This thesis presents the results of an investigation into the uptake and distribution of cadmium (Cd) in two cultivars of potato (Solanum tuberosum L.) shown to contain different concentrations of Cd in the tuber at maturity. An initial glasshouse trial sought to determine whether differences in tuber Cd between these two cultivars resulted from differences in uptake from the soil, or were due to differences in the allocation of Cd to the various tissues within the plant. Total uptake of Cd from the soil did not differ between cultivars, nor did the yield of tubers. However, there were marked differences in Cd distribution within the plant. Most of the differences in tuber Cd concentration could be accounted for by a large (3-fold) retention of Cd in the roots of cultivar Wilwash. The concentration of Cd in the shoots of Wilwash was also higher than of Kennebec, although to a lesser extent than the roots. Further studies were conducted to trace the pathways of Cd uptake and movement within the plant. A split-pot trial, involving long-term growth of potatoes in 109Cd-labelled soil, was undertaken to determine the overall pattern of Cd distribution and the importance of the root system in supplying Cd to the tubers. The root system of the potato plant is different to many plants, in that the main root system (basal roots) is augmented after tuber initiation by roots extending from the stolon and from the tuber itself. The basal roots were found to be the dominant source of Cd to all tissues and accounted for approximately 85 % of tuber Cd. The remaining tuber Cd was sourced directly from the stolon and tuber roots. However, there was no evidence of a direct link between the main (basal) root system and the stolons. Although Cd was found to accumulate in the periderm of the tubers, there was no uptake into the tuber tissue itself. Isotopic studies were undertaken to investigate the short-term movement of newly absorbed Cd in the xylem and the phloem. Cadmium was found to be highly mobile in both the xylem and phloem, with added Cd being rapidly assimilated into all tissues following both root and foliar application. Newly absorbed Cd was rapidly sequestered by the stems when applied to either the soil or to a source leaf, suggesting that the stems may act as a transitional storage pool when rapid turnover of nutrients and other mineral elements is required during tuber bulking. Inhibition of Cd uptake by zinc (Zn), has been proposed as a method for reducing the concentration of Cd in various agricultural crops, including potatoes. The ability of Zn to reduce Cd uptake was found to be highly dependent upon cultivar and on the concentration of Cd in the external medium. Although competition between Zn and Cd was found for cultivar Wilwash when the external concentration of Cd was low, when the concentration of Cd in the external media was high, increasing Zn served to increase Cd uptake. Both synergistic and competitive responses were also noted for cultivar Kennebec. However, the patterns of response were opposite to those evident in Wilwash. The complexity of these interactions highlighted the possible shortcomings in using soil applied Zn to limit Cd uptake by potatoes. / Thesis (Ph.D.) -- University of Adelaide, School of Earth and Environmental Sciences, 2004.

