The question of group-living in animals has attracted a lot of research attention. Today, we have a nuanced understanding of ultimate explanations and proximate mechanisms for group-living, as well as the genetic basis for seemingly puzzling aspects of sociality such as altruism. However, our current view of sociality has been obtained almost entirely in an intraspecific context, i.e. based on groups consisting of individuals of a single species. On the other hand, heterospecific sociality, i.e. groups formed by individuals of multiple species, has been largely ignored in group-living theory and empirical research. This is despite the fact that heterospecific sociality is widely prevalent in nature and is known to occur in many different contexts, in a variety of taxa and in both marine and terrestrial habitats. My dissertation focuses on one of the best-known examples of heterospecific sociality, namely heterospecific foraging associations of terrestrial insectivorous birds (commonly called mixed-species flocks; flocks hereon). Flocks are found all over the world, in a variety of habitats, and include a unique suite of species in each area. Although flocks are the best-studied among different types of heterospecific associations known, most of the research has been descriptive. In other words, while we have descriptions of the richness, size and composition of flocks from many areas, we know little about why and how flocks form. Therefore, one broad objective of this dissertation was to better understand the causes of flock formation. Birds are thought to join flocks either to obtain direct foraging benefits or better protection from predators. I used different approaches to understand which of these two reasons is likely to be more important. Additionally, to situate heterospecific sociality within sociality in general, I also examined whether the mechanisms underlying flocks are similar to single-species groups or unique to a mixed-species condition. In other words, are flocks a different route to obtain the same benefits as single-species groups, or a route to obtain benefits that conspecifics cannot provide? In the previous section, I described why understanding flocks is important from the point of view of sociality. Flocks are also important for the consequences they might have on community organization. While each flock is a collection of interacting individuals of different species, populations of species are linked in a network of interactions across multiple flocks in an area. The theoretical framework guiding our understanding of community organization is currently dominated by the idea of interspecific competition. Mutualisms or positive interactions, if any, are only expected to occur between members of different trophic levels. Only recently has the need to incorporate positive interactions between members of the same trophic level into ecological theory been emphasized. Flocks and other heterospecific associations present an important example of within-trophic level positive interactions. Therefore, the second broad objective of this dissertation was to examine the consequences of flock formation on community organization. The objectives described above were addressed using multiple approaches in this dissertation. “Why” questions in ecology and evolution are generally tackled using manipulative experiments. Given that experiments are neither feasible nor ethical in the case of multispecies flocks in the wild, I addressed the “why” question by focusing on “who” instead. To understand “why” flocks form, I examined what kinds of species participate in flocks, who associates with whom, and who provides and who receives the benefits. This dissertation uses a combination of methods and data, including questions addressed at a global scale using descriptive information on flocks available from across the world. For other questions that were based on entirely new approaches developed in this dissertation, data were collected in a field site in the Western Ghats. In general, given the two broad objectives of this dissertation, the approaches I used were drawn from both behavioural and community ecology. The dissertation is organized in the following way: Chapter 1: General Introduction The first chapter provides the background to the two broad objectives of this thesis, namely understanding the causes and consequences of heterospecific foraging associations in terrestrial bird communities. Chapter 2 (published in The American Naturalist) Based on a global dataset (55 presence-absence matrices from 24 locations in multiple continents) on the composition of flocks, I asked if flocks largely consist of ecologically similar or dissimilar species. Using null models and randomization tests followed by meta-analysis, I found that the association strength of species in flocks was strongly related to similarity in body size and foraging behaviour, and higher for congeneric compared with non-congeneric species pairs. In other words, flocks seem to consist largely of similar species. Extending group-living and social information use theory to a heterospecific context, I discuss potential behavioral mechanisms leading to positive interactions among similar species in flocks as well as ways in which competition costs are reduced. These findings highlight the need to consider positive interactions along with competition when seeking to explain community organisation. Chapter 3 (published in Animal Behaviour) Two kinds of participants are recognized in flocks: those that join other species (‘followers’) and are therefore likely to be the recipients of the benefits of flock participation and those that are joined (‘leaders’). Through comparative analyses, using a large sample of flocks from around the world, I found (1) ‘followers’ tend to be smaller, more insectivorous, and feed in higher strata than matched species that participate in flocks to a lesser extent and (2) ‘leaders’ tend to be cooperative breeders (which are known to have well-developed anti-predatory systems) more often than matched species that are not known to lead flocks. Furthermore, meta-analyses of published results from across the world showed that bird species in terrestrial mixed-species flocks increased foraging rates and reduced vigilance compared to when they were solitary or in conspecific groups. Moreover, the increase in foraging rates was seen only in the case of flock followers and not flock leaders. These findings suggest a role for predation in the evolution of mixed-species flocking. Species that are