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Thesis(M.Sc. (Animal Production)) -- University of Limpopo, 2022 / Donkeys continue to play a significant role in draught power activities for both rural and urban regions in underdeveloped countries, where they are commonly employed for transportation of goods and movement of people at extremely low prices. The study sought to determine donkey farmers' breeding practices as well as donkey morphological characterization in three villages such as Thorp, Archibalt and Genau of the Blouberg Local Municipality. A total of 21 donkey farmers and 74 donkeys were used to collect data. The following Morphological traits characterized were; Head length (HL), Ear length (EL), Neck length (NL), Chest width (CW), Back length (Bal), Body length (BoL), Hips width (HW), Umbilical circumference (UC), Back height (BH), Height at the rump (HR), Thoracic circumference (TC), Chest depth (CD), Withers Height (WH), Front leg length (FLL), Cannon circumference (CC), Cannon length (CL), Cannon height (CH) and Body weight (BW). Descriptive statistics, Chi-square tests, Analysis of variance (ANOVA), Pearson correlation, and Rank Index were used for data analysis. Education level of the farmers in the three villages was significantly different (p<0.05) with the majority of farmers having secondary education. There was no significant difference (p>0.05) amongst the villages on different reasons behind keeping donkeys. The results showed a significant difference (p<0.05) in inbreeding knowledge by the farmers amongst the three villages. The selection criteria used across the three villages were not significantly different (p>0.05). Rank and Indices in selection of male donkeys looked at body size (0.39), growth rate (0.19), Draught power performance (0.14), and for overall preference in female donkeys it was body size (0.26), twinning ability (0.23) and mothering ability (0.15). Body size and growth rate where the most important traits to donkey farmers. The coat colours were not significantly different (p>0.05). In all the eighteen measured traits, only four (BaL, HW, BH and FLL) showed a significant difference (p<0.05) among the three villages. BW in male donkeys was not significantly correlated (p>0.05) with HL, EL, NL, BaL, HW, FLL, CC, CH, CL but was positively correlated (p<0.05) with BoL (r = 0.34), UC (r = 0.35), TC (r = 0.33), CD (r = 0.31), CW (0.94), BH (r = 0.41), HR (0.60), and WH (r = 0.58). BW in female donkeys was not significantly correlated (p>0.05) with NL, BaL, TC, and CL but positively significant correlated (p<0.05) with HL, EL, BoL, HW, UC, FLL and CC CW, BH, HR, WH and CH with correlation coefficient values ranging from 0.34 to 0.75. The farmers had no breeding program in place the donkeys were allowed to mate on their own without designed breeding program. Selection of donkeys to be part of the heard was based on physical attributes, such length It was concluded that donkey farmers in Genau, Archibalt, and Thorp villages engaged in breeding practices that could be valuable in construction of a community-based breeding program.

Depuis les années 1950, l’intensification des pratiques agricoles concourt à une augmentation de la pression anthropique entraînant une raréfaction des espèces spécialistes des parcelles cultivées, ce qui contribue à l’érosion de la diversité biologique des agroécosystèmes. Parmi les espèces en déclin, on compte de nombreuses messicoles dont le bleuet (Centaurea cyanus L.), fleur emblématique des moissons. Or, cette espèce peut rendre des services écosystémiques comme hôte de prédateurs de ravageurs des cultures et ressource privilégiée de certains pollinisateurs qui justifieraient son maintien dans les champs. Nous étudions ici des facteurs biologiques qui pourraient potentiellement contribuer à son déclin : distribution spatiale, potentialité de croissance, diversité génétique des populations, survie des semences, système de reproduction. Nous avons montré, par deux campagnes de relevés, que C. cyanus n’est pas une espèce indicatrice de diversité floristique dans la parcelle cultivée. Toutefois, lorsque que le bleuet est rare dans une région, il est associé à d’autres messicoles peu fréquentes. Par contre, s’il est commun, il est associé aux zones ayant la plus forte diversité végétale. Une expérience de semis dans différents compartiments de l’agrosystème, en absence de traitements herbicides, a mis en évidence que la potentialité de croissance des bleuets est plus élevée dans le plein champ du blé que dans la moutarde et les interfaces blé/bordure. Cette croissance est limitée de manière variable par les communautés adventices présentes dans les compartiments hors champs (bordures). L’analyse de la diversité génétique à l’aide de marqueurs microsatellites de bleuets dans une petite zone agricole montre que les populations sont connectées par des flux de gènes importants. Les barrières écologiques telles que les chemins, semblent être des facteurs de structuration plus importants que la distance géographique séparant les populations. La répartition du bleuet dans le paysage agricole n’est donc pas aléatoire et apparaît dépendante de la fréquence de l’espèce dans la région ainsi que des différents éléments du paysage. Les caractéristiques du cycle biologique du bleuet ont été étudiées grâce à des expériences au champ et en serre. Nous avons montré que la longévité des akènes enfouis dans le sol chute rapidement après deux ans. Le cycle saisonnier de la dormance permet deux cohortes de levées (automne et printemps). L’étude du système de reproduction a permis de mettre en évidence que les pollinisateurs sont nécessaires pour la fécondation et que les populations sont majoritairement auto-incompatibles. Il existe cependant des individus pseudo auto-incompatibles mais