Massey Documents by Type

Permanent URI for this communityhttps://mro.massey.ac.nz/handle/10179/294

Browse

Has files: YesSubject: search.filters.subject.Host-parasite relationships

Search Results

Now showing 1 - 3 of 3
  • Thumbnail Image
    Item
    Host-race specificity in the endemic pygmy mistletoe Korthalsella salicornioides (Viscaceae) : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Plant Biology at Massey University, Palmerston North, New Zealand
    (Massey University, 2016) Pearson, Sofie Margaret
    Korthalsella Tiegh. is a genus of stem hemiparasites in the family Viscaceae, represented in New Zealand by three endemic species: K. clavata, K. lindsayi, and K. salicornioides. The most host-specific is K. salicornioides as it parasitizes two main host genera Leptospermum (Myrtaceae) and Kunzea (Myrtaceae), while the other two species are considered generalists parasitizing a wider range of host species. K. salicornioides is naturally uncommon and sparse, although it can be locally abundant on occasion. Mistletoe populations are at risk primarily due to habitat destruction and subsequent loss of hosts. Cross-infection experiments in K. salicornioides provided some insight into the presence of putative host races, as better mistletoe seedling establishment success rates were apparent when the maternal and recipient hosts were the same. However, because previous molecular sequence data (nuclear internal transcribed spacers and chloroplast trnQ-rps16) for K. salicornioides were not informative about specific host-races, more rapidly evolving molecular markers might be expected to detect host races. In this study, next generation sequencing was used to develop novel microsatellite markers for Korthalsella. Eleven markers were reliably amplifiable and the most polymorphic for K. salicornioides were used to genotype 272 K. salicornioides individuals from 16 populations. Across all populations few alleles were identified, and within-population assessment of genetic variation indicated that many populations have low levels of genetic diversity and high proportions of homozygotes. Despite the presence of few alleles, a high degree of genetic differentiation between most populations was detected and was found to reflect host species and geography. The findings of this study that Korthalsella salicornioides populations have low levels of genetic variation but host-specific races, has important conservation implications. The main conservational focus should be maintaining and increasing host Leptospermum and Kunzea populations. The spread of mistletoe seed on hosts within or between populations may also increase the chances of continued survival. However, it is imperative that genetic material comes from the same host species, and consideration should also be given to the geographic area, especially in the Wairarapa. This study provides insights into the population structure within and between the different host populations and suggests several interesting areas of future study.
  • Thumbnail Image
    Item
    The impact of conservation translocations on vector-borne parasites : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Ecology at Massey University, Palmerston North, New Zealand
    (Massey University, 2015) Schoener, Ellen Renate
    Wildlife conservation in New Zealand relies on translocations of endangered species to safe sites. While knowledge of the biology and behaviour of translocated hosts has steadily increased, the role of parasites in wildlife translocations has been largely overlooked. Parasites can affect their host’s survivorship during translocations by causing disease. However, failure to translocate or reintroduce a host specific parasite with its endangered host can contribute to the extinction of the parasite with unforeseen consequences for the future of the host or even the whole ecosystem. The main aims of this study were to establish baseline data on the impact of North Island saddleback translocations on their avian malaria (Plasmodium spp.) parasites as well as gaining further insight into potential vectors in New Zealand. The study was also intended to contribute to the development of recommendations for future parasite screening programmes for native passerine translocations. Saddlebacks and Plasmodium were chosen because of the detailed saddleback translocation history and its known relationship with the parasite. As a result of this study, several Plasmodium lineages previously unrecorded in saddlebacks and New Zealand were identified, for example, the native Kokako01 and one lineage closest related to two lineages from the Americas. Nonetheless, the most frequent lineages found were the cosmopolitan P. elongatum GRW6 and LINN1, and P. vaughani SYAT05, common in birds introduced to New Zealand. This finding suggests that endemic parasites may have already become rare or extinct. In addition, Plasmodium DNA was detected in both native and introduced mosquitoes that may act as vectors. A qPCR assay was developed that was found to be a cost effective and rapid screening tool for the detection of Plasmodium in native birds suffering from acute infection, presenting with clinical symptoms, and in birds that were found dead. . I conclude that future translocations should consider the movement of endemic parasites with their hosts. How this should happen is open for future studies. However, I urge managers to start considering this issue now as New Zealand has already recorded the extinction of one endemic parasite and many more may have already been lost without knowledge.
  • Thumbnail Image
    Item
    The non-target effects of the introduced parasitoid Trigonospila brevifacies (Hardy) (Diptera: Tachninidae) on the native fauna of New Zealand : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Ecology at Massey University, Palmerston North, New Zealand
    (Massey University, 1999) Munro, Vanessa M W
    The Australian tachinid parasitoid Trigonospila brevifacies (Hardy) (Diptera: Tachinidae) was introduced to New Zealand 30 years ago as a biological control for the exotic orchard pest Epiphyas postvittana Walker (Lepidoptera: Tortricidae). Trigonospila brevifacies, an endoparasitoid of late-instar lepidopteran larvae, was introduced concurrently with Xanthopimpla rhopaloceros Krieger (Hymenoptera: Ichneumonidae), a parasitoid of lepidopteran pupae. Trigonospila brevifacies is now known to attack several non-target pest and non-pest lepidopteran species. The impact of T brevifacies on non-target fauna was investigated. Life history data (i.e., longevity, fecundity, productivity and sex ratio) for T. brevifacies were quantified in the laboratory. These data and field data were used to investigate whether superparasitism is an adaptive reproductive strategy for this species by comparing the return in adult progeny per egg for single and multiple egg clutches. Superparasitism may be advantageous for the survival of rare non-target hosts. Data from a two-year, six-site survey of native forests determined that T. brevifacies attacked eight non-target Lepidoptera. The characteristic common to the phylogenetically diverse host group was that all are concealed feeders. Laboratory testing showed that pre-imaginal conditioning of parasitoid larvae did not confer adults with a preference for the host species in which they were reared. Quantitative food web data from a two-year field survey showed that T. brevifacies was the numerically dominant parasitoid of the species attacking native Tortricidae at sub-canopy levels and that it competed for hosts with 12 native and one other introduced species of parasitoid. The abundance of larval hosts and T brevifacies was compared between the edges and centres of forest patches. Host density was determined by quadrat counts and parasitoid abundance by sticky traps. Both larval hosts and the parasitoid were more abundant at the forest edge. Trap hosts were also used to quantify parasitism levels along edge to forest-centre tansects. Parasitism by T. brevifacies was highest at forest edges declining to almost zero at 30m into a forest, indicating that forest centres with continuous canopy should offer hosts' refuge from T. brevifacies parasitism. Archival and field data were used to determine the present geographical ranges of T. brevifacies and X. rhopaloceros and climatic data were used to predict where else in New Zealand these two parasitoids are likely to colonise in the future.