Thesis (PhD)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: Understanding the distribution, abundance and diversity of species and the mechanisms causing these patterns has been the interest of ecologists and taxonomists for decades. The exceptionally high plant diversity in the Fynbos biome has been well studied. Whilst early arguments suggested that the high plant diversity is not reflected in the arthropod diversity and that insect species richness is low compared to other comparable areas, these observations might have been hampered by the taxonomic impediment. Despite global recognition of the significance of this below-ground component of diversity for ecosystem functioning, soil is one of the most poorly studied habitats of terrestrial ecosystems. Although knowledge is increasing for epigaeic groups, other significant groups such as the Collembola remain especially poorly understood. This thesis starts addressing this serious gap in knowledge concerning the below-ground component of biodiversity in the Fynbos biome and the effects of landscape transformation thereon. As part of the work, considerable attention was given to resolving the taxonomic impediment for the springtail fauna of the Fynbos biome using modern morphological and DNA barcoding methods, while also examining the correlates of soil animal diversity in the biome, by using Collembola (springtails) as exemplars. First, using a combination of published records of Collembola from South Africa, various sampling methods and DNA barcoding, a species list is compiled for the Western Cape. Currently 213 species are known to exist from the Western Cape. A high level of cryptic diversity was also found in several genera, together with several potential species radiations in the Ectonura, Seira, Parisotoma and Cryptopygus. A start is a made at addressing the lack of taxonomic knowledge by describing five new species. Two Ectonura Cassagnau 1980 species are described from Betty’s Bay and Grootvadersbosch respectively and a key to the Neanurinae of South Africa is provided. The first record of the genus Triacanthella Schäffer, 1897 is described from a cave in Table Mountain, while two new species of Delamarephorura are described and the genera Spicatella Thibaud 2002 and Delamarephorura Weiner & Najt 1999 are synonymized. Although fire is thought to be the main form of decomposition in the Fynbos biome, recent work has shown that biological decomposition may be more important than previously thought. I examine the resilience of Collembola after a large-scale fire in Jonkershoek Nature Reserve using quantitative sampling which is temporally replicated. The resilience of invertebrate fauna in the fynbos is not well understood, thus I investigate the diversity of Collembola before and after a major fire. Results show Collembola species richness and abundance recovered surprisingly quickly after the fire. On a larger scale, litterbags were deployed at six sites across the Western Cape using different litter types. Here, a total of 113 morphospecies species was found. Local richness was found to be highest in Kogelberg (32 species), while the turnover between sites was also high. Thus, the degradation of local habitat patches will be as much of a threat to Collembola as to the endemic plants in this region. / AFRIKAANSE OPSOMMING: Begrip van die verspreiding, spesierykheid en verskeidenheid van spesies en die meganismes wat hierdie patrone veroorsaak is al die belangstelling van ekoloë en taksonome vir dekades. Die buitengewoon hoë plant diversiteit in die Fynbos-bioom is goed bestudeer. Terwyl vroeë argumente voorstel dat die hoë plantdiversiteit nie weerspieël word in die geleedpotige diversiteit nie en dat insekspesierykheid laag is in vergelyking met ander gebiede, kon hierdie waarnemings nie gemaak word nie as gevolg van taksonomiese hindernisse. Ten spyte van die wêreldwye erkenning van die belangrikheid van hierdie ondergrondse komponent van diversiteit vir die funksionering van die ekosisteem, is die grond een van die swakste bestudeerde habitatte van terrestriële ekosisteme. Alhoewel kennis vermeerder vir bogrondse groepe, word ander belangrike groepe soos die Collembola swak verstaan. Hierdie tesis begin hierdie ernstige leemte in kennis aanspreek, met betrekking tot die ondergrondse komponent van biodiversiteit in die Fynbos bioom en die gevolge van die landskap transformasie daarop. As deel van die werk, is heelwat aandag gegee aan die oplossing van die taksonomiese hindernis vir die springstert fauna van die fynbos bioom met behulp van moderne morfologiese en DNA metodes, terwyl dit ook die ooreenkomste van grond diere diversiteit ondersoek in die bioom, deur gebruik te maak van Collembola (springsterte) as voorbeelde. Eerste, met behulp van 'n kombinasie van gepubliseerde rekords van Collembola van Suid-Afrika, verskillende kolleksie metodes en DNA metodes is 'n spesielys saamgestel vir die Wes-Kaap. Tans is 213 spesies bekend vir die Wes-Kaap. 'n Hoë vlak van kriptiese diversiteit is ook gevind in verskeie genera, saam met verskeie potensiële spesies radiasies in die Ectonura, Seira, Parisotoma en Cryptopygus. 