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Tropical Lowlands (tropical + lowland)
Selected AbstractsThe riverscape of Western Amazonia , a quantitative approach to the fluvial biogeography of the regionJOURNAL OF BIOGEOGRAPHY, Issue 8 2007Tuuli Toivonen Abstract Aim, To provide a quantitative spatial analysis of the riverscape (open-water bodies and their surrounding areas) of the Western Amazonian lowlands using a consistent surface of remotely sensed imagery. Taking into account the essential significance of fluvial environments for the Amazonian biota, we propose that an enhanced understanding of the Amazonian riverscape will provide new insight for biogeographical studies in the region and contribute to the understanding of these megadiverse tropical lowlands. Location, An area of 2.2 million km2 covering the Western Amazonian lowlands of the Andean foreland region, i.e. the upper reaches of the Amazon river system. Areas in Colombia, Venezuela, Ecuador, Peru, Brazil and Bolivia between longitudes 83 °W and 65 °W and latitudes 5 °N and 12 °S are included. Methods, A mosaic of 120 Landsat TM satellite images was created with 100-m resolution, and water areas of over 1 ha in size or c. 60 m in width were extracted using a simple ratio threshold applicable to a large set of data. With this method, 99.1% of the water areas present in 30-m imagery were mapped with images with 100-m resolution. Water pixels of distinct river segments were assigned to river classes on the basis of their channel properties, and islands and lakes were distinguished separately and classified. Measures of water patterns such as structure, composition, richness and remoteness were provided for various spatial units. Riverine corridors were computed from the open-water mask by outer limits of active channels and floodplain lakes. Analytical results are shown as both thematic maps and statistics. Results, A total of 1.1% of Western Amazonia is covered by open-water bodies over 1 ha in size or 60 m in width. River-bound waters comprise 98% of the total water surface. Whilst isolated lakes are scarce, river-bound oxbow and backchannel lakes are plentiful, comprising 17.5% of all waters. They are particularly frequent along meandering channels, which dominate both in area and length. The riverine corridors including active channels and floodplain lakes cover 17% of the land area. The average distance from any point of land to the nearest water is 12 km. Geographically speaking, the distribution of waters is uneven across the region, and the detailed characteristics of the riverscape are geographically highly variable. Three major, fluvially distinct regions can be identified: central Western Amazonia, the south, and the north-east. The proportional surface areas of the riverine corridors, numbers of lakes, sizes of islands and their distributions depend largely on the types and sizes of the rivers. Main conclusions, Our results support the notion of Western Amazonia as a dynamic, highly fluvial environment, highlighting and quantifying considerable internal variation within the region in terms of fluvial patterns and the processes that they reflect and control. Biogeographically, the variety of types of fluvial environments and their characteristics are important constituents of what influences the distribution of species and dynamics of terrestrial habitats. Spatially consistent riverscape data can serve as a consistent and scalable source of relevant information for other biogeographical approaches in the region. [source] The Branchiopoda (Crustacea: Anomopoda, Ctenopoda and Cyclestherida) of the rain forests of Cameroon, West Africa: low abundances, few endemics and a boreal,tropical disjunctionJOURNAL OF BIOGEOGRAPHY, Issue 9 2005George Y. Chiambeng Abstract Aim, We provide the first in-depth study of the Branchiopoda of the rain forests of Cameroon and also of the African continent. Location, Surface water environments, Cameroon. Methods, Qualitative plankton samples were collected in all types of surface water environments present, ranging from big lakes to water collected in rock crevices or fallen fruit cavities. A tow or hand-held plankton net of mesh size 100 ,m was used, and water volumes filtered were at least several m3 in large water bodies, or half to whole water volume in small water bodies. Results, We recorded 61 species (53 first records for the country), based on 700+ samples collected between September 1998 and March 2002. Anomopoda (92%) was the dominant order, followed by Ctenopoda (6.5%) and Cyclestherida (1.5%). Chydoridae (67%) was the most speciose family followed by Macrothricidae (6.5%) and Daphniidae (5%). Alona (11%) was the dominant genus followed by Chydorus (10%) and Pleuroxus (8%). Several species of Chydorinae, especially of the genus Pleuroxus, are shared with continental Eurasia,North America, but are