Temporal and spatial distribution of the ichthyoplankton in the Canary Islands

A pesar del creciente inter��s en el estudio de las primeras fases de desarrollo de los peces, a��n existen zonas donde esta comunidad es relativamente desconocida. Este es el caso de las Islas Canarias. En la presente tesis, gracias a una serie de muestreos semanales en la regi��n costera de la isla de Gran Canaria durante m��s de dos a��os, se ha caracterizado de manera precisa la composici��n, estructura y variabilidad del ictioplancton presente en esta regi��n subtropical. Clupeidos, Esp��ridos y G��bidos dominaron la comunidad ner��ticas, mientras que Mict��fidos, Gonostom��tidos y Phot��ctidos prevalecieron dentro de las familias oce��nicas. La variabilidad temporal de la comunidad larvaria parece estar m��s relacionada con la temperatura y efectos a peque��a escala (hidrograf��a, productividad local, ciclo lunar), que con el aumento de productividad anual durante el bloom de finales de invierno. Se definieron dos asociaciones estacionales de larvas estrechamente ligadas a las caracter��sticas de la columna de agua: (1) invierno-primavera, en la que dominan Sardinella aurita, Boops boops y Cyclothone braueri, y son caracter��sticas especies como Pomacentridae sp1, Trachurus picturatus o Scomber colias; y (2) verano-oto��o, donde G��bidos y Cyclothone braueri dominan, pero cuyas especies caracter��sticas son Ceratoscopelus warmingii, Pomacentridae sp2 y Anthias anthias, entre otras. Respecto a la variabilidad horizontal, se confirm�� la presencia de dos zonas de retenci��n para los huevos y larvas ner��ticas a barlovento y sotavento (estela c��lida) de la isla. Sin embargo, no se encontraron diferencias significativas en la composici��n de la comunidad larvaria entre las diferentes zonas de la plataforma de la isla. La Zona de Transici��n Costera Canario-Africana se caracteriza por una gran actividad de mesoscala, que afectar�� a la distribuci��n de las larvas ner��ticas de las costas africanas. Esta interacci��n resulta especialmente evidente en el caso de las larvas, principalmente sardina y anchoa, transportadas en filamentos de afloramiento generados en la regi��n de Cabo Juby-Cabo Bojador. Estos filamentos pueden ser atrapados por remolinos cicl��nicos situados al sur de Gran Canaria. Este sistema remolino-filamento podr��, en funci��n de su evoluci��n, actuar como un mecanismo de retenci��n o dispersi��n para las larvas de especies ner��ticas africanas. Parte de estas larvas pueden llegar a las costas de Gran Canaria, suponiendo un aporte para las poblaciones larvarias locales, al menos durante el verano. A pesar de la gran cantidad de informaci��n obtenida a partir de esta tesis, es necesario continuar con este tipo de estudios para evaluar la importancia de este transporte larvario y su aplicaci��n a la gesti��n pesquera.

The spatial distribution of Copernicia alba (Morong) in the district of Bahia Negra, Paraguay

The Humid Chaco of Northeast Paraguay harbors monoculture palm savannas in which Copernicia alba is the only dominant overstory species. The study���s objective was to provide the complete spatial distribution of a simple ecosystem lacking confounding factors of overstory competition and changes in slope. Palms within six, 50 x 50m plots were marked by their GPS location and measured for dbh and total stem height. The spatial distribution was individually analyzed for each plot at the local scale up to 12 m using Ripley���s K test. For the total population including juvenile and adult plants, the sample plots contained both random and clustered distribution patterns. In each of the six plots, the juvenile populations exhibited more clustered patterns than the adult population of each plot.

Upper ocean vertical supply: A neglected primary factor controlling the distribution of neodymium concentrations of open ocean surface waters?

Neodymium (Nd) isotopes are an important geochemical tool to trace the present and past water mass mixing as well as continental inputs. The distribution of Nd concentrations in open ocean surface waters (0��������100 m) is generally assumed to be controlled by lateral mixing of Nd from coastal surface currents and by removal through reversible particle scavenging. However, using 228Ra activity as an indicator of coastal water mass influence, surface water Nd concentration data available on key oceanic transects as a whole do not support the above scenario. From a global compilation of available data, we find that more stratified regions are generally associated with low surface Nd concentrations. This implies that upper ocean vertical supply may be an as yet neglected primary factor in determining the basin-scale variations of surface water Nd concentrations. Similar to the mechanism of nutrients supply, it is likely that stratification inhibits vertical supply of Nd from the subsurface thermocline waters and thus the magnitude of Nd flux to the surface layer. Consistently, the estimated required input flux of Nd to the surface layer to maintain the observed concentrations could be nearly two orders of magnitudes larger than riverine/dust flux, and also larger than the model-based estimation on shelf-derived coastal flux. In addition, preliminary results from modeling experiments reveal that the input from shallow boundary sources, riverine input, and release from dust are actually not the primary factors controlling Nd concentrations most notably in the Pacific and Southern Ocean surface waters.

