Climate change, land use change and invasive species are transforming global biodiversity at multiple scales. Projections are for threats to biodiversity from these global changes to continue into the future, with varied and discernible distribution changes for many species. Concomitantly, these global changes will interact with each other to further exacerbate the problem, as exemplified in this study. In New Zealand, climate change is expected to affect landscapes, fragmented and disturbed by land use change, further increasing the potential invasibility of these landscapes for a suite of existing and emerging invasive species. This thesis is concerned with the combined effects of climate and land use changes on the spatial distribution of the sub-tropical invasive plant, Tradescantia fluminensis (Vell.). The contribution of this thesis is to undertake an integrated assessment of the distribution change for this species in New Zealand. On the basis that climatic variables affect species distribution at larger scales, while land use, habitat, disturbance and dispersal mechanisms affect distribution at smaller scales, two separate analyses were undertaken. At the national scale BioCLIM and the Ecological Niche Factor Analysis (ENFA) were implemented using the variables: minimum temperature (July-August), MTminJ-A, and annual water deficit (November-February). At the landscape scale, only ENFA was implemented, using the variables: MTminJ-A, ECOSAT riparian classes (habitat) and proximity to roads, urban areas and streams (disturbance and dispersal sources). Three scenarios of climate change (CCSR B1-Low, CSIRO9 A1B-Mid and HadCM A1FI-High) and two scenarios of land use change (SmartGrowth and Buildout) were developed to the year 2050, using the CLIMPACTS Open Framework Modelling System and Geographic Information Systems, GIS, techniques respectively. The baseline species distribution model was extrapolated in ENFA, using the 2050 scenarios. Changes to potential threat from this species to protected areas at the landscape level were assessed spatially at the landscape level. This approach and its results are novel for this species. At the national scale the results for the modelling show that climate change will increase the potential habitat suitability of Tradescantia under all combined scenarios of CCSR, CSIRO9 and HadCM for mean minimum temperature (July-August), MTminJ-A and Annual Water Deficit, AWD. At the case study landscape, in the Western Bay of Plenty and Tauranga also the modelling results showed that climate change and land use changes will increase the suitability for Tradescantia by 2050. The 'core' or highest suitability areas increase under all future scenarios. At the national level core suitability increased by about 13% for the CCSR:B1-Low and CSIRO9:A1B-Mid and 22% for HadCM:A1FI-High combined scenario on the North Island. On the South Island, core areas increased by a much lower margin - 1.4%, 2.3% and 2.9% for CCSR:B1-Low, CSIRO9:A1B-Mid and HadCM:A1FI-High combined scenarios respectively. At the landscape level core areas increased by 5%, 8% and 21% for the CCSR:B1-Low+SmartGrowth, Darlam:A1b-Mid+SmartGrwoth and HadCM:A1FI-High+Build-out combined scenarios, respectively. This is true also for the Protected areas within the case study landscape, and indicate that the increasing if Tradescantia is able to track both climate and land use change through its dispersal and migration within the landscape 9 primarily in the inland and upland direction), then is will pose a greater risk to native habitats than at present. Integrated assessments and the outputs they produce are essential to exploring anticipated changes (through scenario-building) and in understanding the change spatial context and magnitude of projected changes from the combined effects of climate and land use changes into the future and need to be integrated into biodiversity-biosecurity management at multiple scales.

I compared the performance of habitat models created from data of differing reliability. Because the reliability is dependent on the probability of detecting the species, I experimented to estimate detectability for a salamander species. Based on these estimates, I investigated the sensitivity of habitat models to varying detectability. Models were created using a database of amphibian and reptile observations at Fort A.P. Hill, Virginia, USA. Performance was compared among modeling methods, taxa, life histories, and sample sizes. Model performance was poor for all methods and species, except for the carpenter frog (Rana virgatipes). Discriminant function analysis and ecological niche factor analysis (ENFA) predicted presence better than logistic regression and Bayesian logistic regression models. Database collections of observations have limited value as input for modeling because of the lack of absence data. Without knowledge of detectability, it is unknown whether non-detection represents absence. To estimate detectability, I experimented with red-backed salamanders (Plethodon cinereus) using daytime, cover-object searches and nighttime, visual surveys. Salamanders were maintained in enclosures (n = 124) assigned to four treatments, daytime__low density, daytime__high density, nighttime__low density, and nighttime__high density. Multiple observations of each enclosure were made. Detectability was higher using daytime, cover-object searches (64%) than nighttime, visual surveys (20%). Detection was also higher in high-density (49%) versus low-density enclosures (35%). Because of variation in detectability, I tested model sensitivity to the probability of detection. A simulated distribution was created using functions relating habitat suitability to environmental variables from a landscape. Surveys were replicated by randomly selecting locations (n = 50, 100, 200, or 500) and determining whether the species was observed, based on the probability of detection (p = 40%, 60%, 80%, or 100%). Bayesian logistic regression and ENFA models were created for each sample. When detection was 80 __ 100%, Bayesian predictions were more correlated with the known suitability and identified presence more accurately than ENFA. Probability of detection was variable among sampling methods and effort. Models created from presence/absence data were sensitive to the probability of detection in the input data. This stresses the importance of quantifying detectability and using presence-only modeling methods when detectability is low. If planning for sampling as an input for suitability modeling, it is important to choose sampling methods to ensure that detection is 80% or higher. / Ph. D.

