Evaluation of the Impact of Genetically Modified Cotton After 20 Years of Cultivation in Mexico

For more than 20 years cotton has been the most widely sown genetically modified (GM) crop in Mexico. Its cultivation has fulfilled all requirements and has gone through the different regulatory stages. During the last 20 years, both research-institutions and biotech-companies have generated scientific and technical information regarding GM cotton cultivation in Mexico. In this work, we collected data in order to analyze the environmental and agronomic effects of the use of GM cotton in Mexico. In 1996, the introduction of Bt cotton made it possible to reactivate this crop, which in previous years was greatly reduced due to pest problems, production costs and environmental concerns. Bt cotton is a widely accepted tool for cotton producers and has proven to be efficient for the control of lepidopteran pests. The economic benefits of its use are variable, and depend on factors such as the international cotton-prices and other costs associated with its inputs. So far, the management strategies used to prevent development of insect resistance to GM cotton has been successful, and there are no reports of insect resistance development to Bt cotton in Mexico. In addition, no effects have been observed on non-target organisms. For herbicide tolerant cotton, the prevention of herbicide resistance has also been successful since unlike other countries, the onset of resistance weeds is still slow, apparently due to cultural practices and rotation of different herbicides. Environmental benefits have been achieved with a reduction in chemical insecticide applications and the subsequent decrease in primary pest populations, so that the inclusion of other technologies—e.g., use of non-Bt cotton- can be explored. Nevertheless, control measures need to be implemented during transport of the bolls and fiber to prevent dispersal of volunteer plants and subsequent gene flow to wild relatives distributed outside the GM cotton growing areas. It is still necessary to implement national research programs, so that biotechnology and plant breeding advances can be used in the development of cotton varieties adapted to the Mexican particular environmental conditions and to control insect pests of regional importance

¿Quién poliniza realmente los agaves? Diversidad de visitantes florales en 3 especies de Agave (Agavoideae: Asparagaceae)

ResumenSe describen los patrones de actividad de los visitantes a las inflorescencias de 3 especies de Agave: Agave difformis, A. garciae-mendozae y A. striata en distintas localidades de la Barranca de Metztitlán, Hidalgo, México. Se define el posible papel de estos visitantes en el proceso de polinización, ya sea como ladrones de polen o néctar, o como polinizadores primarios o secundarios, estos últimos visitan menos flores y/o lo hacen de manera ineficiente. Se filmó la actividad de visitantes durante 24h continuas en 5 inflorescencias. Se encontraron los siguientes grupos de visitantes: esfíngidos, murciélagos, abejas y colibríes. Los horarios de mayor actividad en las 3 especies de Agave se registraron durante la noche, entre las 21:00 y 03:00h. La presencia de visitantes diurnos (abejas y colibríes) en las inflorescencias abre la posibilidad de que estos también actúen como polinizadores. Los polinizadores clasificados como primarios fueron los murciélagos nectarívoros Leptonycteris yerbabuenae, L. nivalis y Choeronycteris mexicana. El polinizador secundario más común fue el esfíngidos Erinnyis ello. El principal ladrón de polen y néctar fue la abeja europea, Apis mellifera, en A. striata, aunque tiene las flores más pequeñas; A. mellifera podría ser considerada como polinizador secundario.AbstractActivity patterns of inflorescence visitors are described for 3 species of Agave: Agave difformis, A. garciae-mendozae and A. striata from different sites at Barranca de Metztitlán, Hidalgo, Mexico. The potential role of the visitors in the pollination process was defined: pollen or nectar robbers, or as primary or secondary pollinators, secondary if they visit less flowers or do so in an inefficient way. Visitor's activity was recorded for 24 consecutive hours on 5 inflorescences. The visitors were from the following groups: hawkmoths, bats, bees and hummingbirds. The peak of the activity in the 3 Agave species was registered between 21:00 to 03:00h. In some cases, diurnal visitors (bees and hummingbirds) could also be pollinators. The primary pollinators were the nectar feeding bats Leptonycteris yerbabuenae, L. nivalis, and Choeronycteris mexicana. The most common secondary pollinator was the hawkmoth Erinnyis ello. The main pollen and nectar robber was the European honey bee, Apis mellifera, however, A. mellifera could also be considered as a secondary pollinator for A. striata, because this species has smaller flowers

