crops, livestock, and soil is controlled by strict quarantine procedures, to prevent further spread across the landscape. O. ramosa presents a unique situation for weed managers: plants are obligate parasites, relying entirely on broadleaved hosts for their water and nutrition; and seeds are tiny (0.3 mm), produced in large numbers (up to 100 000 seeds per plant), and are long-lived, persisting in the soil seed bank for up to 13 years. The dispersal vectors for O. ramosa in South Australia are the focus of this Master’s thesis. Two dispersal vectors were chosen for investigation: sheep and wind. Sheep were examined as possible vector for seeds, both via the gut (internal transport, or endozoochory) and via adhesion on the external surface of the animal (external transport, or epizoochory). Internal transport via sheep was investigated with a classic gut-passage experiment, which showed a peak in excretion of weed seeds at day 2, reducing to zero seeds excreted at day 8, and a half-life of 2 days. Two phases of external transport on sheep was studied: attachment and retention. Attachment was confirmed by finding seeds on the body wool and feet of sheep that had been kept for 7 days on soil with an O. ramosa seedbank. Seed retention was confirmed by placing seeds onto the body and still finding them in wool samples after 7 days. Wind was the other dispersal vector investigated for O. ramosa. A survey of natural wind dispersal was conducted, which confirmed wind as a vector and allowed trap design to be tested. Then a portable field-based wind tunnel was used to investigate the effects of ground cover (bare ground and cereal stubble) and wind speed (low, medium and high) on wind dispersal of O. ramosa seeds. For the stubble treatments, more seeds were trapped within the tunnel, and on bare ground more seeds were trapped exiting the tunnel. Importantly, the data showed that low wind speeds readily move O. ramosa seeds, and that the seeds are capable of aerodynamic lift in the wind profile. Results are discussed in the context of dispersal biology, quarantine procedures, and future work that would further refine knowledge of likely dispersal vectors for O. ramosa. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1459246 / Thesis (M.Sc.) -- University of Adelaide, School of Earth and Environmental Sciences, 2009

Studies of secondary seed dispersal by small mammals have largely been focused on the interaction between nut-bearing tree species and sciurid rodents such as squirrels, and on heteromyid rodents in the southwestern United States. However, there is now evidence that wind-dispersed tree species such as pines also undergo a process of secondary seed dispersal, where animals redistribute (cache) seeds that have already fallen to the ground, often in microhabitats more suitable for successful seed germination. In Florida sandhill, where fire suppression has threatened wind-dispersed longleaf pine ( Pinus palustris) by encouraging the encroachment of hardwoods such as sand live oak ( Quercus geminata), secondary seed dispersal may be an important factor in determining community composition and persistence of longleaf pine systems. Using a combination of seed depots and seed predator exclosures, I looked at both longleaf pine and sand live oak in terms of whether small animals such as squirrels ( Sciurus carolinensis) and cotton mice ( Peromyscus gossypinus) cache the seeds, and where the seeds of these two tree species best germinate. Since sand live oak acorns are prone to infestation by weevils ( Curculio spp.), I also examined whether nut condition affects acorn germination potential. I found that longleaf pine seeds are cached by small mammals to a small degree. While these seeds are not moved great distances from where they originate, they are often redistributed into microhabitats that promote successful seed germination. Caging experiments indicated that seeds were most likely to germinate when buried in open areas between adult trees, and to some degree, under shrub cover. On the other hand, sand live oak acorns appear to face heavy predation by large seed predators such as raccoons ( Procyon lotor) and wild pigs (Sus scrofa). Those acorns that do escape predation, including weevil-infested acorns, may provide an opportunity for seedling establishment. However, it appears that sand live oak depends heavily on vegetative sprouting for regeneration. This suggests that even in the absence of fire, longleaf pines in Florida sandhill are able to persist through secondary seed dispersal by small animals coupled with heavy seed predation on competing sand live oak.