absent from the Mediterranean and desert,steppe,savanna zones of Africa (boreal,tropical disjunction). Daphnia was absent, as in most tropical lowlands. No single species was really abundant, and a majority were rare to very rare, and of restricted occurrence within the rain forest patches. Comparing Africa, South America and Southeast Asia, we found a current total of 196 species for the combined rain forest areas, out of a world total of 500+ species. Systematic trends in richness at three taxonomic levels were the same for all continents: Anomopoda,Ctenopoda,Cyclestherida at ordinal level, Chydoridae,Daphniidae,Macrothricidae,Sididae at family level and Alona,Chydorus,Macrothrix,Diaphanosoma at genus level. Southeast Asia was richest (111 species, 14 endemics) with South America a close second (110 species, 27 endemics). Africa was the most species-poor (95 species, of which only 5 are endemics). Main conclusions, We hypothesize that the post-Miocene cooling and aridization of the world climate hit the freshwater biota of Africa particularly hard, with more extinction here than elsewhere, and little recolonization. Most extinction occurred in the savanna-desert belt, and eight disjunct boreal species (four Pleuroxus, Picripleuroxus laevis, Kurzia latissima, Alonella exigua, and Monospilus dispar) survive morphologically unchanged since pre-Pleistocene times in the Cameroon rain forest. Slow evolution thus appears typical of these cyclic parthenogenetic branchiopods in which sexual recombination occurs only at intervals. Illustrative of the same slow evolution is the fact that the two endemic cladocerans of Cameroon (Nicsmirnovius camerounensis and Bryospilus africanus) belong to tropicopolitan genera of Gondwanan age. [source] LIVING A DISTRIBUTED LIFE: MULTILOCALITY AND WORKING AT A DISTANCEANNALS OF ANTHROPOLOGICAL PRACTICE, Issue 1 2008Brigitte Jordan In the last few years, new collaboration and communication technologies have led to a deterritorialization of work, allowing for the rise of new work- and lifestyles. In this article, I use my own transition from the life of a corporate researcher to that of a multilocal mobile consultant for tracking some of the patterns I see in a changing cultural and economic environment where work and workers are no longer tied to a specific place of work. My main interest lies in identifying some of the behavioral shifts that are happening as people are caught up in and attempt to deal with this changing cultural landscape. Writing as a knowledge worker who now moves regularly from a work,home place in the Silicon Valley of California to another in the tropical lowlands of Costa Rica, I use my personal transition as a lens through which to trace new, emergent patterns of behavior, of values, and of social conventions. I assess the stresses and joys, the upsides and downsides, the challenges and rewards of this work- and lifestyle and identify strategies for making such a life successful and rewarding. Throughout, there emerges an awareness of the ways in which the personal patterns described reflect wider trends and cumulatively illustrate global transformation of workscapes and lifescapes. These types of local patterns in fact constitute the on-the-ground material reality of global processes that initiate and sustain widespread culture change and emergent societal transformations. [source] The role of wood anatomy in phylogeny reconstruction of EricalesCLADISTICS, Issue 3 2007Frederic Lens The systematic significance of wood anatomical characters within Ericales is evaluated using separate and combined parsimony analyses including 23 wood characters and 3945 informative molecular characters. Analyses of wood features alone result in poorly resolved and conflicting topologies. However, when pedomorphic character states are coded as inapplicable, the combined bootstrap topology results in an increase of resolution and support at most deeper nodes compared with the molecular analyses. This suggests that phylogenetic information from the limited number of morphological characters is not completely swamped by an overwhelming amount of molecular data. Based on the morphology of vessels and fibers, and the distribution of axial parenchyma, two major wood types can be distinguished within Ericales: (i) a "primitive" type, nearly identical to the wood structure in the more basal outgroup Cornales, which is likely to have persisted in one major clade, and (ii) a "derived" type that must have evolved in at least two separate evolutionary lines. The occurrence of the first type is strongly correlated with shrubs to small trees growing in cold temperate or tropical montane regions, while the second type is common in tall trees of tropical lowlands. This favors the inclusion of ecologically adaptive features in phylogeny reconstruction. © The Willi Hennig Society 2006. [source] | ||||||||||