Are 150 km of open sea enough? Gene flow and population differentiation in a bat-pollinated columnar cactus

AbstractGenetic differentiations and phylogeographical patterns are controlled by the interplay between spatial isolation and gene flow. To test the extent of gene flow across an oceanic barrier, we explored the effect of the separation of the peninsula of Baja California on the evolution of mainland and peninsular populations of the long-lived columnar cactusStenocereus thurberi. We analyzed twelve populations throughout the OPC distribution range to assess genetic diversity and structure using chloroplast DNA sequences. Genetic diversity was higher (Hd=0.81), and genetic structure was lower (GST=0.143) in mainland populations vs peninsular populations (Hd=0.71,GST=0.358 respectively). Genetic diversity was negatively associated with elevation but positively with rainfall. Two mainland and one peninsular ancestral haplotypes were reconstructed. Peninsular populations were as isolated among them as with mainland populations. Peninsular haplotypes formed a group with one mainland coastal population, and populations across the gulf shared common haplotypes giving support to regular gene flow across the Gulf. Gene flow is likely mediated by bats, the main pollinators and seed dispersers. Niche modeling suggests that during the Last Glacial Maximum (c. 130 ka), OPC populations shrank to southern locations. Currently, Stenocereus thurberi populations are expanding, and the species is under population divergence despite ongoing gene flow. Ancestral populations are located on the mainland and although vicariant peninsular populations cannot be ruled out, they are likely the result of gene flow across the seemingly formidable barrier of the Gulf of California. Still, unique haplotypes occur in the peninsula and the mainland, and peninsular populations are more structured than these on the mainland.</jats:p

Are 150 km of open sea enough? Gene flow and population differentiation in a bat-pollinated columnar cactus.

Genetic differentiations and phylogeographical patterns are controlled by the interplay between spatial isolation and gene flow. To assess the extent of gene flow across an oceanic barrier, we explored the effect of the separation of the peninsula of Baja California on the evolution of mainland and peninsular populations of the long-lived columnar cactus Stenocereus thurberi. We analyzed twelve populations throughout the OPC distribution range to assess genetic diversity and structure using chloroplast DNA sequences. Genetic diversity was higher (Hd = 0.81), and genetic structure was lower (GST = 0.143) in mainland populations vs peninsular populations (Hd = 0.71, GST = 0.358 respectively). Genetic diversity was negatively associated with elevation but positively with rainfall. Two mainland and one peninsular ancestral haplotypes were reconstructed. Peninsular populations were as isolated among them as with mainland populations. Peninsular haplotypes formed a group with one mainland coastal population, and populations across the gulf shared common haplotypes giving support to regular gene flow across the Gulf. Gene flow is likely mediated by bats, the main pollinators and seed dispersers. Niche modeling suggests that during the Last Glacial Maximum (c. 130 ka), OPC populations shrank to southern locations. Currently, Stenocereus thurberi populations are expanding, and the species is under population divergence despite ongoing gene flow. Ancestral populations are located on the mainland and although vicariant peninsular populations cannot be ruled out, they are likely the result of gene flow across the seemingly formidable barrier of the Gulf of California. Still, unique haplotypes occur in the peninsula and the mainland, and peninsular populations are more structured than those on the mainland

Predicted environmental suitability for <i>Stenocereus thurberi</i> using ecological niche models (ENM).

ENM results are shown for: (A) the current, (B) the last glacial maximum [LGM, 21 Ka, MIROC-ESM model], and (C) the last interglacial period (LIG, 120–100 Ka) time periods.</p