Tesis/Trabajos de Grado

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https://hdl.handle.net/1992/52421

Incluye documentos como: monografías, reportes, proyectos, prácticas, informes, entre otros; elaborados como requisito de grado para programas de pregrado y posgrado en la Universidad de los Andes.

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Ecological diversification and phylogenomics of the Caribbean octocoral genus Eunicea
(Universidad de los Andes, 2025-12-04) Sarmiento Segura, Adriana; Sánchez Muñoz, Juan Armando; Prada, Carlos; Crawford, Andrew Jackson
Octocorals represent one of the most diverse lineages of marine benthic animals, encompassing around 3,500 valid species, including gorgonians, soft corals, and sea pens. They are key components of benthic communities, providing tridimensional structures and habitats for numerous reef organisms. In Caribbean reefs, octocorals dominate both in diversity and biomass, often surpassing scleractinian corals. Within this group, the endemic genus Eunicea stands out as the most diverse and abundant, yet its taxonomy, ecological differentiation, and diversification processes remain poorly understood. In Chapter I, a phylogenomic framework based on thousands of SNPs was generated to clarify the evolutionary relationships within Eunicea. The resulting well-supported phylogeny resolved 13 species-level clades and revealed previously unrecognized diversity, including two newly described species, thereby refining the taxonomic boundaries of the genus. Chapter II explored how variation in colony morphology relates to metabolic performance, showing that differences in polyp size, density, and surface-area-to-volume ratios are associated with distinct oxygen metabolism and photosynthetic efficiencies. Despite the presence of symbiotic algae, all species exhibited net oxygen consumption under light conditions, indicating a predominant reliance on heterotrophy and morphological modulation of mixotrophic balance. Finally, Chapter III examined the structure and evolutionary patterns of microbial assemblages across Eunicea species, revealing distinct bacterial communities dominated by Endozoicomonas and Mycoplasma, with significant host–symbiont phylogenetic congruence indicative of co-diversification processes.
Acceso abierto
Climatic asynchrony and speciation: the evolution of breeding cycles and its role on population differentiation in neotropical birds
(Universidad de los Andes, 2025-07-28) Moreno Palacios, Miguel César; Cadena Ordónez, Carlos Daniel; Riehl, Christine; Crawford, Andrew Jackson; Facultad de Ciencias::Biología Evolutiva de Vertebrados
This dissertation investigates how climatic asynchrony shapes reproductive timing and population dynamics in Neotropical birds, integrating macroecological analysis, fine-scale field studies, and bioacoustic monitoring to test the Asynchrony of Seasons Hypothesis (ASH). Chapter 1 presents the first large-scale, quantitative analysis of breeding seasonality in Colombian resident birds, using over 80,000 records from banding programs and GBIF. Generalized additive models and circular statistics revealed that breeding activity is markedly seasonal across Colombia, with peaks in the first half of the year and variation driven by latitude, elevation, and trophic guild. These findings challenge the traditional view of aseasonal reproduction in tropical birds and establish a national-level baseline for phenological research. Chapter 2 shifts to a local scale, examining bird assemblages across a 30 km elevational gradient in the Upper Magdalena Valley. Year-round field sampling and hormone analysis showed clear breeding asynchrony between lowland and foothill populations, with distinct seasonal peaks despite geographic proximity. Breeding activity correlated with gross primary productivity and solar radiation, while hormone levels peaked synchronously across sites, suggesting that local environmental conditions modulate reproductive output even under shared endocrine cues. These results offer empirical support for ASH within a climatically heterogeneous tropical landscape. Chapter 3 uses passive acoustic monitoring to assess whether vocal activity—a behavioral proxy for reproduction—also reflects asynchronous breeding dynamics. Over 120,000 recordings revealed displaced acoustic peaks along the elevational gradient, with lowland sites peaking earlier in the year. Vocal activity was weakly correlated with rainfall but aligned closely with reproductive activity measured in the field. At the species level, focal taxa exhibited asynchronous vocal phenologies across sites, suggesting that bioacoustic patterns mirror reproductive asynchrony and may contribute to ecological divergence. Overall, this work demonstrates that reproductive phenology in Neotropical birds is not only seasonal but also spatially structured across geographic and environmental gradients. Climatic asynchrony—especially variation in productivity and radiation—emerges as a key driver of reproductive divergence, with implications for population differentiation even in the absence of physical barriers. By combining large-scale datasets, field-based endocrine and phenological assessments, and machine learning-based bioacoustics, this dissertation offers a robust framework to explore temporal divergence in tropical birds. The findings advance our understanding of avian life-history evolution and highlight the need to incorporate temporal environmental heterogeneity into models of population dynamics, especially under climate change scenarios.
Acceso abierto
Host-pathogen interaction evaluation using a Lipidomic Profiling of Malassezia furfur Isolates with fungemia-causing potential in the systemic infection model Galleria mellonella
(Universidad de los Andes, 2025-06-04) Torres Moreno, Maritza; Celis Ramírez, Adriana Marcela; Firacative Ropero, Sandra Carolina; Santos Vega, Oscar Mauricio; Facultad de Ciencias::Grupo de Investigación Celular y Molecular de Microorganismos Patógenos (Cemop)
The genus Malassezia comprises lipid-dependent yeasts, which are the main component of the skin mycobiota. These yeasts are also known for their role in dermatological clinical entities. This is due to its opportunistic character. Particularly, Malassezia furfur has been associated with skin conditions such as dandruff and seborrheic dermatitis, as well as invasive infections like fungemia. This thesis aims to evaluate the host-M. furfur interaction in vivo using a lipidomic approach to study isolates of M. furfur with varying capacities to cause fungemia and distinct antifungal resistance profiles, in the Galleria mellonella infection model. As part of this project, the standardization and application of the Galleria mellonella larvae as an alternative model were carried out. In this standardization, the model showed to be a suitable infection model that allows for the virulence differentiation between species. Allowing for the assessment of larval survival, fungal burden, immune response, and histological changes. Using this model, the virulence of M. furfur isolates with different antifungal profiles was evaluated. This showed, differences in biofilm formation, temperature, and oxidative stress tolerance, which are relevant factors for invasive infection establishment. Finally, a lipidomic analysis of isolates with high and low virulence demonstrated that specific lipid profiles correlated with the virulence of the isolates. All together, these findings showed the importance of lipid metabolism in the host-M. furfur interaction, as well as the relevance of the G. mellonella infection model to study this interaction.