Stem and progenitor cell fate (self-renewal, proliferation, survival, differentiation) is tightly controlled by niche factors and the interplay of these factors is particularly important to comprehend for the development of stem cell therapies. During erythropoiesis, erythroid progenitors at the colony forming unit-erythroid (CFU-E) stage are responsive to both stem cell factor (SCF) and erythropoietin (EPO); however, the joint action of SCF and EPO in these cells and the underlying mechanisms remain to be defined. In this study, quantitative data on the activation of signaling pathways and gene expression profiles provided definitive evidence for two parallel but complementary mechanisms that resulted in enhanced generation of red blood cells from mouse bone marrow-derived CFU-E culture in the presence of SCF and EPO. First, SCF and EPO signaling intersected within the extracellular signal-regulated kinase (ERK) pathway and the sustained ERK activation was required for the maximal changes in the expression levels of genes that are involved in the proliferation and survival of CFU-Es. Second, the apparent competition between SCF and EPO in regulating c-Kit expression was found to have a dramatic impact on the terminal differentiation of CFU-Es. The latter mechanism was, for the first time, reported in a primary cell system. In addition, a fetal liver-derived conditioned medium further enhanced the survival and proliferation of bone marrow CFU-Es in the presence of SCF and EPO by not only increasing the ERK signaling duration but also, the amplitude. The agents present in the conditioned media possess significant clinical potential to stimulate erythropoiesis both in vivo and in vitro. In conclusion, our study has provided novel insights into the mechanisms by which combinations of niche factors control the fate of erythroid progenitors at a unique transitional stage and highlighted the important role of the ERK signaling dynamics in adult erythropoiesis.

Stem and progenitor cell fate (self-renewal, proliferation, survival, differentiation) is tightly controlled by niche factors and the interplay of these factors is particularly important to comprehend for the development of stem cell therapies. During erythropoiesis, erythroid progenitors at the colony forming unit-erythroid (CFU-E) stage are responsive to both stem cell factor (SCF) and erythropoietin (EPO); however, the joint action of SCF and EPO in these cells and the underlying mechanisms remain to be defined. In this study, quantitative data on the activation of signaling pathways and gene expression profiles provided definitive evidence for two parallel but complementary mechanisms that resulted in enhanced generation of red blood cells from mouse bone marrow-derived CFU-E culture in the presence of SCF and EPO. First, SCF and EPO signaling intersected within the extracellular signal-regulated kinase (ERK) pathway and the sustained ERK activation was required for the maximal changes in the expression levels of genes that are involved in the proliferation and survival of CFU-Es. Second, the apparent competition between SCF and EPO in regulating c-Kit expression was found to have a dramatic impact on the terminal differentiation of CFU-Es. The latter mechanism was, for the first time, reported in a primary cell system. In addition, a fetal liver-derived conditioned medium further enhanced the survival and proliferation of bone marrow CFU-Es in the presence of SCF and EPO by not only increasing the ERK signaling duration but also, the amplitude. The agents present in the conditioned media possess significant clinical potential to stimulate erythropoiesis both in vivo and in vitro. In conclusion, our study has provided novel insights into the mechanisms by which combinations of niche factors control the fate of erythroid progenitors at a unique transitional stage and highlighted the important role of the ERK signaling dynamics in adult erythropoiesis.