'n Begin is gemaak op die aanspreek van die gebrek van taksonomiese kennis deur vyf nuwe spesies te beskryf. Twee Ectonura Cassagnau 1980 spesies van Bettiesbaai en Grootvadersbosch is beskryf en 'n sleutel tot die Neanurinae van Suid-Afrika word verskaf. Die eerste rekord van die genus Triacanthella Schaffer, 1897 word beskryf van 'n grot in Tafelberg, terwyl twee nuwe spesies van Delamarephorura beskryf word en die genera Spicatella Thibaud 2002 en Delamarephorura Weiner & Najt 1999 gesinomiseer word. Hoewel vuur beskou word as die belangrikste vorm van ontbinding in die Fynbos bioom, het onlangse werk getoon dat die biologiese ontbinding belangriker mag wees as wat voorheen vermoed was. Ek ondersoek die veerkragtigheid van Collembola na 'n groot skaal vuur in Jonkershoek Natuurreservaat met behulp van kwantitatiewe steekproefneming wat tydelik herhaal. Die veerkragtigheid van ongewerwelde fauna in die fynbos word nie goed verstaan nie, dus het ek ondersoek ingestel na die diversiteit van Collembola voor en na 'n groot vuur. Resultate toon dat Collembola se spesierykheid en hoveelheid verbasend vinnig herstel na die vuur. Op 'n groter skaal, is kolleksies by ses plekke regoor die Wes-Kaap gebruik en verskillende blaarafval word vergelyk. Hier word 'n totaal van 113 morfologiese spesies gevind. Daar is gevind dat die hoogste aantal spesies in Kogelberg is (32 spesies), terwyl die omset tussen plekke baie hoog was. So sal die agteruitgang van plaaslike habitatte net soveel van 'n bedreiging inhou vir Collembola as vir die endemiese plante in hierdie streek.

Boreal regions account for a significant portion of Canada's landmass and economic resources (e.g., forestry, mining, and oil and gas). The inadvertent release of pollutants from industrial activities within these regions stress the need for realistic ecological risk assessments, which can be attained through the use of standardized soil toxicity test methods. Despite the geophysical and economic significance of boreal regions, standardized soil toxicity test methods applicable to these regions are lacking. To help alleviate this gap in ecotoxicology, the objectives of this thesis included the development and application of a new suite of boreal species for the assessment of contaminants in boreal soils. Specifically, research was directed towards the development of a new oribatid mite test, using Oppia nitens (C.L. Koch). Oribatid mites represent the most abundant and diverse microarthropod species in forest soils, significantly contributing to nutrient cycling and soil formation processes; however, these organisms are consistently under-represented in soil ecotoxicological assessments. The applicability and limitations of the use of O. nitens were demonstrated such that lethal and sublethal endpoints could be derived from the assessment of soils. The performance of O. nitens across numerous soils varied such that adult survival was unaffected by soil characteristics, however, reproduction was limited by soil organic matter content. An evaluation of the sensitivity of O. nitens, using a model polycyclic aromatic hydrocarbon was also conducted in a standard test soil. Phenanthrene is a common contaminant in soils, and accumulates within organic-rich horizons, within which oribatid mites live. Therefore, the study was designed to examine the toxicity and bioaccumulation potential of phenanthrene to O. nitens, with a comparison of effect to other soil invertebrate species, as presented in the literature. Oppia nitens was susceptible to phenanthrene at levels comparable to other soil invertebrate species, and the bioaccumulation of the phenanthrene increased with increasing exposure concentration, although steady-state was not achieved during the four-week exposure duration. The accumulation was biphasic in nature, likely a result of initial cuticular sorption processes, followed by the contribution of other processes (e.g., dietary uptake). The elimination of the phenanthrene was not complete, in that at the end of the elimination phase, tissue residues were similar to that observed in the initial gradual accumulation (e.g., by cuticular processes). However, the resultant bioaccumulation factors (BAFs) were relatively low, indicative of limited trophic transfer and biomagnification for this species. Following the development of an O. nitens assay, a further study was conducted to compare the sensitivity of O. nitens to other boreal soil invertebrate species, as well as to standard test species. Soil toxicity tests were designed, using field-collected reference and contaminated (petroleum hydrocarbon- and salt-impacted) soils, using an expanded suite of boreal species (plants: Pinus banksiana, Picea glauca, Picea mariana, Populus tremuloides, Calamagrostis canadensis and Solidago canadensis; earthworms: Dendrodrilus rubidus; and springtails: Folsomia nivalis and Proisotoma minuta). The sensitivity of the boreal species was then compared to that of currently published standard soil toxicity test species (agronomic plants: Elymus lanceolatus and Trifolium pratense; earthworms: Eisenia andrei; and springtails: Folsomia candida). Estimated species sensitivity distributions (ESSDs) were generated to determine whether the boreal and standard test battery of species exhibited differences in their overall sensitivity to the contaminated soil. With regards to the petroleum-hydrocarbon impacted