High proportion of cactus species threatened with extinction

This is the author accepted manuscript. The final version is available from Nature Publishing Group via the DOI in this record.Consejo Nacional de Ciencia y Tecnologí

Insects associated to maize under different weed management regimes in Chiapas, Mexico

5 ilus. 2 tab. 32 ref.Se estudiaron los cambios en la riqueza y abundancia relativa de distintos grupos de insectos asociados al cultivo de ma?z, con tres manejos diferentes de arvenses o malezas, durante el ciclo agr?cola 2002, en dos parcelas de la comunidad de Yalum? Villahermosa, Chiapas. Los tratamientos establecidos fueron: ma?z sin arvenses, con tres deshierbas con herbicidas ma?z con arvenses, con una deshierba con herbicidas, y ma?z con dos especies de malezas mel?feras, con deshierbas selectivas. Se recolectaron insectos y arvenses de junio a septiembre. Se obtuvieron 28 especies de plantas, 10934 insectos y ara?as de 101 familias y 255 morfoespecies, las cuales se agruparon seg?n sus h?bitos alimentarios en fit?fagos, depredadores, polinizadores, parasitoides y degradadores. La diversidad de insectos y ara?as fue mayor en los tratamientos con malezas y con malezas mel?feras, los mismos tratamientos donde abundaron los depredadores. Los fit?fagos fueron los m?s abundantes en todos los tratamientos en ambas parcelas. La presencia de arvenses influy? en la riqueza y abundancia de insectos y depredadores presentes en el cultivo de ma?z. Changes in species variety and relative abundance of insect groups associated with maize were studied in relation to three different weed management regimes during the agricultural cycle of 2002 in Yaluma, Villahermosa, Chiapas. Three contrasting weed management regimes were included: a maize monoculture, where weeds were eliminated by applying herbicides three times during the cropping cycle, maize associated with volunteer weeds and subject to a simple herbicide application, and maize in association with two melipherous weed species that underwent selective weeding. The experiment was established in a completely randomized design with three replications. Insects and weeds were collected monthly between June and September. Twenty-eight weed species, and 10934 species of insects and spiders belonging to 101 families and 255 species were collected. The insects were grouped, according to their feeding habits, in phytophagous, predators, pollinators, parasites and decomposers. Insect and spider diversity was higher when the maize was associated with weeds and melipherous plants where predators were abundant. The phytophagous insects were the most abundant group across all weed management treatments. The presence of weeds influenced the variety and abundance of insects and predators present in maize