Acceso abierto
Integrative analysis of the evolutionary relationships of gracile capuchin monkeys (Primates: Cebus) with emphasis on Colombian taxa
(Universidad de los Andes, 2025-06-03) García Restrepo, Sebastián; Link Ospina, Andrés; Lynch, Jessica W.; Urbani, Bernardo; Cadena Ordónez, Carlos Daniel; Facultad de Ciencias::Laboratorio de ecología y bosques tropicales y primatología
The systematics of Cebus remain complex due to high phenotypic variability, a wide geographic distribution, and a lack of integrative studies in northern South America. This research combines morphometric, ecological, biogeographic, and taxonomic approaches to address long-standing uncertainties in the taxonomy, evolutionary history, and biogeography of the genus. In Chapter 1, we applied 2D geometric morphometrics to cranial and mandibular landmarks of 206 adult specimens representing 12 Cebus taxa. The analyses revealed greater variation in skull shape than in centroid size, with significant morphometric differentiation among and within Central American, Andean, and Amazonian populations. These results highlight the diagnostic utility of shape-based analyses and reinforce the need for integrative frameworks, as morphological characters alone are insufficient to resolve species limits in highly variable taxa. Chapter 2 investigates the role of climate as a driver of cranial morphological variation. Using morphometric data from 199 specimens, we found significant associations between skull size and latitude and between mandibular morphology and precipitation-related variables. Differences in cranial morphology were also detected across major biomes. These findings support the hypothesis that ecological selection shapes morphological traits and provide novel insights into the ecogeographic patterns underlying phenotypic variation in Cebus. In Chapter 3, we employed phylogeny-based ancestral range estimation to reconstruct the spatial and temporal diversification of Cebus lineages. Our results support a northern Amazonian origin for the genus, followed by range expansions toward the Andes and a center of diversification near the eastern Andean foothills. Evidence supports a Reinvasion of Amazonia (ROA) scenario for Cebus, which complements previous findings for Sapajus and offers new perspectives on Neotropical primate biogeography. Finally, Chapter 4 addresses nomenclatural issues surrounding Cebus malitiosus, which was originally described from the Sierra Nevada de Santa Marta. We demonstrate that the holotype comprises two different specimens (a skin and a skull), which constitutes a violation of current taxonomic standards. According to the International Code of Zoological Nomenclature (ICZN), we designate the skin as the lectotype and the skull as the paralectotype. This study collectively contributes to resolving taxonomic ambiguities, elucidating historical biogeographic processes, and understanding the eco-morphological diversification of Cebus. The results underscore the importance of integrative taxonomic approaches in documenting primate diversity and informing conservation strategies in one of the Neotropics' most biodiverse regions.
Acceso abierto
Developmental plasticity in anurans of an extreme environment: The inselbergs in Colombia
(Universidad de los Andes, 2025-06-03) Delgadillo Méndez, Diana Alexandra; González Arango, Catalina; Gómez Mestre, Iván; Link Ospina, Andrés; Richter-Boix, Alex; Facultad de Ciencias::Palinología y Paleoecología Tropical
Most species possess a certain degree of plasticity that enables them to persist over various conditions by adjusting their morphology, physiology, and behavior. However, some environments can be more challenging than others, and organisms may struggle to produce appropriate phenotypic responses to extreme environmental conditions. The inselbergs of the Guiana Shield in northern South America have environmental conditions that are harsh for plant life, categorizing them as microclimatic deserts. Moreover, rocky ponds in inselbergs are characterized by their shallow depth, dependence on precipitation, intense temperature fluctuations, and a high risk of desiccation. During the rainy season, these rocky ponds host numerous species of anurans that reproduce in them, providing an ideal model system to examine developmental plasticity in tropical anurans exposed to complex environments. In this PhD thesis, we aim to investigate developmental plasticity in two tropical anuran species that inhabit inselbergs in Colombia and have contrasting reproductive strategies: Leptodactylus lithonaetes, an inselberg specialist that breeds exclusively in temporary rocky ponds, and Leptodactylus fuscus, a widespread generalist found in rocky ponds, savannas, and seasonally flooded habitats. We combined laboratory experiments, pond characterization, locomotor performance assessments, and genomic analyses to understand how various ecological pressures (e.g., desiccation risk, temperature, and predation) and their interactions influence the plastic responses of larvae and recently metamorphosed froglets. In Chapter 1, we examined the plastic response of Leptodactylus lithonaetes tadpoles to different levels of desiccation risk under controlled conditions. We evaluated changes in developmental rate, tadpole morphology (body size and body length), and locomotor performance (acceleration). Contrary to expectations based on studies of temperate species, tadpoles exposed to drying conditions did not accelerate their development. Instead, they exhibited a significantly larger body size and greater body mass compared to those in constant conditions. Moreover, tadpoles in dry conditions showed enhanced locomotor performance, suggesting a compensatory growth strategy that may facilitate escape from drying ponds and possibly reflecting the semi-terrestrial nature of tadpoles. In Chapter 2, we investigated how gene flow, environmental heterogeneity, and evolutionary history influence developmental plasticity to desiccation risk among L. lithonaetes populations along a geographical and bioclimatic gradient. Genetic analyses of nine populations revealed significant genomic differentiation, particularly in southern populations that exhibited lower heterozygosity and evidence of historical bottlenecks. A common-garden experiment with four populations exposed to two drying regimes showed that tadpoles did not adaptively accelerate development in response to desiccation; instead, they reached metamorphosis at smaller sizes. A clinal pattern emerged: northern populations had higher survival and smaller reductions in body size and mass under desiccation, while southern populations experienced higher mortality and greater reductions in body size and mass, suggesting maladaptive responses likely driven by genetic impoverishment. In Chapter 3, we focused on Leptodactylus fuscus to examine how environmental stressors interact to shape developmental trajectories. In a fully factorial experiment, tadpoles were exposed to combinations of temperature, desiccation risk, and predator cues. We measured survival, developmental time, body size, lipid reserves, and post-metamorphic locomotor performance to assess whether interactions between factors were additive, synergistic, or antagonistic. Tadpoles did not adjust their developmental rate in response to any factor. Temperature had the strongest positive effect on larval body mass, size, fat bodies, and locomotor performance. In contrast, risk of pond drying negatively affected mass, size, and snout length at metamorphosis. Predator cues had minimal effects, showing only an antagonistic interaction with temperature regarding locomotor performance. The remaining interactions among ecological factors on metamorphic traits were additive. Developmental canalization may relate to the reproductive mode of L. fuscus, which involves a terrestrial foam-nest phase that may reduce the selection for plasticity. However, limited plasticity in developmental rate could constrain responses to climate change involving higher temperatures and shorter hydroperiods. Overall, the results of this thesis highlight the diversity and complexity of developmental plasticity in tropical amphibians facing extreme environmental pressures. The findings emphasize that plasticity is context-dependent, shaped by ecological constraints, life-history traits, and genetic backgrounds. Our results also stress the importance of continuing to study phenotypic plasticity in complex, more realistic scenarios and expanding the range of species studied to include tropical species and those with different reproductive modes.
