Browsing by Issue Date, starting with "2006-05"
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- Computable general equilibrium models : a literature reviewPublication . Menezes, António Gomes de; Fortuna, Mário; Silva, Francisco; Vieira, José CabralApplied general equilibrium models have become popular tools used on ongoing economic policy debates. In this paper we discuss at length the most proeminent features of applied general equilibrium models in a comprehensive and non-technical way, thus accessible to the reader interested in economic policy but with no prior formal exposure to economic modeling. We rationalize the increasing political demand for such models as policy analysis tools. We argue that applied general equilibrium models are best equipped to model regional economies.
- Botryocladia chiajeana and Botryocladia macaronesica sp. nov. (Rhodymeniaceae, Rhodophyta) from the Mediterranean and the eastern Atlantic, with a discussion on the closely related genus Irvinea.Publication . Afonso-Carrillo, Julio; Rodríguez-Prieto, Conxi; Boisset, Fernando; Sobrino, Cristina; Tittley, Ian; Neto, Ana I.Specimens from the eastern Atlantic, Mediterranean and Adriatic seas previously reported as Botryocladia chiajeana showed differences in morphology, and re-examination of Meneghini's original collection of Chrysymenia chiajeana (basionym B. chiajeana) revealed that only the Mediterranean and Adriatic specimens are in agreement with the original protologue, whereas plants reported from the eastern Atlantic are recognised here as Botryocladia macaronesica Afonso-Carrillo, Sobrino, Tittley & Neto sp. nov. The vegetative and reproductive morphology of western Mediterranean plants is examined in detail for the first time, and B. chiajeana is characterised by the following combination of features: solid axes bearing frequently dichotomously branched vesicles, vesicle walls three layered, outer cortical cells arranged in rosettes, secretory cells borne on modified medullary cells, spermatangia cut off from scattered spermatangial mother cells, cystocarps strongly protuberant and tetrasporangia cruciately divided and exposed on the outer cortical layer at maturity. From the Meneghini collection, a lectotype specimen of C. chiajeana was selected. Botryocladia macaronesica, known so far only from the islands of Azores, Madeira, Canaries and Cape Verde, differs from other Botryocladia species by a unique combination of significant attributes including elongate saccate vesicles, near-continuous cortication of vesicle walls, secretory cells on unmodified medullary cells and completely immersed cystocarps. An analysis of the morphological characters currently used for separating Botryocladia from related genera (i.e. Chrysymenia, Gloiosaccion and Irvinea), showed that there is considerable overlap between Botryocladia and Irvinea. These genera are presently discriminated mostly by molecular evidence as the supposed morphological characters are shown here to vary considerably within the genus Botryocladia.
- Abundance, spatial variance and occupancy: arthropod species distribution in the AzoresPublication . Gaston, Kevin J.; Borges, Paulo A. V.; He, FangLiang; Gaspar, Clara1. The positive abundance-occupancy and abundance-variance relationships are two of the most widely documented patterns in population and community ecology. 2. Recently, a general model has been proposed linking the mean abundance, the spatial variance in abundance, and the occupancy of species. A striking feature of this model is that it consists explicitly of the three variables abundance, variance and occupancy, and no extra parameters are involved. However, little is known about how well the model performs. 3. Here, we show that the abundance-variance-occupancy model fits extremely well to data on the abundance, variance and occupancy of a large number of arthropod species in natural forest patches in the Azores, at three spatial extents, and distinguishing between species of different colonization status. Indeed, virtually all variation about the bivariate abundance-occupancy and abundance-variance relationships is effectively explained by the third missing variable (variance in abundance in the case of the abundance-occupancy relationship, and occupancy in the case of the abundance-variance relationship). 4. Introduced species tend to exhibit lower densities, less spatial variance in these densities, and occupy fewer sites than native and endemic species. None the less, they all lie on the same bivariate abundance-occupancy and abundance-variance, and trivariate abundance-variance-occupancy, relationships. 5. Density, spatial variance in density, and occupancy appear to be all the things one needs to know to describe much of the spatial distribution of species.