Cancer-associated fibroblasts (CAFs) are major components of the carcinoma microenvironment that promote tumor progression. However, the mechanisms by which CAFs regulate cancer cell migration are poorly understood. In this study, we show that fibronectin assembled by CAFs mediates CAF-cancer cell association and directional migration. Compared to normal fibroblasts (NFs), CAFs produce a fibronectin (Fn)-rich extracellular matrix (ECM) with anisotropic fiber orientation, which guides the cancer cells to migrate directionally. CAFs align the Fn matrix by increasing MyoII- and PDGFRa-mediated contractility and traction forces which are transduced to Fn through a5b1 integrin. We further show that prostate cancer cells use av integrin to migrate efficiently and directionally on CAF-derived matrices. We also demonstrate that aligned Fn is a prominent feature of invasion sites in human prostatic and pancreatic carcinoma samples. Collectively, we present a new mechanism by which CAFs organize the Fn matrix and promote directional cancer cell migration.

Legume species nodulate and grow successfully in the Core Cape Subregion, a Mediterranean-climate ecosystem with fynbos vegetation found on infertile soils. The physiological mechanisms enabling tolerance of low availability of phosphorus (P) are yet to be reported in Cape legume species such as Aspalathus linearis and Podalyria calyptrata; species that demonstrated traits typical of plants from nutrient poor soils. In the three research chapters of the thesis, it was anticipated that low P supply would limit plant growth and increase expression of traits for P acquisition.

Moult is an energetically demanding process for birds, and the replacement of flight feathers impacts flight performance. As a result, few birds overlap moult with other key activities such as breeding or migrating. Feather growth rates show little change in relation to body size, so large birds with long flight feathers take a long time to grow individual feathers, making their moult even more challenging. Unless these birds can afford to become flightless for several weeks while they replace all their flight feathers simultaneously, many large birds lack sufficient time to breed and replace all their wing feathers each year. As a result, they have evolved complex moult strategies that replace a subset of feathers each year. Albatrosses and giant petrels are prime examples of birds facing this challenge. This study focusses on Wandering Albatrosses (Diomedea exulans) and Northern Giant Petrels (Macronectes halli) breeding at Marion Island and Southern Giant Petrels (M. giganteus) at Gough Island. I explore primary and secondary moult patterns in Wandering Albatrosses and secondary and greater secondary coverts in giant petrels in relation to breeding activity. I used digital photography to record the wear patterns in the wings of Wandering Albatrosses and giant petrels. Using photographs of upperwings of marked individuals over time allowed the opportunity to track changes in the wear pattern among specific feathers, although scoring feather wear from images works better for darker feathers. The rate of wear among secondaries and their coverts differed across the wing, with the inner feathers wearing faster than the central feathers. Photographing the extended wings of albatrosses and petrels incubating eggs had no impact on hatching success. Using this method I was able to test the often held assumption that wing feather moult is largely symmetrical. In Wandering Albatrosses, moult symmetry was greatest in outer flight feathers, especially primaries. However, the pattern of increasing asymmetry towards the body was not consistent; inner primaries showed less symmetry than outer secondaries and inner secondaries were moulted with greater symmetry than central secondaries. Giant petrels preferentially replaced the inner and outer secondaries and the inner and outer greater secondary coverts, and feather symmetry was greatest in these feathers. All three species indicated some asymmetry in all feathers that had an incomplete annual 2 moult. Depending on the question being asked, I recommend scoring both wings when investigating moult patterns. Wandering Albatrosses typically take a sabbatical year following a successful breeding attempt, and thus failed breeders usually have less time to moult between successive breeding attempts. Following a successful breeding attempt, Wandering Albatrosses from Marion Island replaced a similar number of primary feathers on average (males 7.9 and females 7.3) as birds from the Crozet Islands (males 8.8 and females 8.1) and South Georgia (males 8.6 and females 7.1). Wandering Albatrosses that do not skip a year following a failed breeding attempt, not only replaced fewer feathers on average, but showed a difference in number of feathers replaced between sexes at Marion Island (males 7.4, females 6.1), as previously reported at the Crozet Islands (males 8.3, females 6.5) and South Georgia (males 7.2, females 5.2). These results suggest that females are under greatest pressure when a breeding attempt fails. Because females from South Georgia replace fewer feathers, especially following a failed breeding attempt, they might be under more stress than females from populations breeding at islands in the Indian Ocean (Marion and Crozet). This parallels the contrasting population trends in these regions, with numbers increasing over the last few decades in the Indian Ocean (Marion and Crozet Islands) but decreasing steadily at South Georgia. General Linear Models (GLMs) showed that sex and time available to moult both influenced the number and mass of flight feathers replaced. Sex explained more variation in terms of number of feathers replaced (67%) than time available to moult (33%), but time available to moult explained 68% of the mass of flight feathers replaced. However, there is large variation among birds in the number of primaries and secodaries replaced, independent of time available for moult. Together, sex and time available to moult accounted for only 9.2% (number) and 11.9% (mass) of the variance in feathers replaced. Giant petrels are one of the largest birds that undergo a complete primary moult each year without losing the ability to fly. They do this by overlapping their moult with breeding and by moulting several primaries at once. Being annual breeders, individuals that fail a breeding attempt have more time to moult than successful breeders, and therefore replaced more flight feathers. Northern Giant Petrels having a successful breeding 3 attempt replaced on average the same percentage of secondary and greater secondary coverts in both sexes; Following a successful breeding attempt Southern Giant Petrels (both sexes) replaced more feathers (secondaries and greater secondary coverts) than Northern Giant Petrels. I found that in a failed breeding attempt giant petrels have more time to moult and therefore replaced more secondary feathers than successful breeders. GLMs showed that breeding outcome was the only variable that influenced the mass of feathers replaced in Northern Giant Petrels, accounting for 14% of the variance in feathers replaced, while sex was the only variable in Southern Giant Petrels, accounting for 6% of variance. When both species were modelled together with sex and breeding attempt as explanatory variales, only breeding attempt was significant, accounting for 11% of the variance in the mass of secondaries and coverts replaced. In summary, the assumption that breeding activity, and thus the time between breeding attempts, influences the extent of moult in large birds with incomplete wing moults was supported for Wandering Albatrosses and Northern Giant Petrels. However, time available for moult explained only a small proportion of individual variation in moult extent in these species. Southern Giant Petrels replaced a similar mass of flight feathers, irrespective of breeding outcome. My results suggest that factors other than time between breeding attempts are important in determining the extent of wing moult. My study highlights the important tradeoffs large birds are required to make when balancing moult and reproduction. Annual monitoring of moult patterns in known individuals provides a valuable tool to better understand moult patterns in these large, long-lived birds.

