Términos relacionados

8 resultados encontrados para: AUTOR: Schneider, L.
  • «
  • 1 de 1
  • »
1.
- Artículo con arbitraje
Resumen en: Inglés |
Resumen en inglés

Although recent years have seen an increase in genetic analyses that identify new species of cephalopods and phylogeographic patterns, the loliginid squid of South America remain one of the least studied groups. The suggestion that Doryteuthis plei may represent distinct lineages within its extensive distribution along the western Atlantic coasts from Cape Hatteras, USA (36 N) to northern Argentina (35 S) is consistent with significant variation in a number of environmental variables along this range including in both temperature and salinity. In the present study D. plei samples were obtained from a large number of localities along the western Atlantic coasts to investigate the distribution of these possible species in a phylogeographic context. Phylogeographic analyses were performed using the mitochondrial Cytochrome Oxidase I gene and nuclear Rhodopsin gene. Divergence times were estimated using Bayesian strict clock dating with calibrations based on fossil records for divergence from the lineage containing Vampyroteuthis infernalis (162 mya), the probable origins of the North American loliginids (45 mya), and the European loliginids (20 mya) and fossil statolith from Doryteuthis opalescens (3 mya). Our results suggest a deep genetic divergence within Doryteuthis plei. The currently described specie consists of two genetically distinct clades (pair-wise genetic divergence of between 7.7 and 9.1%). One clade composed of individuals collected in northwestern Atlantic and Central Caribbean Atlantic waters and the other from southwestern Atlantic waters.

The divergence time and sampling locations suggest the speciation process at approximately 16 Mya, which is in full agreement with the middle Miocene orogeny of the Caribbean plate, ending up with the formation of the Lesser Antilles and the adjacent subduction zone, coinciding with a particularly low global sea level, resulting in the practical absence of continental shelves at the area, and therefore an effective geographic barrier for D. plei. Furthermore, this study also provides evidence of previously undocumented sub-population structuring in the Gulf of Mexico.


Resumen en: Inglés |
Resumen en inglés

Land system science axiomatically addresses social–environmental systems by integrating the dynamics of land uses (social) and land covers (environment), invariably including the use of remote sensing data and often, spatially explicit models of land change. This kind of research is illustrated through the Southern Yucatán Peninsular Region project (1997–2008) aimed at understanding, predicting, and projecting spatially explicit land change in a region with juxtaposed land uses-agriculture and a biosphere reserve. The successes of the project, its contributions to contemporary land system science, and the organizational mechanisms that fostered the research are identified as well as various corrections, which if applied, may have refined and extended the project's goals. Overall, the project demonstrates the kind of integrated research required to advance understanding of a social-environment system and the team-based methods used in the process.


Resumen en: Inglés |
Resumen en inglés

Land system science axiomatically addresses social– environmental systems by integrating the dynamics of land uses (social) and land covers (environment), invariably including the use of remote sensing data and often, spatially explicit models of land change. This kind of research is illustrated through the Southern Yucata´ n Peninsular Region project (1997–2008) aimed at understanding, predicting, and projecting spatially explicit land change in a region with juxtaposed land uses-agriculture and a biosphere reserve. The successes of the project, its contributions to contemporary land system science, and the organizational mechanisms that fostered the research are identified as well as various corrections, which if applied, may have refined and extended the project’s goals. Overall, the project demonstrates the kind of integrated research required to advance understanding of a social-environment system and the team-based methods used in the process.


4.
- Artículo con arbitraje
Resumen en: Inglés |
Resumen en inglés

This study explores the temporal and spatial variability and change in rainfall across southeastern Mexico and the mechanisms by which smallholder farmers adapt to this variability, especially droughts. Members of 150 households in 10 communities were interviewed to investigate adaptation strategies among swidden maize smallholders, linked to their perceptions of climate changes. Precipitation data from seven weather stations were analyzed for the 1973–2012 period. Precipitation anomalies were estimated to evaluate the annual and seasonal stability, deficit, or surplus; and linear regressions were used to evaluate trends. Then, these anomalies were linked to variation in reported agricultural practices. Weather station data show a considerable decline in precipitation in most of the study area, coupled with increased drought frequency and an increase in negative anomalies in recent years. Surveys revealed several mechanisms of adaptation, including adjustment of the agricultural calendar (e.g. delaying planting, combined with planting a greater number of varieties of maize), water storage, and livelihood diversification both within and outside of agriculture. These adaptive mechanisms are responsive to demonstrated climatic change over the past 40 years, though globalization affects Mexico's agrarian economy, and farmers likely respond to a combination of economic and climatic factors. Understanding how resource- and climate-dependent swidden farmers respond to co-occurring climatic and economic changes is essential for effective adaptation policy design.


