Sponges contribute to large number of functions in coral reef ecosystems. Among these, bioerosion is perhaps one of the most widely studied, largely due to the important contribution of excavating sponges to the carbonate budget on coral reefs (up to 95 % of the total internal bioerosion). Despite our current knowledge, much of the literature is centred on individual-based observations, and little is known about their ecological role and interactions with other reef taxa in complex coral reef systems. The aim of this thesis was to quantify the ecological interactions of bioeroding sponges with major reef taxa by scaling up individual observations to population and ecosystem-based approaches. A cosmopolitan, abundant and highly competitive bioeroding sponge from Glover’s Atoll, Belize (Cliona tenuis) was used as model species. Monitoring of C. tenuis populations throughout 2009 indicated a trade-off between reproduction and growth, with the highest growth rates (31.4 ± 5.6 mm.y–1) occurring in summer, and a peak in reproductive output during winter. Populations typically show strong left-skewed size frequency distributions, mostly represented by juvenile-size individuals (46%), suggesting that regulating mechanisms (e.g. competition and predation) may be acting in constraining the transition of juveniles to adult sizes. Long-term in situ manipulations showed no effect of predation, yet competition with macroalgae significantly reduced the size of the sponge by 38% ± 11% (SE). While C. tenuis exhibit high growth and recruitment rates that could theoretically result in rapid population growth, the likelihood of sponges forming an alternative stable state as reefs sustain greater levels of disturbance is unclear. An analytical modelling approach of the interplay between macroalgae, coral and sponge was used to explore the likelihood of alternate stable states. The results show that irrespective of successful sponge invasion, inclusion of this third antagonist (in the interplay between coral and macroalgae) can qualitatively affect the likelihood of alternative stable state. The model exhibits emergent properties suggestive of intransitivity between the three competing taxa. Despite the potential of C. tenuis to benefit from disturbance, there are few cases in the literature reporting increases in bioeroding sponge abundance followed disturbance. Therefore, regulating mechanisms such as competition with other taxa, recruitment limitation or mortality are expected to exert demographic control on the populations of bioeroding sponges when space limitation is relaxed due to coral mortality. To determine processes regulating sponge populations, an individual-based spatial modelling approach was used to simulate the population dynamics of C. tenuis in a dynamic ecosystem environment. Using an orthogonal hypothesis testing approach, it was found that competition, and to a lesser extend partial mortality of the sponge tissue, largely regulate the population structure of C. tenuis. While reductions in coral cover may temporarily favour the rapid colonization by sponges, the competitive superiority of macroalgae may steal the opportunity from the opportunists.

Elk (Cervus elaphus) were historically present throughout Kentucky, but were extirpated by the mid 19th century. Kentucky Department of Fish and Wildlife Resources initiated elk reintroduction efforts in 1997, resulting in a self-sustaining population. I designed this project to study the effects of a parasitic nematode, meningeal worm (Parelaphostrongylus tenuis), on Kentucky’s elk herd. I examined potential maternal transfer of P. tenuis antibodies to elk calves, and investigated the relationship between elk habitat use and meningeal worm infection. I captured neonatal elk in 2004-06, fitted them with VHF transmitters, and collected blood samples for an enzyme-linked immunosorbent assay (ELISA) to determine P. tenuis infection. I monitored animals to determine habitat use, and attempted to recapture each individual to collect a follow-up blood sample. I found substantial rates of maternal meningeal worm antibody transfer (55%) over the course of the study. Neither sex nor predicted birth weight was associated with increased likelihood of obtaining maternal antibodies. Habitat variables associated with P. tenuis infection included herbaceous, shrub, and bare cover types, herbaceous mean core area, forest edge density, and forest mean core area. Confounding variables complicated habitat data analysis, but high rates of maternal P. tenuis antibody transmission suggested that meningeal worm infection does not threaten the long-term viability of the Kentucky elk herd.