leur fréquence n’est pas liée à la taille des populations ou à leur niveau d’isolement spatial. Par ailleurs, dès que le coefficient de consanguinité augmente dans les populations, la valeur phénotypique des individus baisse. La dépression de consanguinité s’exprime alors principalement pendant la phase de la germination. L’ensemble de ces caractéristiques biologiques peuvent s’avérer défavorables au bleuet dans les agroécosystèmes simplifiés actuels et ont pu entraîner son déclin dans certaines régions / Agroecosystems are currently experiencing high biodiversity loss, in particular among the plant species specifically adapted to this habitat. This decline results from cropping systems that have been intensified in Western Europe since the 1950s. The cornflower (Centaurea cyanus L.), considered as emblem of the flora associated with traditional cereals, appears as a species that may be at risk and should be monitored. Indeed, cornflower can serve as a host to predators of crop pests and is strongly attractive for the pollinators. This study examines the biological factors that could potentially cause the decline of this species: spatial distribution, potential for growth, population’s genetic diversity, seeds survival and mating system.We have shown that C. cyanus is not a biological indicator of the weed diversity of a field. However, when it is not frequent in a region, cornflower is associated with other rare segetal species. When it is common in a region, C. cyanus is present in areas with higher weed diversity. Sowing seeds in different components of the agrosystem, without herbicide application, shows that the growth of cornflower was higher in the centre of a wheat field than in mustard and the crop edge. Growth success in field margins was variably limited according to the weed communities in the field boundaries. The analysis of the genetic diversity using microarrays has shown that populations in a small agricultural area are connected by important genes flow. The ecological barriers as country road seem to be factors more determinant than geographical distance to structure and divide populations. Therefore, the cornflower distribution in the agricultural landscape is not random and appears to be linked to species frequency in the area and to landscape elements.The cornflower life cycle characteristics were studied through field and greenhouse experiments. We have shown that the longevity of achenes buried in the soil falls rapidly after two years. There is a seasonal dormancy cycle that allows the emergence of two seedling cohorts (fall and spring). Our study of the mating system highlights the fact that pollinators are required for fertilization and that cornflower is strongly self-incompatible. However, there are pseudo self-incompatible individuals, but their frequency is not related to the population size or the spatial isolation level. Individual fitness decreases as the inbreeding coefficient increases in a population. Inbreeding depression is mainly expressed during the germination stage. All these biological characteristics can be detrimental to the cornflower in current simplified agroecosystems and may have led to cornflower decline in some areas

In addition to habitat loss and fragmentation, habitat degradation can have important consequences for biodiversity and population persistence, including effects on ecological and genetic processes beyond decreased demographic viability and the loss of genetic variation. Particularly interesting is the potential for evolutionary changes and adaptation to degraded habitats, that can affect population viability even in the short-term. Here, I explore how environmental changes after habitat degradation affect the evolutionary dynamics of populations of the rainforest cycad Zamia fairchildiana, specifically how habitat degradation affects gene dispersal, inbreeding, directional selection, and genotype-by-environment interactions, and the potential for genetic differentiation between populations. Colonies of Z. fairchildiana showed little genetic differentiation in neutral molecular markers across study sites, thus can be considered as subpopulations. Subpopulations in the disturbed habitat are experiencing different environmental conditions when compared to subpopulation in their native habitat. Disturbed-habitat subpopulations showed a faster life-history. This faster life history is associated with a weaker spatial genetic structure and higher levels of inbreeding in the disturbed-habitat subpopulations. In addition, higher light availability in the disturbed habitat seems to be a major agent of selection on traits like leaf production that have the potential to respond to selection in these subpopulations. Different traits were under selection in the native-habitat subpopulations, suggesting the potential for genetic differentiation between native and disturbed-habitat subpopulations. Genotype by environment interactions in seed germination and seedling survival, in response to light and water availability, further suggested that subpopulations can adaptively diverge between habitats, but the relative role of genetic and environmental factors, particularly maternal effects, on the magnitude and rate of genetic differentiation between subpopulations remains to be evaluated. These results suggest that habitat degradation can have important consequences for the evolutionary dynamics of populations of this cycad, not necessarily typical of habitat loss and fragmentation. This study identified factors and processes important for population persistence in degraded habitats, but population responses to habitat degradation are complex. Thus further studies and long-term experiments are required for better understanding the effects of habitat degradation on population viability.

