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Search Results: 1 - 10 of 84 matches for " Exequiel Ezcurra "
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Revealing an Endemic Herbivore-Palm Interaction in Remote Desert Oases of Baja California  [PDF]
Elisabet V. Wehncke, Xavier López-Medellín, Michael Wall, Exequiel Ezcurra
American Journal of Plant Sciences (AJPS) , 2013, DOI: 10.4236/ajps.2013.42A060
Abstract:

In the Central Desert of northern Baja California, blue fan palm populations (Brahea armata) are found as isolated oases on mountaintops and along canyons with ephemeral flow conditions. Here, the effect of the interaction between the larva of an endemic moth, Litoprosopus bajaensis, and this endemic blue fan palm was documented for the first time. We registered the phenology of palms by counting the number of shoots with flowers or fruits, assessing their damage and calculating the reproductive success per individual palm within three populations: San Pedro Martir, Catavi?a, and La Libertad. Palm populations were severely impacted by this larva, causing high damage to the inflorescences. No differences were found in the number of inflorescence stems produced and damaged among study sites; but the reproductive success of palms was significantly higher in Catavi?a than in the other sites during the entire sampling period, and consequently an important proportion of stems escaped from the herbivore predation. We suggest that differences among sites may be explained by the fact that Catavi?a is the only alluvial canyon and can be considered an area of high nutrient uptake, resource availability, and rooting depths. In contrast the other two are bedrock canyons, where water runs intensely, sweeping away great portions of the nearby vegetation. Catavi?a received the highest precipitation during the winter season of 2010 allowing a continuous production of inflorescence stems and fruits. This preliminary study reveals a new endemic interaction, it occurrence at population and regional levels, and highlights the role of desert oases as resource patches and connectivity pathways for mobile insects. Finally, it also highlights the effects of different water flow dynamics and water pulses in providing an opportunity window of escape from predation for host plant species living in desert environments.

Movimiento foliar en Larrea tridentata (Sesse & Moc. Ex Dc.) Cov. en relación con la sequía y la edad de la hoja
Pedro Luis Valverde,Santiago Arizaga,Exequiel Ezcurra
Acta botánica mexicana , 1993,
Abstract: La gobernadora ( Larrea tridentata) es una planta perenne común de los desiertos de México con hojas bifoliadas, anfiestomáticas y divaricadas. Las hojas pueden cerrar verticalmente sus foliolos y así variar su perfil con respecto a la radiación solar directa. Un experimento de invernadero fue hecho para evaluar (a) la cantidad de movimiento foliar presente en las plantas juveniles y (b) la influencia de la sequía y la edad de la hoja en este movimiento. En el invernadero, la apertura foliar varió significativamente con el estado hídrico del suelo, la hora del día y la edad de la hoja. Los foliolos abrieron en las primeras horas de la ma ana y se cerraron al atardecer. Las plantas sometidas a estrés hídrico mostraron aperturas de foliolos significativamente menores que aquellas plantas que no lo estaban. Los foliolos de las hojas jóvenes se mostraron significativamente más cerrados que los de las hojas maduras y viejas.
Patrones de distribución ficoflorística en el sistema lagunar de Nichupte, Quintana Roo, México
Ligia Collado Vides,Jorge González González,Exequiel Ezcurra
Acta botánica mexicana , 1995,
Abstract: Se hizo un estudio sobre las algas y su distribución en el Sistema Lagunar de Nichupté (SLN). El SLN es una laguna costera, ubicada en el estado de Quintana Roo, en las costas del Mar Caribe. Tiene aguas prácticamente marinas, sedimentos arenosos cubiertos por manchones de pastos y las orillas presentan crecimientos de manglares. Se encontraron 77 especies distribuidas en las siguientes divisiones: 33 en Chlorophyta, 37 en Rhodophyta, 3 en Phaeophyta y 4 en Cyanophyta. Se observó una diferencia florística significativa entre las muestras de algas recolectadas en los bajos arenosos y las de raíces de manglares. Las diferencias principales en la composición ficoflorística se encuentran asociadas al substrato, profundidad y salinidad.
Los petenes de Sian Ka an Quintana Roo y su relación con gradientes de presión hídrica.
Jorge López Portillo,Exequiel Ezcurra,Jose Manuel Maass
Acta botánica mexicana , 1989,
Abstract:
Termorregulación y eficiencia de intercepción de luz en Opuntia pilifera Weber (Cactaceae).
Zenón Cano Santana,Carlos Cordero,Exequiel Ezcurra
Acta botánica mexicana , 1992,
Abstract:
Ecorregiones de la península de Baja California: Una síntesis
González-Abraham, Charlotte E.;Garcillán, Pedro P.;Ezcurra, Exequiel;,;
Boletín de la Sociedad Botánica de México , 2010,
Abstract: the biological singularity of the baja california peninsula has captured the attention of naturalists since long time ago. as result, a rich variety of ecological and biogeographical interpretations have been proposed. they share a common framework, but at the same time show disagreement. an exhaustive review of published literature was done to identify which ecoregions or transition zones show disagreement. we submitted the discordant transition zones to the analysis of regional experts during a workshop, and with the help of a geographical information system we generated decisions by consensus for the majority of discussed zones. reults are shown in a map of ecoregions of the baja california peninsula, as a synthesis of the long time effort of study and analysis developed by individuals and institutions on the natural scenario of the baja california peninsula.