Alternaria spot, caused by Alternaria tenuis, is an important disease of cladodes of the prickly pear cactus (Nopalea cochenillifera) in Brazil. There are no standard methods for assessment of the disease, so a standard area diagram set (SAD) was developed based on disease severity encompassing 2, 4, 7, 12, 22 and 40% of the cladode area spotted. SAD was validated by 10 raters, who analysed 50 cladodes with a range of disease severity, without and with SAD as an assessment aid. The accuracy, precision, reproducibility and repeatability of the estimates with and without the scale were determined using simple linear regression analysis. Without SAD the accuracy and precision of raters estimates were poor, with significantly constant and systematic bias, and determination coefficients (R2) ranging from 0.56 to 0.78. When raters employed SAD, significant reductions were observed in both constant and systematic bias, with R2 ranging from 0.91 to 0.96. In fact, raters achieved the highest repeatability (mean R2 = 0.95) and reproducibility (R2 0.80 in all cases) of estimates when using SAD. The proposed SAD set is suitable for assessment of Alternaria spot of prickly pear cladodes and improves the accuracy and precision of assessments. / A mancha de alternária, causada por Alternaria tenuis, foi detectada em cladódios de palma forrageira miúda (Nopalea cochenillífera) no Brasil em 2001 e, desde então, os relatos de sua ocorrência é conseqüente defoliação de palmas no campo se tornou constante. Devido à inexistência de métodos padronizados para quantificação desta doença desenvolveu-se uma escala diagramática com os seguintes níveis de área lesionada: 2, 4, 7, 12 ,22 e 40%. A validação da escala foi realizada por 10 avaliadores que estimaram a severidade da mancha de alternaria em 50 imagens de cladódios com diferentes níveis de intensidade da doença. A validação se deu em três etapas: i. sem o uso da escala; e ii. Primeira avaliação com a escala; e iii. Segunda avaliação com a escala. O intervalo entre etapas foi de 15 dias. A acurácia, precisão, reprodutibilidade e repetibilidade das estimativas foram avaliadas por meio de análise de regressão linear simples entre a severidade real e a estimada, com e sem auxílio da escala. A escala confeccionada foi de fácil utilização e proporcionou melhoria significativa nas estimativas de severidade, possibilitando bons níveis de acurácia e excelentes níveis de precisão, reprodutibilidade e repetibilidade, podendo ser utilizada em levantamentos de campo, estudos epidemiológicos e comparação de medidas de controle da doença.

Isolated populations have potential to become new species that should have less genetic variation than their ancestors. Small populations are more likely to lose genetic variation, which is, thus, expected to be greater in ancestors. Aliciella caespitosa and A. tenuis, two endemic species, may be derived from small populations of A. subnuda, a widespread species. Chloroplast DNA sequences were used to test this hypothesis. Allozyme data were used to compare genetic variation and numbers of alleles. Chloroplast data do not support the proposed relationships between A. subnuda and the other two species. Allozyme data were not more variable in A. subnuda. The data suggest that A. tenuis is derived from A. caespitosa, although the former did not show lower allozyme diversity. I detected fewer alleles in A. tenuis. These data suggest that the original population of A. tenuis was not small enough to lose genetic variation relative to its progenitor.

Sand dollars are abundant and conspicuous macroinvertebrates in sandy habitats in the Gulf of Mexico. They ingest sediment and associated organisms. Given their high abundances, size, and deposit feeding, they likely are the most important consumer coupling primary productivity with the rest of the food chain in these habitats. Moreover, sand dollars bioturbate sediments and affect species diversity and community structure. Three species of sand dollars in the family Mellitidae, Mellita tenuis, Encope michelini and Encope aberrans, were studied off the West Coast of Florida. Food and feeding of these sand dollar species were studied to understand their relationship to spatial and temporal patterns. Particle size and organic content gut contents, collected from inshore and offshore sites, were analyzed and compared with sediment collected concomitantly. Offshore sediment is coarser and has a higher organic content than inshore sediment . The gut particle sizes are similar for E. michelini and M. tenuis. The gut contents of E. aberrans have larger particles. All three species have gut particles smaller than the ambient sediment. The gut contents and sediment have higher organic content in the fall than the spring. Additionally, the gut organic content varies dielly, with peaks shifting by date. The gut organic content of the three species was higher than the sediment. The gut organic content of E. aberrans was significantly less than that of co-occurring M. tenuis. The particle sizes and organic content of the gut contents of Mellita tenuis and Encope michelini are similar. However food type ingested may differ. Encope aberrans may coexist with E. michelini and M. tenuis because it occupies a different niche. Inconsistent peak feeding times could reflect differences in food availability and predation pressure. Inverse relationships between particle size and organic content exist for sediment and gut contents. High densities of M. tenuis inshore may deplete the organic content of the sediment and reverse the negative relationship between particle size and organic content.