Acceso abierto
Elucidation of role of type three effectors from Xanthomonas axonopodis pv. manihotis
(Universidad de los Andes, 2016) Medina Culma, César Augusto; Bernal Giraldo, Adriana Jimena
El cultivo de la yuca es uno de los más importantes en los países tropicales, sin embargo este cultivo puede ser afectado por diversas enfermedades fúngicas, bacterianas y virales. El añublo bacteriano de la yuca (CBB por sus siglas en inglés) es considerada la enfermedad bacteriana más importante de la yuca. CBB puede generar importantes pérdidas en los cultivos bajo condiciones climáticas adecuadas. CBB es causado por Xanthomonas axonopodis pv. manihotis (Xam) una bacteria gram negativa la cual posee diferentes factores de virulencia. Los efectores tipo tres (T3Es por sus siglas en inglés) son los factores de virulencia más importantes en otras bacterias fitopatógenas. Este trabajo esta enfocado en determinar la importancia de los T3Es de Xam tomando diferentes aproximaciones. En la primera parte del trabajo se encontró el papel que juegan diferentes T3S en virulencia y en la inmunidad vegetal a través de la generación de cepas mutantes en los T3Es y mediante el uso de sistemas heterólogos que permiten identificar el papel de los T3Es en inmunidad vegetal...
Acceso abierto
Dinámicas de transmisión de parásitos gastrointestinales en primates neotropicales: análisis bajo una mirada socio-ecológica
(Universidad de los Andes, 2024-12-12) Galvis Ramírez, Nelson Fabián; Stevenson Díaz, Pablo Roberto; Link Ospina, Andrés; Solórzano García, Brenda; Molina Escobar, Jorge Alberto; Facultad de Ciencias::Centro de Investigaciones Ecológicas la Macarena
Durante las dos últimas décadas tanto en ecología como en epidemiología el poder entender que variables determinan la riqueza de parásitos en primates ha sido de gran interés. Se ha planteado que variables ambientales como la temperatura, la humedad relativa y la precipitación son factores que determinan la riqueza de parásitos en diferentes grupos de vertebrados. Sin embargo, los resultados de los diferentes estudios que han puesto a prueba estas variables han sido inconclusos, por consiguiente, se ha sugerido que existen otras fuerzas que tienen una mayor influencia como el tamaño del grupo, la densidad poblacional, dieta del hospedero y/o las dinámicas comportamentales. Teniendo en cuenta los diferentes supuestos asociados a las variables ambientales, poblacionales y comportamentales, en este estudio evaluamos la potencial relación entre la riqueza de parásitos gastrointestinales con el tamaño del grupo, la densidad poblacional, los patrones de agrupamiento, la estructura social, la dieta, el tamaño corporal y la dominancia social en primates, los cuales son detallados en tres capítulos distintos. En el primer capítulo, mediante un metaanálisis evaluamos si el tamaño poblacional, la densidad poblacional y la dieta explican la riqueza de las cargas parasitarias de 163 especies de primates. También, mediante un estudio de caso evaluamos si la temperatura, la humedad relativa y la pluviosidad explican la riqueza de especies en las cargas parasitarias de monos cariblancos (Cebus versicolor), monos maiceros (Sapajus apella) y monos araña café (Ateles hybridus). Los resultados de este capítulo sugieren que la riqueza de parásitos incrementa positivamente con el tamaño del grupo y la densidad poblacional, como una potencial consecuencia de un mayor riesgo de infección. Al igual que previos estudios, nuestros resultados no evidencian un patrón claro entre la dieta y la riqueza de parásitos en primates, rechazando la hipótesis de que el tipo de dieta puede determinar la comunidad de parásitos del hospedero. También, se encontró que ni la temperatura, la humedad y la precipitación explican la riqueza de parásitos en las tres especies de primates estudiadas. Sin embargo, existe una tendencia a observarse una mayor riqueza de parásitos durante la época seca en la tropa de monos araña café y de cariblancos. Los resultados de este trabajo son un aporte para el entendimiento de los factores que influencian las cargas parasitarias en primates neotropicales, evidenciando la complejidad de las dinámicas de transmisión de parásitos. En el segundo capítulo, implementando análisis de redes sociales describimos como la estructura social, los patrones de cohesividad, la jerarquía social, el tamaño corporal y las relaciones entre individuos medidas a través de métricas de centralidad, influencian las cargas parasitarias y las dinámicas de transmisión de parásitos en monos araña café (Ateles hybridus), monos maiceros (Sapajus apella) y (Cebus versicolor) que habitan en bosques de tierras bajas en Colombia. Los resultados de este estudio resaltan la fluidez en los patrones de agrupación y la estructura social altamente modular de la tropa de monos araña, aportando evidencia a la complejidad de la estructura social tipo fisión – fusión que ha sido reportada en otras especies de monos araña. Adicionalmente, se encontró que esta especie ajusta su patrón de agrupación a la disponibilidad de recursos observándose una menor cohesividad durante las épocas de escases. En contraste tanto en los monos maiceros y los monos cariblancos, se registró una mayor cohesividad y una estructura grupal compacta, la cual no es afectada por la productividad de frutos. Adicionalmente, se encontró que la estructura social no explica la riqueza de parásitos en ninguna de las tres especies de primates. En los monos maiceros y en los monos cariblancos no se encontró una relación entre la cohesividad de los grupos con la riqueza de especies de sus cargas parasitarias, mientras que en los monos araña se evidenció que el patrón de agrupamiento explica las cargas parasitarias, registrándose una mayor riqueza de parásitos durante los periodos de cohesividad social más altos. Al combinar estos resultados con la estructura social altamente modular observada en los monos araña, se evidencia que este estudio soporta la hipótesis del cuello de botella epidemiológico. En las tres especies de primates se determinó la importancia de los integrantes de las tropas a través de la centralidad por fuerza, intermediación y de vector propio. En los monos cariblancos se encontró que los individuos con alta centralidad por fuerza poseen una mayor riqueza de parásitos. No obstante, en los monos araña los individuos con alta centralidad por intermediación tienen una mayor riqueza de especies en sus cargas parasitarias. Aunque en los monos maiceros se encontró la misma tendencia que en los monos araña, al incluir en el modelo la dominancia social, se observó que esta por si sola explica la riqueza de las cargas parasitarias, sugiriendo que los individuos con alta jerarquía tienden a tener comunidades de parásitos más grandes que individuos subordinados. Los resultados de este capítulo aportan al entendimiento de las dinámicas de transmisión de parásitos y a la socio- ecología de los monos araña café, los monos cariblancos y monos maiceros a través de acercamientos analíticos novedosos y registros de información de manera no invasiva. Resalta las dinámicas sociales inherentes de la especie como factores determinantes en la transmisión de parásitos y las cargas parasitarias. Finalmente, en el tercer capítulo describimos como las interacciones sociales, el tamaño corporal y la dominancia