Five Euphorbiaceae species (Jatropha macrocarpa, J. hieronymi, J. excisa, Cnidoscolus tubulosus and Manihot guaranitica) were analysed for seed oil content and fatty acid profiles in order to evaluate their potential as sources of biodiesel. The five species are perennial shrubs adapted to arid and semi-arid environments of north-western Argentina. The seed oil content for all species ranged from 27.9 to 38.7% by dry weight. Fatty acid composition consisted mainly of linolenic, myristic, palmitic, stearic, arachidic, oleic and linoleic acids, with linoleic and oleic acid being the most abundant. Among the five species analysed, J. macrocarpa has the best potential to be used as a biodiesel source. The average total seed oil content (35.8%) and a high value of oleic acid (27.3%) together with the lowest values of linoleic acid (55.8%) make this species a promising crop as a source of biodiesel in arid and semi-arid regions.

Seasonal variation in the consumption of cactus fruit by the bat Glossophaga longirostris was related to the availability of this resource in the arid pocket of Lagunillas in the Venezuelan Andes. When fruits were scarce, G. longirostris ate items not preferred in other seasons. The intraspecific flowering periods of the most common cactus species, Stenocereus griseus and Subpilocereus repandus, were synchronized but the number of flowers open per night was low. S. griseus and S. repandus had separate flowering and fruiting periods, possibly to reduce competition for dispersers and pollinators while providing food resources for bats throughout the year. G. longirostris is bimodally polyestrous with extended reproductive periods, probably as a response to the continual availability of cactus flowers and fruits. A strong interdependence between columnar cacti and G. longirostris was demonstrated. Sexual reproduction of the cacti would be greatly reduced without the bats, which in turn could not live in the arid study area without the food sources provided by these cacti.

Effects of seed passage through digestive tracts of principal animal dispersers (bats and birds) on seed germination were investigated for two columnar cactus species, Stenocereus griseus and Subpilocereus repandus. In general, seeds ingested showed more rapid germination times and higher overall germination rates than untreated seeds. The bat Glossophaga longirostris, and the birds Mimus gilvus and Tachyphonus rufus seem to be the most efficient cacti dispersers in terms of quality of treatment. The increment of germination speed and particularly the decrease of imbibition time, could favour the probability of germination in dry areas such as arid and semi-arid environments.