The role of waterbirds in the dispersal of aquatic organisms in southern Africa

Dispersal is a fundamental process with far-reaching ecological and evolutionary consequences. Not all organisms are capable of dispersing on their own and instead produce propagules that must be transported to new habitat by a vector. Propagule dispersal by frugivorous bird species is well researched, but only very recently has the capacity of highly mobile waterbirds to disperse aquatic organisms received similar attention in the dispersal literature. Dispersal is important for the organisation of communities, and therefore understanding the frequency and scale of waterbird-mediated dispersal provides insight into the structure of wetland communities. Additionally, the study of waterbird-mediated dispersal in arid southern Africa provides an opportunity to expand our knowledge on the persistence of populations of aquatic organisms in heterogeneous environments. Recently, field and laboratory studies have demonstrated the remarkable ability of waterbirds to disperse the propagules of both plants and aquatic invertebrates. However, these studies have largely been based in the northern hemisphere and many have focussed on long-distance dispersal by migratory waterbirds. Therefore, it is difficult to generalise how waterbird-mediated dispersal plays out in different landscapes and throughout the annual cycle. Furthermore, there is still little knowledge of the spatial patterns of propagule dispersal and the mechanisms that cause these patterns to vary in space and over time. This thesis aims to addresses several of these knowledge gaps in waterbird-mediated dispersal and presents the first detailed study of propagule dispersal by waterbirds anywhere in Africa. In Chapters 2 - 5, I adopt a field- and experimental-based approach to develop a general understanding of waterbird-mediated dispersal in southern Africa. Firstly, making use of faecal samples and feather brushings collected from several waterfowl (duck) species at three locations in South Africa, I determine the quantity and viability of propagules transported via endozoochory and ectozoochory. I then assess the relative contributions of each dispersal mode to the dispersal of plants and aquatic invertebrates in the field. I show that endozoochory is the dominant dispersal mechanism, but it may be complementary to ectozoochory as different propagules are transported via this mode. Secondly, by making use of an experimental feeding trial with two captive waterfowl species, Egyptian Goose and Red-billed Teal, I explore how seed traits mediate a trade-off in recoverability and germinability against gut retention times. I show that small, hard-seeded species are retained for longer and therefore may be dispersed further. Thirdly, I incorporate gut retention time data and Egyptian Goose and Red-billed Teal movement data, acquired from GPS satellite transmitters across five study populations in southern Africa, into a mechanistic model to explore spatial patterns of seed dispersal. The model demonstrates that waterfowl generally facilitate dispersal on the local scale of below 5 km, but on occasion can transport seeds as far as 500 km from a seed source. There was variation in dispersal distances between the vectors and across the study populations and the results indicate that dispersal is affected by both intrinsic and extrinsic drivers of animal movement. In Chapters 6 and 7, I apply the concept of waterbird-mediated dispersal more broadly to address (1) the role of waterbirds in the dispersal of aquatic invaders; and (2) the determination of seed dispersal functional groups amongst a waterfowl community. I conducted a literature review to objectively describe the role of waterbirds in the dispersal of aquatic weeds. Waterbirds are important vectors of aquatic invasive species and consideration of the spatially explicit manner in which birds move is imperative to our understanding of invasive spread. In the second case, I used diet data from the 16 waterfowl species indigenous to southern Africa to explore whether finer level seed dispersal functional groups were evident. I found support for several functional groups of seed disperser based on unique plant families in the diet and suggest that important functional differences do occur between groups of waterfowl species

Synthesis of potentially biologically active aromatic and hetero-aromatic compounds

