The minimum ecologically viable population size (MEVP) of a species describes the minimum size at which the species itself or another species in the same ecosystem goes extinct as a result of the loss of inter-specific interactions. The MEVP shows a good potential for use as a tool for exploring the mechanisms behind species extinctions, but presently only a small amount of research has been done that takes advantage of this. In this study the MEVP is used to investigate what properties of species can be used as good indicators of ecological importance. 100 large computer generated food webs were created with an assembly model and the reduction in density that was necessary to induce an extinction event in the web was subsequently determined for each species within the webs. This change in density was then correlated with 28 different properties, measured for each species. The results show that properties that measure how well connected a species is, as well as measures of the species role as a prey item in the web are the ones with the greatest potential to find species with high MEVP. Further, the results put emphasis on the importance of regarding the web as a whole when working with species extinctions, while also highlighting the usefulness of the MEVP concept.

In Nova Scotia subtidal habitats, the invasive bryozoan Membranipora membranacea interacts with native bryozoan Electra pilosa on kelps, which offer high space availability but are highly dynamic, and on non-kelp algae, which provide low space but high stability. Settlers and colony cover of M. membranacea at various stages critical to its population dynamics, as well as relative abundance and encounter outcomes of M. membranacea and E. pilosa, were quantified on these substrates. I also examined the effects of various factors on growth rates of E. pilosa. For M. membranacea populations, the roles of kelp and non-kelp substrates varied intra- and inter-annually, as well as spatially. Membranipora membranacea was relatively more abundant on kelps than on Fucus, likely due to large colony size, faster growth, and strong overgrowth abilities. While kelps provide spatial resources for seasonal peaks in abundance of M. membranacea, non-kelp refuges can preserve local populations in time.

No description available.

No description available.

The Karkloof blue butt erfly, Orachrysops ariadne (Butler), is endemic to the Mistbelt grassland of KwaZulu-Natal province, South Africa, and is currently Red-listed as 'Vulnerable' . O. ariadne is univoltine and on the wing in March and April, when it utilizes eight species of nectar plants. This study confirmed that the larval hostplant is Indigofera woodii H. Bol. var. laxa H. Bol., an erect variety. It was also confirmed that this butterfly is ant-dependent, with the young larva being taken into the nest of Camponotus natalensis (F. Smith) where development continues, including pupation. This study compares the ecological conditions at the four known locations so as to make informed decision s regarding its conservation. A large proportion of the grassland in KwaZulu-Natal has been aforested and cultivated, and at least 92% of the Mistbelt has been transformed, with only about 1% in good condition remaining. Predictions on the habitat and habit at requirements of this species are necessary for developing a conservation strategy and action plan. Here , we propose O. ariadne as an indicator species for Mistbelt grass land. Saving enough of the remaining Mistbelt grassland is crucial, not just for the survival of the Karkloof blue, O. ariadne, but also for the Mistbelt grassland community as a whole. The population structure and movement of Orachrysops ariadne and O. subravus were studied by mark-release-recapture methods in 1999. There were 290 O. ariadne marked over 48 days between March and April, 124 (42 .8%) were recaptured at least once. Of 631 O. subravus marked over two months between September and November, 311 (49 .3%) were recaptured at least once. Both species exhibited protandry, male appearance about one to two weeks earlier. The sex ratio of O. ariadne is heavily male biased 5.6 :1 (246 males and 44 females), and the sex ratio of O. subravus is 1.6:1 (387 males and 244 females). The Jolly-Seber model was used to estimate daily population numbers (N ᵢ), survival rates (Ø ᵢ), recruitment rates (B ᵢ), proportion of marked animals in the total population (α ᵢ ), and the number of marked animals at risk (M ᵢ) . Average residence times of male adults were generally similar in both species in the range of 5.36-5.44 days, and were slightly longer for male than for female O. subravus (by 4.09 days). 0. ariadne is a strong and rapid back and forth flier, covering mean recapture distances of 157 m, almost twice that of 0. subravus, principally in search of scarce nectar sources. The extreme rarity of 0. ariadne is not so much to do with behaviour, survivorship or longevity, but rather the butterfly is limited in distribution by suitable habitat for both larva and adult. The aim of management is to optimize the habitat so that it best meets the present and future needs of the butterfly. The effects of the current fire regime on the butterfly, host plant and ant host were evaluated here. It is recommended that burning only take place after the larvae have hatch ed and gone underground with the ant host. Using GPS and GIS, core, quality habitat characteristics were defined. In cooperation with the landowner at one site, alien invasive plants are being removed to increase the area of quality habitat. Availability of host plants is limiting for success of the butterfly in the field. Guidelines are provided for propagation and introduction of the host plant, so as to provide the butterfly with more oviposition sites. / Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 2002.

Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal

Invasive alien species (IAS) pose a serious threat to ecosystems and societies worldwide. Local ecological knowledge (LEK) is increasingly valued as a means of understanding environmental issues; however, its application in the context of IAS research has been limited. The overall objective of this study was to document the LEK of farmers and Weed Supervisors to gain insight into a recent IAS, Odontites serotina. I conducted semi-structured interviews with farmers and Weed Supervisors with O. serotina management experience. Results indicated that the socio-economic impacts for farmers were severe in affected rural communities. However, participants had developed promising control techniques, including the application of compost mulch. I used this LEK as well as data on species occurrence, environmental variables, and measures of propagule pressure to forecast the potential distribution of O. serotina across Manitoba. The risk map generated will be useful for guiding future monitoring and public outreach efforts.