Made available in DSpace on 2014-06-11T19:35:44Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-08-27Bitstream added on 2014-06-13T20:46:52Z : No. of bitstreams: 1 lima_jt_dr_rcla.pdf: 1902367 bytes, checksum: 643e995723baa05601e16df2db548e28 (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Coptotermes gestroi e Heterotermes tenuis são espécies de cupins pertencentes à família Rhinotermitidae consideradas importantes pragas urbanas no Brasil, sendo que a segunda também é encontrada em ambientes agrícolas. No ambiente urbano, tais espécies são encontradas consumindo várias fontes celulósicas, algumas até aparentemente similares. O processo de forrageamento dos cupins subterrâneos é dinâmico e muda ao longo do tempo. Contudo, devido aos seus hábitos crípticos, existem alguns pontos polêmicos que precisam ser esclarecidos, principalmente visando melhorar e embasar as novas estratégias de manejo, tais como a tecnologia de isca. Em vista do exposto, a presente pesquisa propôs analisar e comparar, por meio de bioensaios, as respostas comportamentais de C. gestroi e H. tenuis considerando diferentes formas de apresentação do alimento e frente a recursos alimentares equivalentes. Uma vez que uma colônia pode utilizar várias fontes alimentares, também foi observado o comportamento de busca por novos alimentos, verificando o forrageamento desses insetos frente a recursos alimentares previamente visitados por outros cupins. Para esses bioensaios foram utilizados diferentes tipos de arenas experimentais compostas por câmaras “ninho” e câmaras alimentares. Adicionalmente, foi observado o comportamento de tunelamento dos forrageiros em solos heterogêneos, acrescidos de pistas físicas, químicas e biológicas, simulando aqueles presentes em áreas urbanas. Para tanto, foram utilizadas arenas bidimensionais compostas por duas placas de vidro separadas por uma moldura, a qual delimitava a área de tunelamento disponível para os indivíduos. Todos os dados obtidos foram analisados gráfica e estatisticamente, sendo que o nível de significância (a) adotado foi igual a 0,05. De acordo com os resultados obtidos nos experimentos com diferentes formas de apresentação... / Coptotermes gestroi and Heterotermes tenuis, termites of the Rhinotermitidae family, are considered important urban pests in Brazil. The latter is also found in rural areas. In urban environments, these species consume many cellulose sources, some apparently similar. The foraging behavior of subterranean termites is dynamic and changes throughout time. However, due to their cryptic behavior, some questions still remain, especially regarding the construction of a framework and the improvement of new control strategies involving baits. The present study was aimed at analyzing and comparing the behavioral responses of C. gestroi and H. tenuis using bioassays involving different food presentations and equivalent food resources. Since a colony can feed on many food sources, the searching behavior of new food items was examined as well as foraging of food items previously visited by other termites. Bioassays consisted of different types of arenas with a “nest” and feeding chambers were carried out. Also, the tunneling behavior of foragers in heterogeneous soils and physical, chemical, and biological cues was examined, simulating those present in urban areas. Bioassyas consisted of two glass plates separated by a frame delimitating the tunneling area available for the termites were carried out. The results were analyzed and significance level was set at p = 0.05. Based on the results obtained in the experiments with different forms of presentation of the food item, both species had similar behavioral patterns, showing a bias toward food items completely buried in the substrate. Regarding the exploitation of equivalent food sources, no differences were observed between consumption and recruiting for the first food sources visited compared to other sources available. Thus, C. gestroi and H. tenuis did not concentrate their efforts in the consumption of the first food item found. In tenacity... (Complete abstract click electronic access below)