vulnerable to predation follow species whose vigilance they can exploit. By doing so, they are able to reduce their own vigilance and forage at higher rates. Chapter 4 (to be submitted to Behavioural Ecology and Sociobiology) In this study, conducted in a tropical evergreen forest in the Western Ghats of India, I used intraflock association patterns to generate a community-wide assessment of benefits of flock participation for different species. I assumed that individuals needed to be physically proximate to particular heterospecific individuals within flocks to obtain any direct foraging benefit (flushed prey, kleptoparasitism, copying foraging locations). Alternatively, for all anti-predation benefits, physical proximity to particular heterospecifics is not required, i.e. just being in the flock vicinity will suffice. Therefore, I used the choice of locations within flocks to infer whether individual species are obtaining direct foraging or antipredation benefits. A small subset of the bird community (5/29 species), composed of all members of the sallying guild, showed non-random physical proximity to heterospecifics within flocks. All preferred associates were from non-sallying guilds, suggesting that the sallying species were likely obtaining direct foraging benefits, either in the form of flushed or snatched prey. The majority of species (24/29) chose locations randomly with respect to heterospecifics within flocks, and thus were likely obtaining anti-predation benefits. In summary, my study indicates that direct foraging benefits are important for only a small proportion of species in flocks and therefore that predation is likely to be the main driver of flocking. Chapter 5 (to be submitted to Oecologia) Two types of species – intraspecifically gregarious and sallying species – are thought to play important roles in flocks because studies have shown they attract other flock participants. However, it is not clear why these types of species are attractive, i.e. are they cues for flocks or do they directly provide benefits to other species? It is also not known whether these types are essential for flock formation. In this study, in a tropical evergreen forest in the Western Ghats of India, I used a novel approach to address these questions. Flocks contain anywhere between two and tens of species. My approach focused on the simplest, i.e. two-species, flocks. In two-species flocks, attraction between species must be based on direct benefit to at least one of the species. Therefore, only species combinations that result in benefit to at least one species will occur as two species flocks. Further, by examining leading and following behaviour in these combinations, I could also determine the direction of benefit-flow. Finally, given that all flocks pass through a two-species step, examining which two-species combinations are joined by other species helped understand species roles in flock formation. I found that intraspecifically gregarious species, but not sallying species, were disproportionately represented in two-species flocks, always provided the benefits when present, and that flocks containing them were joined significantly more often. Therefore, intraspecifically gregarious species, but not sallying species, play a role in providing flock benefits and flock formation. Moreover, given that most (7/8) intraspecifically gregarious species in my study site played these roles, the intraspecifically gregarious species guild can be considered an example of a within-trophic level “keystone”. Chapter 6 (“in press” in Oikos) There is a growing recognition of the need to integrate non-trophic interactions into ecological networks for a better understanding of whole-community organization. To achieve this, the first step is to build networks of individual non-trophic interactions. In this study, I analyzed the network of interdependencies among bird species that participated in flocks in an evergreen forest site in the Western Ghats, India. I found that flock networks contain a small core of highly important species that other species are strongly dependent on, a pattern seen in many other biological networks. Further, I found that structural importance of species in the network was strongly correlated to functional importance of species at the individual flock level. Finally, comparisons with flock networks from other Asian forests showed that the same taxonomic groups were important in general, suggesting that species importance was an intrinsic trait and not dependent on local ecological conditions. Hence, given a list of species in an area, it may be possible to predict which ones are likely to be important. Chapter 7: Conclusions In this section, I provide a summary of the main findings of this dissertation, discuss the main conclusions with regard to each of the two broad objectives and finally suggest future lines of investigation to further understand the causes and consequences of flock formation and heterospecific sociality in general. In summary, the work presented in this dissertation provides a picture of how and why flocks form and their likely consequences for community organization. The main driver of flock formation seems to be protection from predators, although a few species do obtain direct foraging benefits. Additionally, given that I found flocks to largely be groupings of similar species, the mechanisms through which benefits are obtained are likely to be similar to those in single-species groups. In other words, flocks are possibly a way for species that are unable to group with conspecifics, to obtain group-living benefits. My finding, that flocks largely consisted of similar species, also questions the stereotyping of interactions between similar species in communities as competitive. Other results from this study demonstrate the importance of intraspecifically gregarious species in flocks. Such species are the main providers of benefits to other flock participants and seem essential for flock formation. Finally, network analysis showed that a small core of species, mainly including species known to provide benefits at the individual flock level, are disproportionately important in the emergent community-level network of interdependencies. Such species are possibly one of the first examples of within-trophic level “keystones” discovered. Apart from the findings, this study also provides a set of new approaches and analytical frameworks that can be used to examine other multispecies foraging groups and heterospecific foraging associations in other contexts.