determinan las cargas parasitarias en una tropa de monos maiceros (Sapajus apella). Adicionalmente, se evaluó si la productividad de frutos carnosos determina los patrones comportamentales de los individuos de la tropa, su masa corporal o si esta es explicada por su estatus social. También, de manera experimental se determinó si las cargas parasitarias representan un costo energético para el hospedero. Además, determinamos la compensación social para los individuos dominantes de la tropa. Durante 18 meses se realizaron monitoreos comportamentales usando muestreos de animal focal de todos los miembros adultos y sub-adultos de la tropa. Sistemáticamente se colectaron datos de las actividades diarias de la tropa y sus patrones comportamentales. Mensualmente se colectaron muestras fecales de todos los individuos adultos y sub-adultos. Mensualmente se registró la biomasa de los miembros del grupo, seis meses después, el 50% de los miembros recibió un tratamiento antiparasitario y se continuó con el monitoreo de la masa corporal de los individuos del grupo. Se encontró que la dominancia es la variable que mejor explica la riqueza de especies en las cargas parasitarias de la tropa de monos maiceros, sugiriendo un potencial costo asociado con el estatus social. Sin embargo, experimentalmente encontramos que las cargas parasitarias no representan un costo energético significativo para el hospedero. Observamos que la masa corporal se mantuvo relativamente estable durante los periodos de escasez, en contraste en los periodos de abundancia la mayoría de los individuos ganaron peso. Los individuos sub-adultos subordinados presentaron una mayor ganancia comparado con el resto de los miembros. Actividades como movimiento, acicalamiento y juego fueron más frecuentes durante la escasez sugiriendo un maximización de energía. También, se encontró diferencias comportamentales asociadas al estatus social, observándose al macho alfa alimentarse más frecuente y por periodos más largos, infligió más agresiones y recibió más acicalamiento que los subordinados. Adicionalmente, el macho fue más pesado que el promedio de la población. Nuestros resultados soportan la hipótesis que la ganancia en masa corporal está determinada por la disponibilidad de recursos y que el tamaño corporal está asociado con la dominancia. Aunque la posición social trae consigo un costo asociado con el riesgo de infección, se observaron una serie de beneficios sociales con el estatus. Sin embargo, el mantenimiento de esta posición genera un alto gasto en energético a través de despliegues de agresiones, evidenciándose en una pérdida de peso durante las épocas de escases y una ganancia menor de biomasa que individuos subordinados.
Acceso abierto
Life in a hot valley: effects of environmental and anthropogenic factors on the spatial dynamics of mammal and ground-dwelling bird communities in the Magdalena River Valley in Colombia
(Universidad de los Andes, 2024-12-11) Montes Rojas, Andrés Fernando; Link Ospina, Andrés; Pardo Vargas, Lain E.; Cadena Ordóñez, Carlos Daniel; Facultad de Ciencias::Centro de Investigaciones Ecológicas la Macarena
The lowland ecosystems of the Magdalena River Valley exhibit a marked gradient, from tropical dry forests in the south of the valley to tropical rainforests and swamps in the north. These ecosystems have a composition of fauna and flora characterized not only by a high level of diversity but also by a high level of vulnerability due to the productive processes there. Activities such as cattle ranching, agriculture, mining, and urban expansion have led to an enormous transformation of the forests, threatening the species that live there. Under these conditions, forest-dwelling animals, such as medium and large mammals and some birds, are exposed to pressures that compromise their long-term persistence in the landscape. This project focused on the effects of environmental and anthropogenic factors on the diversity and occupancy patterns of mammals and ground-dwelling birds along the lowland forests of the Magdalena River Valley. It uses camera trap data from eight study sites (30 to 35 camera traps per site) located along the gradient. The study is divided into three chapters, in the first I used a multispecies occupancy model to assess the response of mammals and birds to the extreme conditions of an arid ecosystem and human activity, and how this response may vary with two species' traits, body mass and percentage of carnivory. In the second chapter, I focused on the effects of environmental and anthropogenic disturbance gradients on the community structure and occupancy patterns of mammals and ground-dwelling birds along the Magdalena River valley. Finally, in the third chapter, I evaluated the effectiveness of a conservation strategy based on restoration corridors to improve landscape connectivity for ground-dwelling fauna.
Acceso abierto
Interaction between Cutibacterium acnes, bacteriophages and keratinocytes as a study model of acne phage therapy
(Universidad de los Andes, 2024-12-10) Farfán Esquivel, Juan Camilo; Vives Flórez, Martha Josefina; González Escobar, John Mario; Valderrama Aguirre, Augusto Elías; Piuri, Mariana; Facultad de Ciencias::Microbiologia Ambiental y Bioprospeccion; Facultad de Medicina::Ciencias Básicas Médicas
Acne is one of the most prevalent skin disorders worldwide. It is an inflammatory disease in which several factors are part of its pathogenesis: hormonal activity, hyperkeratosis, hyperseborrhea and colonization with the bacterium Cutibacterium acnes (formerly Propionibacterium acnes) (Cong et al., 2019; Kurokawa et al., 2009; Williams et al., 2012). There are six phylotypes identified for this microorganism: IA1, IA2, IB, IC, II, and III. In healthy skin, all phylotypes coexist in population equilibrium. However, in acne the population of phylotype IA1 is increased (Dagnelie et al., 2019). This phylotype stimulates cytokine production in sebocytes, keratinocytes, and neutrophils, maintaining and increasing inflammation in the skin (Barnard et al., 2016; Fitz-Gibbon et al., 2013). To treat acne, there are several drugs available, including antibiotics, which are useful due to their anti-inflammatory properties (Marson & Baldwin, 2019). Some of these drugs present side effects that compromise patient adherence to treatment. Also, it has been reported bacterial resistance for commonly used antibiotics to treat acne (Dessinioti & Dréno, 2020) making necessary to identify new alternatives to antibiotic therapy (World Health Organization, 2015). One alternative is phage therapy: using bacteriophages (phages), bacterial viruses, to control bacterial infections (Kutter et al., 2010). One of the advantages of phage therapy is its specificity since phages are generally species-specific; even some are restricted to the strain level (Hyman & Abedon, 2010). Besides, there are studies that had reported immunomodulatory properties for some bacteriophages, for instances, reducing inflammatory cytokine production (Van Belleghem et al., 2019). The principal objective of this project is to evaluate the effectivity of C. acnes bacteriophages from two perspectives: their potential to control the phylotype IA1 and its effect on the impact of C. acnes on skin cells. Host range for a collection of 10 lytic phages to isolates of different