No description available.

No description available.

No description available.

<p>Breeding dispersal can be a way for an individual to improve its fitness. Own reproductive success has been shown to be a cue to dispersal among many bird species. Natural selection should favor dispersal to higher-quality territories and a larger territory is predicted to improve fitness. Data from male rock pipits, <em>Anthus petrosus littoralis</em>, on the Swedish west coast indicated, as predicted, that dispersal follows an unsuccessful breeding year. However, no fitness improvement was detected after dispersal, leading to the conclusion that dispersing in itself does not lead to better fitness. Instead it was the acquisition of a larger territory that was the main cause of fitness improvement, unrelated to whether a male returned to an old territory or dispersed to a new one. However, remaining in one's old territory showed to be more beneficial than dispersing. There was a high variation within the rock pipit populations of Nidingen and Malön, due to year-to-year territory quality variation and individual quality among the birds, which could have had a big effect on the outcome of the analyses of the effects of dispersal.</p> / <p>Att byta revir kan vara ett sätt för en individ att förbättra sin fitness. Den egna reproduktiva framgången har påvisats påverka beslutet om revirbyte. Naturligt urval borde favorisera byte till ett revir av högre kvalitet och ett större revir förutsägs förbättra fitness. Data från skärpiplärkor, <em>Anthus petrosus littoralis</em>, tyder på att ett misslyckat häckningsår leder till spridning. Däremot påvisades ingen förbättring av fitness efter spridning, vilket leder till slutsatsen att spridningen i sig inte leder till bättre fitness. Istället var det anskaffandet av ett större revir som var den huvudsakliga orsaken till fitnessförbättring, orelaterat till om en hanne utökade sitt gamla revir eller flyttade till ett nytt. Däremot visade det sig vara bättre att stanna kvar i sitt gamla revir än att flytta. Det fanns en stor variation bland Nidingens och Malöns populationer av piplärka, på grund av årlig variation i revirkvalitet och individuell kvalitet bland fåglarna, vilket kan ha haft en stor effekt på resultatet av analyserna av spridningseffekterna.</p>

Female and male mammals have different behavioral strategies for maximizing their reproductive success. Pregnancy and lactation obligate female mammals to provide greater parental investment than males; thus, females compete with each other for food and space to rear their offspring, while male mammals compete with each other for female mates. Therefore, natural selection should favor any behavior among females that increases their access to food and space to rear successful offspring and any behavior among males that increases their access to females. In two enclosure experiments, the gray-tailed vole, Microtus canicaudus, was used as a model species to study (1) the relative influence of male competition versus access to females on space use by males and (2) facultative sex-ratio adjustment at the population level in response to low and high population densities, skewed adult sex ratios, and season. Home-range sizes of male voles did not appear to expand beyond an overlap with about five members of either sex. Intrasexual competition with 3-4 males and/or overlap with five females appear to set the upper limits to home-range size. Space use by males is influenced by intrasexual competition and by access to females with an upper limit of overlap with either sex. Additionally, facultative sex-ratio adjustment in response to changing population densities and skewing adult sex ratios did not occur, but a seasonal effect was detected with significantly more males produced in autumn than in spring. Under the conditions of this experimental study, I was not able to measure sex ratios of individual litters, but if any sex-ratio adjustment occurred in response to densities and adult sex ratios, it was not detectable at the population level. / Graduation date: 1999

Breeding dispersal can be a way for an individual to improve its fitness. Own reproductive success has been shown to be a cue to dispersal among many bird species. Natural selection should favor dispersal to higher-quality territories and a larger territory is predicted to improve fitness. Data from male rock pipits, Anthus petrosus littoralis, on the Swedish west coast indicated, as predicted, that dispersal follows an unsuccessful breeding year. However, no fitness improvement was detected after dispersal, leading to the conclusion that dispersing in itself does not lead to better fitness. Instead it was the acquisition of a larger territory that was the main cause of fitness improvement, unrelated to whether a male returned to an old territory or dispersed to a new one. However, remaining in one's old territory showed to be more beneficial than dispersing. There was a high variation within the rock pipit populations of Nidingen and Malön, due to year-to-year territory quality variation and individual quality among the birds, which could have had a big effect on the outcome of the analyses of the effects of dispersal. / Att byta revir kan vara ett sätt för en individ att förbättra sin fitness. Den egna reproduktiva framgången har påvisats påverka beslutet om revirbyte. Naturligt urval borde favorisera byte till ett revir av högre kvalitet och ett större revir förutsägs förbättra fitness. Data från skärpiplärkor, Anthus petrosus littoralis, tyder på att ett misslyckat häckningsår leder till spridning. Däremot påvisades ingen förbättring av fitness efter spridning, vilket leder till slutsatsen att spridningen i sig inte leder till bättre fitness. Istället var det anskaffandet av ett större revir som var den huvudsakliga orsaken till fitnessförbättring, orelaterat till om en hanne utökade sitt gamla revir eller flyttade till ett nytt. Däremot visade det sig vara bättre att stanna kvar i sitt gamla revir än att flytta. Det fanns en stor variation bland Nidingens och Malöns populationer av piplärka, på grund av årlig variation i revirkvalitet och individuell kvalitet bland fåglarna, vilket kan ha haft en stor effekt på resultatet av analyserna av spridningseffekterna.

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.

Individual-based simulation modelling is an excellent method for testing hypotheses, while including realistic and stochastic population parameters. This thesis considers the evolution of dispersal or inbreeding through individual-based simulation modelling. The occurrence of exclusive inbreeding and exclusive outbreeding is found in a number of organisms and are referred to as mixed mating. Mixed mating is suggested to be in response to low levels of inbreeding depression as well as simultaneous inbreeding- and outbreeding depression while intermediately related mating partners are not available. The results of this thesis show that stable mixed mating strategies evolve in the presence of both inbreeding and outbreeding depression, as well as, under conditions where low levels of inbreeding depression are present. Also, inclusive fitness allows higher levels of inbreeding in genetic systems where the mating partners are more related to each other. Dispersal evidently evolves in response to inbreeding depression. A number of other factors, such as local mate competition and the cost of dispersal also influence the rate of dispersal. In addition to these factors, it is shown in this thesis that male dispersal evolves when there is variation in patch sex ratios. Simulation data also supports parent offspring conflict models, as males have reduced dispersal rates when they, rather than their parents, determine the dispersal rate. Population structure is affected by dispersal rates. Using individual-based simulation modelling and various sampling strategies, reveals that few molecular markers, for a few individuals, are sufficient to accurately detect population subdivision, especially when the sub-populations are large. It is, however, indicated that planning prior to sampling are important for proper assessment of population structure. Lastly, molecular data from the pollinating fig wasp Platyscapa awekei reveals that this species suffers from low levels of inbreeding depression. However, when this data are simulated, stable mixed mating did not evolve although it is observed in P. awekei. Sex ratio variation, high local mate competitions and male only broods are therefore suggested to drive male dispersal. It is consequently advantageous to use various techniques to unravel the evolution of a trait and gain insight into the system. / Thesis (PhD)--University of Pretoria, 2009. / Genetics / unrestricted