Landscape change and biodiversity decline is a global problem and has sparked world-wide initiatives promoting biological conservation techniques such as reintroductions, protected area networks, and both preservation and restoration of landscape connectivity. Despite the increasing abundance of such working landscapes (i.e. “human-modified” landscapes), we know relatively little about their ecological mechanics; these landscapes can be vast, encompassing areas too large to obtain high resolution ecological data to test ecological process. To investigate the ecological mechanics of working landscapes, I use a small, tractable, landscape mesocosm situated in east-central Alberta, Canada, The Cooking Lake Moraine (a.k.a. the Beaver Hills Biosphere). The chapters within this dissertation quantify biodiversity across a hierarchy of measurements (from genes to communities) and investigate consistencies in ecological processes generating patterns in these biodiversity measurements across spatial scales. As a result, I investigate both a depth, and breadth, of spatial ecological processes underlying the efficacy of biodiversity conservation techniques in heterogeneous working landscapes. In Chapter I, I explore between-landscape functional connectivity by investigating the genetic contribution of reintroduced individuals to an ostensibly successfully reintroduced population within the mesocosm. I find that contemporary animals are the result of recolonization from adjacent sources rather than putative reintroduction founding individuals, indicating greater mesocosm functional connectivity to adjacent landscapes than previously thought. In Chapter II, I probe within-landscape functional connectivity by quantifying the contribution of protected areas, natural, and anthropogenic landscape features to animal movement across the mesocosm. I find that natural features had the largest effect on animal movements, despite the presence of protected areas. Chapter III investigates protected area network efficacy on biodiversity conservation by quantifying the contribution of protected areas, natural, and anthropogenic landscape features to mammalian functional diversity across multiple spatial scales within the mesocosm. I find that protected areas rarely predict functional diversity across spatial scales; instead natural features positively predict functional diversity at small spatial scales while anthropogenic features are negatively associated with biodiversity at large spatial scales. Finally, Chapter IV ties the previous three chapters together by testing implicit assumptions of the species occurrence data collected in each. I compare GPS collar data (Chapter II) to species occurrence data collected on wildlife cameras (Chapter III) to demonstrate that the magnitude of animal movements better predict species occurrence than the commonly assumed proximity of animal space use. Across chapters, two central themes emerge from this dissertation. First, the importance of natural features at small spatial scales, and anthropogenic features at large spatial scales, within the landscape matrix is predominant in predicting multiple measures of biodiversity. And second, we cannot assume predictable efficacy of conservation strategies or even the ecological process inferred from the data collected to test these strategies. / Graduate

Invasive species are becoming more common as human interactions within coastal waters and the aquarium trade continues to increase. The establishment of the invasive lionfish complex Pterois volitans and P. miles from the Indo-Pacific to the Western Atlantic, Gulf of Mexico, and the Caribbean Sea has had significant negative effects on reef fish biodiversity and economically important species. Their rapid colonization and success has been attributed to their biological and ecological life history traits as well as their absence of predation. Past research has highlighted these characteristics; however, there is a knowledge gap in lionfish parasitism. This research explored the enemy release hypothesis as a key success factor in rapid establishment in the invaded range on a biogeographical scale. The diversity of lionfish parasitism was compared among 15 geographically diverse sites within the invaded range, incorporating the time of introduction at each site. Eight new parasites are described for the first time in the invasive lionfish: (1) a Cymothoid isopod: Rocinela stignata, (2) four nematodes: Raphidascais sp., Contraceacum sp., Paracuria adunca and Hysterothylaceum sp., (3) one digenean: Tergestia sp., (4) two acanthacephalans: Serracentis sp. and Dollfusentis sp., and (5) two cestodes: Nybelinia sp. and Tentacularia sp. Lionfish from the east coast of Florida exhibited the highest abundance in parasite fauna while other invaded areas yielded low abundance and diversity. Comparisons between lionfish parasitism from the past native range studies and the invaded range suggest that vectors of time, life history traits, and trophic interactions structure the lionfish parasite community. Lionfish in the Western Atlantic and Caribbean were found to be host for generalists parasite species within the coastal ecosystem. Consequently, lionfish have relatively low parasite abundance, supporting the enemy release hypothesis and its direct relation to their invasion success.