Linhagens endogâmicas (F@1,0) são usualmente utilizadas para a produção de híbridos de milho. Devido a elevada depressão por endogamia no milho, as linhagens endogâmicas apresentam baixa produtividade, encarecendo o custo das sementes de híbridos simples e tornando-os inacessíveis para grande parte dos agricultores dos países em desenvolvimento. Uma alternativa para contornar o problema seria utilizar linhagens parcialmente endogâmicas (0,0 < F < 1,0), selecionadas para capacidade de combinação e uniformidade. Relatos de literatura mostram que (a) híbridos simples de linhagens S3 (F=0,875) devem apresentar performances superiores as de híbridos triplos e duplos de linhagens endogâmicas; (b) a correlação genética entre híbridos simples de linhagens S3 e de linhagens endogâmicas (F@1,0) é elevada (r=0,94); e (c) a produtividade de linhagens S3 é em média 20% superior a de linhagens endogâmicas. Entretanto, a maior dificuldade em se produzir híbridos simples de linhagens parcialmente endogâmicas refere-se à manutenção destas, por apresentarem variabilidade genética. Devido a isto, o objetivo deste estudo foi avaliar a viabilidade de se produzir e utilizar híbridos simples de linhagens parcialmente endogâmicas S3. Para isso, oito linhagens S3 da população BR-105 e dez linhagens da população BR-106, as quais estão alocadas em grupos heteróticos distintos, selecionadas para capacidade de combinação e uniformidade, originais e mantidas por intercruzamentos e seleção moderada por cinco gerações, foram utilizadas. Durante as gerações de manutenção, pelo menos 50 plantas foram usadas. Estas linhagens e cruzamentos destas com dois testadores de grupos heteróticos diferentes, foram avaliados em quatro ambientes no ano agrícola de 1999/2000. Além disso, as linhagens originais e mantidas foram genotipadas utilizando o marcador molecular AFLP para estimar a similaridade genética entre elas. Os resultados obtidos mostraram que, excetuando-se uma linhagem da população BR-105 em que provavelmente ocorreu contaminação, apenas dois caracteres nas linhagens per se e apenas um caráter nos cruzamentos apresentaram alterações positivas e significativas, de treze caracteres avaliados. Entretanto estas alterações são muito pequenas para serem detectadas visualmente. Os resultados das similaridades genéticas entre as linhagens originais e mantidas, mostraram valores elevados, sendo que o limite superior do intervalo de confiança para a maioria das linhagens atingiu o valor 1,0, indicando que a manutenção das linhagens da forma como foi conduzida as suas integridades genéticas foram mantidas. Estes resultados permitiram concluir que seria viável a utilização de linhagens parcialmente endogâmicas S3 para a produção comercial de híbridos simples de milho. / Inbred lines (F@1.0) are usually used for the production of maize single-crosses. Because of the high inbreeding depression in maize, the inbred lines are lower yielding, which causes the seed prices to be costly and then inaccessible for most of the farmers in the developing countries. One way to circumvent the problem would be the use of partly inbred lines (0.0< F<1.0) selected for combining ability and for uniformity within the lines. Reported results have shown that: (a) theoretically, single-crosses from S3 lines (F=0.875) are expected to have superior performance than that of three-way and double-crosses; (b) the genetic correlation of single-crosses from S3 lines and from their inbred lines (F@1.0) counterparts is fairly high (r=0.94); and (c) S3 lines are on the average 20% higher yielding than highly inbred lines. However, the main difficulty in the production of single-cross from partly inbred lines is the maintenance of their genetic integrity because of the variability within them. Therefore, the ob-jective of this research was to study the feasibility of the development and the production of single-crosses from S3 lines. The genetic material included eight original S3 lines from the BR-105 population, and ten original S3 lines from the BR-106 population, selected for combining ability and for uniformity within them, and their counterparts maintained by sib-mating and mild selection for five generations. During the generations of maintenance at least 50 plants per line were used. The populations BR-105 and BR-106 have been