Large Recovery of Fish Biomass in a No-Take Marine Reserve
Octavio Aburto-Oropeza, Brad Erisman, Grantly R. Galland, Ismael Mascare?as-Osorio, Enric Sala, Exequiel Ezcurra
PLOS ONE , 2011, DOI: 10.1371/journal.pone.0023601
Abstract: No-take marine reserves are effective management tools used to restore fish biomass and community structure in areas depleted by overfishing. Cabo Pulmo National Park (CPNP) was created in 1995 and is the only well enforced no-take area in the Gulf of California, Mexico, mostly because of widespread support from the local community. In 1999, four years after the establishment of the reserve, there were no significant differences in fish biomass between CPNP (0.75 t ha?1 on average) and other marine protected areas or open access areas in the Gulf of California. By 2009, total fish biomass at CPNP had increased to 4.24 t ha?1 (absolute biomass increase of 3.49 t ha?1, or 463%), and the biomass of top predators and carnivores increased by 11 and 4 times, respectively. However, fish biomass did not change significantly in other marine protected areas or open access areas over the same time period. The absolute increase in fish biomass at CPNP within a decade is the largest measured in a marine reserve worldwide, and it is likely due to a combination of social (strong community leadership, social cohesion, effective enforcement) and ecological factors. The recovery of fish biomass inside CPNP has resulted in significant economic benefits, indicating that community-managed marine reserves are a viable solution to unsustainable coastal development and fisheries collapse in the Gulf of California and elsewhere.
ECORREGIONES DE LA PENíNSULA DE BAJA CALIFORNIA: UNA SíNTESIS
CHARLOTTE E. GONZáLEZ-ABRAHAM,PEDRO P. GARCILLáN,EXEQUIEL EZCURRA,EL GRUPO DE TRABAJO DE ECORREGIONES
Boletín de la Sociedad Botánica de México , 2010,
Abstract: La singularidad biológica de la península de Baja California ha capturado el interés de los naturalistas por largo tiempo. Fruto de ello ha sido la publicación de una rica variedad de interpretaciones geográficas de su escenario ecológico y biogeográfico. Aunque coincidentes en un marco común general, presentan también numerosas discrepancias. En este trabajo se revisa exhaustivamente la literatura publicada sobre el tema con el objeto de identificar las fronteras o zonas de transición que presentan mayor diversidad o discrepancia. Se sometió el diagnóstico al examen y discusión de un taller de expertos, el cual contó con el apoyo de un sistema de información geográfica, generando decisiones consensuadas. Los resultados se presentan en un mapa de regiones ecológicas de la península de Baja California como una síntesis del estudio e interpretación sobre las ecorregiones naturales de la península de Baja California.
Local Extinction and Unintentional Rewilding of Bighorn Sheep (Ovis canadensis) on a Desert Island
Benjamin T. Wilder, Julio L. Betancourt, Clinton W. Epps, Rachel S. Crowhurst, Jim I. Mead, Exequiel Ezcurra
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0091358
Abstract: Bighorn sheep (Ovis canadensis) were not known to live on Tiburón Island, the largest island in the Gulf of California and Mexico, prior to the surprisingly successful introduction of 20 individuals as a conservation measure in 1975. Today, a stable island population of ~500 sheep supports limited big game hunting and restocking of depleted areas on the Mexican mainland. We discovered fossil dung morphologically similar to that of bighorn sheep in a dung mat deposit from Mojet Cave, in the mountains of Tiburón Island. To determine the origin of this cave deposit we compared pellet shape to fecal pellets of other large mammals, and extracted DNA to sequence mitochondrial DNA fragments at the 12S ribosomal RNA and control regions. The fossil dung was 14C-dated to 1476–1632 calendar years before present and was confirmed as bighorn sheep by morphological and ancient DNA (aDNA) analysis. 12S sequences closely or exactly matched known bighorn sheep sequences; control region sequences exactly matched a haplotype described in desert bighorn sheep populations in southwest Arizona and southern California and showed subtle differentiation from the extant Tiburón population. Native desert bighorn sheep previously colonized this land-bridge island, most likely during the Pleistocene, when lower sea levels connected Tiburón to the mainland. They were extirpated sometime in the last ~1500 years, probably due to inherent dynamics of isolated populations, prolonged drought, and (or) human overkill. The reintroduced population is vulnerable to similar extinction risks. The discovery presented here refutes conventional wisdom that bighorn sheep are not native to Tiburón Island, and establishes its recent introduction as an example of unintentional rewilding, defined here as the introduction of a species without knowledge that it was once native and has since gone locally extinct.
Oxiurasis en puerto natales (Prov. De Magallanes)
EXEQUIEL BARROSO
Revista chilena de pediatría , 1947,
Abstract:
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