Life-history patterns in lions Panthera leo living in savanna woodlands of the Kruger National Park, South Africa, were investigated and compared with those of the Tanzanian ‘plains-like’ ecosystems (e.g. Serengeti Plains and Ngorongoro Crater). First, lower levels of mortality in the juvenile age classes were found in Kruger lions, which in turn, extend the inter-birth period. A further difference was a prolonged period of association of sub-adult males with their natal pride, either directly or in a land tenure system that has not been described previously. Most (80%) of young male coalitions rather than becoming nomadic, remained close to their natal territory after leaving the pride, either as non-territorial sub-adults or adults and even as territorial adults. Only 20% of coalitions did not stay close to their natal range, one of which acquired a territory 20 km away from its natal pride. The pattern of territory acquisition, in fact, was one in which the majority of holders acquired territories close to their natal ranges. These behaviour patterns contrast markedly with those from ‘plains-like’ ecosystems where dispersing males usually move far away from their natal pride’s range (>200) km and often remain nomadic for extended periods of time. Dense bush and access to sufficient prey resources in the form of resident buffalo Syncerus caffer herds may be important factors allowing extended residence near the natal pride’s territory. Buffalo were more available in our study area habitat than in neighbouring habitats, and comprised the majority of male lion kills. Extended male residence contrasts markedly with current theory on dispersal in polygynous mammals, which holds that only one sex (females for lions) gain an advantage by staying close to the territory of their natal pride. In Kruger it seems that both sexes gain an advantage by not dispersing far, and use currently undocumented mechanisms to avoid inbreeding.

Life-history patterns in lions Panthera leo living in savanna woodlands of the Kruger National Park, South Africa, were investigated and compared with those of the Tanzanian ‘plains-like’ ecosystems (e.g. Serengeti Plains and Ngorongoro Crater). First, lower levels of mortality in the juvenile age classes were found in Kruger lions, which in turn, extend the inter-birth period. A further difference was a prolonged period of association of sub-adult males with their natal pride, either directly or in a land tenure system that has not been described previously. Most (80%) of young male coalitions rather than becoming nomadic, remained close to their natal territory after leaving the pride, either as non-territorial sub-adults or adults and even as territorial adults. Only 20% of coalitions did not stay close to their natal range, one of which acquired a territory 20 km away from its natal pride. The pattern of territory acquisition, in fact, was one in which the majority of holders acquired territories close to their natal ranges. These behaviour patterns contrast markedly with those from ‘plains-like’ ecosystems where dispersing males usually move far away from their natal pride’s range (>200) km and often remain nomadic for extended periods of time. Dense bush and access to sufficient prey resources in the form of resident buffalo Syncerus caffer herds may be important factors allowing extended residence near the natal pride’s territory. Buffalo were more available in our study area habitat than in neighbouring habitats, and comprised the majority of male lion kills. Extended male residence contrasts markedly with current theory on dispersal in polygynous mammals, which holds that only one sex (females for lions) gain an advantage by staying close to the territory of their natal pride. In Kruger it seems that both sexes gain an advantage by not dispersing far, and use currently undocumented mechanisms to avoid inbreeding.

Microbial interactions and communication in the soil require the transport of metabolites between organisms producing and responding to soluble compounds. However, little quantitative information is known about the range or speed of the transport of such compounds and of microbial cells, and their effect on microbial dispersal. In this study, a combination of theoretical modelling and experimental microcosm systems have been employed to determine the combined effects of microbial growth, nutrient diffusion and utilisation and motility on the transport of cells through particulate material. A mathematical model has been constructed with defined hypotheses regarding these processes which generates predictions of the changes in cell concentration with time and with distance. Predictions of the model are tested experimental in sand microcosms inoculated with luminescence-marked motile and non-motile strains of <I>Pseudomonas fluorescens</I> and supplied with glucose. The model has been tested under different matric potentials and nutrient concentrations to simulate factors considered to be of importance in the soil environment.

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.