assigned to distinct heterotic groups. The original, the maintained lines and their crosses with testers from different heterotic groups were evaluated in four environments in the growing season of 1999/2000. Also, the S3 lines were genotyped with the AFLP molecular marker in order to estimate the genetic similar-ity between the original and their maintained counterparts. The results showed that out of the 13 traits evaluated only two traits in the lines per se, and only one trait in the crosses changed significantly from the original lines to the maintained counterparts. However those changes are too low to be visually detected. The estimates of the genetic similarities between the original and their maintained counterparts S3 lines were high, and the upper bound of the confidence interval for most of the lines reach the limit value, i.e., 1.0. These results showed that the ap-proach uses for the maintenance of the S3 lines was effective and thus the genetic integrity of the lines were maintained. The results of this research could allow one to expect that would be feasible the use of partly inbred S3 lines for the commercial production of maize single-crosses.

A obtenção de genótipos superiores no melhoramento de plantas depende da existência de variabilidade genética. A existência de coleções de germoplasma representativas e a utilização de um tamanho adequado de amostra são fundamentais para a preservação das frequências alélicas e genotípicas, diminuindo a perda de variabilidade genética e postergando o aparecimento dos efeitos da deriva genética. Assim, teve-se como objetivo avaliar os efeitos da deriva genética em caracteres quantitativos em subpopulações de milho. Este estudo foi realizado a partir das populações originais BR-105 e BR-106, das quais 10 subpopulações foram obtidas em cada um dos cinco ciclos sucessivos de amostragem com tamanho efetivo reduzido, totalizando 50 subpopulações para cada população original, as quais foram posteriormente autofecundadas, gerando um nível a mais de endogamia. Os tratamentos foram constituídos de 10 amostras da população original sem autofecundação, 10 amostras com autofecundação, 50 subpopulações obtidas da população original e 50 subpopulações autofecundadas, totalizando 120 tratamentos para cada população, avaliados separadamente. Utilizou-se o delineamento em blocos casualizados no esquema de parcelas subdivididas em faixas hierárquico, em quatro ambientes com duas repetições por ambiente. Os caracteres avaliados foram produção de grãos (PG), prolificidade (PROL), comprimento e diâmetro de espigas (CE e DE), número de fileiras por espiga (NFE), número de grãos por fileira (NGF), altura de planta e espiga (AP e AE), florescimento masculino e feminino (FM e FF) e número de ramificações do pendão (NRP). Foram estimados os efeitos da deriva genética entre as médias das subpopulações nos dois níveis de endogamia e os efeitos da depressão por endogamia nas subpopulações dentro dos ciclos. Posteriormente, realizaram-se análises de regressão linear para as subpopulações nos dois níveis de endogamia, separadamente, e em conjunto. Foi verificada uma grande variação nas médias das subpopulações ao longo dos ciclos, indicando que a deriva genética causou diferenciação entre as mesmas e que estas se diferenciaram das populações originais. Detectaram-se efeitos significativos da deriva genética nas populações não autofecundadas para todos os caracteres avaliados, em maior número para PG, já que este caráter é mais sensível à deriva genética por possuir maior grau de dominância que os demais. Houve diminuição no número de estimativas de deriva significativas para as populações autofecundadas, incluindo mudanças na magnitude e no sinal das mesmas em relação às populações não autofecundadas. Para as estimativas de depressão por endogamia, os caracteres PG, NGF, FM e FF apresentaram maior quantidade de estimativas significativas que os demais. Para a maioria dos caracteres, a regressão linear explicou a maior parte da variação encontrada com o aumento dos coeficientes de endogamia. As populações BR-105 e BR-106, por terem estruturas genéticas distintas, apresentaram performances diferentes quanto aos efeitos da deriva genética. Enfim, como a deriva genética interfere na integridade genética das populações, torna-se importante considerar