University of Costa Rica

About: University of Costa Rica is a education organization based out in San José, Costa Rica. It is known for research contribution in the topics: Population & Venom. The organization has 9817 authors who have published 16781 publications receiving 238208 citations. The organization is also known as: UCR & Universidad de Costa Rica.

Tropical nematode diversity: vertical stratification of nematode communities in a Costa Rican humid lowland rainforest

Abstract: Comparisons of nematode communities among ecosystems have indicated that, unlike many organisms, nematode communities have less diversity in the tropics than in temperate ecosystems. There are, however, few studies of tropical nematode diversity on which to base conclusions of global patterns of diversity. This study reports an attempt to estimate nematode diversity in the lowland tropical rainforest of La Selva Biological Research Station in Costa Rica. We suggest one reason that previous estimates of tropical nematode diversity were low is because habitats above the mineral soil are seldom sampled. As much as 62% of the overall genetic diversity, measured by an 18S ribosomal barcode, existed in litter and understorey habitats and not in soil. A maximum-likelihood tree of barcodes from 360 individual nematodes indicated most major terrestrial nematode lineages were represented in the samples. Estimated ‘species’ richness ranged from 464 to 502 within the four 40 × 40 m plots. Directed sampling of insects and their associated nematodes produced a second set of barcodes that were not recovered by habitat sampling, yet may constitute a major class of tropical nematode diversity. While the generation of novel nematode barcodes proved relatively easy, their identity remains obscure due to deficiencies in existing taxonomic databases. Specimens of Criconematina, a monophyletic group of soil-dwelling plantparasitic nematodes were examined in detail to assess the steps necessary for associating barcodes with nominal species. Our results highlight the difficulties associated with studying poorly understood organisms in an understudied ecosystem using a destructive (i.e. barcode) sampling method.

Aggressive and Courtship Displays of the Male Anna's Hummingbird

Abstract: -The aggressive and courtship displays and vocalizations of the male Anna’s Hummingbird (Culypte anna) are described in detail, and various types of evidence and observations are used to reconstruct the typical courtship sequence. Initial contact is made by the female flying to the male’s territory and attempting to feed; she may have previously visited several other territories in order to evaluate territory quality. The well-known dive display is an aggressive maneuver by the male, although it may play a role very early in the courtship sequence. Following a lengthy chase towards the female’s nesting area, she alights low in dense vegetation. The male then gives the displays most critical for courtship: a back-and-forth “shuttle” display and high-intensity song. These hitherto undescribed displays occur immediately preceding copulation, and are probably the most important isolating mechanisms for the species. Many of the elements of courtship in C. an~la are widespread in hummingbirds. Practice and probably learning play a major role in the maturation of song and dive displays in the individual. The courtship sequence in this hummingbird probably represents the resultant of various selective pressures, some acting mainly on males and others on females. Hummingbirds are becoming among the beststudied of North American birds, particularly with respect to energetic aspects of nesting (Horvath 1967, Calder 197 1, 1974, Calder and Booser 1973, Smith et al. 1974) territoriality and foraging (Stiles 197 la, Ewald and Carpenter 1978, Kodric-Brown and Brown 1979, Pyke 1978, Gass 1979) and relationships with the flowers they visit and pollinate (Stiles 1973, Carpenter 1978, Waser 1978, KodricBrown and Brown 1979, Price and Waser 1979). Recent field studies in California have disclosed a striking amount of hybridization among several (newly?) sympatric species (Lynch and Ames 1970, Wells et al. 1978, Wells and Baptista 1979). Study of hybrids and parental types in nature offers a unique opportunity to document the ecological and behavioral effects of such hybridization. Analyses of these phenomena, however, have been hindered by the lack of reliable descriptions of courtship and aggressive displays of the species concerned. The conspicuous dive displays have been described with varying degrees of completeness and accuracy by Bent (1940) Banks and Johnson (196 l), Wells et al, (1978) and Wells and Baptista (1979), among others, but except for the perceptive discussions of Pitelka (1942, 19 5 1 a, b) their role in courtship has been misunderstood. Moreover, a whole family of close-range displays in these hummingbirds, far more crucial in courtship per se, has been overlooked. Finally, I know of no good descriptions of display sequences nor, indeed, of copulation itself in these birds. Behavioral isolating mechanisms in North American hummingbirds cannot be properly appraised without a clear understanding of what actually constitutes their courtship. Through several years of close study of the ecology and behavior of the Anna’s Hummingbird (Calypte annu) and other California species (Stiles 1973) I was able to observe courtship and aggressive displays ofthese birds in detail. My purpose here is to describe and interpret the vocalizations and displays of the Anna’s Hummingbird, to serve as a basis for comparisons with other species.

Present and Future Challenges of Coastal Erosion in Latin America

Abstract: Silva, R.; Martinez, M.L.; Hesp, P.; Catalan, P.; Osorio, A. F.; Martell, R.; Fossati, M.; Miot da Silva, G.; Marino-Tapia, I.; Pereira, P.; Cienfuegos, R.; Klein, A., and Govaere, G., 2014. Present and future challenges of coastal erosion in Latin America. The coastal zones of Latin America have many landforms and environments, including sedimentary cliffs, deeply incised estuaries, headlands, barrier coasts and low lying, muddy coastal plains. These forms will respond differently to the expected changes in climate and associated sea level rise, which may produce coastal erosion in the future. Considering the coasts of Latin America overall, erosion is not yet a serious threat, although it is widespread and it is severe in some parts. Major erosion problems are frequently associated with human intervention in sediment supply, with poor planning or with the morphodynamic nature of the coast. Permanent erosional processes, locally or regionally, are caused by tectonic subsidence, deforestation and...

Analytical properties of Einasto dark matter haloes

Abstract: Recent high-resolution N -body CDM simulations indicate that nonsingular three-parameter models such as the Einasto profile perform better than the singular two-parameter models, e.g. the Navarro, Frenk and White, in fitting a wide range of dark matter haloes. While many of the basic properties of the Einasto profile have been discussed in previous studies, a number of analytical properties are still not investigated. In particular, a general analytical formula for the surface density, an important quantity that defines the lensing properties of a dark matter halo, is still lacking to date. To this aim, we used a Mellin integral transform formalism to derive a closed expression for the Einasto surface density and related properties in terms of the Fox H and Meijer G functions, which can be written as series expansions. This enables arbitrary-precision calculations of the surface density and the lensing properties of realistic dark matter halo models. Furthermore, we compared the Sersic and Einasto surface mass densities and found differences between them, which implies that the lensing properties for both profiles differ.