Identifying the diversity of contexts that can lead to hybridization is important for understanding its prevalence and dynamics in natural populations. Despite the potential of ecological succession to dramatically alter species co-occurrence and abundances, it is unknown whether it directly promotes hybridization and, if so, has long-lasting consequences. Here, we summarize 30 years of survey data across 10 populations to show that in western and mountain bluebirds, heterospecific pairing occurs during repeatable and transient colonization events at the early stages of species turnover. Despite mixed pairing occurring only during early succession, genetic data showed presence of hybrids at both early and late successional stages. Moreover, hybrids showed novel patterns of variation in morphology and behavior, emphasizing that even ephemeral contexts for hybridization can have important evolutionary consequences. Our results suggest that because ecological succession often brings together closely related competitors in disparate numbers but lasts for only a brief period of time, it may be a widespread but underappreciated context for hybridization.

The thesis focuses on segmentation of images with leaves of woody species. The aim was to investigate existing image segmentation methods, choose suitable method for given data and implement it. The chosen method should segment existing datasets, photographs from cameras as well as photographs from lower-quality mobile phones. Inputs are scanned leaves and photographs of various quality. The thesis summarizes the general methods of image segmentation and describes own algorithm that gives us the best results. Based on the histogram, the algorithm decides whether the input is of sufficient quality and can be segmented by Otsu algorithm or is not and should be segmented using GrowCut algorithm. Next, the image is improved by morphological closing and holes filling. Finally, only the largest object is left. Results are illustrated using generated output images. Powered by TCPDF (www.tcpdf.org)

Kyoto University (京都大学) / 0048 / 新制・課程博士 / 博士(工学) / 甲第15728号 / 工博第3342号 / 新制||工||1505(附属図書館) / 28273 / 京都大学大学院工学研究科合成・生物化学専攻 / (主査)教授 森 泰生, 教授 濵地 格, 教授 跡見 晴幸 / 学位規則第4条第1項該当

The simultaneous increase in biological invasions and habitat alteration through the building of coastal infrastructure is playing an important role in reshaping the composition and functioning of nearshore marine ecosystems. This thesis examined patterns of marine invasions across anthropogenic and natural habitats and explored some of the processes that influence establishment and spread of invaders. The goals of this thesis were four-fold. First, I examined the habitat distribution of marine nonindigenous species (NIS) spanning several taxonomic groups and geographical regions. Second, I conducted systematic subtidal surveys in anthropogenic and natural habitats and investigated the distribution of nonindigenous ascidians on Southern Vancouver Island, British Columbia, Canada. Third, I tested methods for in-situ larval inoculations and utilized these techniques to manipulate propagule supply and assess post-settlement mortality of ascidians across habitat types. Fourth, I investigated the role of biotic resistance, through predation by native species, on the survival of ascidian colonies in anthropogenic and natural habitats. Results from this research showed that anthropogenic habitats are hubs for marine invasions and may provide beachheads for the infiltration of nearby natural sites. Specifically, a literature review of global scope showed that most NIS are associated with anthropogenic habitats, but this pattern varied by taxonomic group. Most algal and mobile invertebrate NIS were reported from natural habitats, while most sessile NIS were reported from artificial structures. Subtidal field surveys across both anthropogenic and natural habitats showed that nonindigenous ascidians were restricted largely to artificial structures on Southern Vancouver Island and that this pattern is consistent across their global introduced ranges. Field manipulations using the ascidian Botrylloides violaceus as a model organism, showed that post-settlement mortality is high and that large numbers of larvae or frequent introduction events may be needed for successful initial invasion and successful infiltration of natural habitats. Experiments also showed that predation by native species can limit the survival of B. violaceus in anthropogenic and natural habitats. This dissertation contributes knowledge about the patterns and processes associated with habitat invisibility; provides insight into factors affecting colonization; and supplies valuable information for predicting and managing invasions. / Graduate / 0329

Aspects of the ecology of B. monticularis were studied with a view to the species' conservation. This investigation indicates that the present distribution is half that of the past distribution and that only one third of the original habitat remains uncultivated. It is estimated that this area could, theoretically, support 1435 rabbits. The shrubs, Pteronia erythrocaetha and Kochia pubescens constitute the bulk of the species' diet; grasses are included in the diet whenever rainfall gives rise to new growth. Spatial use, social structure and activity pattern conform to the general leporid pattern of polygamy, solitary living and nocturnality. The breeding season extends from August to May and litters of one, possibly two, altricial young are produced after a gestation of 35-36 days. / Dissertation (MSc)--University of Pretoria, 1989. / gm2013 / Zoology and Entomology / Unrestricted