seus efeitos na coleta e manutenção dos bancos de germoplasma e nas populações utilizadas no melhoramento genético de plantas. / Obtaining superior genotypes in plant breeding depends on the existence of genetic variability. The existence of representative germplasm collections and the use of appropriate sample size are essential for preserving allelic and genotypic frequencies, reducing loss of genetic variability and delaying genetic drift effects. This study aimed to evaluate the effects of genetic drift in quantitative traits in subpopulations of maize. The original populations used were BR-105 and BR-106, of which 10 subpopulations were obtained in each five successive sample cycles with reduced effective size, accounting 50 subpopulations for each original population that were subsequently selfed to generate an additional level of inbreeding. The treatments consisted in 10 samples of the original population, 10 samples of the selfed original population, 50 non selfed subpopulations obtained from the original population and 50 selfed subpopulations, accounting 120 treatments for each population evaluated separately. It was used the randomized block strip-plot design, in four environments with two replications. The traits assessed were grain yield (GY), prolificacy (PROL), ear length and ear diameter (EL and ED), number of rows per ear (NRE), kernel-row number (KRN), plant and ear height (PH and EH), days to anthesis and silking (DA and DS), and number of tassel branches (NTB). It was estimated the effects of genetic drift between subpopulations means at both inbreeding levels, and the effect of the inbreeding depression in subpopulations within cycles. It was also performed linear regression analysis for subpopulations at both levels of inbreeding separately and together. A large variation was observed in the subpopulations means over cycles, indicating that genetic drift caused differentiation between them, and that they differed from the original populations. The effects of genetic drift were significant for all traits in the non selfed subpopulations, especially for GY, which is more sensitive to genetic drift effects by having a greater degree of dominance than the other traits. There was a decrease in the number of significant genetic drift estimates for selfed populations, including changes in magnitude and signs, compared to the non selfed populations. GY, KRN, DA and DS had higher number of significant inbreeding depression estimates than the other traits. Linear regression analysis explained most of the variation found with increasing homozygosity. As BR-105 and BR-106 populations have distinct genetic structures, they showed different performances regarding the effects of genetic drift. Therefore, genetic drift interferes in the genetic integrity of populations and it is important to consider its effect on the collection and maintenance of germplasm banks and populations used in plant breeding.

O objetivo dessa pesquisa foi avaliar aspectos genéticos que relacionados à produção in vitro de embriões na raça Guzerá. O primeiro estudo focou na estimação de (co) variâncias genéticas e fenotípicas em características relacionadas a produção de embriões e na detecção de possível associação com a idade ao primeiro parto (AFC). Foi detectada baixa e média herdabilidade para características relacionadas à produção de oócitos e embriões. Houve fraca associação genética entre características ligadas a reprodução artificial e a idade ao primeiro parto. O segundo estudo avaliou tendências genéticas e de endogamia em uma população Guzerá no Brasil. Doadoras e embriões produzidos in vitro foram considerados como duas subpopulações de forma a realizar comparações acerca das diferenças de variação anual genética e do coeficiente de endogamia. A tendência anual do coeficiente de endogamia (F) foi superior para a população geral, sendo detectado efeito quadrático. No entanto, a média de F para a sub- população de embriões foi maior do que na população geral e das doadoras. Foi observado ganho genético anual superior para a idade ao primeiro parto e para a produção de leite (305 dias) entre embriões produzidos in vitro do que entre doadoras ou entre a população geral. O terceiro estudo examinou os efeitos do coeficiente de endogamia da doadora, do reprodutor (usado