soil, the suite of boreal species was more sensitive relative to the suite of standard test species; however, upon exposure to the salt-impacted soils, no differences in sensitivity were evident between the boreal and standard suite of test species. In both soils, the performance of O. nitens was similar to that observed by the collembolan species. The evaluation of boreal species and soils also took into consideration the use of distinct soil horizons. The layering of horizons was feasible from the initial collection to reassembly for testing in the laboratory, and plant growth was unaffected by this design. However, soil invertebrates demonstrated a preference or avoidance tendency for one horizon over another, and as a result, the assessment of individual horizons was recommended for all future testing. The compilation of research presented herein provides the basis for the standardization of ecologically-relevant test species and methods for the assessment of contaminated soils in boreal regions.

La compétition par interférence et ses effets sur la dynamique des populations suscitent un intérêt croissant. La température a aussi un fort effet sur la physiologie et les comportements individuels ainsi que sur les dynamiques des populations. Face au changement climatique, comprendre les interactions compétition-température-dynamique des populations est un enjeu majeur en biologie des populations. Les interactions entre individus sont liées à leur taille corporelle. La structure en taille de populations de deux clones du collembole Folsomia candida a été suivie pendant 2 à 4 ans à 4 températures. L'analyse des séries temporelles de leur structure à 21°C a révélé une dépendance de la dynamique aux conditions individuelles d¿accès à la ressource, liées aux plus grands individus. Nous avons modifié la structure de populations à 21°C et observé leur retour à l'équilibre, puis observé le comportement d'accès à la ressource. Cela a démontré le rôle des grands adultes dans la régulation des populations, en interférant avec les plus petits pour l'accès aux ressources. Grâce à un modèle de populations structurées intégrant l'interférence, nous avons montré que son intensité croissante cause : l'amortissement des cycles de générations, la survie de grands individus, des cycles induits par l'interférence. Nous avons enfin comparé les normes de réactions à la température sur des individus isolés et dans des populations afin de comprendre les interactions compétition-température dans la régulation des populations. Plusieurs niveaux de complexité permettent de comprendre l'effet des changements environnementaux sur les populations. / Interference competition and its effects on population dynamics are of growing interest. Temperature also plays an important role on the physiology and individual behavior as well as on population dynamics populations. In the context of climate change, understanding the effect of interactions between individuals on population dynamics and their interactions with temperature is an important issue for population biology. Interactions between individuals are related to their body size. The size structure of several populations of two clones of Collembola Folsomia candida was monitored for 2-4 years at four temperatures from 11 ° C to 26 ° C. The time series analysis of their structure at 21 ° C revealed a dependence of the dynamics on individual access to the resource related to the presence of large individuals. We then changed some population structures at 21 ° C and observed their return to equilibrium. We observed real-time access to the resource behavior. These studies have shown the role of large adults in population control by interfering with smaller individuals for access to resources. Through a structured model incorporating interference competition, we have shown that its intensity may have different effects on the dynamics of structured populations: damping single generation cycles, allowing the survival of large individuals, and causing interference induced cycles. Finally, we compared the reaction norms to temperature on isolated individuals and populations in order to understand the competition-temperature interactions in regulating populations. Several levels of complexity allow us to understand the effect of environmental change on populations

This thesis is presented as a collection of research papers synthesising knowledge gained during the period of candidacy. Its underlying focus is the examination of evolution from a variety of perspectives for terrestrial arthropods (springtails) in an Antarctic setting. These perspectives include investigation of the ways in which springtail populations respond both physiologically and genetically to environmental variability over historical and contemporary time-scales. While the physiological and genetic may seem two worlds apart, this thesis recognises that, in reality the two are inextricably linked. Thus, when genetic differentiation between populations of the same species can be demonstrated, physiological differentiation of these populations may also be predicted (and vice versa). Therefore, across several locations and springtail species, physiological and genetic parameters of individuals and populations are examined both separately