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We coordinated biogeographical comparisons of the impacts of an exotic invasive tree in its native and non-native ranges with a congeneric comparison in the non-native range. Prosopis juliflora is taxonomically complicated and with P. pallida forms the P. juliflora complex. Thus we sampled P. juliflora in its native Venezuela, and also located two field sites in Peru, the native range of Prosopis pallida. Canopies of Prosopis juliflora, a native of the New World but an invader in many other regions, had facilitative effects on the diversity of other species in its native Venezuela, and P. pallida had both negative and positive effects depending on the year, (overall neutral effects) in its native Peru. However, in India and Hawaii, USA, where P. juliflora is an aggressive invader, canopy effects were consistently and strongly negative on species richness. Prosopis cineraria, a native to India, had much weaker effects on species richness in India than P. juliflora. We carried out multiple congeneric comparisons between P. juliflora and P. cineraria, and found that soil from the rhizosphere of P. juliflora had higher extractable phosphorus, soluble salts and total phenolics than P. cineraria rhizosphere soils. Experimentally applied P. juliflora litter caused far greater mortality of native Indian species than litter from P. cineraria. Prosopis juliflora leaf leachate had neutral to negative effects on root growth of three common crop species of north-west India whereas P. cineraria leaf leachate had positive effects. Prosopis juliflora leaf leachate also had higher concentrations of total phenolics and L-tryptophan than P. cineraria, suggesting a potential allelopathic mechanism for the congeneric differences. Our results also suggest the possibility of regional evolutionary trajectories among competitors and that recent mixing of species from different trajectories has the potential to disrupt evolved interactions among native species.

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a b s t r a c tTrypanosoma cruzi congenital transmission in wild bats (Molossus molossus), associated with infected Rhodnius prolixus in a natural habitat from a rural locality in western Venezuela, is reported. T. cruzi blood circulating trypomastigotes in a pregnant bat were detected by parasitological methods. Polymerase chain reaction (PCR) assays carried out in samples from the heart and the fetus of the same infected female, revealed the presence of T. cruzi-specific DNA in both of the tissues, demonstrating transmission of the infection from the mother to the offspring. Eighty percent of the captured bats and 100% of the examined fetuses from pregnant specimens were shown to be infected by T. cruzi, indicating that M. molossus is a very susceptible species for this parasite, and that T. cruzi congenital transmission is a common phenomenon in nature. To our knowledge, this seems to be the first report on congenital T. cruzi transmission in wild bats in Venezuela. The circulation of T. cruzi lineage I in the study area was demonstrated by typing the isolates from bats and triatomine bugs captured in the same habitat. The potential epidemiological implication of these findings in areas where Chagas disease is endemic is discussed.

RESUMENDurante un afio se realiz6 el estudio fenol6gico de tres cacticeas columnares Stenocerewgriseus (Haw.) Britton & Rose, Pilosocereus sp., Cereur hexagonw (L.) Mill., y una cacticea decumbente, Monvillea cf. smithiana (Britton & Uose) Backeberg., en el enclave seco interandino de La Tatacoa, Colombia. Los polinizadores y/o dispersores de las cacticeas fueron capturados mensualmente y se recolectaron las muestras fecales para la identificaci6n de 10s granos de polen y las semillas de 10s frutos consumidos. La floraci6n de todas las especies fue prolongada y mostraron patrones bimodales, multimodales, o irregulares. La fructificaci6n en todas las especies tambikn se extendib durante todo el afio, con un desfase de dos meses con respecto a la floraci6n. Aunque no se encontrb una correlaci6n significativa entre 10s valores mensuales de precipitaci6n y la producci6n de Bores y frutos, la floracibn durante la kpoca seca fue mayor en S. griseus, mientras que Pilosocereus sp. y C. hexagonus mostraron 10s valores m6s altos durante la tpoca de Iluvias. La producci6n de frutos tambikn fue estacional, con un increment0 durante la kpoca de lluvias para S. griseus y C. hexagonus. La floraci6n y fructificacibn en M. cf. smithiana no mostraron diferencias significativas entre la Cpoca seca y la Iluviosa. Los murciklagos Glossophaga longirostris, Carollia perspicillata, Sturnira lilium y algunas aves como Melanerpes rubricapillw (Picidae) y Mimus gilvus (Mimidae), y una mariposa nocturna (Sphingidae), fueron algunos de 10s polinizadores y/o consumidores de estas especies de cacticeas. ABSTRACTA one-year phenological study of three columnar cacti, Stenocereus griseus (Haw.) Britton & Rose, Pilosocereus sp., Cereus hexagonus (L.) Mill., and a decumbent cactus Monvillea cf. smithiana (Britton & Rose) Backeberg., was carried out in the Andean arid region of La Tatacoa, Colombia. Pollinators and/or dispersers of the cacti species also were studied monthly, and fecal samples were collected for the identification of pollen and seeds. The flowering of all species was prolonged and showed bimodal, multimodal, or irregular patterns. Fruiting in all species also was prolonged and followed flowering with a lag of less than two months. Although there were no simple correlations between rainfall and flowering or fruiting, flower production during the dry season was higher for S. griseus, while Pilosocereus sp. and C. hexagonus showed higher flower production during the wet season. Fruit production was also seasonal, with higher production during the wet season for S. griseus and C. hexagonus. The patterns of flowering and fruiting in M. cf. smithiana showed no relationships with dry and wet seasons. The bats Glossophaga longirostris, Carollia perspicillata, Sturnira lilium, the birds Melanerpes rubricapillw (Picidae) and Mimw gilvus (Mimidae), and moths of the family Sphingidae, were identified as pollinators and/or fruit consumers of these cacti species.