Llanos Of Colombia Research Articles

Ecological niche modeling of the Leopardus tigrinus complex sheds light on its elusive evolutionary history

Abstract The evolutionary history and taxonomy of the Leopardus tigrinus species complex have been studied based on several approaches, mostly employing genetic and morphological data, leading to distinct classification schemes. We approached this problem from an ecological perspective, with 2 main goals: (i) to evaluate ecological niche differences among regional L. tigrinus populations to determine the extent of ecological divergence among them; and (ii) to identify environmental barriers to historical dispersal that could have driven differentiation among the proposed groups. We modeled the ecological niche of all taxonomic/geographic groups proposed so far to comprise the L. tigrinus complex using the Maximum Entropy algorithm, and evaluated geographic and ecological niche differences among them. Furthermore, we investigated possible environmental barriers to historical dispersal that could have driven differentiation among regional groups. We evaluated 4 hypothetical barriers across 3 time periods to assess their potential historical effect. We found high ecological divergence between northeastern tigrina populations and the northern Andean and Central American tigrinas. Other groups within the L. tigrinus complex are less divergent. In addition, the Guiana Shield tigrina, where the type locality of the species is located, seems to be ecologically similar to populations from northeastern Brazil while also showing some overlap with Andean populations. The Panama center, the Llanos of Colombia and Venezuela, and the Amazon region were identified as historical barriers for tigrina dispersal across all time periods. The inferred historical barriers and ecological divergence observed in this study contribute to the inference of evolutionary differentiation among geographic groups comprising the L. tigrinus complex, revealing areas of consistently low habitat suitability that have likely contributed to divergence among regional populations.

Modelling the reproductive performance of tropical beef herds using long-term experimental grazing data on Urochloa humidicola pastures in the Llanos of Colombia

Long-term reproductive performance of beef breeding herds grazing sown pastures in the neotropical savanna environment of Eastern Colombia (Llanos) is not well documented, while the lifelong reproductive consequences of raising replacement heifers subject to different growth regimes is also intriguing. The study aimed to assess the effects of liveweight (LW), age, and their interaction on conception probabilities of Bos indicus replacement females by analyzing two seven- and eight-years lasting experiments that used commercial Brahman heifers subject initially to different growth rates on Urochloa humidicola pastures. The experiments included two periods, namely the growth period from weaning until 270 kg LW during which heifers were subjected to three stocking rates to attain different rates of gain, and the subsequent reproduction phase subject to common grazing for all growth treatments. The conception data fitted well logistic regressions in which LW and age were the predictor variables during the first two conceptions but the relationship disappeared in subsequent conceptions. Prediction equations compared well with extensive data from northern Australia that showed similar trends. Liveweight of adult cows only increased consistently during pregnancy, but following weaning their LWs returned to the initial low LWs attained at conception. Over the length of the experiments, weaning rates as percentages of calves born were 88% for the two treatments with higher LW gains during the growth period, and 81% for the lowest gaining treatment. Calving intervals were 19-20 months across treatments. It is suggested that the data and equations provided can guide decision making in extensive breeding herds.

New record for Colombia, updated distribution map, and comments on the defensive behavior of Thamnodyastes dixoni Bailey & Thomas, 2007 (Serpentes, Dipsadidae, Xenodontinae)

The original description of Thamnodynastes dixoni Bailey & Thomas, 2007 was based on few specimens, and the morphological variation, distributional range, and ecological aspects of this species are virtually unknown. The species is known to occur in the Llanos of Colombia and Venezuela. In Colombia, it was recorded only in four localities. We report a fifth occurrence of T. dixoni in Colombia and the first in the Department of Meta. The new record extends this species’ distribution nearly 150 km (in a straight line) from the nearest previously known occurrence at Paz de Ariporo, Department of Casanare. Additionally, we also provide comments about the species’ defensive behavior, not reported elsewhere, and a thorough revision on the species’ geographical distribution.

Amphibia, Anura, Hylidae, Boana wavrini (Parker, 1936): distribution extension in the Colombian Llanos

We report the presence of Boana wavrini in Arauca and Vichada departments (Llanos of Colombia). These localities extend the known range of this species by more than 283 km to the north from the previously known occurrences. In addition, we describe some aspects of the natural history of this species.

Minimizing the biodiversity impact of Neotropical oil palm development.