PDF PDF
Resumen en: Inglés |
Resumen en inglés

Squid of the genus Lolliguncula Steenstrup, 1881 are small bodied, coastal species capable of tolerating low salinity. Lolliguncula sp. are found exclusively in the New World, although only one of the four recognized species (Lolliguncula brevis) occurs in the Atlantic Ocean. Preliminary morphological analyses suggest that Lolliguncula brevis populations in the North and South Atlantic may represent distinct species. The principal objective of the present study was to verify the phylogenetic relationships within the genus and test for the presence of possible cryptic species. Both gene and species tree topologies indicated that Lolliguncula brevis specimens from the North and South Atlantic represent distinct phylogenetic clades. In contrast with previous studies, L. panamensis was identified as the basal species of the genus. Our results provide important insights into the phylogenetic relationships among the Lolliguncula specimens analyzed, and confirm the genetic separation of Lolliguncula brevis populations of the North and South Atlantic at the level of sister species.


6.
- Artículo con arbitraje
Resumen en: Inglés |
Resumen en inglés

This research examines the spatio-temporal trends in Advanced Very High Resolution Radiometer (AVHRR) Global Inventory Modelling and Mapping Studies (GIMMS) normalized difference vegetation index (NDVI) time series to ascribe land use change and precipitation to observed changes in land cover from 1982 to 2007 in the Mexican Yucatán Peninsula, using seasonal trend analysis (STA). In addition to discrete land cover transitions across the study region, patterns of agricultural intensification, urban expansion and afforestation in protected areas have enacted changes to the seasonal patterns of apparent greenness observed through STA greenness parameters. The results indicate that the seasonal variation in NDVI can be used to distinguish among different land cover transitions, and the primary differences among these transitions were in changes in overall greenness, peak annual greenness and the timing of the growing season. Associations between greenness trends and precipitation were weak, indicating a human-dominated system for the 26 years examined. Changes in the states of Campeche, Quintana Roo and Yucatán appear to be associated with pasture cultivation, urban expansion-extensive cultivation and urban expansion-intensive cultivation, respectively.


7.
- Artículo con arbitraje
High mortality for rare species following hurricane disturbance in the southern Yucatán
Vandecar, Karen L. ; Lawrence, Deborah (coaut.) ; Richards, Dana (coaut.) ; Schneider, Laura (coaut.) ; Rogan, John (coaut.) ; Schmook, Birgit Inge (coaut.) ; Wilbur, Henry (coaut.) ;
Contenido en: Biotropica Vol. 43, no. 6 (November 2011), p. 676–684 ISSN: 0006-3606
Resumen en: Inglés |
Resumen en inglés

Hurricanes are an important part of the natural disturbance regime of the Yucatán Peninsula with the potential to alter forest structure and composition, yet investigations of species-level responses to severe winds are limited in this region. The effect of a category 5 hurricane (Hurricane Dean, 21 August 2007) on dry tropical forests across the southern Yucatán was examined with respect to tree damage, mortality, and sprouting. Damage was assessed 9–11 mo following the hurricane in 92 (500 m2) plots stratified by wind speed and normalized difference vegetation index (NDVI) change classes over a 25,000 km2 study area. We investigated the relative importance of biotic (i.e., species, size, and wood density) and abiotic (i.e., wind speed) factors to better explain patterns of damage. Overall mortality was low (3.9%), however, mortality of less common species (8.5%) was elevated more than fourfold above that of 28 common species (1.8%), indicating immediate selective consequences for community composition. Species varied in the degree and type of damage experienced, with susceptibility increasing with tree diameter and height. Wood density influenced damage patterns only in areas where a critical threshold in storm intensity was exceeded (wind speeds ≥210 km/h). Although overall, damage severity increased with wind speed, common coastal species were more resistant to damage than species distributed farther inland. Our findings suggest that selective pressure exerted by frequent hurricane disturbance has, and will, continue to impact the floristic composition of forests on the Yucatán Peninsula, favoring certain wind-resistant species.