na fertilização in vitro) e dos embriões sobre resultados de produção in vitro de embriões na raça Guzerá. Foi detectado efeito da endogamia da doadora e dos embriões sobre as características estudadas. O quarto (e último) estudo foi elaborado para comparar a adequação de modelos mistos lineares e generalizados sob método de Máxima Verossimilhança Restrita (REML) e sua adequação a variáveis discretas. Quatro modelos hierárquicos assumindo diferentes distribuições para dados de contagem encontrados no banco. Inferência foi realizada com base em diagnósticos de resíduo e comparação de razões entre componentes de variância para os modelos em cada variável. Modelos Poisson superaram tanto o modelo linear (com e sem transformação da variável) quanto binomial negativo à qualidade do ajuste e capacidade preditiva, apesar de claras diferenças observadas na distribuição das variáveis. Entre os modelos testados, a pior qualidade de ajuste foi obtida para o modelo linear mediante transformação logarítmica (Log10 X +1) da variável resposta. / The objective of this research was to evaluate genetic aspects permeating in vitro embryo production in Guzerá cattle. The first study aimed for estimating genetic and phenotypic (co)variances among embryo production traits and detecting possible genetic association with the age at first calving (AFC). Low and medium heritabilities were detected for oocyte and embryo production traits. A weak genetic association between artificial reproduction traits and AFC was identified. The second study evaluated genetic and inbreeding trends in the Brazilian Guzerá population. Female donors and in vitro produced embryos were considered as two subpopulations in order to perform comparisons and infer over differences in inbreeding and genetic annual variations. Embryos\' subpopulation showed higher genetic gains for age at first calving and milk production than donors\' subpopulation and the general population. Higher annual mean inbreeding values were also detected for the embryos\' subpopulation. The third study examined the effects of donor, sire (used for in vitro fertilization) and embryos\' inbreeding coefficient over in vitro embryo production traits in Guzerá cattle. Donors\' and embryos\' inbreeding effects over the analyzed traits were detected. Fourth and final study was designed to compare the performance of Linear and Generalized Linear Mixed Models under Restricted Maximum Likelihood method when fitting discrete variables. Four hierarchical models assuming different distributions for the response variable were fit to the (count) data. Inference was performed upon residual diagnostics and comparison of variance component ratios between models within each trait. Poisson models outperformed both linear (with and without variable transformation) and negative binomial models for goodness of fit and predictive ability despite clear differences in each trait\'s distribution. Logarithmic transformation (Log10 X +1) showed lowest goodness of fit among all models tested.

The topic of this thesis is Canaan dog including dog assistant education. The first part is theoretical and introduces the reader to the Canaan dog breed. The origin of this rare and very old breed is Izrael and first dogs were imported to the Europe and America in 60s of 20th century. The lack of Canaan dogs in Europe causes problems with breeding and transmission of genetic diseases. Especially in the Czech republic there is only few dogs. The teoretical part introduces a transmission of genetic diseases and other diseases. The practical part is focused on a creation of a genealogy of Canaan dogs in the Czech republic. Further I studied inbreeding. In the second part I studied the use of dog in education. The practical part are two education programs, which I created. The first training program is about dogs behaviour, it's also tested in practice and its completed results are part of the appendix. Pupils will learn important information about dogs, how to handle and understand a dog or information about a primitive breed like rare Canaan dog. The second education program is designed for high school students. The program is about inbreeding and includes text and worksheet. Key words: Canaan dog, genetic, heritage, genetic diseases of dogs, inbreeding, animal assistant education.