Oil palm agriculture is rapidly expanding in the Neotropics, at the expense of a range of natural and seminatural habitats. A key question is how this expansion should be managed to reduce negative impacts on biodiversity. Focusing on the Llanos of Colombia, a mixed grassland-forest system identified as a priority zone for future oil palm development, we survey communities of ants, dung beetles, birds and herpetofauna occurring in oil palm plantations and the other principal form of agriculture in the region--improved cattle pasture--together with those of surrounding natural forests. We show that oil palm plantations have similar or higher species richness across all four taxonomic groups than improved pasture. For dung beetles, species richness in oil palm was equal to that of forest, whereas the other three taxa had highest species richness in forests. Hierarchical modelling of species occupancy probabilities indicated that oil palm plantations supported a higher proportion of species characteristic of forests than did cattle pastures. Across the bird community, occupancy probabilities within oil palm were positively influenced by increasing forest cover in a surrounding 250 m radius, whereas surrounding forest cover did not strongly influence the occurrence of other taxonomic groups in oil palm. Overall, our results suggest that the conversion of existing improved pastures to oil palm has limited negative impacts on biodiversity. As such, existing cattle pastures of the Colombian Llanos could offer a key opportunity to meet governmental targets for oil palm development without incurring significant biodiversity costs. Our results also highlight the value of preserving remnant forests within these agricultural landscapes, protecting high biodiversity and exporting avian 'spill-over' effects into oil palm plantations.

Territorial rule in Colombia and the transformation of the Llanos Orientales by Jane M. Rausch (review)

Reviewed by: Territorial rule in Colombia and the transformation of the Llanos Orientales by Jane M. Rausch Andrés Ernest Guhl Territorial rule in Colombia and the transformation of the Llanos Orientales. Jane M. Rausch. Gainesville, Florida: University Press of Florida, 2013. x and 187 pp., maps, tables, glossary and index (ISBN 978-0-8130-4466-8) (US $69.95) This book is the latest from Emerita Professor of History, Jane M. Rausch. Her books provide a complete survey of the history of the Llanos region of Colombia, and emphasizes the “region’s interaction with the highland core from 1946 to 2010 – in order to investigate recent developments that have occurred in Colombia’s eastern frontier” (vii). Her other three books cover the history of the Llanos during colonial times (A Tropical Plains Frontier: The Llanos of Colombia, 1531–1831), the consolidation of the country as an independent republic (The Llanos Frontier in Colombian History: 1830–1930), and the region’s transformations associated with the modernization of Colombia since 1930 until the beginning of an extremely violent period known as la violencia in which political parties battled against each other for political power in rural areas of the country (Colombia: Territorial Rule and the Llanos Frontier). As in her previous books, Rausch demonstrates through rigorous research that the llanos have played a more important role in Colombia’s evolution than usually acknowledged. The book is divided into six chapters. The first five chapters are chronologically arranged, and each one of them provides an overview of the llanos region and its relationship with the highlands during a specific time period. The first chapter provides a summary of the most important aspects of the territorial history of the llanos since colonial times until 1946. The following four chapters deal with la violencia (1946–1953), the dictatorship of Gustavo Rojas Pinilla (1953–1957), The National Front and beyond (1958–1978), and what the Rausch calls the contemporary era (1978–2010). The last chapter of the book provides a synthesis of how the region and the concepts used to describe and analyze it have changed through time. She also highlights the growing body of new researchers in the region trying to study the area by shunning away from the traditional historical analysis where the llanos are just a peripheral area with little influence in the rest of the country, therefore expanding the analytical reach of historical research. Frontier is the most important concept Rausch uses for her analysis of territorial transformation in the region. Although she acknowledges that the concept has been contested and reinterpreted since Frederick Jackson Turner proposed it in 1893, she finds it as a useful tool to approach the territorial transformation in the region. From the beginning of the book Rausch defines frontier as “a geographical region originally inhabited by native people that lies at the edge Hispanic settlement” (viii). Throughout the book, she uses this concept to describe and delineate the region where territorial power is contested among the Colombian state and other actors. However, she also uses frontier’s meaning as an international boundary, emphasizing the close ties of the region to Venezuela. Furthermore, she stresses the importance of studying the Colombian llanos in relation to the larger llanos region (Colombia and Venezuela). Rausch’s book analyzes the recent historical territorial transformation of the llanos taking into account the geographical differences of the four departments that presently make up the region (Meta, Vichada, Arauca and Casanare). Although the llanos are synonymous with cattle ranching and a llanero way of life, there are two different llanos areas. The first two departments are located in what is called the altillanura (the high llanos), while Arauca and Casanare are [End Page 237] in the floodable llanos located north of the Meta River. This difference means two distinct ways of cattle ranching that take into account these two different environments. Furthermore, the author also divides the area into “llanos arriba” (upper llanos) and “llanos abajo”. This distinction more or less corresponds to the Andean range piedmont and its region of influence (llanos arriba), where the territorial transformation has been more significant since mechanized agriculture and agribusiness replaced traditional cattle ranching activities. This...