Many species have suffered severe range contractions as a result of human impacts, and require careful management if they are to persist. An understanding of the ecology, population structure and mating system is important for the conservation of these endangered species. Translocation has become a widely used tool in the conservation of threatened species; however, without proper planning and monitoring, many programmes end in failure. The bridled nailtail wallaby is one of the most endangered macropods in Australia, having suffered an extensive range contraction from the semi-arid region of eastern Australia to a single remnant population of ~ 500 animals at Taunton National Park in Queensland. In 1996, a translocated population of bridled nailtail wallabies was established at Idalia National Park, on the western edge of the former range of this species. The aims of this study were to: 1) determine the factors underlying variation in reproductive success among animals released at Idalia; 2) investigate the effects of a range decline on the genetic variation and population structure of the remnant population at Taunton; 3) assess the impact of captive breeding and translocation on the genetic diversity and structure of the established population at Idalia; and 4) investigate male and female mating strategies in this species. Chapter two investigated reproductive success among males released at Idalia National Park. The bridled nailtail wallaby is a sexually dimorphic, polygynous species and there is a large amount of variation in male reproductive success. Animals of different origin were released, including animals bred in captivity off the park, animals bred on-site in enclosures, and wild-caught animals from the remnant population that were moved directly to Idalia. There was significant variation in reproductive success among males released, but the origin of those animals did not explain this variation. Instead, large males were the most reproductively successful regardless of origin. Survival probability and release location were also important factors. This study highlighted the importance of considering mating system when choosing animals for translocation and suggests that, for polygynous species, a greater proportion of females and males of high breeding potential should be released. In Chapter three I investigated the genetic diversity and fine-scale genetic structure of the remnant population at Taunton. This last remaining population has been isolated for at least 60 years, corresponding to 30 generations for this species. Animals are patchily distributed in assemblages of different size that cover ~ 10% of suitable habitat on the park. Genetic diversity was surprisingly high within the population remnant and this species showed one of the highest levels of heterozygosity and allelic diversity of any macropod. The three sub-populations of animals sampled over 10 km were significantly differentiated, and fine-scale spatial genetic structure was also observed within a continuous sub-population of animals covering just 750 ha. Females were more related to each other than expected from random, whereas males were less related to each other than expected. Fine-scale genetic structure was observed among females but not males, providing evidence for female philopatry and male-biased dispersal. I suggest that fine-scale population structure and restricted gene flow among females but not males may maintain genetic diversity in this remnant population. Chapter four assessed the effect of translocation of animals of different origin on genetic diversity in bridled nailtail wallabies. Both wild-caught and captive-bred animals were initially released, but subsequent releases consisted of captive-bred animals only. In this study, I compared genetic diversity of released animals to animals sampled in the remnant population. Heterozygosity did not differ between the remnant and translocated population, however allelic diversity was significantly reduced among all groups released. Animals bred in captivity were significantly differentiated from the source population, whereas animals moved directly from Taunton were not. Releasing more captive-bred animals into the population after the initial release resulted in a decline in overall heterozygosity and allelic diversity. This study highlights the importance of sourcing animals directly from remnant populations in order to maintain genetic diversity and minimize genetic drift between source and recipient populations. The bridled nailtail wallaby has a polygynous mating system and reproductive success is skewed toward large males. However unlike most polygynous, sexually dimorphic macropods, the bridled nailtail wallaby is highly solitary; animals only associate to breed and males do not form stable dominance hierarchies. In Chapter five I investigated behavioural strategies used by males to secure matings, and mate choice among females. I found that males of different size adopted different mating strategies. Large males spent more time guarding females against other males and maintaining contact with them, whereas smaller males spent less time with guarded females in order to search for other females in oestrus. Females also preferred larger males and were more likely to engage in mate chases if there was a large number of males within the group.

Thesis (Ph. D.)--University of Texas at Austin, 2007. / Vita. Includes bibliographical references.

Thesis (Ph. D.)--University of Canterbury, 2007. / Typescript (photocopy). "September 2007." Includes bibliographical references (p. 147-179). Also available via the World Wide Web.

Diss. (sammanfattning) Umeå : Univ., 2003. / Härtill 6 uppsatser.

Diss. (sammanfattning). Uppsala : Sveriges lantbruksuniversitet, 2005. / Härtill 5 uppsatser.

Thesis (Ph.D.)--University of Adelaide, School of Agriculture and Wine, Discipline of Plant and Pest Science, 2004? / Errata slip inserted at front. Includes bibliographical references (leaves 142-161). Also available online.

Thesis (Ph.D.)--University of Adelaide, School of Agriculture and Wine, Discipline of Plant and Pest Science, 2004? / Title from screen page; viewed 8 Feb 2005. Includes bibliographical references. Also available in a print form.

Diss. (sammanfattning) Alnarp : Sveriges lantbruksuniversitet, 2007. / Härtill 5 uppsatser + 3 appendix.

Thesis (Ph. D.)--University of Hong Kong, 2007. / Title proper from title frame. Also available in printed format.