Prescriptions for the Control of a Clonal Invasive Species Using Demographic Models

Until recently, little research has focused on determination of the population dynamics of invasive species and evaluating their genetic variation. Consequently, not much is known of what drives clonal invasive species and their demography. Here, we describe the population dynamics of Kalanchoe delagoensis (Crassulaceae), considered invasive to several countries. We quantified the demography of a population in central Mexico using integral projection models (IPM) in a population that reproduced asexually exclusively through plantlets. The effect of clonal recruitment on population growth rate (λ) was evaluated by changing plantlet survival and simulating management scenarios that used previous data of watering and seven experimental herbicide treatments. The finite rate of population increase indicated that this Kalanchoe delagoensis population is growing (above one) and with water availability, growth rates will only accelerate. The IPM showed that plantlet survival and recruitment were the most critical steps in the cycle for the population, and simulations of different management scenarios showed that reducing plantlet survival significantly decreased λ only in two out of the seven herbicides used

Variación morfométrica de Neobuxbaumia mezcalaensis y N. Multiareolata (Pachycereeae, cactacea)

En este trabajo se evaluó la variación morfométrica a través de 46 caracteres vegetativos y reproductivos mediante análisis multivariados en dos especies de cactáceas columnares, Neobuxbuamia mezcalaensis y N. multiareolata. Los resultados revelaron que existe variación entre especies y entre poblaciones, especialmente para los caracteres vegetativos. Además una variación clinal para los parámetros geográficos, edáficos y climáticos con los caracteres: altura de individuo, distancia entre costillas, número de espinas centrales, longitud de espinas centrales, de flor, del pericarpelo, de escama de flor, diámetro de lóbulo del estigma, diámetro de fruto, relación longitud/diámetro de fruto, volumen de fruto, longitud de espina de fruto, número de aréolas y relación largo / ancho de semilla en N. mezcalaensis. La variación de los caracteres morfométricos vegetativos de las poblaciones de N. mezcalaensis es igual de variable como en N. multiareolata. El análisis discriminante separo a los individuos de N. mezcalaensis, N. multiareolata; así como de N. polylopha, especie que nunca ha sido confundida con ninguna de las anteriores y N. squamulosa especie segregada de N. mezcalaensis. Se reconocieron 14 caracteres con valor diagnóstico que permiten distinguir a los cuatro taxones: número de costillas, tamaño de aréola, disposición de espinas y longitud de espina central; así como longitud de flor, del tubo, del estilo, forma del fruto, longitud del tubérculo del fruto y tamaño de la semilla. Se confirma con base en los análisis multivariados que N. multiareolata es una entidad bien definida y diferente de N. mezcalaensis. _______In the present study the morphometric variation of two species of columnar cacti, Neobuxbuamia mezcalaensis and N. multiareolata, was evaluated by 46 vegetative and reproductive characters through multivariate analyses. The results revealed the existence of variation between species and among populations, especially for vegetative characters. Moreover, a clinal variation for geographic, edaphic and climatic parameters related to the following characters: high of the plant, distance between ribs, number of central spine, length of central spine, flower length, pericarp length, floral scale length, stigma lobule diameter, fruit diameter, fruit length / diameter ratio, fruit volume, fruit spine length, number of areole and seed length/wide ratio for N. mezcalaensis. Morphometric vegetative characters of N. mezcalaensis populations show similar variation as N. multiareolata. Discriminant analysis separated individuals of N. mezcalaensis from those of N. multiareolata, as well as individuals of N. polylopha, species never confounded with any of the two mentioned and individuals of N. squamulosa, species segregated from N. mezcalaensis. Fourteen characters were recognized with diagnostic value, because they allow to distinguishing the four taxa: number of ribs, areole size, spine arrangement, central spine length, flower, floral tube and style lengths, fruit shape, fruit tubercle length, and seed size. The multivariate analyses confirmed the distinction between N. multiareolata and N. mezcalaensis.Tesis (Maestría en Ciencias, especialista en Botánica).- Colegio de Postgraduados, 2007.CONACY

Prescriptions for the Control of a Clonal Invasive Species Using Demographic Models

Until recently, little research has focused on determination of the population dynamics of invasive species and evaluating their genetic variation. Consequently, not much is known of what drives clonal invasive species and their demography. Here, we describe the population dynamics of Kalanchoe delagoensis (Crassulaceae), considered invasive to several countries. We quantified the demography of a population in central Mexico using integral projection models (IPM) in a population that reproduced asexually exclusively through plantlets. The effect of clonal recruitment on population growth rate (λ) was evaluated by changing plantlet survival and simulating management scenarios that used previous data of watering and seven experimental herbicide treatments. The finite rate of population increase indicated that this Kalanchoe delagoensis population is growing (above one) and with water availability, growth rates will only accelerate. The IPM showed that plantlet survival and recruitment were the most critical steps in the cycle for the population, and simulations of different management scenarios showed that reducing plantlet survival significantly decreased λ only in two out of the seven herbicides used

What are the demographic consequences of a seed bank stage for columnar cacti?

The dynamics of plant populations are often limited by the early stages in their life cycles. However, information regarding seed bank dynamics and how these may influence the whole life cycle of plant species is remarkably scarce or not considered explicitly. This lack of knowledge is due mainly to the challenges in quantifying seed vital rates. Studies of arid land plant species have historically been focused on the drivers of sporadic recruitment. However, little attention has been given to the demographic consequences of early developmental stages, and how seed banks affect their dynamics. Here, we evaluate the effects of seed bank survival and seedling recruitment vital rates on the population dynamics and viability of 12 columnar cacti species. Recent evidence suggests that cacti seeds may remain viable for the short-term. We assess how changes in the vital rates of these processes and the inclusion of a seed bank affect population growth rate (&#x3BB;). We found that a seed bank in the examined matrix population models significantly increased &#x3BB; as well as the vital rate elasticities of &#x3BB; to growth and fecundity, whereas that of overall survival decreased. Our numerical simulations showed that seed survival had a more considerable effect on &#x3BB; than seedling recruitment and establishment. We suggest that the seed bank may explain the structure and population dynamics. Thus, we reconsider that this early stage in demographic models will generate more informed decisions on the conservation and management of columnar cacti.</p

On a Probable Catalytic Interaction between Magnetite (Fe3O4) and Petroleum

Magnetic and nonmagnetic iron compounds were detected as part of asphaltene deposits formed on tubing wall surface. To shed light on the probable role of the iron compounds in the formation of such deposits, magnetite (Fe3O4), one of the intrinsic components of the iron oxide multilayer scale of any carbon steel surface, was contacted with crude oil at 170 °C, a temperature similar to that of the bottom well, and subsequently aged at room temperature. Characterization of the samples was made by using XRD, Mo¨ssbauer, IR, TGA, EDS, and microscopic (SEM and TEM) techniques. Small amounts of new iron phases, magnetic (oxidized magnetite) and nonmagnetic (iron oxyhydroxides), an increase in the content of CdC and C-O bonds of the organic phase, and an increase of the thermal stability of the organic phase indicated the formation of iron complexes of Fe ions and FeOOH with the oxygen functionalities