Constructing an Arable Layer Through Chisel Tillage and Agropastoral Systems in Tropical Savanna Soils of the Llanos of Colombia

ABSTRACT Integration of crop and livestock systems (agropastoralism) is a key strategy for intensifying agricultural production on infertile acid savanna soils, and for reversing problems of soil degradation in the tropics. The main objective of this study was to evaluate the impact of strategies including vertical tillage (1, 2 or 3 passes of chisel), crop rotations (rice-soybean), and agropastoral systems (rice-grass alone pasture; rice-grass/legume pasture) on the build-up of an arable layer and on grain yields of upland rice and soybean. We assessed the build-up of an arable layer in terms of improved soil physical characteristics (bulk density, penetration resistance), soil nutrient availability, soil phosphorus (P) pools, plant growth, and nutrient acquisition during the fourth year after the establishment of different treatments on native savanna soil. The soil used in this study was an Oxisol in the eastern plains (Llanos orientales) of Colombia. Agropastoral treatments (rice-grass alone pasture; rice-grass/legumes pasture) with vertical tillage decreased soil bulk density in the 0–20 cm soil layer by 12% when compared with the unmanaged native savanna. Consistent with bulk density, penetration resistance was also markedly decreased for 0–20 cm depth. Three passes of chisel (rice-soybean rotation) and pasture treatments (grass alone and grass/legume) improved the availability of Bray (II) P, K, Ca, and Mg in the 0–5 cm layer. The biologically available resin-Pi and NaHCO3-Pi each represented 5% of the total P and were significantly affected by chisel down to 10–20 cm depth. The moderately resistant NaOH-P represented, on average, 33% of total P in the 0–20 cm soil layer, and both NaOH-Pi and NaOH-Po were significantly affected by chisel tillage. Results on grain yields of upland rice showed that three passes of chisel could have a negative effect on grain yield, and that yields which declined over time declined more in agropastoral treatments than in rice-soybean rotation. These results indicate that the use of vertical tillage and agropastoral treatments can contribute to the build-up of an arable layer in low fertility savanna soils of the Llanos of Colombia as indicated by improved soil physical properties and nutrient availability. However, to take advantage of the constructed arable layer to improve crop yields, there is a need for developing better crop management strategies to control weeds.

Disc harrowing intensity and its impact on soil properties and plant growth of agropastoral systems in the Llanos of Colombia

Oxisols such as those of the Colombian Eastern Plains (Llanos) are susceptible to physical, chemical and biological degradation once brought into cultivation, especially under intensive use of machinery. The main objective of this study was to determine the impact of intensive disc harrowing (2, 4 or 8 disc harrow passes per year over 3 years) on soil physical and chemical properties, soil phosphorus dynamics, plant growth and nutrient acquisition of contrasting agropastoral systems on an Oxisol. The three main systems tested after 2 years of upland rice cultivation were grass-alone pasture ( Brachiaria dictyoneura), green manure ( Crotalaria juncea), and maize ( Zea mays). Native savanna treatment was used as a control. Intensive disc harrowing improved macroporosity values of 0–5 cm soil layer up to 59% for grass-alone pasture system compared to native savanna. Disc harrowing significantly reduced bulk densities for pasture and green manure systems compared to the native savanna in the 0–5 cm soil layer. Intensive disc harrowing significantly improved volumetric moisture content of green manure and maize systems at 5–10 cm soil depth. The distribution of biologically, moderately and sparingly available P, organic P and total P varied under green manure, maize and grass-alone pasture systems. Two passes of disc harrow per year were sufficient for grass-alone pasture, while maize showed greater aboveground production and nutrient acquisition at 8 passes of disc harrow per year. The maize and green manure cropping systems were better than the grass-alone pasture system at separating the effect of increased number of disc harrow passes on soil physical and chemical characteristics.

