Biological, Earth and Environmental Sciences - Masters by Research Theses
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Item Blood host preferences and competitive inter-species dynamics within an African malaria vector species complex inferred from signs of animal activity around aquatic larval habitats distributed across a gradient of fully domesticated to fully pristine ecosystems in southern Tanzania(University College Cork, 2023) Walsh, Katrina; Killeen, Gerard; Butler, Fidelma; Kaindoa, Emmanuel; AXA Research Fund; University College CorkThe effectiveness of current first-choice vector control interventions on the semi-zoophagic vector Anopheles arabiensis are limited, among other things, by insecticide resistance and their ability to acquire non-human bloodmeals. Across much of southern Tanzania, in areas where humans and cattle are readily available, it is the predominant member sibling species of the Anopheles gambiae complex. However, little is known about its population dynamics or blood utilization behaviours in pristine natural ecosystems, where these known preferred hosts are scarce or completely absent. This study investigated larval habitat occupancy and species composition of the An. gambiae complex, together with the availability of various potential mammalian blood host species, across a gradient of fully domesticated to fully pristine ecosystems in southern Tanzania. Potential aquatic habitats were surveyed at 40 locations encompassing permanent human settlements, a community-owned Wildlife Management Area with varying degrees of human activity, and Nyerere National Park (NNP), which had very little. To investigate the effects of potential host availability on the species composition of the complex, all direct observations, tracks and signs of humans, livestock and wild animals observed around the surveyed larval habitats were recorded in parallel. The resulting data were analysed by logistic regression using generalized linear mixed models. Odds of habitat occupancy by An. gambiae complex larvae decreased by 62% (P<0.0001) across the full range of natural ecosystem integrities observed, from fully domesticated to completely pristine areas, suggesting that the availability of suitable blood hosts had a modest effect on overall habitat utilization by this taxon. However, while only An. arabiensis, a key vector of residual malaria transmission, was found in fully domesticated ecosystems, its non-vector sibling species An. quadriannulatus also occurred in conserved areas and dominated the most pristine natural ecosystems. The proportion of An. arabiensis versus An. quadriannulatus was positively associated with the number of times humans and/or cattle (P=0.0007) were detected at a location and negatively associated with distance inside NNP and away from human settlements (P<0.0001). Nevertheless, An. arabiensis was found even in absolute pristine environments that were >40km away from any signs of human or livestock, suggesting this species can survive on blood from one or more wild animal species. High proportions of An. quadriannulatus inside NNP were positively associated with the number of times impala were detected (P<0.0001), suggesting they may be a preferred blood source for this non-vector, giving it a competitive advantage over An. arabiensis where this antelope is abundant. Despite being detected less frequently, bushpig were also positively associated with high proportions of An. quadriannulatus, suggesting they provide a second preferred blood source, particularly in the miombo woodlands of the buffer zone where impala were scarce. Overall, it seems that the availability of preferred hosts influences the competitive balance between these sibling species and that refugia populations of An. arabiensis can persist in wild areas, thus presenting both challenges and opportunities for control interventions: While such refuge populations deep inside pristine conservation area may confound attempts to repeat historical successes with eliminating this species from areas outside its natural range, it may also constitute a reservoir of diverse, unselected genomes with original wild-type insecticide susceptibility traits that could repopulate areas around human settlements that had otherwise been considered lost from the natural gene pool.Item Biodiversity, people, and logistics: the balancing act of urban park management(University College Cork, 2023) Horan, Sadhbh; Harrison, Simon; Lettice, EoinIn a time when global populations are moving to urban centres, the need for adequate green spaces in towns and cities for the health of both people and nature is paramount. The management of such spaces in Ireland is idiosyncratic and requires investigation. Multiple studies have tried to quantify the key influences to take into consideration when managing an urban park and for this thesis it was determined that the intersection of biodiversity, people and logistics encompassed theses influences. The aim of this study was to determine how best to manage parks in terms of habitat, amenity and management choice, based on the three selected influences. Diversity of vascular plants and fungi were assessed at six parks in Cork city. In addition, park user questionnaires and SOPARC (System for Observing Play and Recreation in Communities) observations were made to quantify people’s park use and opinions. Finally, in order to determine what systems were already in place, structured interviews were undertaken with individuals and organisations who manage urban parks in Ireland. Results show that dry meadow is the optimal choice of habitat for Irish parks due to it high level of biodiversity, its popularity among park visitors, and its compatibility with park amenities however the choice of habitat needs to take abiotic and social factors into account also. Basic amenities such as footpaths and litter bins were preferred over elaborate ones such as outdoor exercise equipment, while overall, recreational facilities were more popular than sports facilities. Logistically, in urban centres where a park management sector was present, it was often underfunded and understaffed, and so while the progress made by these groups is commendable, they are simply not rigorous enough to sustain the growing number and need for urban parks in Ireland. Urban green spaces require a complex understanding of each of the three influences highlighted in this study both across urban centres and within