Weighted norm inequalities for singular integral operators satisfying a variant of Hörmander's condition

summary:In this paper we establish weighted norm inequalities for singular integral operators with kernel satisfying a variant of the classical Hörmander's condition

Parasite threats from the ornamental fish trade

The ornamental fish trade is an important commodity sector that involves the capture or farming of fish species for their aesthetic value. Since the 1960s, technological advances have enabled multiple countries to trade numerous ornamental fish species globally. As such, the ornamental fish trade is a pathway for the introduction of exotic fish species and their associated parasites and pathogens into endemic environments, with the potential for detrimental effects on biodiversity, ecosystems, industries, and their dependent local communities. Governments can establish quarantine measures to detect, prevent and mitigate the risks of introducing exotic parasites and pathogens. For example, Australia has established import requirements for ornamental fish species based on risk assessments undertaken by the Australian government Department of Agriculture and Water Resources (DAWR). However, Australian risk assessments largely focus on parasites and pathogens of global significance in food fish production (i.e., salmonids and prawns). As such, established biosecurity requirements for the import of ornamental fish to Australia (DAWR 2018), focus on pathogenic bacteria (e.g., Aeromonas salmonicida (Lehmann and Neumann, 1896)) and viruses (e.g., spring viraemia of carp virus (SVCV)) known to impact aquaculture, while a much broader parasite fauna of ornamental fishes remains to be assessed. The aim of this thesis was to address three specific gaps of knowledge of the ornamental trade. First, I examined limitations in data collation of t ornamental fish imported to Australia (Chapter 2). Second, I examined the diversity of parasite fauna infecting traded marine and freshwater ornamental fish species (Chapter 3 and 4), and; third, I evaluated the validity of cutting-edge molecular methods to detect parasites infecting imported ornamental fishes at border control (Chapters 5 and 6). Accurate data that describes the supply and demand of the global ornamental trade is essential for the development of comprehensive biosecurity protocols to protect endemic ecosystems and natural resources from introduced pathogens and parasites. To quantify the species diversity and volume of ornamental fishes imported to Australia, I examined publicly available data of aquarium fish imports to Australia between 2010-2016, collated and curated by DAWR (Chapter 2). I found that DAWR provides publicly available records of imported ornamental fish species ascribed to categories that offered limited resolution regarding the specific species identity. Taxonomically sound evaluation of Australian aquarium imports would be useful to understand the importance of the Australian aquarium trade in the translocation of potentially hazardous parasites and pathogens, and aid international conservation policies. Following, I surveyed freshwater and marine ornamental fish populations imported from Asia (i.e., Singapore, Malaysia, Thailand and Sri Lanka) to Australia for the presence of protozoan (Chapter 3) and metazoan parasites (Chapter 4). Fish were received following veterinary certification by exporting countries declaring no clinical signs of pests or diseases, and visual inspection by Australian Quarantine Services. Fish necropsies revealed a diverse array of parasite species, including 18 putative types of myxozoans (e.g. Ceratomyxa, Kudoa and Myxobolus spp.), and 14 parasitic monogenean species (e.g. Dactylogyrus, Gyrodactylus, Urocleidoides, and Trianchoratus spp.). One of the major findings was that goldfish, Carassius auratus Linnaeus, 1758, which are the most frequently traded freshwater fish species world-wide, exhibited high parasite diversity (Chapter 3 and 4). Subsequently, I conducted an exhaustive review of the history of the goldfish trade and parasite richness to provide insight into how the international trade of this species may have facilitated parasite co-introduction and co-invasion (Chapter 5). I found that more than 113 parasite species infect goldfish in their native range, of which 26 species were likely co-introduced with the international trade of goldfish (or other cyprinids). These included harmful, generalist parasite species in freshwater aquaculture fishes such as Ichthyophthirius multifiliis Fouquet, 1876, Lernaea cyprinacea Linnaeus, 1758, and Schyzocotyle acheilognathi (Yamaguti, 1934). It is concluded that the goldfish trade likely continues to facilitate the introduction and invasion of exotic parasites on a global scale. It is clear that pre-export health requirements for the importation of ornamental fish species into Australia are not being met (Chapters 3-5), and that cryptic parasites are not detected during visual inspections at border control. Thus, inspection prior to exportation and at border control must account for the highly cryptic nature of parasites and pathogens and consider alternatives to current pre-export conditions and visual inspections at border control. For this reason, I proposed screening fish transport water for the presence of parasite environmental DNA (eDNA) as a detection method for enhanced biosecurity (Chapter 6). I examined water samples from 11 target populations (cyprinids susceptible to Dactylogyrus spp. infections) and seven non-target fish populations (non-cyprinids, not susceptible to Dactylogyrus spp. infections) imported from southeast Asia to Australia for the presence of eDNA from five Dactylogyrus species (Monogenea: Dactylogyridae) using novel species-specific quantitative PCR (qPCR) assays. Dactylogyrus spp. eDNA was detected in all targeted fish populations, showing that eDNA presents a considerable advantage over visual inspections and parasitological necropsies. However, Dactylogyrus spp. eDNA was also detected in water from non-cyprinid fish populations that are not susceptible to and were not infected by Dactylogyrus parasites, highlighting the risk of false positive detections associated with contaminated water sources used to transport ornamental fish species. Environmental DNA screening for parasite DNA offers a highly sensitive and non-invasive detection tool during pre-export monitoring of ornamental species and could aid quarantine officers to triage high-risk ornamental fish exports based on eDNA detection of parasite DNA in the exporting country. Nonetheless, quarantine officers should be vigilant in the limitations posed by contaminated water sources if eDNA screening methods are used at border control. Parasite eDNA detection in water samples from non-cyprinid fish populations in Chapter 5 suggested the possibility of false positive detections by eDNA screening. For this reason, I tested the reliability of eDNA screening methods by qPCR for biosecurity purposes in an experimental system simulating the export process (Chapter 7). Experimentally infected live fish (i.e., the monogenean Neobenedenia girellae (Hargis, 1955) infecting Lates calcarifer (Bloch, 1790)) were used to detect parasite eDNA in water samples, simulating the export process from packaging to delivery over a 48 h period. The consignments included 'infected fish', 'treated fish', and 'contaminated water' (containing dead parasites) delivered by 'exporting companies'. Quantitative PCR tests were inaccurate when detecting eDNA collected from low parasite intensities (mean intensity ± S.D. = 6.80 ± 4.78 parasites/fish). Quantitative PCR tests detected parasite eDNA in 50% of infected fish indicating a high plausibility of false negative detections because of low eDNA concentrations in water samples. Furthermore, parasite eDNA was detected in70% of non-infected fish in contaminated water samples, indicating the possibility of false positive detection of DNA from dead parasites present in the water. Environmental DNA screening methods, while more sensitive than current biosecurity protocols, are limited for accurate and reliable use where differentiation between live parasite infections and dead, non-viable parasites in the water is paramount. This thesis highlights the limitations of the DAWR current data collation framework to accurately examine aquarium fish import data and determined that a large diversity of protozoan and metazoan parasites are not detected at border control. Import conditions for ornamental species are not being met by exporting companies. While eDNA screening methods offer a potential tool for the detection of cryptic pathogens, the limitations of this technique need to be considered for development as a detection tool to demonstrate freedom from parasite infection in the ornamental fish trade