phylotypes showed that no phage is IA1-specific. However, four phages (PhiA, PhiC, Phi5, and Phi7.3) showed a diminished activity for other phylotypes. Also, plating efficiency demonstrated that these phages have differences in their efficiency to lyse phylotype IA1 isolates, being PhiA and Phi7.3 more active against IA1 isolates compared with other phylotypes. To investigate the phage’s potential to control C. acnes in skin cells a colonization model with three phylotypes (IA1, IB, and II) on Human Epidermal Keratinocytes (HEKa) co-cultures were stablished. Bacterial impact on HEKa was evaluated by cytotoxicity estimation through MTT assay, and by counting of viable cells with trypan blue. It was found that phylotypes IA1 and IB have a similar cytotoxic effect, dependent upon bacterial cell density inoculation, while phylotype II did not cause such cytotoxic effect. Inoculation with all phylotypes caused a delay in logarithmic growth phase, though the effect of phylotype IA1 on cell growth was sharper. Interestingly, phylotype II produced an increased cell proliferation. Finally, IL-1b expression was also evaluated with RT-qPCR from keratinocytes inoculated with the three different phylotypes. All bacterial isolates may increase IL-1b expression. However, only IA1 increased this cytokine expression in HEKa in a higher and more consistent manner. After the establishment of the HEKa colonization model with C. acnes IA1, it was assessed the potential of phages to ameliorate bacterial effect on keratinocytes. Phages PhiA, PhiC, Phi5, and Phi7.3 reduce C. acnes IA1 inoculum in a C. acnes-HEKa co-culture. Also, it was recorded a reduction of cytotoxicity on a different level for each phage, dependent upon concentration and purification. Purified PhiA, PhiC, and Phi7.3 were able to restore cell growth of C. acnes IA1-inoculated HEKa, which was higher for the last two phages. Alongside, inoculation of phages Phi7.3 and Phi5 reduced the IL-1b expression of colonized keratinocytes, regardless of their cytotoxicity and cell growth behavior. Overall, it is concluded that phages have a dual expected effect for acne phage therapy: the reduction of IA1 negative impact on keratinocytes and the control of this phylotype. The results here shown support the potential application of phage therapy in acne treatment, given the innocuity of phages to keratinocytes and the reduction of bacterial impact in these skin cells. Although this study explores interactions between phages, C. acnes, and skin cells, it opens the field to more detailed and comprehensive research on phage interactions with skin immunity and their influence on skin microbiota.
Acceso abierto
Understanding the transmission dynamics of the sylvatic cycle of Trypanosoma cruzi by Rhodnius prolixus in the Colombian Orinoco
(Universidad de los Andes, 2024-07-30) Urbano Tibaduiza, Plutarco María; González Rosas, Camila; Ramírez González, Juan David; Rodrigues Roque, André Luiz; Link Ospina, Andrés; Facultad de Ciencias::Cimpat. Centro de Investigaciones en Microbiología y Parasitologia Tropical
The overall objective of this research project is to assess the effect of ecosystem transformation on the vector transmission cycle of Chagas disease in the department of Casanare. This will be achieved through three chapters. In the first chapter, the variation in the transmission ecology of T. cruzi was determined in different species of wild palms in the Colombian Orinoco by characterizing the feeding sources and natural infection of R. prolixus collected in M. flexuosa, A. aculeata, and A. butyracea. This chapter was titled “Transmission ecology of Trypanosoma cruzi by Rhodnius prolixus (Reduviidae: Triatominae) infesting palm-tree species in the Colombian Orinoco, indicates risks to human populations”. This first chapter has been published in the journal PLOS Neglected Tropical Diseases (IF 3.8, Q1, Annex 1, https://doi.org/10.1371/journal.pntd.0011981). The second chapter was titled “Exploring dietary differences among developmental stages of triatomines infected with Trypanosoma cruzi in different habitats”. This chapter has been published in the International Journal of Parasitology (IF 4.0, Q1, Annex 2, https://doi.org/10.1016/j.ijpara.2024.05.001). Lastly, the third chapter was titled “Population dynamics of Rhodnius prolixus and risk of transmission of Trypanosoma cruzi in natural forest patches in the Colombian Orinoco region” and will be submitted to the journal Parasites and Vectors (IF 3.4, Q1). In the following sections, each of the chapters is presented in more detail, including an introduction, objectives, methods, and results.
Embargo
Pathogenicity and resistance to antifungals-fungicides in Fusarium and Neocosmospora A One health approach
(Universidad de los Andes, 2024-06-05) Sáenz Moncaleano, Valeri Andrea; Celis Ramírez, Adriana Marcela; Jiménez Alzate, María del Pilar; Bernal Giraldo, Adriana Jimena; Facultad de Ciencias::Grupo de Investigación Celular y Molecular de Microorganismos Patógenos (Cemop)
The primary objective of this doctoral thesis was to determine the presence of Fusarium and Neocosmospora in humans, animals, and plants through a One Health approach. To achieve this, we conducted phenotypic and molecular studies on samples obtained from various environments and human strains in Colombia to identify Fusarium or Neocosmospora. Our research revealed that Neocosmospora keratoplastica and Neocosmospora falciformis are prevalent in samples collected from humans, animals, and the environment (soil and sand). Notably, we describe Sea Turtle Egg Fusariosis (STEF) in sea turtles in Colombia for the first time. Furthermore, to find differences in how Fusarium/Neocosmospora interacts with hosts, we employed a Galleria mellonella animal model. We inoculated the larvae with clinical, animal, and environmental samples to carry out this experiment. We observed similar effects on mortality when the larvae were exposed to 1.5x106 UCF / ml of inoculum and incubated in a maintained incubation at 25 ° C. Also, it was observed that human, animal, and environmental samples can induce mortality in larvae at 37°C. Moreover, we determined the in vitro susceptibility profile of 52 isolates towards antifungal and fungicides. Our findings confirmed high Minimum Inhibitory Concentrations (MICs) to itraconazole, posaconazole, propiconazole, tebuconazole, and difenoconazole. However, amphotericin B and voriconazole showed susceptibility in most of the isolates. Subsequently, we aimed to investigate the antifungal effectiveness of molecules involved in Protein Kinase signaling pathways against Fusarium/Neocosmospora clinical isolates (n=12). To do this, we performed an in vitro test using four different inhibitors: the Pkc1 inhibitor (NPC15437), the p38 MAPK inhibitor (SKF 86002), the human Hsp90-Cdc37 inhibitor (Celastrol), and the antiparasitic drug Miltefosine. Our results indicate that the PKC1 inhibitor (NPC15437) and Miltefosine have promising antifungal activity. Finally, we address the challenges of diagnosing fungal keratitis in clinical and microbiologic settings. This was achieved through a survey of healthcare workers and collaboration with ophthalmologists, clinical microbiologists, and biodesigners to perform the design drafts and initial sketches of a medical device for corneal scraping.