Spatial Distribution of Cryptic Species Diversity in European Freshwater Amphipods (Gammarus fossarum) as Revealed by Pyrosequencing

In order to understand and protect ecosystems, local gene pools need to be evaluated with respect to their uniqueness. Cryptic species present a challenge in this context because their presence, if unrecognized, may lead to serious misjudgement of the distribution of evolutionarily distinct genetic entities. In this study, we describe the current geographical distribution of cryptic species of the ecologically important stream amphipod Gammarus fossarum (types A, B and C). We use a novel pyrosequencing assay for molecular species identification and survey 62 populations in Switzerland, plus several populations in Germany and eastern France. In addition, we compile data from previous publications (mainly Germany). A clear transition is observed from type A in the east (Danube and Po drainages) to types B and, more rarely, C in the west (Meuse, Rhone, and four smaller French river systems). Within the Rhine drainage, the cryptic species meet in a contact zone which spans the entire G. fossarum distribution range from north to south. This large-scale geographical sorting indicates that types A and B persisted in separate refugia during Pleistocene glaciations. Within the contact zone, the species rarely co-occur at the same site, suggesting that ecological processes may preclude long-term coexistence. The clear phylogeographical signal observed in this study implies that, in many parts of Europe, only one of the cryptic species is present.

Estimating Spatial Distribution of American Lobster Homarus Americanus Using Habitat Variables

The spatial distribution of the American lobster Homarus americanus is influenced by many factors, which are often difficult to quantify. We implemented a modeling approach for quantifying season-, size-, and sex-specific lobster spatial distribution in the Gulf of Maine with respect to environmental and spatial variables including bottom temperature, bottom salinity, latitude, longitude, depth, distance offshore, and 2 substratum features. Lobster distribution was strongly associated with temperature and depth, and differed seasonally by sex. In offshore waters in the fall, females were dominant at higher latitudes and males at lower latitudes. This segregation was not apparent in the spring although females were still dominant at higher latitudes in offshore waters. Juveniles and adults were also distributed differently; juveniles were more abundant at the lower latitudes in inshore waters, while adults were more widespread along the entire coast. These patterns are consistent with the ecology of the American lobster. This study provides a tool to evaluate changes in lobster spatial distribution with respect to changes in key habitat and other environmental variables, and consequently could be of value for the management of the American lobster.

The spatial distribution of water in the inner coma of Comet 9P/Tempel 1: Comparison between models and observations

The near nucleus coma of Comet 9P/Tempel 1 has been simulated with the 3D Direct Simulation Monte Carlo (DSMC) code PDSC++ (Su, C.-C. [2013]. Parallel Direct Simulation Monte Carlo (DSMC) Methods for Modeling Rarefied Gas Dynamics. PhD Thesis, National Chiao Tung University, Taiwan) and the derived column densities have been compared to observations of the water vapour distribution found by using infrared imaging spectrometer on the Deep Impact spacecraft (Feaga, L.M., A���Hearn, M.F., Sunshine, J.M., Groussin, O., Farnham, T.L. [2007]. Icarus 191(2), 134���145. http://dx.doi.org/10.1016/j.icarus.2007.04.038). Modelled total production rates are also compared to various observations made at the time of the Deep Impact encounter. Three different models were tested. For all models, the shape model constructed from the Deep Impact observations by Thomas et al. (Thomas, P.C., Veverka, J., Belton, M.J.S., Hidy, A., A���Hearn, M.F., Farnham, T.L., et al. [2007]. Icarus, 187(1), 4���15. http://dx.doi.org/10.1016/j.icarus.2006.12.013) was used. Outgassing depending only on the cosine of the solar insolation angle on each shape model facet is shown to provide an unsatisfactory model. Models constructed on the basis of active areas suggested by Kossacki and Szutowicz (Kossacki, K., Szutowicz, S. [2008]. Icarus, 195(2), 705���724. http://dx.doi.org/10.1016/j.icarus.2007.12.014) are shown to be superior. The Kossacki and Szutowicz model, however, also shows deficits which we have sought to improve upon. For the best model we investigate the properties of the outflow.