The first part of this dissertation deals with employing the use of multi-component coupling reactions (MCC) for the synthesis of large diverse compound libraries. A review of selected literature identified the growing need for more potent and selective HIV/AIDS drugs due to the extremely high mutation rate of the HI virus. We thus chose to test our synthesised compound library against the HIV enzyme, reverse transcriptase (RT) in the hopes of identifying a potential novel non-nucleoside reverse transcriptase inhibitor (NNRTI). Two different MCC approaches were used in order to give two different classes of compounds; firstly the Groebke-Blackburn reaction for the synthesis of imidazo[1,2-a]pyridines and secondly a reaction developed by Poigny and co-workers for the synthesis of 3-amino-1-cyano-indolizines. We were successful in utilizing the Groebke-Blackburn to synthesise a variety of imidazo[1,2-a]pyridines in varying yields. However, all of the compounds showed poor inhibition of the RT enzyme in the biological assay. We thus turned our attention to the synthesis of the 3-amino-1-cyano-indolizines, which proved to be very difficult. It was discovered that this reaction did not proceed to completion and the product generally isolated from this MCC reaction was the more stable aldol condensation intermediate. In some of the experiments we were able to isolate mostly small quantities of indolizine compound, but when tested against the RT enzyme the results once again were very poor. A short review in the second section of this dissertation showed the lack of methodology available for the synthesis of the dihydrobenzo[b]phenanthridine motif which constitutes the backbone of a secondary metabolite known as Jadomycin B. The major aim of this segment of the project was thus to develop methodology to synthesise this biologically important scaffold. However, our methodology failed to yield the desired product as it was not possible to reduce the nitrile intermediate to the required amine. In an attempt to determine whether similar methodology could be used for the synthesis of pyranonaphthoquinone containing compounds an unexpected and novel reaction was discovered. It was found that treatment of [2-(1,4-dimethoxynaphthalen-2-yl)phenyl]methanol with brominating agent NBS results in the synthesis of a naphthopyranone ring system known as 12-methoxy-6H-dibenzo[c,h]chromen-6-one. Following this discovery it was attempted to elucidate the mechanism by which NBS performs this novel reaction. Unfortunately we were unable to determine the exact mechanism responsible for this transformation conclusively. The most likely mechanism shows NBS oxidising the benzylic alcohol to an aldehyde, which is then converted to an acid bromide facilitating ring closure. Finally we wished to determine if this strategy could be applied in the synthesis of related naphthopyranone ring systems, which was shown to be possible with the synthesis of 3-bromo-2-methoxy-6H-benzo[c]chromen-6-one

Translocation experiment gives new insights into the navigation capacity of an African duck

Aim: Movement is integral to the distribution and abundance of wildlife. We undertook an experimental test of the navigation capacity of Egyptian Geese Alopochen aegyptiacus to better understand the movements of moult-migratory waterfowl and the implications of navigation capacity for their ecology. Location: Southern Africa. In June 2015, we translocated six post-flightless moult Egyptian Geese 1250 km south, from north-west South Africa (Barberspan) to the south-west coast (Strandfontein). We compared their movements to those of 29 previously tracked resident Egyptian Geese from the source and translocation sites, and three additional sites (Voelvlei; Jozini Dam; Lake Manyame, north-central Zimbabwe). Methods: We used solar-powered satellite GPS to track movement patterns and compared the movement paths of different birds using net-squared displacement analysis and multiple regression analysis of different measures of movement paths. Results: Over time periods up to 658 days, none of the translocated Egyptian Geese returned to Barberspan and only one appeared to fly towards it. Translocated birds showed some novel and risky behaviours. Longer, searching-type movements were evident with the onset of both the breeding and moulting seasons. Quantitative comparisons suggested that translocated birds retained elements of learned behaviours. Main conclusions: Navigation by Egyptian Geese appears to have a strong learned (internal) element, with long-distance movement triggered by internal states such as the need to moult. Translocated animals modified their movement patterns in ways that mostly allowed them to survive. Our results have interesting implications for understanding the dynamics of individual populations; a strong reliance on learned behaviours may explain the unresolved conundrum of why no African duck species has colonized Europe without human assistance. Our analysis demonstrates the complexity of influences on animal movement and highlights the importance of navigation capacity for conservation biogeography

A framework for testing assumptions about foraging scales, body mass, and niche separation using telemetry data

Ecological theory predicts that if animals with very similar dietary requirements inhabit the same landscape, then they should avoid niche overlap by either exploiting food resources at different times or foraging at different spatial scales. Similarly, it is often assumed that animals that fall in different body mass modes and share the same body plan will use landscapes at different spatial scales. We developed a new methodological framework for understanding the scaling of foraging (i.e. the range and distribution of scales at which animals use their landscapes) by applying a combination of three well-established methods to satellite telemetry data to quantify foraging patch size distributions: (1) first-passage time analysis; (2) a movement-based kernel density estimator; and (3) statistical comparison of resulting histograms and tests for multimodality. We demonstrate our approach using two sympatric, ecologically similar species of African ducks with quite different body masses: Egyptian Geese (actually a shelduck), and Red-billed Teal. Contrary to theoretical predictions, the two species, which are sympatric throughout the year, foraged at almost identical spatial scales. Our results show how ecologists can use GPS tracking data to explicitly quantify and compare the scales of foraging by different organisms within an animal community. Our analysis demonstrates both a novel approach to foraging data analysis and the need for caution when making assumptions about the relationships among niche separation, diet, and foraging scale