individual parks and cities in order for optimal management to take place.Item New insights into the summer distribution of basking sharks (Cetorhinus maximus) in the northeast Atlantic(University College Cork, 2022) Stasiuleviciute, Edita; Rogan, Emer; Jessopp, Mark John; Department of Communication, Climate Action and Environment; Department for Culture, Heritage and the Gaeltacht, Ireland; Sustainable Energy Authority of IrelandBasking sharks, Cetorhinus maximus, have undergone widespread historic exploitation in the northeast Atlantic and are of conservation concern. A greater knowledge on their spatial and temporal habitat use in response to environmental conditions is required to better inform subsequent monitoring and management strategies. Several efforts to describe the occurrence and distribution of basking sharks have been already made, however nothing at large spatial scales. Sighting information on basking sharks was derived from three aerial survey programmes which covered extensive inshore and offshore waters within the northeast Atlantic. The occurrence of basking sharks in the area was highly seasonal, with individuals predominately observed during the summer months (May-August). Hotspots of occurrence were within the coastal waters off the south and west of Ireland, whereas areas such as southwest of England and west of Scotland, previously considered to be hotpots for basking sharks, were not aggregation sites during summer months, suggesting a seasonal change in distribution. Based on satellite-derived environmental variables and climate indices, this study revealed that distribution of basking sharks was associated with (1) lower chl-a concentrations (< 2.27 mg/m³), (2) shallow coastal waters which are most likely important summer feeding grounds; and (3) positive North Atlantic Oscillation (NAO) winter index, most likely through association with prey species. Sea surface temperature (SST) had no significant effect on the distribution of basking sharks. This study provided new insights into the seasonal occurrence of basking sharks on a large scale within the northeast Atlantic. The results produced here could be incorporated into future management frameworks for assessing the threat and conservation needs for this regionally protected species, as well as providing guidance for future research efforts.Item Spatiotemporal variability in Antarctic krill (Euphausia superba) around South Georgia from Antarctic fur seal (Arctocephalus gazella) diets at two long term monitoring sites(University College Cork, 2022-11-29) Coleman, Jamie; Jessopp, Mark John; Hollyman, Phillip; Collins, Martin; Trathan, PhillipDespite its biological, biogeochemical, and economic importance, there is much about Antarctic krill (Euphausia superba Dana, 1852) that is still poorly understood. This is especially true for its recruitment into South Georgia’s waters, which is highly variable and difficult to predict. Krill fluctuations exert bottom-up pressures on the entire ecosystem which can be reflected in changes in the breeding success and diet of dependent higher predators, such as Antarctic fur seals - Arctocephalus gazella (Peters, 1875). This study compares two long-term datasets (2008-2021) of Antarctic fur seal diet from Bird Island and King Edward Point, South Georgia, to investigate year-round krill dynamics. Foraging tracks from breeding female fur seals demonstrated that seals from the two sites forage in distinct regions. Krill length-frequency distributions generally followed a synchronous pattern across both sites with summer increases in length associated with growth, and winter decreases associated with ongoing senescence, mortality and possibly krill shrinkage, coupled with recent recruits with smaller body lengths entering the population. Using a multivariate approach, mixed layer depth, sea surface temperature, chlorophyll a, and salinity together explained 43% of the dissimilarities in krill length-frequency distributions predated by fur seals between seasons. Bird Island seals took significantly larger krill than those at KEP, possibly a result of continued krill growth during advection between the two areas, or differences in local oceanography. Krill cohorts visibly developed across years with large-scale recruitment of smaller krill occurring every 4-5 years. An anomalous period between 2017 and 2020 occurred when synchrony between sites broke down and later re-established. The beginning and end of this anomalous period appears to coincide with switches in the El Niño Southern-Oscillation, however more data are needed to formally test this link. This study highlights the importance of having multiple spatially separated long-term monitoring sites; this is particularly important in this ecological system as it can vary over a range of scales, including local scales, and it is also recognised to be experiencing significant changes.Item Modulation of plant growth by day length dependent regulation of the TOR signaling pathway(University College Cork, 2022-07-13) Hamilton, Ferga; Henriques, Rossana; Wingler, AstridPlant growth occurs through cell growth and proliferation, which are high energy demanding processes. Plants need to coordinate growth responses with their environmental conditions to ensure the best use of their resources. This accurate regulation depends on the circadian clock, an internal time keeping mechanism that informs the plant of day length duration (photoperiod). The TOR (Target of Rapamycin) kinase pathway is a central hub where cellular energy levels are perceived and translated into specific growth responses across kingdoms. In plants, the TOR pathway has been associated with rapid growing tissue including embryos, shoot and root meristems. Downstream of TOR, the 40S ribosomal protein S6 Kinase 1 (S6K1) modulates both cell growth and proliferation. Since S6K1 accumulation is modulated by the circadian clock, this thesis investigated how changes in S6K1 levels would affect plant growth when the clock function is impaired by mutation in ZTL (ZEITLUPE) which encodes a F-box protein that targets for degradation several components of the Arabidopsis clock. The findings show that de-regulation of TOR signaling pathway components impacts plant growth and development. This negative effect is reinforced by a defective circadian function, suggesting that plants require a running clock to match the TOR pathway activity with specific environmental conditions.