Mating systems are classifications of the outcome of individual strategies aimed at maximising reproductive success. These systems have two components; one describes how individuals socially relate and bond to mating partners and the other describes the genetic outcome of actual mating activities. Reproductive activity is under strong endocrine and behavioural regulation where inter-sexual discrepancies in the regulation of reproductive success have resulted in the majority of mammal species exhibiting polygynous mating systems, with only 5% of mammals being socially monogamous. However, in monogamous species there can be a discrepancy between social pair bonds and sexual mating activities. Aardwolves are extreme diet specialists ii on a temporally fluctuating resource, Trinervertermes spp. A number of studies have described them as socially monogamous but at the same time observed a high frequency of extra pair copulations (EPCs). A recent study also linked sex variation in den use to polygamous mating. However, it is unclear to what extent these EPC's contribute to individual fitness, and how these contrasting mating strategies influence space use and reproductive physiology. The aim of this project was to determine if there was seasonality in reproductive activity and to test if endocrine physiology, home range size and space use were similar between males and females as predicted for a socially monogamous species. We assessed reproductive endocrinology in zoo-housed aardwolves and quantified if physiological and behavioural data in wild aardwolves relate more to predictions based on social monogamy or polygamy. We found physiological support for previous behavioural observations of reproductive seasonality in both zoo-housed and wild aardwolves. We suggest that the seasonal breeding strategy in aardwolves is as a direct consequence of their strong dietary preference on a temporally fluctuating resource, where it is important for aardwolves to time periods of high physiological investment in reproduction with high seasonal abundance of these termites. Our data on zoo-housed aardwolves also showed that the social environment appeared to modify physiological responses to variation in environmental conditions. We suggest that due to strict seasonal breeding in wild aardwolves females are time constrained in receptivity which, combined with their largely solitary behaviour, implies that males have to be dynamic in the onset of their reproductive activity to closely match that of locally receptive females. Therefore, it may be adaptive for aardwolves to retain social receptivity even if resource distributions cause these animals to forage alone. We also found that physiological and behavioural traits correspond better to predictions based on social monogamy than polygamous mating in a population of wild aardwolves. However, earlier studies in the same population found that behavioural traits were more related to predictions based on polygamous mating. Therefore, our data and other studies show how a difference between traits can relate to either social monogamy or polygamous mating in wild aardwolves in the same study area. We suggest that social mating system components regulate the observed endocrine and behavioural parameters more than actual mating patterns, which implies that social components pose a stronger selective pressure on physiology and behaviour than sexual mating patterns. Overall, we conclude that due to the discrepancy in traits that correspond to predictions based on different mating systems, aardwolves do not fit discreetly into any current mating system classification. We suggest that the evolutionary causes for the potentially conflicting mating strategies as well as the fitness benefits of these strategies need to be further investigated. / Dissertation (MSc)--University of Pretoria, 2013. / gm2013 / Zoology and Entomology / unrestricted

During the past decade there has been an explosion in the probiotic industry due to an increase in concern for health. It is well known that these probiotic products offer consumers numerous health benefits and that viability of cultures in these products need to be maintained at high levels. It is therefore important to test for antimicrobial compounds or substances that may come into contact with probiotics and thereby negatively affect and decrease their viability. Garlic (Allium sativum) has been used as a natural medicinal remedy for thousands of years and research has shown that it has antimicrobial activity against a wide variety of microorganisms. Although it has been tested against numerous pathogenic microorganisms, there have been few studies on its effect on beneficial bacteria, specifically probiotic Bifidobacterium species. A great amount of work and money is put into preparing probiotic products with sufficient numbers of viable bacterial cells. All these are devoted to ensure that the consumers seize the optimal purported health benefits from probiotic cultures incorporated within the different products. Hence it is necessary to recognize any compound or substance that poses a threat to viability of these probiotic cells, thereby rendering them ineffective. Therefore, the current study aimed at determining whether garlic had any antibacterial activity towards selected Bifidobacterium