Spatial Distribution of Stem Cell-Like Keratinocytes in Dissected Compound Hair Follicles of the Dog

Hair cycle disturbances are common in dogs and comparable to some alopecic disorders in humans. A normal hair cycle is maintained by follicular stem cells which are predominately found in an area known as the bulge. Due to similar morphological characteristics of the bulge area in humans and dogs, the shared particularity of compound hair follicles as well as similarities in follicular biomarker expression, the dog is a promising model to study human hair cycle and stem cell disorders. To gain insight into the spatial distribution of follicular keratinocytes with stem cell potential in canine compound follicles, we microdissected hair follicles in anagen and telogen from skin samples of freshly euthanized dogs. The keratinocytes isolated from different locations were investigated for their colony forming efficiency, growth and differentiation potential as well as clonal growth. Our results indicate that i) compound and single hair follicles exhibit a comparable spatial distribution pattern with respect to cells with high growth potential and stem cell-like characteristics, ii) the lower isthmus (comprising the bulge) harbors most cells with high growth potential in both, the anagen and the telogen hair cycle stage, iii) unlike in other species, colonies with highest growth potential are rather small with an irregular perimeter and iv) the keratinocytes derived from the bulbar region exhibit characteristics of actively dividing transit amplifying cells. Our results now provide the basis to conduct comparative studies of normal dogs and those with hair cycle disorders with the possibility to extend relevant findings to human patients.

Spatial distribution of isotopic compositions of Globigerina bulloides and Neogloboquadrina pachyderma (dex.) and the faunal assemblages of planktic foraminifera in surface sediment samples along the Chilean continental slope between 23��S and 44��S

We report on the spatial distribution of isotopic compositions of the two planktic foraminifera species Globigerina bulloides and Neogloboquadrina pachyderma (dex.), and the faunal assemblages of planktic foraminifera in 91 surface sediment samples along the Chilean continental slope between 23��S and 44��S. Both d13C and d18O data of N. pachyderma (dex.) show little variability in the study area. North of 39��S, the isotopic values of N. pachyderma (dex.) are heavier than those of G. bulloides, whereas south of 39��S, this relation inverses. This is indicative for a change from a well-mixed, deep thermocline caused by coastal upwelling north of 39��S to well-stratified water masses in a non-upwelling environment south of 39��S. In addition, the faunal composition of planktic foraminifera marks this change by transition from an upwelling assemblage north of 39��S to a high-nutrient-non-upwelling assemblage south of 39��S, which is characterized by decreased contributions of upwelling indicators such as G. bulloides, N. pachyderma (sin.), and Globigerinita glutinata. In general, we can conclude that food and light rather than temperature are the primary control of the planktic foraminiferal assemblage between 23��S and 44��S off Chile. Our data point to higher marine productivity at upwelling centers north of 25��S and at 30-33��S. South of 39��S, significant supply of nutrients by fluvial input most likely boosts the productivity.

On the spatial distribution of woody plant species in a tropical montane cloud forest