Wealth, water and wildlife: Landscape aridity intensifies the urban luxury effect

AbstractAimUrban biodiversity, and its associated ecosystem services, is an important component of the quality of life of urban residents. The "luxury effect" posits a positive association between biodiversity and socioeconomic status in urban areas, and is thus reflective of environmental injustice, as the benefits associated with biodiversity are not equitably shared across society. We aimed to determine the generality of the luxury effect, and to identify the factors causing its variation across published studies.LocationUrbanized landscapes globally.Time periodCurrent.Major taxa studiedTerrestrial animals and plants.MethodsWe tested the luxury effect across a sample of 337 estimates of the relationship between biodiversity measures and socioeconomic status from 96 studies via a meta‐analysis, addressing three hypotheses: (a) the luxury effect is more pronounced where water availability is limited, (b) the luxury effect is more pronounced in developing than developed countries, (c) the luxury effect is stronger in exotic compared to native species.ResultsThere was a significant overall luxury effect: there was a positive association between terrestrial biodiversity measures and socioeconomic status. The strength of the luxury effect was greater in arid areas. There was limited support for a stronger luxury effect in exotic species, but no support for any association with development status.Main conclusionsMany key and emerging climate impacts are concentrated in urban areas. Therefore, the degree of environmental injustice represented by the luxury effect may be amplified in the future, especially in arid regions. The objective to increase urban biodiversity through more equitable management and provision of water resources could form part of a wider strategy for sustainable development of cities to promote environmental justice, enhancing the quality of life of urban residents across all sectors of society. Challenges remain to ensure that any such strategy prioritizes conservation goals for native biodiversity

Functional Traits Drive Dispersal Interactions Between European Waterfowl and Seeds

Endozoochory by waterfowl is important for a broad range of angiosperms, most of which lack a fleshy fruit. This dispersal function contributes to the formation and maintenance of plant communities and may allow range shifts for plant species under global change. However, our current understanding of what seed or plant traits are important for this dispersal mechanism, and how they relate to variation in waterbird traits, is extremely limited. We addressed this question using a unique dataset identifying the plant species whose seeds are ingested by 31 different waterfowl species in Europe. We used RLQ and fourth-corner analyses to explore relationships between (1) bird morphological and foraging strategy traits, and (2) plant traits related to seed morphology, environmental preferences, and growth form. We then used Generalized Additive Models to identify relationships between plant/seed traits and the number of waterfowl species that disperse them. Although many waterfowl feed intentionally on seeds, available seed trait data provided little explanation for patterns compared to plant traits such as Ellenberg indicators of habitat preference and life form. Geese were associated with terrestrial plants, ingesting seeds as they graze on land. Diving ducks were associated with strictly aquatic plants, ingesting seeds as they feed at greater depths. Dabbling ducks ingest seeds from plants with high light and temperature requirements, especially shoreline and ruderal species growing in or around the dynamic and shallow microhabitats favored by these birds. Overall, the number of waterfowl vector species (up to 13 per plant species) increases for plants with greater soil moisture requirements and salinity tolerance, reflecting the inclination of most waterfowl species to feed in coastal wetlands. Our findings underline the importance of waterfowl dispersal for plants that are not strictly aquatic, as well as for plants associated with high salinities. Furthermore, our results reveal a soil moisture gradient that drives seed-bird interactions, in line with differences between waterfowl groups in their microhabitat preferences along the land-water continuum. This study provides an important advance in our understanding of the interactions that define plant dispersal in wetlands and their surroundings, and of what plants might be affected by ongoing changes in the distributions of waterfowl species

Dispersal of aquatic and terrestrial organisms by waterbirds: A review of current knowledge and future priorities