Acceso abierto
Traveling through the transcriptome and volatilome to understand Malassezia host-bacteria interactions
(Universidad de los Andes, 2024-06-05) Ríos Navarro, Andrea; Celis Ramírez, Adriana Marcela; Muñoz Camargo, Carolina; Villegas Torres, Maria Francisca; Murillo, Walter; Facultad de Ciencias
Malassezia is a lipid-dependent yeast inhabiting human and animal skin, representing about 80% of mycobiota. Although Malassezia is considered commensal, it has been associated with skin diseases that affect the general population. The mechanisms by which these yeasts get this pathogenic role are unknown. Malassezia species exhibit a wide lipid metabolic diversity, enhancing their adaptation processes to the host. However, the involvement of these dynamic processes in the host, and the beginning of the transition from beneficial to pathogenic remain unclear. Likewise, the function of secondary metabolites like volatile compounds in interactional processes with the host and resident or transitory microbiota is undefined. Previous studies about other microorganisms suggest these compounds could also be involved in biological interactions. On the other hand, the yeast and host approach to global gene expression when interacting has yet to be reported. Moreover, Malassezia lipid composition could be involved in the pathogenic processes. This research aims to answer the following question through a metabolomic and transcriptomic approach: What is the effect of the Malassezia metabolism (differential gene expression and volatile compounds production) in its interaction with the host and other bacteria? This question would be solved by implementing a keratinocyte in vitro model supplemented with lipids and infected with M. globosa, followed by a transcriptome analysis throughout RNAseq. Additionally, the determination of the volatile profile for Malassezia spp. was performed by Headspace-solid phase microextraction (HS-SPME) and gas chromatography coupled mass spectrometry (GC-MS) to separate and characterize the volatile compounds. After this, we assessed the interaction processes between volatile compounds and Staphylococcus aureus as a microorganism model from microbiota.
Acceso abierto
Molecular epidemiology driving precision medicine: Unraveling some genetic and environmental determinants in certain Colombian populations
(Universidad de los Andes, 2024-06-04) Lago Martínez, Juliana; Groot De Restrepo, Helena; Briceño Balcázar, Ignacio; Valderrama Aguirre, Augusto Elias; Facultad de Ciencias::Laboratorio de Genética Humana
The interplay between molecular epidemiology and precision medicine, coupled with collaborative initiatives may drive Colombia into a new era of healthcare tailored to the individualized genetic profile in the Colombian population. Studying chronic diseases such as Neuromyelitis Optica spectrum disease (NMOSD), chronic kidney disease (CKD), hemophilia A (HA) and B (HB), and von Willebrand disease (VWD) in Colombia is crucial to better understand their prevalence, presentation patterns, and treatment needs in the population. This enables the development of effective prevention, diagnostic, and medical care strategies tailored to the country's specific needs. Increased attention to diversity will increase the accuracy, utility, and acceptability of using this genomic information for clinical care (6). Considering this context, where chronic diseases pose significant health challenges, ME approaches through affordable genetic and bioinformatic research has been applied in this thesis work to address these issues. Three different studies exemplify this integration. The first chapter, divided into two sections, will focus on, first the characterization of HLA class II alleles in NMOSD patients in Colombia, and second, identifying new NMOSD disease biomarkers as well as understanding the studied population structure. The second chapter will focus on understanding the impact of genetic polymorphisms on mercury levels and CKD, and the third chapter will focus on identifying the genetic mutations associated with inherited bleeding disorders in Colombia and developing and implementing low-cost genetic diagnostic methods. Given that Colombia may present one of the highest prevalence rates of NMOSD in Latin America (14), we highlighted the need for further investigation into the contributing factors of this disease. In this sense, understanding the specific HLA class II genetic landscape in our population can provide valuable insights into the complex interplay between genetic predisposition and environmental factors influencing NMOSD susceptibility. Our first study represents the first exploration of HLA patterns in NMOSD patients in Colombia and, to our knowledge, has one of the largest HLA characterized NMOSD cohorts studied in Latin America. The inclusion of multidimensional genetic biomarker data from large numbers of subjects exemplifies the consideration of human genomics within precision public health research (15). In addition to these genomic biomarkers, the ability to detect other biomarkers including the transcriptome is also increasing significantly. This is also considered in Chapter 1, where FOXP3 gene expression was measured and compared to healthy controls as a possible new biomarker of the disease. The second chapter presents a study placed in the field of environmental health. The integration of human genomic research within environmental health research may help to elucidate how individual-level factors (e.g., genetic data) and macro-level factors interact to influence health, providing a better understanding of mechanisms underlying complex gene-environment interactions (15). In Colombia, where environmental exposures may vary across regions, understanding how these factors interact with genetic predispositions becomes crucial. The study on the impact of genetic polymorphisms on mercury (Hg) levels and CKD sheds light on the intricate relationship between genetic variations, environmental exposures, and disease outcomes in the Colombian population. Ultimately, the investigation into inherited bleeding disorders in Bogotá incorporated genetic and bioinformatic methods to enhance the precision of diagnoses. This not only refines the detection of individuals with specific genetic conditions but also streamlines the creation of personalized treatment plans based on the individual's genetic background. Consequently, these findings play a crucial role in comprehending the economic and health implications of precision public health initiatives, particularly regarding their support for health equity. With improved data, healthcare resources can be better managed and allocated (15). In conclusion, this thesis represents an effort to delve into the molecular etiology of some chronic human diseases, from autoimmune disorders to metabolic and genetic conditions. This effort provided valuable insights that can guide the development of more effective diagnostic approaches in the clinical setting and in the development of biomarkers that can support the public health fields of both early diagnosis and intervention to limit the burden of these diseases.