[Truncated abstract] The extent to which marine populations are connected by larval dispersal is crucial to their distribution, maintenance and diversity. Thus, for the effective conservation of threatened systems such as coral reefs, understanding patterns of connectivity is essential. However, the biophysical mechanisms that retain or disperse larvae within and among populations are poorly understood. Though the open ocean environment provides the opportunity for long-distance dispersal, if this potential is only rarely realised, recruits produced from afar are unlikely to contribute to the local-scale demography of populations over ecological time frames, but will limit broad-scale genetic diversification over evolutionary time. This thesis explores the extent of genetic and demographic connectivity of two species of reef-building corals over a range of spatial scales among the discontinuous reef systems of northwest Australia. ... Putative source and sink dynamics were not random, but were associated with levels of disturbance and recovery from a recent and catastrophic coral bleaching. When S. hystrix samples from another two offshore systems were included in the analysis, large differences among systems showed that gene flow over hundreds of kilometres is rare over microevolutionary time scales that account for connections over multiple generations. Levels of subdivision over the same spatial scales were markedly lower in the acroporid coral, Acropora tenuis, than in S. hystrix. These results are congruent with expectations based on reproductive mode; in contrast to S. hystrix, which releases brooded larvae that are competent to settle immediately, A. tenuis broadcasts its gametes, and after external fertilisation, the larvae need to develop for several days before they are competent to settle. Despite the differences in levels of broad-scale subdivision, in both species significant differentiation was detected between reefs within systems (>10 km), and between sites within some reefs (< 10 km). These results indicate not only that dispersal between reefs and even some reef patches is restricted, but also that hydrodynamics influence retention of brooded and spawned larvae in similar ways. Further analysis of A. tenuis populations from two coastal systems detected significant differences in genetic diversity among the four major systems of northwest Australia. Additionally, genetic divergence between the coastal and offshore zones was greater than expected by the geographic separation of systems, indicating that connectivity between these zones via transport of A. tenuis larvae on oceanic currents occurs rarely even over microevolutionary time scales. This study has two primary implications for conservation. First, since coastal and offshore reefs of northwest Australia appear to be discrete genetic entities, they have independent evolutionary potential to adapt to local conditions and environmental change. Second, systems, reefs and some reef patches of northwest Australia are demographically independent units. Therefore, designs of coral reserve networks should consider routine dispersal distances of kilometres to a few tens of kilometres.

Le curage des sédiments des cours d'eau est nécessaire pour limiter les risques d'inondations et permettre la navigation fluviale. A cause des activités humaines, les sédiments de curage sont souvent contaminés en métaux, ce qui rend leur gestion problématique. Dans ce contexte,la phytostabilisation, une technique de traitement consistant à utiliser des plantes et des amendements minéraux pour réduire la mobilité des métaux dans des matrices solides contaminées, a été testée sur un sédiment de curage prélevé à proximité d'une fonderie de zinc et contaminé principalement par cet élément. Les plantes (Agrostis tenuis et Festuca rubra) ont été cultivées en serre, dans des mésocosmes d'environ 40 kg, qui contenaient l'un des trois substrats suivants : sédiment, sédiment + hydroxylapatite et sédiment + amendement sidérurgique ; des mésocosmes témoins non-végétalisés ont été placés dans les mêmes conditions. L'objectif principal de ce travail était de caractériser l'évolution de la spéciation du zinc induite par deux ans de phytostabilisation. Dans un premier temps, les associations géochimiques du zinc dans les différents milieux ont été observées sur des lames minces à l'échelle du micromètre grâce à l'utilisation combinée de techniques de micro-analyse (MEB-EDS, μXSRF). La spéciation du zinc dans chacune de ces associations a ensuite été déterminée par spectroscopie EXAFS résolue latéralement (μEXAFS). Le traitement des spectres μEXAFS par analyse en composantes principales (ACP) a permis