1. We review progress in our understanding of the importance of waterbirds as dispersal vectors of other organisms, and identify priorities for further research. 2. Waterbirds are excellent for long-distance dispersal (LDD), whereas other vectors such as fish and mammals disperse similar propagules, but over shorter distances. Empirical studies of internal and external transport by waterbirds have shown that the former mechanism generally is more important. Internal transport is widely recognised for aquatic plants and aquatic invertebrates with resting eggs, but also is important for other organisms (e.g., terrestrial flowering plants not dispersed by frugivores, bryophytes, tardigrades, fish eggs). 3. Waterbird vectors also are important in terrestrial habitats, and provide connectivity across terrestrial–aquatic boundaries. There are important differences in the roles of different waterbird species, especially those using different habitats along the aquatic–terrestrial gradient. Early attempts to predict zoochory based on propagule morphology have been found wanting, and more research is needed into how the traits of vectors and vectored organisms (including life history, dormancy and growth traits) explain dispersal interactions. Experimental studies have focused on the potential of propagules to survive internal or external transport, and research into factors determining the establishment success of propagules after dispersal is lacking. 4. Recent spatially explicit models of seed dispersal by waterbirds should be expanded to include invertebrate dispersal, and to compare multiple bird species in the same landscape. Network approaches have been applied to plant–waterbird dispersal interactions, and these are needed for invertebrates. Genetic studies support effective LDD of plants and invertebrates along waterbird flyways, but there remains a lack of examples at a local scale. Next Generation Sequencing and genomics should be applied to waterbird-mediated dispersal across the landscape. More studies of biogeography, community ecology, or population genetics should integrate waterbird movements at the design stage. 5. Zoochory research has paid little attention to the dispersal of non-pathogenic microbes (both eukaryotic and prokaryotic). Nevertheless, there is evidence that dispersal via avian guts can be central to the connectivity of aquatic microbial metacommunities. More work on microbial dispersal by waterbirds should explore its implications for biogeochemistry, and the interchange with gut flora of other aquatic organisms. In the Anthropocene, the role of migratory waterbirds in LDD of plants and other organisms is particularly important, for example in compensating for loss of large migratory mammals and fish, allowing native species to adjust their distributions under global warming, and spreading alien species along flyways after their initial introductions by human vectors. Recent technological advances have opened exciting opportunities that should be fully exploited to further our understanding of dispersal by waterbirds.AJG was supported by projects from the Ministerio de Ciencia e Innovación (PID2020-112774GB-I00/AEI/10.13039/501100011033) and Ministerio de Economía y Competitividad (CGL2016-76067-P). ESG received the grant RYC2019-027216-I funded by MCIN/AEI/10.13039/501100011033 and from ESF Investing in your future. GGS received a postdoctoral fellowship from CNPq (grant no. 150887/2022-1) ÁLK was supported by a János Bolyai Research Scholarship of the Hungarian Academy of Sciences, New National Excellence Programme of the Ministry of Innovation and Technology ÚNKP-21-5-DE-457, NKFIH FK-138698 grants