Although there are many studies on mammalian bone histology, there are only a few that have examined the bone histology of artiodactyls, or focused specifically on osteohistological changes during ontogeny. The current study investigates the microanatomy and histology of giraffe limb bones through ontogeny. Mid-diaphyseal sections of humeri, radii, metacarpals, femora, and tibiae of 14 individuals representing individuals of known sex, as well as at different ontogenetic stages (foetal, juveniles, subadults, and adults). Thin sections were prepared for all the bones, and microanatomical (using Bone Profiler) and histological analyses were conducted on each of the sections. The study examined three main aspects, 1) Crosssectional shape changes in limb bones through ontogeny, 2) Histological changes through ontogeny in each of the limb bones, and 3) Histovariability among skeletons. The results of the study show that the foetus and juvenile individuals have round cross-sections, with small vacant medullary cavities, while cross sections of older individuals tend to be oval with variable amounts of cancellous bone surrounding the medullary cavity. The highest bone compactness values were obtained for the humerus and femur of the foetus, whereas the radius, metacarpal, and tibia bone compactness values are similar across the age classes. In terms of histology, this study found that the earlier ontogenetic stages had highly vascularised fibrolamellar bone in their cortices, which contrasts with that of the subadults and adults where more slowly deposited bone tissue occurs. These observations indicate that after rapid initial growth during early ontogeny, osteogenesis (and overall growth) slows down. This research also documents the fusion of the metacarpal III and IV, and the associated changes that occur in the histology. The study also highlights that the tibia is the only bone that has long radial vascular canals in the cortex. Overall the results of this study have provided a much better understanding of the bone histology of giraffes during ontogeny and has therefore filled an important gap in our knowledge of mammalian bone tissues. Furthermore, this study has direct implications for any future palaeohistological studies of fossil giraffids from Langebaanweg in South Africa.