Dissecting the assembly process of benthic communities from neotropical streams

§ La conservación y rehabilitación de la estructura y funcionamiento de los ecosistemas requiere de un conocimiento profundo de las causas y consecuencias de su biodiversidad. Sin embargo, este conocimiento es aún escaso en regiones Neotropicales. § En esta tesis, utilizo el marco conceptual de las metacomunidades para caracterizar los posibles efectos que tienen los procesos de dispersión (en tiempos ecológicos y evolutivos), selección (impulsada por factores abióticos) y deriva ecológica en la diversidad y distribución de las comunidades bentónicas fluviales. 2 § La zona de estudio, de un área de aproximadamente 40,000 km , abarcó entre 26 y 32 segmentos de ríos prístinos del Orinoco colombiano. Los puntos de muestreo abarcaron un gradiente de elevación de 300 a 3400 m.s.n.m. que incluyó un conjunto heterogéneo de ecorregiones y paisajes. § Mediante una aproximación de ligar patrones y posibles mecanismos, esta tesis proporciona evidencias de que la dispersión, la selección y la deriva están directamente involucradas en el proceso de ensamblaje de las comunidades bentónicas fluviales. § Mis hallazgos indican que uno o más eventos de limitación de la dispersión en un marco de tiempo evolutivo (eventos de aislamiento alopátrico) formaron diferentes pools de especies dentro de la cuenca del Orinoco. La extensión de estos pools coincide parcialmente con la distribución de las ecorregiones, lo que sugiere que los eventos que moldearon los paisajes fluviales y la estructura de la vegetación afectaron de manera similar la diversidad y distribución de las especies bentónicas en ecosistemas fluviales. § Adicionalmente, dentro de cada ecorregión, la dispersión, la selección y la deriva están interactuando para restringir la estructura y la dinámica de las comunidades y metacomunidades entre y dentro de los ríos. Dependiendo de la comunidad (p.e. diatomeas o insectos), el papel de cada uno de estos procesos puede prevalecer sobre el de los demás. § Estos hallazgos tienen implicaciones tanto para la investigación básica como para la aplicada (p.e. biomonitoreo) en las disciplinas de la ecología de metacomunidades y de agua dulce, así como en la conservación y la biogeografía.§ The conservation and rehabilitation of ecosystem structure and functioning requires of a deep knowledge on the causes and consequences of its biodiversity. The assembly of Neotropical communities, particularly in riverine ecosystems, remains to be dissected. § I used the metacommunity framework to dissect the relative influences of dispersal (in ecological and evolutionary timeframes), selection (driven by abiotic factors) and ecological drift on the assembly process of freshwater benthic communities. § The study was carried out at 26-32 different stream segments within an area of 2 about 40,000km , in the Colombian Orinoco. The area encompasses an elevation gradient from 3400 to 300m a.s.l. and includes a heterogeneous assembly of ecoregions and landscapes. § By using a pattern-matching approach, I provide evidences supporting that dispersal, selection and drift are directly involved in the assembly of freshwater benthic communities. § My findings indicate that one or more events of dispersal limitation (i.e. allopatric isolation) in an evolutionary timeframe shaped distinct pools of taxa in the Orinoco basin. The extent of these pools partially matches the distribution of the ecoregions, suggesting that those events molding the riverscapes and the vegetation structure similarly affect the diversity and distribution of benthic species. § Within each ecoregion, dispersal, selection and drift interact to constrain the structure and dynamics of communities and metacommunities among and within streams. Depending on the taxa belonging to each pool of species, the role of one of these processes may prevail over the others. § These findings have implications for both basic and applied research in the disciplines of metacommunity and freshwater ecology as well as of conservation and biogeography.Linking functional diversity patterns of algae and invertebrates to scale-dependent constrains of rivers from the Orinoco basinTesis con fines de doble titulación bajo el Convenio de cotutela entre la Universidad de Girona y la Universidad Nacional de Colombia.Doctorad