Abstract The cloud forest is a special type of forest ecosystem that depends on suitable conditions of humidity and temperature to exist; hence, it is a very fragile ecosystem. The cloud forest is also one of the richest ecosystems in terms of species diversity and rate of endemism. However, today, it is one of the most threatened ecosystems in the world. Little is known about tree species distribution and coexistence among cloud forest trees. Trees are essential to understanding ecosystem functioning and maintenance because they support the ecosystem in important ways. For this dissertation, an analysis of woody plant species distribution at a small scale in a north-Peruvian Andean cloud forest was performed, and some of the factors implicated in the observed patterns were identified. Towards that end, different natural factors acting on species distribution within the forest were investigated: (i) intra-specific arrangements, (ii) heterospecific spatial relationships and (iii) relationships with external environmental factors. These analyses were conducted first on standing woody plants and then on seedlings. The woody plants were found to be clumped in the forest, either considering all the species together or each species separately. However, each species presented a specific pattern and specific spatial relationship among different-age individuals. Dispersal mode, growth form and shade tolerance played roles in the final distribution of the species. Furthermore, spatial associations among species, either positive or negative, were observed. These associations were more numerous when considering individuals of the interacting species at different developmental stages, i.e., younger individuals from one species and older individuals from another. Accordingly, competition and facilitation are asymmetric processes and vary throughout the life of an individual. Moreover, some species appear to prefer certain habitat conditions and avoid other habitats. The habitat definition that best explains species distribution is that which includes both environmental and stand characteristics; thus, a combination of these factors is necessary to understanding species' niche preferences. Seedling distribution was also associated with habitat conditions, but these conditions explained less than the 30% of the spatial variation. The position of conspecific adult individuals also affected seedling distribution; although the seedlings of many tree species avoid the vicinity of conspecifics, a few species appeared to prefer the formation of cohorts around their parent trees. The importance of habitat conditions and distance dependence with conspecifics varied among regions within the forest as well as on the developmental stage of the stand. The results from this thesis suggest that different species can coexist within a given space, forming a ���puzzle��� of species as a result of the intra- and interspecific spatial relationships along with niche preferences and adaptations that operate at different scales. These factors not only affect each species in a different way, but specific preferences also vary throughout species' lifespans. Resumen Resumen El bosque de niebla es uno de los ecosistemas m��s amenazados del mundo adem��s de ser uno de los m��s fr��giles. Son formaciones azonales que dependen de la existencia de unas condiciones de humedad y temperatura que permitan la formaci��n de nubes que cubran el bosque; lo que dificulta en gran medida su conservaci��n. Tambi��n es uno de los ecosistemas con mayor riqueza de especies adem��s de tener uno de los mayores porcentajes de endemismos. Uno de los aspectos m��s importantes para entender el ecosistema, es identificar y entender los elementos que lo componen y los mecanismos que regulan las relaciones entre ellos. Los ��rboles son el soporte del ecosistema. Sin embargo, apenas hay informaci��n sobre la distribuci��n y coexistencia de los ��rboles en los bosques de niebla. Esta tesis presenta un an��lisis de la distribuci��n a peque��a escala de las plantas le��osas en un bosque de niebla situado en la cordillera andina del norte de Per��; as�� como el an��lisis de algunos de los factores que pueden estar implicados en que se origine la distribuci��n observada. Para este prop��sito se estudia c��mo influyen factores de diferente naturaleza en la distribuci��n de las especies (i) organizaci��n intra-espec��fica (ii) relaciones espaciales heterospec��ficas y (iii) relaci��n con factores ambientales externos. En estos an��lisis se estudiaron primero las plantas j��venes y las adultas, y despu��s las pl��ntulas. Los ��rboles aparecieron agregados en el bosque, tanto considerando todos a la vez como cuando se estudi�� cada especie por separado. Sin embargo, cada especie mostr�� un patr��n distinto as�� como una particular relaci��n espacial entre individuos j��venes y adultos. El modo de dispersi��n, la forma de vida y la tolerancia de la especies estuvieron relacionados con el patr��n general observado. Se vio tambi��n que ciertas especies aparec��an relacionadas con otras, tanto de forma positiva (compartiendo zonas) como negativa (apareciendo en ��reas distintas). Las asociaciones fueron mucho m��s numerosas cuando se consideraron los pares de especies en diferente estado de desarrollo, es decir, individuos j��venes de una especie e individuos mayores de la otra. Eso indicar��a que los procesos de competencia y facilitaci��n son asim��tricos y adem��s var��an durante la vida de la planta. Por otro lado, algunas especies aparecen preferentemente bajo ciertas condiciones de h��bitat y evitan otras. La definici��n de h��bitat a la que mejor responden las especies es cuando se incluyen tanto variables ambientales como de masa; as�� que ambos tipos de variables son necesarias para entender la preferencia de las especies por ciertos nichos. La distribuci��n de las pl��ntulas tambi��n estuvo relacionada con condiciones de h��bitat, pero eso s��lo llegaba a explicar hasta un 30% de la variabilidad espacial. La posici��n de los adultos de la misma especie tambi��n afect�� a la distribuci��n de las pl��ntulas. En bastantes especies las pl��ntulas evitan la cercan��a de adultos de su misma especie, padres potenciales, aunque algunas especies aisladas mostraron el patr��n contrario y aparecieron preferentemente en las mismas ��reas que sus padres. La importancia de las condiciones de h��bitat y posici��n de los adultos en la disposici��n de las pl��ntulas var��a de una zona a otra del bosque y adem��s tambi��n var��a seg��n el estado de desarrollo de la masa.