Kakapo (Strigops habroptilus) are a flightless, nocturnal parrot endemic to New Zealand. Thought to be extinct within their natural range, kakapo are currently listed as nationally critical. The current population of 86 individuals is managed by the Department of Conservation’s National Kakapo Team on two offshore islands in southern New Zealand, with all females of breeding age on Codfish Island (Whenua Hou). Kakapo only breed once every two to five years, coinciding with the mast fruiting of specific plant species. On Codfish Island, the proportion of adult female kakapo that breed in rimu (Dacrydium cupressinum) fruiting years is dependent on the quantity of fruit produced, with fewer females attempting to breed during low mast years. The purpose of this research is to investigate why only some adult female kakapo breed in low rimu fruiting years on Codfish Island, specifically assessing if foraging home range size and/or habitat selection influence breeding. A total of 506 location points were collected at night for 18 adult female kakapo between March and May 2006. These were used to estimate foraging home ranges and to assess if kakapo select for particular types of vegetation. Ecological Niche Factor Analysis was used to determine the relative importance of habitat variables in the distribution of female kakapo and to predict areas of suitable breeding habitat when rimu fruit is limited. The breeding success of individuals in 2005, a low rimu mast year, was used to identify if differences in home ranges or habitat selection occurred between breeding and non-breeding females. The large variation in foraging home range sizes recorded in this research was consistent with previous studies. Foraging home range sizes were on average twice the size for breeders than for non-breeders, suggesting that adult female kakapo may be limited in their ability to breed by the size of the area they occupy. Adult female kakapo did not randomly use vegetation on Codfish Island as some vegetation types were not used, while others were common inside foraging home ranges. Adult female kakapo utilise a broad niche and are capable of surviving in a wide range of habitats. However, breeding females were more specialised in their niche requirements than non-breeders, with breeders utilising areas with higher abundances of mature rimu trees. Females occurred in high elevation, flat areas of the island but this may have been because this is where appropriate vegetation types occurred. During low rimu mast years, breeding adult females were predicted to occupy habitat in high elevation, plateau areas with a high abundance of rimu. Areas identified as sub-optimal habitat for breeding included the coastal areas, the lower elevation area of the main valley and some ridgelines. The home ranges of all 10 breeding females contained some optimal habitat, while females who did not breed were more likely to be located in sub-optimal habitat. Although there were significant areas of optimal breeding habitat not occupied by adult female kakapo, other kakapo may have been present in these areas. To increase the proportion of females that breed in low rimu mast years, it may be necessary to remove sub-adult females or surplus adult males living in optimal breeding habitat from the island. Alternatively, females in sub-optimal breeding habitat could be fed supplementary foods or transferred to other islands where there is unoccupied suitable breeding habitat available.

No description available.

Understanding the events and processes responsible for patterns of within species diversity, provides insight into major evolutionary themes like adaptation, species distributions, and ultimately speciation itself. Here, I combine ecological, genetic and spatial perspectives to evaluate the roles that both historical and contemporary factors have played in shaping the population structure and genetic variation of foxsnakes (Pantherophis gloydi). First, I determine the likely impact of habitat loss on population distribution, through radio-telemetry (32 individuals) at two locations varying in habitat patch size. As predicted, individuals had similar habitat use patterns, but restricted movements to patches of suitable habitat at the more disturbed site. Also, occurrence records spread across a fragmented region were non-randomly distributed and located close to patches of usable habitat, suggesting habitat distribution limits population distribution. Next, I combined habitat suitability modeling with population genetics (589 individuals, 12 microsatellite loci) to infer how foxsnakes disperse through a mosaic of natural and altered landscape features. Boundary regions between genetic clusters were comprised of low suitability habitat (e.g. agricultural fields). Island populations were grouped into a single genetic cluster suggesting open water presents less of a barrier than non-suitable terrestrial habitat. Isolation by distance models had a stronger correlation with genetic data when including resistance values derived from habitat suitability maps, suggesting habitat degradation limits dispersal for foxsnakes. At larger temporal and spatial scales I quantified patterns of genetic diversity and population structure using mitochondrial (101 cytochrome b sequences) and microsatellite (816 individuals, 12 loci) DNA and used Approximate Bayesian computation to test competing models of demographic history. Supporting my predictions, I found models with populations which have undergone population size drops and splitting events continually had more support than models with small founding populations expanding to stable populations. Based on timing, the most likely cause was the cooling of temperatures and infilling of deciduous forest since the Hypisthermal. On a smaller scale, evidence suggested anthropogenic habitat loss has caused further decline and fragmentation. Mitochondrial DNA structure did not correspond to fragmented populations and the majority of foxsnakes had an identical haplotype, suggesting a past bottleneck or selective sweep. / Thesis (Ph.D, Biology) -- Queen's University, 2011-01-11 10:40:52.476