The Core Cape Subregion (CCR) is made up of a mosaic of highly weathered and nutrient leached soil substrates in the Western Cape. Plant available phosphorus (P) in these soils is very low, generally ranging from 0.4-3.7 µg P g-1 soil and as a result plants have evolved a number of traits to enhance P-acquisition, such as increased root surface area (SA) and specific root length (SRL), cluster root and root hair proliferation and exudation of organic acids and acid phosphatases (APase) from the roots. Crop yield is limited worldwide due to the unavailability of P and P-fertilization is showing limited success due to soil retention. Sustainable management of this would include exploiting plants with natural adaptations for enhanced P acquisition and utilization. The aim of this study was to discover whether cluster root forming species are more efficient at P acquisition than non-cluster root species. This was achieved by focusing on two objectives: (1) to characterize root traits for increased P acquisition in different soils of the CCR and (2) comparing P-uptake and utilization efficiencies of cluster root species to non-cluster root species under glasshouse and natural conditions. Plants from Fabaceae, Polygalaceae, Proteaceae, Cyperaceae, and Juncaceae were grown in two different glasshouse experiments and observed in a field study.

The common hippopotamus (Hippopotamus amphibius) is endemic to Africa but threatened by range restriction, exploitation and competition with humans and domestic livestock for access to critical resources such as fresh water and grazing. Collectively these impacts have resulted in population declines throughout most of their range with the consequence that hippos are classified as Vulnerable on the IUCN Red list. Despite these threats to their persistence and their important ecological role as ecosystem engineers there have been surprisingly few studies concerning factors that influence their current distribution and habitat use. Such research is important for developing effective conservation and management plans to improve the protection of vulnerable and ecologically important species such as hippo. South Africa is home to one of a few growing hippo populations and one of the last persisting in an estuarine habitat. The St Lucia Estuary, one of three Ramsar Wetlands of International Importance located in the iSimangaliso Wetland Park (itself a UNESCO World Heritage site), in northern KwaZulu-Natal is not only the largest estuarine system in Africa, but is also home to one of South Africa's largest hippo populations. In this study I explore aspects of the spatial and behavioural ecology of hippo within the St Lucia Estuary. More specifically, I investigate select abiotic and biotic predictors of hippo presence and the frequency with which they return to their diurnal lie-up sites. I used binary logistic regression models to evaluate the effects of the selected habitat features on hippo occurrence at two spatial scales (broad and fine). I used a negative binomial with log-link model to evaluate the effects of the selected habitat features on the frequency of use of sites (hippo persistence) in the fine-scale study. In addition, I employed both instantaneous scan sampling and continuous sampling methods in an attempt to determine the diurnal activity budgets and social interactions of a single group near the mouth of the St Lucia Estuary. I used non-parametric tests to evaluate differences in behaviour with daytime and across sampling days with a view to an improved understanding of how the environment influences the behaviour of hippo in an environment subject to ongoing human modification.

The dicynodonts are an extinct group of herbivorous non-mammalian synapsids that were fairly abundant in Gondwanan deposits of the middle Permian to the Early Triassic periods. The extinct genus Endothiodon was first described by Sir Richard Owen in 1876, and is well known from the late Permian deposits of the Karoo Basin of South Africa. It is characterized by rows of internal teeth on the premaxilla and dentary arranged in replacement waves called Zahnreihen; longitudinal ridges running from the premaxilla to the pineal crest; and a prominent pineal boss with a pineal foramen. Endothiodon is well-represented by cranial and postcranial material in the Karoo vertebrate collections at various museums in South Africa. The repeated taxonomic revision of this genus over the years has led to much confusion about what constitutes the type species, E. bathystoma. Recently, an almost complete skeleton of Endothiodon (SAM-PK-K011271) was recovered from the uppermost Pristerognathus Assemblage Zone of the Karoo Supergroup. The fossil comprises the skull and most of its postcranial elements preserved in articulation. The current study provides a comprehensive description of the anatomy of this specimen, which permitted its identification as E. bathystoma. Furthermore, by comparison with other South African Endothiodon specimens this study determined that this specimen is the second largest E. bathystoma specimen known to date. The well-preserved skull and postcranial skeleton of SAM-PK-K011271 makes it an ideal reference specimen for E. bathystoma and has permitted a good assessment of its overall anatomy. The findings of this study provide a perfect stepping-stone for future studies to further address E. bathystoma’s skeletal reconstruction and biomechanical functions, as well as other aspects of the palaeobiology of this animal.