Made available in DSpace on 2016-06-02T19:31:36Z (GMT). No. of bitstreams: 1 DissKGM.pdf: 564144 bytes, checksum: 6b591c0ae516731c5cece36f0e7e31ed (MD5) Previous issue date: 2006-02-20 / The Cerrado Domain is the second largest Brazilian phytogeographic province, occupying originally 23% of Brazil s land surface, under seasonal climate. The cerrado presents a floristic and physiognomic variation, ranging from grassland to tall woodland. Anemochorous species are proportionally more important in the cerrado than in Brazilian rain forests, especially in open physiognomies. Morphological designs of wind-dispersed diaspores appear to slow their rates of descent, increasing their chances of exposure to winds and of reaching safe sites to germinate. Wind-dispersed species are constrained to fruit during the best time for seed dispersal. Also, the height of seed release and surrounding vegetation are fundamental to long-distance dispersal. We selected the wind-dispersed species from three phytosociological surveys (disjoint and core sites) and classified them into autogyro, rollingautogyro, floater, or undulator, according to the diaspore morphology and aerodynamic behavior in still air. For each species, we had data on its fruiting period. We tried to assess whether there was a seasonality and, if there was, whether it was synchronized with some climatic conditions. The number of fruiting anemochorous cerrado species was highest at the dry season, coinciding with reduced precipitation. Next, we studied the anemochorous diaspore spectra and index of divergence from species to anemochorous diaspore diversity (IDD) in three cerrado physiognomies (campo cerrado, cerrado sensu stricto, and cerradão) in a disjoint site and three cerrado physiognomies (cerrado sensu stricto) in different floristic pronvinces. There was a floristic unit among the cerrado physiognomies, with the ecotonal ones containing both grassland and woodland elements. Both nuclear and disjoint sites were ecologically similar regarding the species distribution. However, there were differences when species abundances were considered. In denser sites, vegetation reduces wind velocity in ... / O Domínio do Cerrado é a segunda maior região fitogeográfica brasileira, originalmente cobrindo 23% do território brasileiro, sob influência de clima estacional. O cerrado apresenta variação florística e fisionômica, indo desde uma fisionomia campestre até uma florestal. Espécies anemocóricas são proporcionalmente mais importantes no cerrado do que em florestas tropicais, especialmente em fisionomias mais abertas. As características morfológicas dos diásporos anemocóricos parecem diminuir suas razões de descida, aumentando a chance de exposição aos ventos e de encontrar locais seguros para germinar. Espécies anemocóricas tendem a frutificar na melhor época para dispersar suas sementes. Também a altura de liberação e a vegetação circundante são fundamentais para a dispersão à longas distâncias. Selecionamos as espécies anemocóricas de três levantamentos fitossociológicos, um realizado em área nuclear, dois em área disjunta, e as classificamos em autogiro, autogiro-rotativas, flutuantes e planadoras, de acordo com a morfologia e comportamento do diásporo no ar parado. Tínhamos o período de frutificação para cada espécie anemocórica de uma área disjunta e tentamos observar a existência de estacionalidade na frutificação e a relação desta com algumas variáveis climáticas. O número de espécies frutificando foi maior na estação seca, coincidindo com o período de menores pluviosidade e umidade relativa do ar. Depois, estudamos os espectros de diásporos anemocóricos e os índices de divergência de diversidade (IDD) de espécies a tipos de diásporo anemocórico de três fisionomias do cerrado (campo cerrado, cerrado sensu stricto e cerradão) em uma área disjunta; e de três fisionomia de cerrado (cerrado sensu stricto) em províncias florísticas diferentes. Além de haver uma unidade florística na área disjunta, com a fisionomia ecotonal contendo elementos campestres e florestais, as áreas nuclear e disjuntas foram ecologicamente ...

Dispersal, especially long-distance dispersal, is an important component in many disciplines within biology. Many species are passively dispersed by wind, not least spore-dispersed organisms. In this thesis I investigated the dispersal capacity of bryophytes by studying the colonization patterns from local scales (100 m) to landscape scales (20 km). The dispersal distances were measured from a known source (up to 600 m away) or inferred from a connectivity measure (1–20 km). I introduced acidic clay to measure the colonization rates over one season of a pioneer moss, Discelium nudum (I–III). I also investigated which vascular plants and bryophytes that had colonized limed mires approximately 20–30 years after the first disturbance (IV). Discelium effectively colonized new disturbed substrates over one season. Most spores were deposited up to 50 meters from a source but the relationship between local colonization rates and connectivity increased with distance up to 20 km (I–III). Also calcicolous wetland bryophyte species were good colonizers over similar distances, while vascular plants in the same environment colonized less frequently. Common bryophytes that produce spores frequently were more effective colonizers, while no effect of spore size was detected (IV). A mechanistic model that take into account meteorological parameters to simulate the trajectories for spores of Discelium nudum fitted rather well to the observed colonization pattern, especially if spore release thresholds in wind variation and humidity were accounted for (III). This thesis conclude that bryophytes in open habitats can disperse effectively across landscapes given that the regional spore source is large enough (i.e. are common in the region and produce spores abundantly). For spore-dispersed organisms in open landscapes I suggest that it is often the colonization phase and not the transport that is the main bottle-neck for maintaining populations across landscapes. / <p>At the time of the doctoral defence the following papesr were unpublished and had  a status as follows: Paper 2: Epubl ahead of print; Paper 3: Manuscript; Paper 4: Manuscript</p>