Acceso abierto
Environmental demogenetics of the potato late blight in Colombia
(Universidad de los Andes, 2024-06-04) Patarroyo Velásquez, Camilo Andrés; Restrepo Restrepo, Silvia; Dupas, Stéphane; Rojas Flechas, Alejandro; Santos Vega, Oscar Mauricio; Facultad de Ingeniería::Grupo de Micología y Fitopatologia
The potato late blight is known for its role in the Irish potato famine during the 19th century. This disease has been extensively studied ever since. However, despite being one of the most well-studied plant diseases in the world, it remains one of the biggest threats to global food security. The late blight is caused by the Oomycete Phytophthora infestans. In Colombia, due to the prevalence of this disease and the extended use of susceptible potato cultivars, the main control strategy against this disease is the continuous application of fungicides. This strategy has three main issues: first because of the toxicity of these compounds, it can negatively affect the health of growers and consumers, second repeated exposure of P. infestans to these fungicides leads to the development of resistance, and third its continuous use increases the costs of potato production. One way of reducing the use of fungicides without sacrificing the crop's safety is using epidemiological models of the late blight. These models project the proliferation of P. infestans in function of the environmental conditions. This allows the growers to only spray fungicides during the most favorable periods for the pathogen proliferation. These previous approaches are mechanistic and deterministic and do not consider the genetics of the pathogen. This work aimed to develop an integrative simulation model for the distribution of P. infestans in Colombia. The key novel idea of this model was to combine genetic, demographic, and environmental information in the simulation modeling and, therefore, in the predictions that could be obtained from it. This dissertation is divided into four chapters. The first chapter focuses on exploring the genetic landscape of P. infestans in Colombia. This chapter uses a novel machine learning-based tool to classify P. infestans microsatellite genotypes into their corresponding clonal lineage. In the second chapter, a new method to infer the rate of sexual reproduction of P. infestans was developed. Then, the integrative model for the distribution of P. infestans was developed in the third chapter. Genetic information gathered in the first two chapters and environmental and epidemiological information were used to build the proposed model. Finally, in the fourth chapter, the forecasting done by the model developed in the third chapter was used to produce easy-to-follow fungicide application schedules and recommendations that could be directly communicated to the growers through the miCampoApp application. This work then provides new tools for the analysis of genetic data from P. infestans and other polyploid organisms capable of both sexual and asexual reproduction. It also introduced a new modeling approach for the distribution of P. infestans and the appearance of the potato late blight in Colombia that can also be applicable in other regions with collected field data. Finally, this work proposes a way of directly communicating the model’s forecasting to the growers as part of a bigger agricultural cooperative structure.
Acceso abierto
Ecological dynamics of macroinvertebrates from inselbergs of the Colombian Guiana Shield
(Universidad de los Andes, 2023-02-02) Aristizábal Botero, Ángela; Realpe Rebolledo, Emilio Antonio; 10535677; Molina Escobar, Jorge Alberto; LAZOEA
Entender las dinámicas ecológicas implica ser capaz de esclarecer las conexiones e interacciones entre los factores bióticos y abióticos al interior y entre ecosistemas. En este proyecto estudiamos las conexiones entre la biodiversidad local y el entorno físico único de los afloramientos de granito del Escudo Guayanés, una de las formaciones rocosas más antiguas de la Tierra. En estos afloramientos, también conocidos como inselbergs, hay concavidades que por la acción erosiva del viento y el agua se convierten en charcos que periódicamente pueden retener aguas lluvias o provenientes de los ríos o lagunas. Esto permite el desarrollo de una biodiversidad única de microorganismos, plantas y animales. Aunque la fauna de los sistemas formados por estos charcos sobre afloramientos rocosos en regiones templadas, áridas y semiáridas ha sido ampliamente documentada, se sabe poco sobre sistemas similares en el Neotrópico. El primer desafío del proyecto fue caracterizar la compleja estructura tridimensional (3D) del hábitat. Para ello, utilizamos la fotogrametría a través de imágenes tomadas con un vehículo aéreo no tripulado (dron o UAV por sus siglas en inglés). Con los análisis realizados llegamos a la conclusión de que las imágenes tomadas con drones pueden ayudar a reconstruir la variación espacial de las estructuras de los microhábitats. Tarea que sería imposible de cuantificar mediante observaciones a nivel del suelo o utilizando imágenes de satélite. Además, logramos reconstruir indicadores de la calidad del hábitat, tales como la actividad fotosintética y la conectividad de los charcos mediante el modelamiento de la elevación del terreno y las microcuencas. A pesar de que los inselbergs son reconocidos por su diversidad de plantas, poco se sabía sobre la fauna acuática asociada a estos hábitats en la ecozona neotropical. En el segundo capítulo, exploramos la biodiversidad acuática de los macroinvertebrados presentes al inicio y en una fase tardía de la temporada de lluvias. Esta sección presenta el primer estudio de biodiversidad y la primera caracterización de las características fisicoquímicas del agua de este ecosistema en la región. Encontramos una fuerte estacionalidad con diferencias tanto taxonómicas como funcionales en las comunidades de estos organismos. Al inicio de la fase de inundación de los charcos las comunidades estaban dominadas por micro crustáceos pioneros y otros organismos recolectores. Por su parte, los depredadores casi duplicaron su abundancia relativa una vez avanzó la temporada de lluvias. En el grupo de especies pioneras también se registraron depredadores especializados como libélulas con adaptaciones que les ayudan a explotar los recursos al principio de las inundaciones. Finalmente, en el capítulo tres, mostramos una fuerte diferenciación en las comunidades de odonatos que habitan charcos que difieren en su hidroperíodo. Para ayudar a explicar esta variación en el uso del hábitat, realizamos un experimento de historia de vida a gran escala con tres familias de Odonata. En este probamos si las náyades eran capaces de utilizar ligeras variaciones en las concentraciones de minerales disueltos y el nivel del agua como señales de la desecación inminente del charco que habitan. El capítulo ilustra cómo la plasticidad del desarrollo desencadenada por diferentes señales puede ayudar a los odonatos a evitar la mortalidad y explotar hábitats de corta duración. También contribuye a una mejor comprensión de los requisitos y la flexibilidad de los odonatos en respuesta a las condiciones ambientales. En general, en este proyecto usamos nuevas tecnologías, inventarios faunísticos, análisis multivariado y experimentos de historia de vida para obtener más información sobre los procesos ecológicos fundamentales que determinan la composición de las comunidades locales de macroinvertebrados. Esto puede facilitar su inclusión en iniciativas informadas para la gestión responsable de los ecosistemas y la conservación de la biodiversidad.