8.
Libro
Integrated land-change science and tropical deforestation in the Southern Yucatán: final frontiers / edited by B. L. Turner II, Jacqueline Geoghegan and David R. Foster
Turner II, Billie Lee (editor) ; Geoghegan, Jacqueline (editora) ; Foster, David R. (editor) ;
Oxford, England, United Kingdom : Oxford University Press , 2004
Clasificación: Y/333.75137 / I5
Bibliotecas: Campeche , Chetumal , San Cristóbal
Cerrar
SIBE Campeche
ECO040002406 (Disponible)
Disponibles para prestamo: 1
Cerrar
SIBE Chetumal
ECO030000902 (Disponible)
Disponibles para prestamo: 1
Cerrar
SIBE San Cristóbal
ECO010000042 (Disponible)
Disponibles para prestamo: 1
Índice | Resumen en: Inglés |
Resumen en inglés

This highly topical study of tropical deforestation in Mexico reports on the first phase of the Land-Cover and Land-Use Change in the Southern Yucatan Peninsular Region Project (LCLUC-SYPR): a large, multi-institutional, and team-based study designed to understand and project land changes in a development frontier that pits the rapidly growing needs of smallholder farmers to cut down forests for cultivation against federally sponsored initiatives committed to various international programmes of forest preservation and complementary economic programmes. The SYPR project is a response to inderdisciplinary defined research themes deemed critical to global environmental change and complementary international research agendas (e.g. environment and development, ecosystem assessment, biotic diversity). Pivotal among these agendas are those posed by the Land-Use/Cover Change (LUCC) effort of the International Geosphere-Biosphere Programme and the International Human Dimensions of Global Environmental Change Programme as it is linked through such US sponsors as the National Aeronautics and Space Administration (NASA) and the National Science Foundation (NSF). The themes (i.e. questions and subjects) posed by these programmes and organization are 'integrated' or 'synthesis' in kind, meaning that they rest within the intersection of formal disciplines and are intended to fit into a larger, systems framework about human-environment relationships and the structure and function of the biosphere. The editors of this volume, as most of its contributors, come from the disciplines of geography, ecology, and economics. The lead editor, the geographer B. L. Turner II, has spent most of his career in pursuit of understanding different aspects of tropical deforestation and agriculture.

Índice

1. Introduction Three Frontiers of the Southern Yucatan Peninsular Region and SYPR Project
I: Human-Environment Relationships, 1000 BC - AD 1900
2. The Long View: Human-Environment Relationships 1000 BC - AD 1900
3. Forest Extraction to Theme Parks: The Modern History of Land Change
II: Land-Cover Characteristics and Change
4. Forest Types and their Implications
5. Recovery of Nutrient Cycling and Ecosystem Properties following Swidden Cultivation: Regional and Stand-Level Constraints
6. Land Cover and Land Use: Classification and Change Analysis
III: Agents and Institutions of Land Change: Household Economy and Cultivation
7. Institutions, Organizations, and Policy Affecting Land Change: Complexity Within and Beyond the Ejido
8. The Ejido Household: The Current Agent of Change
9. Subsistence Sustained: Swidden or Milpa Cultivation
10. Jalapeno Pepper Cultivation: Emergent Commercial Land Use
11. The Semi-Market and Semi-Subsistence Household: The Evidence and Test of Smallholder Behavior
IV: Spatial Modeling of Land Change: Empirical Approaches in Data-Sparse Environments
12. Spatially Explicit, Statistical Land-Change Models in Data-Sparse Conditions
13. The SYPR Integrative Assessment Model: Complexity in Development
Retrospective: The Three Frontiers Revisited
Glossary and Acronyms
Index