spp. In vitro studies revealed that garlic has an inhibitory effect on these specific probiotic bacteria. The disk diffusion assay revealed antibacterial activity of garlic preparations characterized by inhibition zones ranging from 13.0 ± 1.7 to 36.7 ± 1.2 mm. Minimum inhibitory concentration (MIC) values for garlic clove extract ranged from 75.9 to 303.5 mg/ml (estimated to contain 24.84 to 99.37 μg/ml allicin) while the minimum bactericidal concentration (MBC) ranged from 10.24 to 198.74 μg/ml xix allicin. Susceptibility of the tested Bifidobacterium species to garlic varied between species as well as between strains even within a small numbers of the tested bifidobacteria. Among the tested Bifidobacterium spp., B. bifidum LMG 11041 was most susceptible to garlic, whereas B. lactis Bi-07 300B was the most resistant. These results were contrary to what has been generally published in literature, that garlic selectively kills pathogens without negatively affecting beneficial bacteria. Garlic clove, garlic powder, garlic paste and garlic spice showed varying degrees of potency, with fresh garlic clove extract and garlic paste extract having the highest and lowest antibifidobacterial activity, respectively. It became necessary to investigate the actual antibacterial mechanism of action of garlic on Bifidobacterium spp., upon realization that its extracts inhibits growth of or kills some of these bacteria, whose contribution to health and well being of consumers is to a large extent dependent on their viability. This was determined by using scanning electron microscopy (SEM) and Fourier-transform infrared (FT-IR) spectroscopy. Scanning electron microscopy was used to investigate the effect of garlic on the morphology and cell surface properties of the tested strains while FT-IR spectroscopy was used to determine any biochemical changes taking place in garlic-treated bifidobacteria. Scanning electron microscopy showed various morphological changes such as cell elongation, distorted cells with bulbous ends and cocci-shaped cells. Behavioural changes were also observed such as swarming of cells was also observed. FT-IR spectra confirmed that garlic damaged Bifidobacterium cells by inducing biochemical changes within the cells. It identified some of the main targets sites of garlic on bifidobacteria, mainly, the nucleic acids and fatty acids (lipids) in the cell membrane. Flow cytometry analysis was used to determine the level at which the garlic decreased the viability of Bifidobacterium cells as well as the extent of damage induced by the garlic. Results revealed a drop in viability with associated decrease in stainability of some the cells, for all strains upon treatment with garlic clove extract. The inability of cells to be stained by nucleic acid stains, hence presence of cells referred to as ‘ghost cells’, has been associated with extensive damage and lysis of cellular membranes resulting in loss nucleic acids. Interestingly, re-inoculation of the cells analysed by flow cytometry into a fresh growth medium and their subsequent reanalysis using the same technique showed an increase in percentage of viable cells and a decrease in percentages of damaged, unstained and dead cells. This suggested that injured cells were able to recover and regress to their active state. Therefore, Bifidobacterium cells exposed to sub lethal amounts of garlic can repair any damage and regrow. However, it was not determined how long active compounds of garlic remain stable within the gastrointestinal tract. This study is the first, according to our knowledge, to show that garlic exhibits antibacterial activity against beneficial bacteria specifically, probiotic bifidobacteria. Furthermore, the results revealed that the mechanism of action of garlic towards bifidobacteria is similar to that which was reported for pathogenic bacteria. Bacterial death and growth inhibition occurs due to damage to the fatty acids/lipids in the cell membrane, modification of the nucleic acids (DNA and RNA). This study is of significant importance to consumers, medical practitioners as well as to the probiotic industry. It suggests that if garlic comes into contact with probiotic bifidobacteria, they die and thus become unable to deliver the promised health benefits to the consumers. Therefore, consumers should be advised against ingestion of probiotic products and garlic simultaneously, as this study reveals that garlic does indeed inhibit some probiotic Bifidobacterium spp. The probiotic industry should also consider including this information on their product labels to make consumers aware of this fact. Failure to include this information may lead to market deterioration due to loss of interest in the products as soon as consumers realize they do not get their money’s worth from the products. Lastly, medical practitioners should also be made aware of this as they also prescribe probiotics to patients for various health reasons. The effect of food matrices on the antibacterial effects, as well as determination of how long the active compounds of garlic remain within the gastrointestinal tract, in relation to levels of garlic ingested will confirm whether indeed there is concern. But for now, in light of results of the current study, caution needs to be taken in simultaneous use of probiotics and garlic, until further testing indicates otherwise. / Dissertation (MSc)--University of Pretoria, 2013. / gm2014 / Microbiology and Plant Pathology / unrestricted