Nemertodermatida is a group of microscopic marine worm-like animals that live as part of the marine meiofauna in sandy or muddy sediments; one species lives commensally in a holothurian. These benthic worms were thought to disperse passively with ocean currents, resulting in little speciation and thus wide or even cosmopolitan distributions. Individuals occur in low abundance and have few light microscopically available characters, which altogether may explain why only eight species had been described between the discovery of the taxon in 1930 and this thesis. We used molecular methods to address the diversity and phylogeny of this group for the first time. In a study of two nominal species with samples from all around the world, a high degree of cryptic speciation was discovered and several new species described. Diagnoses were based on molecular data complemented by morphological characters, where available. Given the patchy geographical record it can be assumed that the majority of the biodiversity of Nemertodermatida is yet to be described. A phylogenetic study including all but three known species revealed a deep divergence between the two families of Nemertodermatida but non-monophyly of the taxon was rejected by an Approximately Unbiased test. Confocal laser scanning microscopic studies of several species show that the pattern of the body-wall musculature and the nervous system are specific for different genera. The muscular system of all species consists of a basic orthogonal grid with specific diagonal musculature and specialized muscles associated with body openings. The mouth appears to be transient feature in Nemertodermatida, developing only after hatching and being reduced again in mature worms. The nervous system is highly variable with very different ground patterns between the genera, such as an epidermal net, a centralized neuropile or a commissural brain. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Manuscript. Paper 4. Manuscript.</p>

Oxidative stress, caused by increased levels of reactive oxygen species (ROS)and reactive nitrogen species (RNS) and/or a decrease in antioxidant capacity, can result in the oxidation of various bio-molecules, such as proteins, lipids and deoxyribonucleic acid (DNA). These oxidized bio-molecules may contribute to pathologies such as cardiovascular diseases, neurodegenerative disorders and cancer. The Sympathetic Activity and Ambulatory Blood Pressure in Africans (SABPA) study was initiated in 2008 to investigate the coping styles and catecholamine metabolic markers of Africans, contributing to their higher sympathetic output and poorer psychosocial wellbeing. This study forms part of the SABPA study, but with a specific aim to investigated lipid and protein oxidation markers in hypertensive Africans versus their normotensive counterparts. Analytical methods for the quantification of specific lipid and protein oxidation markers were optimized and validated. Urine samples from 172 urbanized black South Africans were collected and 3-nitrotyrosine (3NT) and thiobarbituric acid reactive substances (TBARS) were quantified in these samples, using the optimized spectrophotometric and LC-MS/MS methods. Statistical analyses showed that in both males and females, TBARS and 3NTcorrelated with each other. In males, 3NT also correlated with physical activity level (PAL) and C-reactive protein (CRP), while TBARS also correlated with body mass index (BMI). In females 3NT correlated with BMI, while TBARS correlates with PAL. These correlations meant that they could influence the calculations of the true effect of 3NT and TBARS levels between normotensive and hypertensive subjects. After analyses of covariance (ANCOVA) analyses it was determined that the hypertensive male subjects had higher TBARS values than the normotensive male subjects did (p-value = 0.03) and the normotensive female subjects had higher 3NT levels compared to the hypertensive female subjects (p-value = 0.04). These results partially supported the hypothesis that that elevated concentrations of specific urinary lipid and protein oxidation markers will be observed in the hypertensive test subjects compared to their normotensive counterparts. The results also indicated that there were indeed a difference in lipid and protein oxidation between hypertensive and normotensive subject. / Thesis (MSc (Biochemistry))--North-West University, Potchefstroom Campus, 2013

Oxidative stress, caused by increased levels of reactive oxygen species (ROS)and reactive nitrogen species (RNS) and/or a decrease in antioxidant capacity, can result in the oxidation of various bio-molecules, such as proteins, lipids and deoxyribonucleic acid (DNA). These oxidized bio-molecules may contribute to pathologies such as cardiovascular diseases, neurodegenerative disorders and cancer. The Sympathetic Activity and Ambulatory Blood Pressure in Africans (SABPA) study was initiated in 2008 to investigate the coping styles and catecholamine metabolic markers of Africans, contributing to their higher sympathetic output and poorer psychosocial wellbeing. This study forms part of the SABPA study, but with a specific aim to investigated lipid and protein oxidation markers in hypertensive Africans versus their normotensive counterparts. Analytical methods for the quantification of specific lipid and protein oxidation markers were optimized and validated. Urine samples from 172 urbanized black South Africans were collected and 3-nitrotyrosine (3NT) and thiobarbituric acid reactive substances (TBARS) were quantified in these samples, using the optimized spectrophotometric and LC-MS/MS methods. Statistical analyses showed that in both males and females, TBARS and 3NTcorrelated with each other. In males, 3NT also correlated with physical activity level (PAL) and C-reactive protein (CRP), while TBARS also correlated with body mass index (BMI). In females 3NT correlated with BMI, while TBARS correlates with PAL. These correlations meant that they could influence the calculations of the true effect of 3NT and TBARS levels between normotensive and hypertensive subjects. After analyses of covariance (ANCOVA) analyses it was determined that the hypertensive male subjects had higher TBARS values than the normotensive male subjects did (p-value = 0.03) and the normotensive female subjects had higher 3NT levels compared to the hypertensive female subjects (p-value = 0.04). These results partially supported the hypothesis that that elevated concentrations of specific urinary lipid and protein oxidation markers will be observed in the hypertensive test subjects compared to their normotensive counterparts. The results also indicated that there were indeed a difference in lipid and protein oxidation between hypertensive and normotensive subject. / Thesis (MSc (Biochemistry))--North-West University, Potchefstroom Campus, 2013