Mild Velocity Dispersion Evolution of Spheroid-like Massive Galaxies since z~2

Making use of public spectra from Cimatti et al (2008), we measure for the first time the velocity dispersion of spheroid-like massive (M_star ~ 10^11 M_sun) galaxies at z ~ 1.6. By comparing with galaxies of similar stellar mass at lower redshifts, we find evidence for a mild evolution in velocity dispersion, decreasing from ~240 km/s at z ~ 1.6 down to ~180 km/s at z ~ 0. Such mild evolution contrasts with the strong change in size (a factor of ~4) found for these type of objects in the same cosmic time, and it is consistent with a progressive larger role, at lower redshift, of the dark matter halo in setting the velocity dispersion of these galaxies. We discuss the implications of our results within the context of different scenarios proposed for the evolution of these massive objects.Comment: 5 pages, 2 Figures. Accepted in ApJL. Minor changes from former submissio

Perspectiva del derecho del medio ambiente y de las políticas ambientales de la Unión Europea (Segundo semestre 2017)

Perspectiva del derecho del medio ambiente y de las políticas ambientales de la Unión Europea (Segundo semestre 2017

Perspectiva del Derecho del Medio ambiente y de las Políticas ambientales de la Unión Europea

Perspectiva del Derecho del Medio ambiente y de las Políticas ambientales de la Unión Europe

Menos violencia, más crecimiento- Caso colombiano: 2005-2015

Este artículo presenta un análisis de como se ha visto afectado el crecimiento económico a nivel departamental en Colombia durante el periodo 2005-2015 por la variación de la criminalidad -- El objetivo del mismo, es establecer las relaciones existentes entre las variables, por el aumento en la inversión en seguridad que se dio durante la presidencia de Álvaro Uribe Vélez en el periodo 2002-2006 -- Para ello, se parte de la hipótesis de que la inversión en seguridad aumenta la confianza en el país, lo que estimula la inversión nacional y extranjera, y finalmente se ve reflejado de manera significativa y positiva en el crecimiento económico -- Para corroborar esto se implementa un modelo de panel de datos dinámico de la forma Arellano Blundell-Bond, donde los resultados corroboran la relación inversa entre el índice de criminalidad, que es utilizado como proxy de la inversión en seguridad y el nivel de producción departamentalThis article presents an analysis of how economic growth at the departmental level in Colombia between the years 2005-2015 has been affected by crime -- The objective is to establish the existing relationships between these variables, by the increase in security expenditure that occurred during the presidency of Álvaro Uribe Velez in the period 2002-2006, so it is based on the hypothesis that investment in security increases confidence in the country, which stimulates domestic and foreign investment, and finally is reflected in a significant and positive way in economic growth -- To corroborate this, a dynamic data panel model of the Arellano Blundell-Bond form is implemented, where the results corroborate the inverse relationship between the crime and the departmental outpu

Perspectiva del Derecho del medio ambiente y de las politicas ambientales de la Unión Europea (Segundo semestre 2016)

Perspectiva del Derecho del medio ambiente y de las politicas ambientales de la Unión Europea (Segundo semestre 2016