Aggregation and species association of 9 species of phytophagous and predaceous mites were studied for 6 yr in an orchard with 100, 2 m tall 'Red Delicious' apple trees. To quantify aggregation, a method was developed that is powerful, and easily interpreted. It relates the proportion of habitat occupied to mean density of the organism, and allows discrimination of aggregation differences between data sets. We found that plant feeders were more aggregated than predators, and active life stages were less aggregated than eggs. Specifically, webspinning spider mites (Tetranychus urticae + Eotetranychus sp.) were the most aggregated. Panonychus ulmi was less aggregated than the webspinning mites, and Bryobia rubrioculus was the least aggregated of the spider mites. Zetzellia mali, the slowest moving predator, had the greatest aggregation of all the predators. The rapid moving phytoseiids were the least aggregated of all the mite species studied, with the specialist predator Metaseiulus occidentalis having the greatest aggregation, the generalist predator Typhlodromus pyri having medium aggregation, and the fast moving Amblyseius andersoni having the least aggregation. Predator-predator, predator-prey, and prey-prey associations were measured using Yule's V association index. Predator-predator associations were the strongest and most consistent, showing a consistent seasonal pattern of neutral-negativeneutral association. Negative associations of T. pyri with other predators were the strongest, which is consistent with evidence that this mite can detect other predators. Predator-prey seasonal associations were weak and mixed, and interactions between prey species were generally weakly positive, probably because of similar habitat preferences. Predaceous mites were generally more aggregated when competing with other predators, possibly allowing the coexistence of 3 predators simultaneously for 6 years via mechanisms proposed by the "aggregation theory of coexistence". G. occidentalis showed the greatest change of aggregation when other predators were present, Z. mali and T. pyri also showed significant changes in aggregation when they were with other predators, but A. andersoni (the largest, fastest predator in our study) showed no changes in aggregation. T. pyri's aggregation increased the most when in the presence of Z. mali, perhaps because of egg predation by the stigmaeid, or because T. pyri could detect the other predator. / Graduation date: 1999

Motile zoospores of P. dissotocum and P. catenulatum were added to 20 and 60 mesh silica sand and a sandy loam soil to investigate the duration of motility. Both Pythium species remained motile for up to 24 hours in all soil textures tested. However, the duration and percentage of the motile population varied depending upon the soil type and species tested. The duration of survival of motile and encysted zoospores of P. dissotocum and P. catenulatum in air dried and saturated sterile silica sand was also tested. P. dissotocum, under air dried conditions, did not survive while P. catenulatum was capable of surviving 4 and 16 days as motile and encysted zoospores, respectively. Both fungi could be recovered at high percentages after 5 weeks under saturated conditions. The survival structure is believed to be in the form of a zoospore cyst.

No description available.

No description available.

Banana passionfruit (Passiflora mollissima) is a noxious weedy vine that is problematic in coastal regions throughout New Zealand. I investigated the pollination and dispersal mutualisms that facilitate its spread, in the Marlborough Sounds. Flower observations revealed that visits were almost exclusively from introduced honey bees and bumble bees, indicating an invasive mutualism. I investigated the pollination system of banana passionfruit by comparing fruit set, fruit size, seed set, germination success and the effects of inbreeding depression on seedlings when grown in competition, between hand-selfed, handcrossed, bagged and open flowers. Fruit set was significantly reduced when pollinators were excluded (3.0%) indicating reliance on pollinators for reproduction. While banana passionfruit is partially selfcompatible, fruit set was significantly reduced in selfed flowers (17.5%) compared to crossed flowers (29.5%), and we found significant pollen limitation (natural [18.0%] was significantly lower than crossed). A significant degree of inbreeding depression was apparent in germination success but not in fruit size, seed set or seedling growth and survival. Surprisingly, open flowers had significantly lower germination success (10.1%) than the other three treatments (crossed = 16.5%, selfed = 15.0%, bagged = 25.3%). Overall, natural flowers produce more seedlings per flower (1.7) than bagged flowers (0.9), but less than hand-selfed (3.0) and crossed (5.3) flowers. To investigate dependence on dispersal, germination success was compared between hand-cleaned seeds, fleshy seeds and intact fruits in the field and glasshouse. Seeds germinated readily in all treatments, with no significant difference between cleaned and fleshy seeds, so seeds do not require frugivore handling to germinate. In the field, tagged fruits were removed quickly after ripening. Significantly fewer fruit were wholly removed from off-road locations than locations on road edges, but removal rate was high in both cases (93% and 70%) indicating dispersal by both humans and wild animals. I found no evidence of dispersal by birds. Infra-red camera evidence revealed possums and rats consuming fruits in the field. In addition, 2818 seeds were extracted from 1.5 kg of pig excrement collected from Te Weu Weu Bay in February 2006. Seeds readily germinated following extraction from pig and possum droppings with a final germination success, in the glasshouse, of 45.6% and 53% respectively. None of the few intact seeds excreted by rats germinated. Therefore, together with direct weed control, limiting the spread of banana passionfruit through the control of pigs and possums may improve management success and reduce the spread of banana passionfruit.

No description available.