3,098 research outputs found

    Inbreeding In Darwin’S Medium Ground Finches (Geospiza Fortis)

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    Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/137549/1/evo02574.pd

    Approaching Freshet beneath Landfast Ice in Kugmallit Bay on the Canadian Arctic Shelf: Evidence from Sensor and Ground Truth Data

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    The Mackenzie River is the largest river in the North American Arctic. Its huge freshwater and sediment load impacts the Canadian Beaufort Shelf, transporting large quantities of sediment and associated organic carbon into the Arctic Ocean. The majority of this sediment transport occurs during the freshet peak flow season (May to June). Mackenzie River-Arctic Ocean coupling has been widely studied during open water seasons, but has rarely been investigated in shallow water under landfast ice in Kugmallit Bay with field-based surveys, except for those using remote sensing. We observed and measured sedimentation rates (51 g m-2 d-1) and the concentrations of chlorophyll a (mean 2.2 ?g L-1) and suspended particulate matter (8.5 mg L-1) and determined the sediment characteristics during early spring, before the breakup of landfast ice in Kugmallit Bay. We then compared these results with comparable data collected from the same site the previous summer. Comparison of organic quality in seston and trapped material demonstrated substantial seasonal differences. The subtle changes in biological and oceanographic variables beneath landfast ice that we measured using sensors and field sampling techniques suggest the onset of a spring melt occurring hundreds of kilometres farther south in the Mackenzie Basin.Le fleuve Mackenzie est le plus grand fleuve de l’Arctique nord-américain. Son énorme bassin d’eau douce et sa masse de sédiments ont des effets sur la plateforme externe de la mer de Beaufort canadienne, transportant ainsi de grandes quantités de sédiments et de carbone organique associé dans l’océan Arctique. La plus grande partie du transport des sédiments se produit pendant la saison haute d’écoulement du courant d’eau douce dans la mer (de mai à juin). Même si le couplage du fleuve Mackenzie et de l’océan Arctique a fait l’objet d’études approfondies durant les saisons d’eau libre, il a rarement été étudié en eau peu profonde sous la banquise de la baie Kugmallit au moyen d’études sur le terrain, sauf dans le cas d’études faisant appel à la télédétection. Nous avons observé et mesuré les taux de sédimentation (51 g m-2 d-1) et les concentrations de chlorophylle a (moyenne de 2,2 ?g L-1) et de matière particulaire en suspension (8,5 mg L-1), puis déterminé les caractéristiques des sédiments au début du printemps, avant la rupture de la banquise dans la baie Kugmallit. Ensuite, nous avons comparé ces résultats à des données comparables recueillies au même emplacement l’été précédent. La comparaison de la qualité organique du seston et des matières emprisonnées faisait ressortir d’importantes différences saisonnières. Les changements subtils sur le plan des variables biologiques et océanographiques sous la banquise que nous avons mesurés à l’aide de capteurs et de techniques d’échantillonnage sur le terrain laissent entrevoir un début de fonte du printemps se produisant à des centaines de kilomètres plus au sud, dans le bassin du Mackenzie

    Annual variation in Finch numbers, foraging and food supply on Isla Daphne Major, Galápagos

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    (1) We report some effects of an annually variable and unpredictable rainfall upon Darwin's Finches on the Galápagos. Finch numbers, foraging and food supply were studied on I. Daphne Major in December of 1973 and 1977, and compared. 1973 was the second of two successive wet years and 1977 was a drought year.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47731/1/442_2004_Article_BF00346966.pd

    Exploitation of Opuntia cactus by birds on the Galápagos

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    (1) There is a close association between Opuntia helleri (cactus) and Geospiza conirostris (cactus finch) on Isla Genovesa, and between Opuntia echios and Geospiza scandens on Isla Daphne Major. The two finch species consume nectar and pollen, pollinate the obligatorily out-crossing flowers, consume the aril around the seeds, crack the seeds and occasionally disperse them.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47738/1/442_2004_Article_BF00349186.pd

    The SUMO Ligase Protein Inhibitor of Activated STAT 1 (PIAS1) is a constituent PML-NB protein that contributes to the intrinsic antiviral immune response to herpes simplex virus 1 (HSV-1)

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    Aspects of intrinsic antiviral immunity are mediated by promyelocytic leukaemia (PML)-nuclear body (PML-NB) constituent proteins. During herpesvirus infection, these antiviral proteins are independently recruited to nuclear domains that contain infecting viral genomes to cooperatively promote viral genome silencing. Central to the execution of this particular antiviral response is the small ubiquitin-like modifier (SUMO) signalling pathway. However, the participating SUMOylation enzymes are not fully characterized. We identify the SUMO ligase Protein Inhibitor of Activated STAT1 (PIAS1) as a constituent PML-NB protein. We show that PIAS1 localizes at PML-NBs in a SUMO interaction motif (SIM)-dependent manner that requires SUMOylated or SUMOylation competent PML. Following infection with herpes simplex virus 1 (HSV-1), PIAS1 is recruited to nuclear sites associated with viral genome entry in a SIM-dependent manner, consistent with the SIM-dependent recruitment mechanisms of other well characterized PML-NB proteins. In contrast to Daxx and Sp100, however, the recruitment of PIAS1 is enhanced by PML. PIAS1 promotes the stable accumulation of SUMO1 at nuclear sites associated with HSV-1 genome entry, whereas the accumulation of other evaluated PML-NB proteins occurs independently of PIAS1. We show that PIAS1 cooperatively contributes to HSV-1 restriction through mechanisms that are additive to those of PML and cooperative with those of PIAS4. The antiviral mechanisms of PIAS1 are counteracted by ICP0, the HSV-1 SUMO-targeted ubiquitin ligase, which disrupts the recruitment of PIAS1 to nuclear domains that contain infecting HSV-1 genomes through mechanisms that do not directly result in PIAS1 degradation

    El calentamiento mundial y las Galapagos

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