Insects, including wild bees (Hymenoptera: Anthophila) are exceptional model organisms to assess the effect of climate variation on species richness along altitudinal gradients. Climate variables and weather conditions are of extreme importance for insects particularly since their capacity of body temperature regulation is determined by the ambient temperature. Additionally, bee diversity has proven to be strongly related to the availability of host plants, determinant factors for their presence or absence and both of which are limited at higher altitudes. Therefore, the study of wild bee diversity at various altitudes in the tropics could provide information on possible responses of bee species and communities to climate variations, important to estimate effects of climate change on an important ecosystem service such as pollination. Bees being ecologically important insects with close links to plants, high richness and abundance are well-suited as terrestrial habitat bioindicators. The group is sensitive to environmental disturbances relies upon local plant communities and comprises an assemblage of species with varying social structure, nesting guilds and other life history traits. Additionally, bees are likely more susceptible to negative effects of small effective population size. The life history traits determine the individual and community response to environmental changes. Records from the literature revealed a collector and seasonal bias, with greater effort applied around big cities or specific collecting locations and mainly in the wet season. A preliminary checklist of bees of Angola was created and comprises 209 bee species from 47 genera and five families, but a major proportion of the country's area remains to be surveyed. A national inventory of Angolan bees is proposed, making use of standardized methods and sampling either one quarter degree cell or half degree cells, ideally in both dry and rainy seasons. Wild bee communities were sampled along an altitudinal gradient (760-1651 m.a.s.l) in the biodiversity rich and critically endangered Angolan escarpment. Pan traps, malaise traps and sweep netting were used at twelve sampling points, with an average of 70 m difference in altitude between points. Sweep netting proved to be the most efficient technique. Overall, 845 individuals were collected, representing 51 identified species, 34 genera and five bee families. Contrary to the trends observed in other studies in the tropics, a consistent increase in bee diversity (carried out at genera level) with increasing altitude, from the lower altitude (H'=2,14) to the higher altitude of the gradient (H'=2,26) was found. In addition, community structure differed along the gradient, with distinctive communities in low elevation sites being dominated by Braunsapis, Ceratina, Hypotrigona and Anthidiellum, and high elevation sites the distinctive communities were dominated by Amegilla, Macrogalea, Patellapis and Xylocopa. This result might be consistent with findings from studies of other taxa that attribute to the Angolan escarpment an importance as a centre of endemism and speciation. The results from this study are possibly explained by a combination of factors where the exceptional geomorphology and landscape shape the (direct) influence of environmental variables such as temperature and precipitation on the vegetation communities along the gradient therefore (indirectly) affecting bee community assemblages, particularly for the more specialized bee genera and species. Limited research has been done on the variation of bee body size along altitudinal gradients, but the few studies that have been carried out indicate that future changes (warming) in climatic conditions will most probably alter bees body size (by reduction), consequently affecting their thermoregulatory capacity and, at a larger scale, the overall patterns of community assembly. Along the tropical altitudinal gradient of this study, bee body size was found to increase with altitude by 58% (mean length at lower altitude = 5.06mm against mean = 7.99mm at higher altitude elevation sites) at the community level but also at the intra-specific level, with Macrogalea candida increasing 4% in size between the lower altitude and summit of the transect (mean length at lower altitude = 8.76mm against mean = 9.12mm at higher altitude elevation sites), suggesting that the fairly small temperature gradient along the transect was sufficient to select for body size – either directly, but more likely through multiple avenues, including indirect effects such as changes in rainfall, plant community composition and plant phenology. This result constitutes, to my best knowledge, the first demonstration of Bergmann's rule applicability at different levels of biotic organization of bee communities in the tropical region. Effective conservation planning is highly dependent on robust, spatially explicit biodiversity data. The generation of comprehensive insect profiles through long term monitoring studies at the national level can identify areas with high species turnover and endemism – patterns that could be missed if only vertebrate data were considered. In under-developed countries like Angola, where a poorly documented but highly rich biodiversity is severely threatened by unregulated land use, and research is hampered by financial constraints and lack of human resources, the combined use of indicator taxa for both terrestrial (bees) and freshwater (Odonata) environments might be a reasonable surrogate for total biodiversity status assessments. The results from this study highlight the need for long term monitoring to efficiently assess bee diversity, especially in critically endangered landscapes where anthropogenic pressures are high.