and, where possible, in concert. The physiological aspect of this thesis focuses on the springtail Gomphiocephalus hodgsoni from continental Antarctica. In addition to providing the first metabolic rate data for a continental Antarctic springtail, seasonal variation in metabolic rates is examined across multiple temporal and spatial scales to evaluate the ways in which individuals and populations respond to environmental variability. Metabolic activity in this species is intricately linked to a variety of factors, both intrinsic and extrinsic. These include biological function, temperature profiles in the local microclimate, and body mass and genetic differences among populations. In the genetically-focused aspect of this thesis, population genetic patterns of G. hodgsoni from several continental locations and Cryptopygus antarcticus antarcticus from locations across the Antarctica Peninsula are compared. Here, the importance of differing evolutionary histories in influencing patterns of contemporary genetic population structure is highlighted. While both species have been similarly affected genetically by Pleistocene (2 Ma – present) glacial cycling, it is clear that differences in timing of colonisation events and subsequent population expansions have left distinct genetic signatures in each species. In a separate molecular study, phylogenetic analyses are employed to study members of the circum-Antarctic springtail family Isotomidae. Thesis Abstract The genetic ancestry among these closely related species is shown to reflect a diverse evolutionary origin in the Miocene (23 – 5 Ma), subsequent to which both vicariant and dispersal processes have been important. Phylogenetic re-constructions tease out the relationships among sister species, and the identification of several genetically distant lineages suggests that a revision of current species designations is required. Finally, two studies that integrate the physiological and molecular genetic are presented. First, metabolic rate variation across several locations on sub-Antarctic Marion Island in the springtail Cryptopygus antarcticus travei is examined. This variation is related to the genetic structure of populations to show that historical and contemporary environmental characteristics have left their trace in the expression of both genetic and physiological variability of these populations. Second, the perceived association between metabolic rate and genetic (mutation) rate is investigated more closely - a sophisticated Bayesian correlation analysis detects that there is an indirect relationship between metabolic rate and underlying species phylogeny in C. a. travei. Thus, the physiological and molecular genetic elements of this thesis test or advance important hypotheses within their own fields, and the integrated approach applied is a new step in interpreting evidence of physiological adaptation in Antarctic species. In its multi-faceted approach to evolutionary studies, this thesis enhances understanding of the current picture of springtail evolution in polar environments.

No description available.

Springtails (Collembola) are wingless arthropods that are impressively adapted to cutaneous respiration in temporarily rain-flooded habitats by non-wetting skin morphology. Recapitulating the robust and effectively liquid-repellent surface characteristics of springtail skin in engineered materials may offer exciting opportunities for demanding applications. Herein, we present a strategy for mimicking morphological surface features of springtail skin in polymer membranes produced by reverse imprint lithography. We report the fabrication of multi-level silicon masters that, in turn, serve as templates for the replication of flexible polymer membranes. We examined the robust wetting characteristics of polymer membranes by in situ plastron collapse tests and condensation tests. The mechanical stability of the polymer membranes was tested using a tribometer set-up and compared with needle-shaped pillar structures made from similar material. The fabricated membranes are flexible, free-standing, and adaptable to various substrate materials and shapes that allow for emerging applications.

Springtails (Collembola) are wingless arthropods that are impressively adapted to cutaneous respiration in temporarily rain-flooded habitats by non-wetting skin morphology. Recapitulating the robust and effectively liquid-repellent surface characteristics of springtail skin in engineered materials may offer exciting opportunities for demanding applications. Herein, we present a strategy for mimicking morphological surface features of springtail skin in polymer membranes produced by reverse imprint lithography. We report the fabrication of multi-level silicon masters that, in turn, serve as templates for the replication of flexible polymer membranes. We examined the robust wetting characteristics of polymer membranes by in situ plastron collapse tests and condensation tests. The mechanical stability of the polymer membranes was tested using a tribometer set-up and compared with needle-shaped pillar structures made from similar material. The fabricated membranes are flexible, free-standing, and adaptable to various substrate materials and shapes that allow for emerging applications.