A New Species of Cnemidophorus (Sauria: Teiidae) from the Llanos of Colombia and Venezuela

-A new species of whiptail lizard is described from the Llanos of Colombia and Venezuela. Cnemidophorus gramivagus is a member of the lemniscatus species group. It is most similar to C. lemniscatus, but differs in color and pattern in all age classes of both sexes, and attains a much larger size than C. lemniscatus. Additionally, female C. gramivagus become reproductively mature at a larger size than C. lemniscatus. A description of both juvenile and adult color patterns is provided along with an analysis of ontogenetic color pattern change. Comparative meristic data are provided for both taxa. In the early 1970's, in the Venezuelan Llanos, J.R.D. observed and collected a large series of Cnemidophorus, which he tentatively assigned to C. lemniscatus. He noted that these specimens differed from what is known as typical C. lemniscatus in color, pattern, size, and behavior. These bright green lizards readily climbed trees and fence posts (Dixon and Staton, 1977). Such climbing behavior is rarely observed in C. lemniscatus or other Cnemidophorus species in general. At present five species of whiptails are recognized on mainland South America (Maslin and Secoy, 1986). Two of these (C. lemniscatus and C. ocellifer) are recognized as members of the lemniscatus species group (Lowe et al., 1970). All occur south of the Rio Amazonas except C. lemniscatus and the new taxon described herein. Cnemidophorus lemniscatus occurs along the Rio Amazonas (to at least Manaus) and throughout northern South America and Central America. A careful comparison was made of the Llanos population with C. lemniscatus from adjacent Venezuelan populations as well as several other localities throughout its range. Data were collected on 23 meristic characters and four morphometric characters from both the new taxon and C. lemniscatus. These characters and their acronyms are defined in Appendix 1. A numbering sys1 Present address: Arizona-Sonora Desert Museum, Route 9, Box 900, Tucson, Arizona 85743, USA. tem was developed for all observed color patterns and each recognizable pattern was coded. Females were dissected and their ovaries were examined to determine at what size they become reproductively mature. One hundred forty of the new taxon and 310 C. lemniscatus were examined. The new taxon's color patterns were distinctly different from those of C. lemniscatus in all age classes of both sexes. It attains a much larger snout-vent length (SVL; x = 92 mm vs. 67 mm) than C. lemniscatus. Additionally, it becomes reproductively mature at a much greater size. While the two forms were not observed sympatrically by us, C. lemniscatus was observed in the northern floodplain of the Llanos, 63 airline km from the type locality of the new taxon. Although it appears that the two forms may be sympatric, further collecting is needed to ascertain precisely their boundaries. After reviewing the taxonomic history and examining the available type specimens of C. lemniscatus, and observing the aforementioned differences in color, pattern, length, and size at reproductive maturity, we propose that this large whiptail lizard of the Llanos grasslands be known

A Tropical Plains Frontier: The Llanos of Colombia, 1531–1831. By Jane M. Rausch. (Albuquerque: University of New Mexico Press, 1984. xv + 317 pp. Illustrations, notes, index, maps, bibliography. $29.95)

Previous articleNext article No AccessBook ReviewsA Tropical Plains Frontier: The Llanos of Colombia, 1531–1831. By Jane M. Rausch. (Albuquerque: University of New Mexico Press, 1984. xv + 317 pp. Illustrations, notes, index, maps, bibliography. $29.95)Charles BergquistCharles Bergquist Search for more articles by this author PDFPDF PLUS Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinkedInRedditEmail SectionsMoreDetailsFiguresReferencesCited by Volume 30, Number 4October 1986 Published for the American Society for Environmental History and the Forest History Society Article DOIhttps://doi.org/10.2307/4004742 Journal History This article was published in the Journal of Forest History (1974-1989), which was continued by Forest & Conservation History (1990-1995). © 1986 Forest History Society, Inc. All rights reserved.PDF download Crossref reports no articles citing this article.