Includes abstract. / Includes bibliographical references. / Yellowtail, Seriola lalandi, is an important line-caught fish in South African waters, yet little information is available on their life-history. This study aims to add information on the diet and feeding habits, reproductive biology and the age and growth of yellowtail in South Africa. The diet of 62 yellowtail caught in the Western Cape of South Africa between 2011 and 2012 was investigated. Fish sampled by line and speargun ranged from 488 to 916 mm fork length (FL). Prey items were removed from stomachs, sorted, counted and weighed in order to calculate the percentage number (% N), percentage weight (% W), frequency of occurrence (% F) and index of relative importance (% IRI). Of the 62 stomachs examined 11 (17.7 %) were empty, 16 (26.0 %) contained only unidentifiable remains and 47 (82.5 %) contained identifiable remains. Prey items covered 18 species belonging to five classes: bony fishes, crustaceans, cephalopods, polychaetes and bivalves. Small pelagic fish were the dominant prey type, followed by crustaceans. The remaining taxa were of negligible importance. Some dietary differences were observed between sample areas. Most notable was the increased importance of crustaceans at Dassen Island on the West Coast compared to the sites at Robben Island, False Bay and Struisbaai. The reproductive characteristics of yellowtail were documented from fish collected from 1974 to 2012. Samples were collected from Cape Infanta on the South Coast to Lamberts Bay on the West Coast of South Africa. Histological validation of macroscopic staging criteria revealed that active and developing ovaries are commonly staged incorrectly. A protracted spawning season from November to February with peak spawning in December and January was deduced from GSI values. No hydrated eggs were observed. Females matured at 550 mm FL (95 % CI = 532 - 570 mm) and males matured at 585 mm FL (95 % CI = 555 - 619 mm). The age and growth characteristics of yellowtail in South African waters were determined from readings of whole sagittal otoliths collected from 1974 to 2012. Whole otoliths were considerably easier to read than sectioned otoliths. A total of 524 whole otoliths were taken from fish ranging from 430 to 1080 mm FL, of which 141 (27 %) were discarded and 384 (73%) were readable. Agreement between all three readers was 13 % (n = 50) and between any two was 71 % (n = 274). Maximum ages for male and female yellowtail were 7 and 8 years respectively. Age at 50 % maturity (A50) for males it was 2.3 years while females matured (A50) at 3.6 years. Von Bertalanffy growth parameters did not differ between males and females (P > 0.05). A statistical penalty was used to keep the estimated growth parameters within biological limits and produced a von Bertalanffy growth equation with an L∞ and K of1064 mm and 0.17 y-1 respectively. The growth performance index (φ) of yellowtail in South African waters was found to be 3.51. This is high for the family Carangidae but on par with other species in the genus Seriola. The life history characteristics for yellowtail in South African waters closely resemble those of other yellowtail populations. The diet of yellowtail in South African waters represents that of a robust generalist feeder that is not reliant on specific prey for its survival. The age, growth and reproductive characteristics of yellowtail in South African waters indicate that they are a fast growing and relatively early maturing species. These life-history characteristics indicate that the stock is resilient in relation to other line-fish species, but the large proportion (41%) of fish caught below the 50 % size at maturity suggests that a revision of the minimum size limit should be considered.

For several decades Vachellia and Senegalia have been assumed to be ecological equivalents in African savannas. Their supposedly close evolutionary relationship has, however, been totally revised in light of recent molecular phylogenetic data. These data highlight the deep divergence (± 30 Ma) between these genera and also their independent transitions into African savannas. Distant divergence and independent transitions into savannas between Vachellia and Senegalia suggest their possible ecological niche divergence, which could explain the observed differences in invasiveness between them. This thesis provides the first ecophylogenetic study to assess the level of ecological niche divergence between these economically, socioeconomically and ecologically important tree genera in Africa. I address this question by first determining the scale(s) of coexistence between Vachellia and Senegalia and determine their phylogenetic community structure at both the landscape-regional scale and the plot-scale. I then conduct a large glasshouse experiment using seven species from each genus to determine conserved functional differences between them during seedling establishment in the presence, and also the absence, of grass competition. While I find evidence of some Grinnellian niche differentiation between Vachellia and Senegalia at the landscape-regional scale, their greater-than-expected co-occurrence in plots suggests they generally partition an Eltonian niche in savannas. Glasshouse trait data also reveal that Vachellia has a conserved strategy for rapid vertical growth when free from grass competition and Senegalia has a conserved root tissue density response to grass competition. I argue that the rapid growth (bolting) strategy of Vachellia in the absence of grass competition provides a functional explanation for why this genus is observed to be relatively more invasive in grassy ecosystems. I also argue that the root tissue density response of Senegalia enables stable coexistence at the plot scale with Vachellia as it increases competitive ability among grasses leaving establishment less tied to times of low grass biomass. I conclude that this study provides overwhelming support for ecological niche divergence between Vachellia and Senegalia and that this divergence may underpin their observed differences in invasiveness. That the coexistence of these genera is largely attributable to Eltonian niche partitioning also provides fresh support for the contention that tree-tree competition structures tree communities in African savannas. Finally, niche divergence suggests that, when promoting diversity and managing invasion, Vachellia and Senegalia species will require different management practices.