Acceso abierto
Anaerobiosis: a new gamer in phage-host interaction
(Universidad de los Andes, 2023-02-02) Hernández Villamizar, Santiago; Vives Flórez, Martha Josefina; 51912705; Celis Ramírez, Adriana Marcela; Rodríguez Villamizar, Fernando; Centro de Investigaciones Microbiológicas - CIMIC
La fagoterapia es una alternativa viable para controlar infecciones bacterianas, sin embargo, entender como la bacterias y fagos interactúan dependiendo del ambiente es crucial para tener un tratamiento efectivo. Muchas de las aplicaciones de fagos son realizadas sobre ambientes anaerobios (intestino, heridas), entonces entender el efecto de la falta o limitación de oxígeno en la interacción fago-hospedero se hace necesaria. Desde 1975 no se han publicado investigaciones para elucidar el efecto de la ausencia de oxígeno en el proceso de infección del fago. En este estudio nosotros reportamos este efecto en un modelo Salmonella sp.-fago, dada su importancia como patógeno y contaminante bacteriano en ambiente anaerobios, y el potencial de la fagoterapia para controlarla. Encontramos que el ciclo de replicación viral, la reducción de la población bacteriana por unidad de tiempo, y el desarrollo de resistencia son influenciadas por la anaerobiosis de la siguiente manera: a) el fago es afectado en la longitud de su ciclo de vida y en su capacidad para controlar la población bacteriana; b) se observó que el tamaño celular bacteriano está asociado a la cantidad de proteína FtsZ y que se altera la aparición de resistencia en contra del fago. Asimismo, los resultados de los análisis transcriptómicos sugieren que la infección en condiciones aeróbicas induce metabolismo anaerobio, específicamente nitrato reducción, y hay subexpresión de genes asociados con respiración aeróbica en la bacteria. En la infección anaeróbica no se observó cambios al metabolismo de generación de energía usado por la bacteria en crecimiento anaeróbico, pero sí se evidenció aumento en la transcripción de genes relacionados con el transporte de aceptores de electrones usados en anaerobiosis. Independiente la condición de oxígeno, los resultados mostraron que la mayoría de los genes con expresión diferencial en la infección fueron aquellos clasificados en la categoría de función desconocida o no pudieron ser anotados. Los resultados en conjunto dan un panorama de cómo la ausencia de oxígeno pude afectar la interacción fago-hospedero, y cuyas consecuencias deberían ser consideradas al momento de usar los fagos biotecnologicamente.
Acceso abierto
Origin, development, and function of colored inguinal and axillary spots in cryptic lineages of poison frogs (Amphibia: Anura: Dendrobatoidea)
(Universidad de los Andes, 2022-07-28) Palacios Rodríguez, Pablo; Brunetti, Andrés Eduardo; Vives Flórez, Martha Josefina; 29336400; 51912705; Rojas, Bibiana; Molina Escobar, Jorge Alberto; Grupo de Ecofisiologia, Comportamiento y Herpetología
The study of biological models exhibiting dual cryptic-aposematic anti- predatory strategies based on their coloration, can shed important light on some of the great controversies in the evolution of aposematism. Among them, the greatest vulnerability faced by the first conspicuous individuals within a population; the link between conspicuous coloration and other traits indicative of condition, physiological performance and development of toxicity; and the consequences of aposematic coloration in contexts of courtship, sexual selection and reproductive isolation. In this context, this thesis investigates the functional and evolutionary origin, and the ecological correlation of the femoral and inguinal colorful spots in frog lineages of the superfamily Dendrobatoidae historically considered as cryptic.
Acceso abierto
Speciation of the genus phytophthora: divergence of a recently emerged phytophthora species attacking solanum betaceum crops in south america
(Universidad de los Andes, 2017) Mideros Bastidas, Maria Fernanda; Restrepo Restrepo, Silvia; 39784728; Cano, Liliana; Crawford, Andrew
Acceso abierto
Systematics and phylogeography of southern ocean deep-sea octocorals
(Universidad de los Andes, 2016) Dueñas Montalvo, Luisa Fernanda; Wilke, Thomas; Crawford, Andrew Jackson; 335316; Lessios, Harilaos; Realpe Rebolledo, Emilio Antonio; Sánchez Muñoz, Juan Armando
Octocorals are very diverse marine organisms that inhabit virtually every marine ecosystem, therefore are widely distributed around the globe. The origin of their huge diversity has been questioned for several decades, however very few studies have addressed this issue until now. This doctoral thesis explored the systematic relationships of octocoral deep-sea fauna distributed in Antarctic and Sub-Antarctic regions, and evaluated the role of the Antarctic Circumpolar Current (ACC) as a driving force for the diversification of octocoral deep-sea populations. It also assessed the evolution of four octocoral traits and the role of these traits on diversification rate shift. To answer the previous questions we used different approaches and methods that included phylogenetics, molecular dating, character evolution, phylogeography and population genetics. Here, we present the first assessment of phylogeographical patterns and the role of the ACC in the genetic connectivity for two deep-sea octocorals in the Pacific and Southern Ocean: Tokoprymno maia, which is a brooding octocoral, and Hemicorallium imperiale, which is a broadcast spawner. We also explored the systematic relationships of the deep-sea bamboo corals of the subfamily Keratoisidinae, and described two new species Keratoisis magnifica and Keratoisis peara. Finally, we inferred the most comprehensive time-calibrated phylogeny of all Octocorallia to date. We estimated the time of origin of this group around the Triassic, where he first octocorals appear to have been soft-bodied colonies, azooxanthellate, deep-water and cold-water organism. The study of marine benthic organisms has increased in the last decade, particularly for deep-sea fauna. This thesis has contributed greatly in the general knowledge of diversity patterns, temporal diversification processes, and population dynamics for Octocorallia. Our contribution has also laid a basis for further evolutionary studies on these incredible diverse organisms.
Acceso abierto
Bird-parasite interactions in tropical forests : an ecological and evolutionary perspective
(Universidad de los Andes, 2018) Pulgarín Restrepo, Paulo César; Cadena Ordónez, Carlos Daniel; 79787809; Guhl Nannetti, Felipe; Marzal Reynolds, Alfonso
"The results of this dissertation are a step forward in the understanding of host-parasite interactions in tropical and temperate areas. Overall, the first chapter indicates that host-species are more important than water-related variables in explaining parasite prevalence across environmental gradients, which offers opportunities to study the factors responsible for parasitic infections and how are parasite communities structured in tropical forest. The second chapter we found that prevalence and lineage diversity of haemosporidians varied significantly over the year, being higher during breeding and migration while decreasing during wintering. We found that Gray-cheeked Thrushes shared few parasite lineages with tropical resident birds and slightly more lineages with other migratory and resident-boreal species. My results indicate that long-distance migratory songbirds may not be important dispersers of blood parasites because there are ecological and evolutionary barriers to the interchange of parasites across vastly separated areas. Finally in the third chapter I found that Santa Marta and New Guinea differed in parasite diversity and degree of host-parasite specialization (both were higher in New Guinea), however, I provide evidence for reciprocal elevational zonation between haemosporidian parasites and closely related species of bird as well as variation in prevalence patterns between bird species replacing each other with elevation in both mountain systems. Although these patterns are consistent with predictions of the hypothesis that parasites limit host geographic ranges, additional work including studies of vector ecology and experiments are necessary to determine whether patterns in fact imply causal relationships. I summary my thesis offers a wide perspective on the ecology and evolution of host-parasite interactions in a variety of systems that includes population and community approaches of the host and parasites."--Tomado del Formato de Documento de Grado.

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