Selecting and Evaluating New Technology for Small Farmers in the Colombian Andes

The tropical highlands of the Northern Andes are well suited to permanent, intensive cropping. Before the Spanish introduction of, and emphasis on, cattle raising, these areas were intensively cultivated by the Indian populations who grew maize, beans, squash, manioc, and other crops. Volcanic or alluvial soils are found in most of the region, and thus soil fertility is not as serious a constraint as it is in the tropical lowlands of the coast, the Llanos of Colombia and Venezuela, and the Amazon of those two countries and Ecuador. Moreover, the Northern Andes generally has sufficient rainfall and a distribution pattern which permits two crops per year. With favourable soils and climate, human population densities have always been high. Based on calculations using the most recent censuses for the three countries, approximately 53 percent of the population of the Northern Andes, almost 25 million people, is concentrated in the mountain areas. Excluding Venezuela, the statistics become 69 percent and 23 million, respectively. Small farmers predominate numerically in the Northern Andes; however, large farmers control most of the land in the more fertile valleys, forcing many of the small farmers to locate on the steeply sloping mountain lands.

Simulation of beef cattle production systems in the Llanos of Colombia: Part 2—Results of the modelling

Verifications and validations were conducted of a simulation model of beef cattle production on tropical ranges of the Colombian Llanos. Liveweight changes were simulated for individual cows sampled at random, for cow herds alternately grazing native savanna and molasses grass ( Melinis minutiflora) and for steers grazing native savanna. Correlation coefficients between observed and simulated liveweight change were high. Simulations of the calving rates of cow herds from two experiments at Carimagua Research Station were also conducted and there was reasonably good agreement between observed and simulated data. Shortcomings of the model included an inability to simulate the heavy weight losses of grazing animals on molasses grass during the dry season and under-estimates of calving rates for the most productive herds. An experiment was conducted with the validated model from which it was concluded that grazing molasses grass and weaning of calves at 84 days of age would do little to increase calving rate.

A New Hylid Frog from the Llanos of Colombia

Hyla kennedyi is a new, terrestrial member of the Hyla rostrata species group from the Colombian llanos. It differs from other members of the rostrata group in structural features, thigh pattern and breeding call.

Review of 1970 Petroleum Developments in South America, Central America, and Caribbean Area

This review includes information on petroleum developments during 1970 in 30 countries. Petroleum was produced in 10 countries and total production was 1,737,678,000 bbl (4,760,290 b/d), an increase of 2.4% from the previous year. Venezuela furnished 78% of the total as it produced at a high rate of 3,708,000 b/d and registered an increase of 3.2% from the previous year's production. The largest percentage increase in production was 10.1 by Argentina, as the average rate was 392,347 b/d. Production increased 3.7% in Colombia, but declined in all other countries. A total of 1,978 wells was drilled, 351 more than in 1969. Exploration drilling was carried out in 15 countries; however, commercial production was not found in any new country this year. Party-months of geologic and geophysical work were: surface geology, 329; seismograph, 659; gravity, 52; magnetometer, 13; other, 53. Forty-two percent of this work was in Argentina and 17% was in Brazil. Successful exploration drilling was featured in eastern Ecuador and in the offshore southeast of Trinidad; on the discouraging side was the unsuccessful offshore drilling in Argentina and Nicaragua. Significant for future exploration was the awarding of exploration blocks in the North Coast Marine Area of Trinidad, the contracting for exploration of large areas of the llanos of Colombia, and further progress toward the awarding of service contracts for 5 blocks in south Lake Maracaibo.

Exploration in Llanos of Colombia: ABSTRACT

The Llanos of Colombia, comprising the eastern portion of the country, is an alluvium-covered, featureless, grassy plain that covers an area of about 75,000 square miles. Except for a short dry season from December to March heavy rains occur almost every day. Access to the area is difficult and for the major portion of the year special track equipment or helicopters must be used for exploration operations. Structurally the Llanos form an asymmetrical basin similar to that of eastern Venezuela or western Canada. There is a shelf area to the east with sediments dipping uniformly off the Guiana shield and increasing in thickness to the west to form a major trough in front of the thrust faulted Eastern Cordillera. The entire geological sedimentary column outcrops along the we tern border of the Llanos with excellent reservoirs, source rocks, and attendant oil seeps. Approximately 26,500,000 acres are held in the basin by six major oil companies at this time. To date the geology of the bordering Eastern Cordillera has been mapped in considerable detail, reconnaissance seismograph, gravity, and local magnetometer surveys have been run over the more attractive portions of the basin, and 22 wells have been drilled. Although some encouraging oil shows have been encountered in wells in the southern margin of the basin, no commercial oil has been discovered to date. End_of_Article - Last_Page 1254------------