Environmental pollution of heavy metals has become an increasing problem. Environmental risk assessments can be conducted to investigate and determine the potential risk of polluted terrestrial environments. Traditionally, risk assessments are based on total soil metal concentrations on a dry weight basis. Assessments based on total concentrations do not account for metal bioavailability. The bioavailable fraction of the metal is that available for metabolic uptake over a biological membrane, and it is largely controlled by the physiochemical characteristics of the soil solution. For soil-dwelling organisms the most important physiochemical parameters governing copper toxicity are pH and dissolved organic carbon. To incorporate these parameters into risk assessments mechanistic chemical equilibrium models can be used, such as biotic ligand models. These have previously been applied to mainly aquatic environments and only in recent years they have been expanded to the terrestrial realm. The overall aim of this thesis was to test the applicability of a leachate-based biotic ligand model, which takes pH dependency into account, for ecotoxicological risk assessment of soil-dwelling organisms. Toxicity data with associated soil solution pH for seven soil-dwelling organisms and microbially mediated soil processes were obtained from the Swedish Geotechnical Institute. Physiochemical soil characteristics of three Swedish field sampled soils amended with biochar were also obtained from the Swedish Geotechnical Institute. The toxicity data were used to derive two key parameters for calibration of the soil biotic ligand model through linear regression analysis i.e., the pH dependency and the species-specific intrinsic sensitivity. The calibrated biotic ligand models were applied to the field soils and species sensitivity distributions were derived for each soil to calculate hazardous metal concentrations. A simplified risk assessment of the soils was performed based on the results of the leachate-based biotic ligand models and on measured total concentrations on a dry weight basis.  As expected, the results of the regression analysis showed a strong pH dependency between toxicity effect concentrations and pH. For all included test organisms, the copper toxicity effect concentration decreased as the pH of the soil solution increased. Although Cu2+ toxicity increased with increasing pH, the considered organisms showed individual and varying pH-dependencies especially at pH 3-4 and pH 7-8. Further, the results showed that the risk assessment based on the Swedish EPA method, which use total metal concentrations on a dry weight basis, yielded different results than risk assessment based on the leachate-based biotic ligand models. The soils that had been amended with biochar contained lower total Cu concentrations on a dry weight basis compared to those which had not been amended. Consequently, total Cu concentrations exceeded the guideline value for sensitive land-use only in the non-amended soils. Total Cu concentrations exceeded the guideline value for less sensitive land-use in all field soils. Similar to total Cu concentrations on a dry weight basis, the total dissolved Cu concentrations also decreased with added biochar. The same trend could not be seen for Cu2+ in CaCl2 leachates. DOC in the leachates decreased with added biochar, suggesting that biochar sorbs DOC. A majority of the total dissolved Cu was bound to DOC and only a small fraction left as free ions.  The lower DOC concentrations led to higher Cu2+ concentrations in the leachate. Consequently, two of the biochar amended soils had Cu2+ concentrations exceeding the calculated HC50 (protection level for LSL). The predicted toxic effect concentrations ranged from 0.001 μg/L for the most sensitive organism Tomato shoot (L. esculentum) to 3.53 μg/L for the least sensitive organism Soil induced respiration (SIR). The most sensitive field soil had the highest measured pH and had been amended with 6% biochar, the two least sensitive field soils had the lowest measured pH and had been amended with 3 and 6% biochar respectively. The risk assessment based on the soil-BLM approach yielded different, but not less conservative, results compared to the traditional risk assessment based on total concentrations on a dry weight basis. The expected result was for the BLM-based risk assessment to be less conservative as it takes the site-specific bioavailability into account. The leachate-based soil-BLM seems to be sensitive to changes and variations of the input parameters in the speciation. To improve the robustness of the model, and accuracy of risk assessments, additional organisms should be included in the SSDs and speciation should be performed on soils with a wider range of pH. The potential of leachate-based BLMs for risk assessment has been demonstrated. The results invite to further v development of leachate-based soil-BLMs and has the potential to increase the knowledge of the chemistry and toxicology of copper in soils as well as the effects and behaviour of biochar as a metal sorbent.

No description available.