l'identification de la sphalérite (ZnS), de la gahnite (ZnAl2O4) et de la franklinite (ZnFe2O4), qui sont des minéraux primaires certainement d'origine anthropique, et de la ferrihydrite (oxyhydroxyde de fer mal cristallisé) zincifère, d'une association zinc-phosphate, d'un phyllosilicate zincifère et de l'hydrotalcite (oxyhydroxyde d'aluminium) zincifère. Dans un second temps, les espèces zincifères ainsi identifiées ont été quantifiées à l'échelle macroscopique par spectroscopie EXAFS sur poudre. Les spectres EXAFS ainsi obtenus ont été simulés par combinaisons linéaires des spectres EXAFS des espèces zincifères précédemment identifiées, ce qui a permis d'évaluer l'effet du traitement sur la spéciation moyenne du zinc. En deux ans, elle a évolué de façon significative dans les mésocosmes amendés non-végétalisés, puisque l'on observe une diminution de la proportion de ZnS, la phase zincifère initialement majoritaire dans le sédiment, et la néoformation d'un phosphate de zinc. L'évolution de la spéciation du zinc est spectaculaire dans les mésocosmes végétalisés (amendés ou non), puisque dans ce cas, ZnS a été totalement oxydée et d'autres phases zincifères, telles qu'un phosphate de zinc et un phyllosilicate zincifère et / ou de l'hydrotalcite zincifère, se sont formées. La gahnite et la franklinite n'ont été observées qu'à l'échelle microscopique et sont donc des phases minoritaires. L'étude de la surface des racines des plantes par MEB-EDS, μSXRF et μEXAFS a permis de mettre en évidence la présence de précipités d'oxydes de manganèse (birnessite) riches en zinc, et parfois en plomb et en cuivre. Cette espèce chimique a été observée uniquement à la surface des racines et représente probablement une contribution minoritaire au processus global de l'immobilisation du zinc. Au bout de deux années, la phytostabilisation a permis la formation de phases zincifères plus stables que ZnS dans les conditions atmosphériques d'un dépôt de surface, indiquant que le zinc présent dans le sédiment phytostabilisé est potentiellement moins mobile que dans le sédiment seul. Ainsi, dans notre cas, la phytostabilisation limiterait donc la dispersion du zinc dans l'environnement.

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En la Pampa deprimida de la Provincia de Buenos Aires se ubica una de las principales zonas de cría de ganado vacuno, en la cual existen problemas de salinidad y alcalinidad en las partes más bajas. Allí se encuentra Lotus tenuis como especie herbácea naturalizada y muy valorada por su aporte a la oferta forrajera de los sistemas ganaderos de la región. Existe la necesidad de incrementar la producción de especies forrajeras adaptadas a condiciones edáficas cada vez más estresantes. En este sentido, en este trabajo se destacó la búsqueda, caracterización y selección de germoplasma productivo de Lotus tenuis, ya adaptado a dichas áreas marginales. Específicamente se evaluó la respuesta a estrés salino impuesto por shok y por aclimatación en dos estadíos de la etapa vegetativa, contemplando los cambios morfo-fisiológicos y bioquímicos resultantes. Se identificaron y seleccionaron individuos de una población con variabilidad en la tolerancia al estrés salino y se incrementó la búsqueda de recursos genéticos, incluyendo en las evaluaciones a distintas especies del género Lotus (las especies L.corniculatus y L. creticus, y especies consideradas modelo: Lotus japonicus MG20, Lotus japonicus Gifu, Lotus filicaulis, Lotus burtii), a varias poblaciones naturales de L. tenuis, y a tres variedades comerciales de L. tenuis, con el fin de ser utilizadas en un futuro en los programas de mejora. En ninguna de las especies evaluadas y en ninguno de los dos estados fenológicos estudiados, la salinidad provocó la muerte de las plantas. Las mayores disminuciones de peso fresco y de peso seco se detectaron cuando los tratamientos salinos se aplicaron en plantas de temprana edad (dos hojas verdaderas). Los parámetros de crecimiento que explicaron dicha disminución fueron, principalmente la disminución de la cantidad de tallos y ramificaciones por planta, y el diámetro del tallo principal. El área foliar bajo condiciones salinas sólo disminuyó en dos poblaciones de L. tenuis, de las 19 / Pesqueira, J. (2009). Cambios bioquímicos, morfológicos y ecofisiológicos en plantas del género Lotus bajo estrés salino [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/5765 / Palancia