Lake Patzcuaro (Mexico): a controversy about the ecosystem water regime approached by field references, climatic variables, and GIS

In this paper, a basic question is asked about a well-documented case study in Mexico: how well do we know Lake Patzcuaro? We address water balance as fundamental to the question. Past studies provide ambiguous explanations about the role of either underground infiltration and/or runoff, relative to the lake-level fluctuation. Thus, our suspicions over the database reliability led us to inspect historic records on water levels and climatic variables; check out the altitude of ground references, and analyze traces of runoff watercourses over the terrestrial basin by means of GIS. By making data re-arrangement and corrections, it became evident that the lake is subject to long-term cycles with ca. 40-year peaks, including short-term seasonal cycles within. Sensitivity to climatic conditions was determined, as well as the active influence of runoff as an important hydrologic component that contributes to cause serious damage to the land surface by erosion. Rearrangement of raw data highlights the occurrence of past misinterpretations founded on biased information.     

Chemical composition of the sponge Chondrosia reniformis from [2pt] the Canary Islands

Lake Zempoala was studied throughout 16 months in 1996–1997. It is a shallow monomictic lake situated at 2800 masl at the Neovolcanic Belt, well within the Mexican tropical zone. Most of the phytoplankton species in this lake may be characterized as temperate, according to their geographical distribution. A break down in phytoplankton biomass was observed before the lake's circulation, and open to question if a clear-water phase could be present in a tropical lake.     

Characterization of small shallow ponds with color video imagery in Central Mexico

We present a method to evaluate ecological characteristics of small shallow ponds in Central Mexico based on video remote sensing and image processing techniques in a GIS environment. We used a set of color video imagery obtained from heights lower than 700 m above ground. Our analysis established statistical correlations between the average reflectance values contained in video imagery (digital numbers DN per Blue-Green-Red band) and the average values of limnetic variables: (1) water suspended solids concentration; (2) water turbidity; (3) total macrophytes coverage; (4) free floaters and emergent macrophytes coverage; (5) zooplankton abundance; and (6) chlorophyll-a concentration in water. We found strong correlation between DN values and vegetation presence, suspended solids concentration and water turbidity (R= 0.85 to 0.98), but weak correlations with phytoplankton and zooplankton abundance. This cheap and fast method can be used to describe general conditions of ponds related with vegetation abundance, turbidity and suspended solids.     

Ethnobotany ofAnoda Cristata (L.) schl. (Malvaceae) in central Mexico: Uses, management and population differentiation in the community of Santiago Mamalhuazuca, Ozumba, state of Mexico

Anoda cristata is a common weed used for food and medicine in central Mexico where it grows among field crops during the rainy seasons. People prefer robust, tender plants from the agricultural fields because these “develop better.” Hence, the plants are tolerated within the conventional agricultural activities and benefit indirectly from the improvements in the agrohabitat. People do not select individuals with specific morphological characteristics but rather they select for plants at the level of the habitat. This step may precede that of direct management of individual plants. It is possible that these differences in the level of interaction between humans and plants (i.e., within the ruderal and agrestal habitats) may promote morphological and genetic differences over time,

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Etnobotánica de anoda cristata (Malvaceae) en México: Usos, Manejo y diferenciación poblacional en la Comunidad de Santiago Mamalhuazuca, Ozumba, estado de México

Resumen   Anoda cristata es una maleza muy común utilizada como medicina y alimento en el centro de México durante la época de lluvias La gente prefiere las plantas robustas y tiernas que crecen en los campos de cultivo porque se “desarrollan mejor.”Ahí, las plantas son toleradas dentro de las prácticas agrícolas tradicionales y se benefician indirectamente de las alteraciones que se hacen al agrohabitat. La gente no selecciona conscientemente individuos con características morfológicas específicas, sino que seleccionan a las plantas a nivel del hábitat. Este paso puede ser previo al manejo indirecto de individuos particulares. Es posible que estas diferencias en el nivel de interactión entre los hombres y las plantas (entre el hábitat ruderal y arvense) puede promover diferencias morfológicas y genéticas a través del tiempo.

     

Two new remarkable Nolinaceae from Central Mexico

Two new species of Nolinaceae are described and illustrated. The first is a ponytail palm,Beaucarnea compacta, occuring in xerophytic scrub in the Sierra Madre Oriental near Atarjea, Guanajuato. The second new species isCalibanus glassianus, adding the second species to the genusCalibanus. This new species is found in the transition between tropical deciduous forest to subontane scrub in the Sierra Madre Oriental near Xichú, Guanajuato.

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Se describen e ilustran dos nuevas especies de Nolinaceae. La primera es una pata de elefante o palma petacona,Beaucarnea compacta. Se distribuye en matorrales xerófitos de la Sierra madre Oriental cerca de Atarjea, Guanajuato. La segunda nueva especie esCalibanus glassianus, que adiciona una especie más al géneroCalibanus. Esta nueva especie se encuentra en la transición de bosques tropicales caducifolios con matorrales xerófilos de la sierra Madre Oriental en los alrededores de Xichú, Guanajuato.

     

Species richness of helminth parasites in Mexican amphibians and reptiles

Abstract. Amphibians and reptiles represent an important group of vertebrates in Mexico; on a global scale 10% of the biodiversity of these groups is found in the country, attaining extraordinarily high levels of endemism (60.7% and 53.7%, respectively). However, fewer than 20% of the known species of amphibians and reptiles in Mexico have been surveyed for helminths, so the inventory is far from complete. We assembled a data base that includes a total of 1246 records (entries) of which 460 correspond to helminths in amphibians and 786 to helminths in reptiles. In total, only 41 species of amphibians (14% of those occurring in Mexico) and only 118 species of reptiles (17% of those occurring in Mexico) have been studied for helminth parasites. From amphibians, 119 species of helminths belonging to 60 genera have been recorded, while 239 species of helminths representing 113 genera have been described from Mexican reptiles. One feature of the distribution of helminths of Mexican amphibians and reptiles is its asymmetry, as seen in representation of helminth groups, host groups and geographical range. However, such statistical asymmetry might be an artefact of sampling effort. Based on our data, we estimate that if all the herpetofauna of Mexico could be studied in the following years, approximately 827 additional species of helminths from amphibians and approximately 1403 from reptiles would be described.