Susceptibility and status of avian influenza in ostriches

The extensive nature of ostrich farming production systems bears the continual risk of point introductions of avian influenza virus (AIV) from wild birds, but immune status, management, population density, and other causes of stress in ostriches are the ultimate determinants of the severity of the disease in this species. From January 2012 to December 2014, more than 70 incidents of AIV in ostriches were reported in South Africa. These included H5N2 and H7N1 low pathogenicity avian influenza (LPAI) in 2012, H7N7 LPAI in 2013, and H5N2 LPAI in 2014. To resolve the molecular epidemiology in South Africa, the entire South African viral repository from ostriches and wild birds from 1991 to 2013 (n = 42) was resequenced by next-generation sequencing technology to obtain complete genomes for comparison. The phylogenetic results were supplemented with serological data for ostriches from 2012 to 2014, and AIV-detection data from surveillance of 17?762 wild birds sampled over the same period. Phylogenetic evidence pointed to wild birds, e.g., African sacred ibis (Threskiornis aethiopicus), in the dissemination of H7N1 LPAI to ostriches in the Eastern and Western Cape provinces during 2012, in separate incidents that could not be epidemiologically linked. In contrast, the H7N7 LPAI outbreaks in 2013 that were restricted to the Western Cape Province appear to have originated from a single-point introduction from wild birds. Two H5N2 viruses detected in ostriches in 2012 were determined to be LPAI strains that were new introductions, epidemiologically unrelated to the 2011 highly pathogenic avian influenza (HPAI) outbreaks. Seventeen of 27 (63%) ostrich viruses contained the polymerase basic 2 (PB2) E627K marker, and 2 of the ostrich isolates that lacked E627K contained the compensatory Q591K mutation, whereas a third virus had a D701N mutation. Ostriches maintain a low upper- to midtracheal temperature as part of their adaptive physiology for desert survival, which may explain the selection in ratites for E627K or its compensatory mutations markers that facilitate AIV replication at lower temperatures. An AIV prevalence of 5.6% in wild birds was recorded between 2012 and 2014, considerably higher than AIV prevalence for the southern African region of 2.5% 3.6% reported in the period 2007 2009. Serological prevalence of AI in ostriches was 3.7%, 3.6%, and 6.1% for 2012, 2013, and 2014, respectively. An annual seasonal dip in incidence was evident around March/April (late summer/autumn), with peaks around July/August (mid to late winter). H5, H6, H7, and unidentified serotypes were present at varying levels over the 3-yr period.La extensa naturaleza de los sistemas de producción de avestruz enfrenta el riesgo continuo de la presentación del virus de la influenza aviar (AIV) originado de aves silvestres, pero el estado inmunológico, el manejo, la densidad de población, y otras causas de estrés en avestruces son determinantes importantes en la severidad de esta enfermedad en esta especie. De enero del 2012 a diciembre del 2014, se registraron más de 70 casos de virus de influenza aviar en avestruces en Sudáfrica. Estos virus incluyeron virus de baja patogenicidad H5N2 y H7N1 en el año 2012, virus de baja patogenicidad H7N7 en el año 2013 y virus de baja patogenicidad H5N2 en 2014. Para resolver la epidemiología molecular en Sudáfrica, todo el repositorio de muestras virales de avestruces y aves silvestres en Sudáfrica del año 1991 al 2013 (n = 42) fue re-analizado por análisis de secuencias de próxima generación para obtener genomas completos para su comparación. Los resultados filogenéticos se complementaron con datos serológicos para avestruces del año 2012 al 2014, y con los datos de detección en la vigilancia del virus de influenza aviar de 17?762 aves silvestres muestreadas durante el mismo período. La evidencia filogenética señaló el papel de aves silvestres como los, ibis sagrados africanos (Threskiornis aethiopicus), en la difusión de virus de influenza de baja patogenicidad H7N1 a las avestruces en las provincias del Este y del Cabo Occidental durante el año 2012, en incidentes separados que no pudieron ser relacionados epidemiológicamente. Por el contrario, los brotes con virus H7N7 de baja patogenicidad en el año 2013, que se limitaban a la Provincia Occidental del Cabo parecen haberse originado a partir de una introducción de un solo punto de aves silvestres. Se determinó que dos virus H5N2 detectados en avestruces en el año 2012 de baja patogenicidad eran introducciones nuevas, que no estaban relacionadas epidemiológicamente con los brotes de influenza aviar en el año 2011. Diecisiete de 27 (63%) virus de avestruces contenían el marcador PB2 E627K, y dos de los aislados de avestruz que carecían del marcador E627K contenían la mutación compensatoria Q591K, mientras que un tercer virus tenía una mutación D701N. Las avestruces mantienen una temperatura baja en la parte media y baja de la tráquea como parte de su fisiología de adaptación para sobrevivir en el desierto, lo que puede explicar la selección de las ratites para la mutación E627K o sus mutaciones compensatorias que son marcadores que facilitan la replicación del virus de influenza aviar a temperaturas más bajas. Se registró una prevalencia del virus de influenza aviar de 5.6% en las aves silvestres, entre 2012 y 2014, considerablemente más alta que la prevalencia del virus de influenza aviar de la región de África meridional de 2.5% ?3.6% reportada en el periodo entre los años 2007-2009. La prevalencia serológica de la influenza aviar en avestruces fue del 3.7%, 3.6% y 6.1% para los años 2012, 2013 y 2014, respectivamente. Fue evidente una caída estacional en la incidencia anual alrededor de Marzo y Abril (finales de verano/otoño), con picos alrededor de Julio y Agosto (mediados a finales de invierno). Los subtipos H5, H6, H7, y serotipos no identificados estuvieron presentes en diferentes niveles durante el período de tres años.http://www.aaapjournals.info/loi/avdiProduction Animal Studie

Bird tolerance to humans in open tropical ecosystems

AbstractAnimal tolerance towards humans can be a key factor facilitating wildlife–human coexistence, yet traits predicting its direction and magnitude across tropical animals are poorly known. Using 10,249 observations for 842 bird species inhabiting open tropical ecosystems in Africa, South America, and Australia, we find that avian tolerance towards humans was lower (i.e., escape distance was longer) in rural rather than urban populations and in populations exposed to lower human disturbance (measured as human footprint index). In addition, larger species and species with larger clutches and enhanced flight ability are less tolerant to human approaches and escape distances increase when birds were approached during the wet season compared to the dry season and from longer starting distances. Identification of key factors affecting animal tolerance towards humans across large spatial and taxonomic scales may help us to better understand and predict the patterns of species distributions in the Anthropocene.</jats:p