Inbreeding depression is one of the factors that can increase the risk of extinction of small populations, and therefore understanding its effects is currently an important issue in conservation biology. Until recently, few studies on inbreeding depression were carried out in wild populations. These recent studies have highlighted the variability in detecting inbreeding depression among natural populations and the multitude of factors that can influence its expression. Many of the factors affecting inbreeding depression in wild populations remain largely unexplored and most of the recent studies in this area have tended to focus on incidents of inbreeding in populations with a history of large population size. The aim of this study is to investigate the relative importance inbreeding depression has had on individual fitness parameters in a population of New Zealand's Stewart Island robins Petroica australis rakiura introduced to Ulva Island. This island population has historically gone through several population bottlenecks. Four main factors that potentially influence the rate of inbreeding and the extent of inbreeding depression, were investigated: environmental variability, life history stage, genetic load and dispersal. Generalized Linear Mixed Modelling was first used to determine how weather affected nest survival. Weather effects were then incorporated into models containing demographic factors to control for environmental variability, and finally parental, maternal and paternal inbreeding co-efficients (=f) were added to models to determine the relative importance of inbreeding depression. Interactions between inbreeding depression and environmental factors were explored. Three different life history stages were compared to determine the differences in inbreeding depression at each stage as well as cumulative effects over time. The genetic load of the population was estimated using lethal equivalents allowing for standardised comparison of inbreeding depression with other species. The likelihood of inbreeding in the population was also explored by investigating the factors affecting dispersal patterns and evaluating evidence for inbreeding avoidance. Inbreeding depression was found to be mild in the robin population. Weather did not have strong effects on nest survival or interactions with inbreeding. Female age was the only factor interacting with inbreeding, with younger inbred females experiencing significantly reduced offspring juvenile survival. Parental and paternal f did not significantly affect brood survival at any life history stage, however, maternal f showed significant effects on nest juvenile survival with the strongest effect occurring when survival was examined cumulatively over all life history stages. The Stewart Island robin had a relatively low lethal equivalent value compared to the closely related North Island robin and other avian species. This difference was associated with the Stewart Island robin having a low genetic load, most likely due to historical genetic purging during periods of population bottleneck. The Ulva Island robin population did not appear to be avoiding inbreeding through dispersal. Dispersal distance was most strongly influenced by the location of the natal nest of the dispersing offspring. In conclusion, the genetic history of the population was likely to have had the strongest impact on the severity of inbreeding depression in the Ulva Island robin population. The results of the thesis highlight the need to examine a number of factors to be able to explain variability in inbreeding depression among populations.

Many bumblebee species are suffering from the effects of habitat fragmentation and population isolation. In some cases, populations have lost genetic diversity due to genetic drift and it is possible they are now at heightened risk of extinction. Inbreeding may be particularly costly to bumblebees because, as Hymenoptera, their complementary sex determination system can lead to the production of sterile or inviable diploid males. However, little is known about the effect that diploid male production has on bumblebee colony fitness. Here, the consequences of brother-sister mating in the bumblebee Bombus terrestris are investigated, and the production of diploid males was found to exert considerable costs at the colony level by reducing productivity and survival. Diploid males may therefore act as indicators of the genetic health of populations, and their detection could be used as an informative tool in hymenopteran conservation. Due to the costs associated with inbreeding, selection may have favoured the evolution of kin recognition systems in bumblebees. Data are presented that suggest that B. terrestris can discriminate between kin and non-kin as gynes were less willing to mate with siblings compared to non-relatives. Theory predicts that inbreeding may impose further costs on bumblebees through increased levels of parasitism, but empirical data are scarce. The relationship between population genetic diversity and parasite prevalence is assessed using Hebridean island populations of Bombus muscorum and Bombus jonellus. In the more outbred B. jonellus, there was no relationship between parasite prevalence and population heterozygosity. But prevalence of the gut parasite Crithidia bombi and the tracheal mite Locustacarus buchneri were found to be higher in populations of B. muscorum that had lower genetic diversity. In addition to assessing infection status, the activity of the immune system was assessed in each individual bee. However, there was no relationship between population heterozygosity and these immune parameters. This suggests that, in some Hymenopteran species, as populations lose genetic diversity the impact of parasitism will increase, potentially pushing threatened populations closer to extinction. Therefore, preventing population fragmentation by the creation of suitable habitats and by ensuring connectivity between habitat patches are important aspects of hymenopteran conservation. Finally, this thesis investigates the potential threat of pathogen spread from commercially reared bumblebees used for crop pollination to wild bumblebees. Although no direct evidence for parasite spillover is found, the prevalence of C. bombi was significantly higher in B. terrestris by the end of the season on farms that used commercial bumblebees compared to farms that did not. This high prevalence does suggest that pathogen spillover is a potential threat and it would be preferable to reduce the usage of commercial bumblebees where possible. For example, sowing wild flower mixes could boost natural pollinator populations, which in turn would benefit soft fruit pollination. Overall, this thesis contributes to our knowledge of the consequences of inbreeding in bumblebees and the relationship between genetic diversity and parasite prevalence. It provides a greater understanding of the factors that might be pushing threatened pollinators towards extinction and as a whole provides important information that may inform conservation practitioners, whose aim is to protect the future of our hymenopteran pollinators.