The floral biology, reproductive system, and visitation behavior of pollinators of four species of columnar cacti, Stenocereus griseus, Pilosocereus moritzianus, Subpilocereus repandus, and Subpilocereus horrispinus, were studied in two arid zones in the north of Venezuela. Our results support the hypothesis that Venezuelan species of columnar cacti have evolved toward specialization on bat pollination. Additional information on the floral biology of a fifth species, Pilosocereus lanuginosus, was also included. All species showed the typical traits that characterize the pollination syndrome of chiropterophily. All species but Pilosocereus moritzianus were obligate outcrossers. Nectar and pollen were restricted to nocturnal floral visitors. Two species of nectar-feeding bats, Leptonycteris curasoae Miller and Glossophaga longirostris Miller, were responsible for practically all the fruit set in these cacti. Frequency of bat visitation per flower per night was highly variable within and between species of cactus, with average frequencies varying between 27 and 78 visits/flower/night. In general terms, the pattern of floral visitation through the night was significantly correlated with the pattern of nectar production and nectar sugar concentration for all species of cactus. Under natural pollination, fruit:flower ratios varied from 0.46 in Subpilocereus repandus to 0.76 in Stenocereus griseus. The efficiency of bat pollination in terms of seed:ovule ratio was high in all species, varying between 0.70 and 0.94.

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INFORMACIÓN DEL ARTÍCULO ResumenSe investigaron los refugios diurnos del murciélago Eptesicus innoxius en dos zonas diferentes en la provincia de Guayas, Ecuador: el bosque intervenido de la isla Santay y la plantación agroforestal de cacao en Milagro. En ambas zonas cuatro especies de murciélagos insectívoros aéreos (Eptesicus innoxius, Myotis nigricans, Molossus bondae y Molossus molossus) usaron como refugio, huecos pequeños en ramas y troncos de árboles vivos y muertos, y solo uno de ellos (E. innoxius) usó además los espacios de las cortezas desprendidas. El uso de refugios dentro del bosque y el cacaotal por E. innoxius, estuvo estrechamente relacionado con la ubicación del acceso, el entorno espacial inmediato y la cercanía de cuerpos de agua. Todas las especies de murciélagos insectívoros aéreos (menos M. bondae) formaron colonias en los techos y áticos deshabitados de las instalaciones humanas de la isla. Eptesicus innoxius utilizó el mayor número de refugios disponibles y fue común en todos los ambientes, por lo que estimamos que su población puede recuperarse y ampliarse su distribución en ambientes degradados. El pequeño tamaño y la morfología alar de esta especie (< 6,5 g, alas alargadas y estrechas) explicaría su gran adaptabilidad y agilidad. Palabras Clave:Bosque inundable, bosque seco, Eptesicus innoxius, murciélagos insectívoros, sistema agroforestal Clasificación JEL: Q1. AbstractThe day shelters of the Eptesicus innoxius bat were investigated in two different zones in the province of Guayas, Ecuador: the intervened Santay Island forest and the cacao agroforest plantations in Milagro. In both areas, four species of aerial insectivorous (Eptesicus innoxius, Myotis nigricans, Molossus bondae and Molossus molossus) bats used small holes in branches and trunks of living and dead trees as shelters, and only one of them (E. innoxius) also used spaces of detached tree bark. The use of shelters within the forest and cacao plantations by E. innoxius was closely related to the location of the access, the immediate space environment and the proximity of water bodies. All aerial insectivorous bat species (except M. bondae) formed colonies in uninhabited roofs and attics of human installations on the island. Eptesicus innoxius used the largest number of available shelters and was common in all environments, so we estimate that its population can recover and expand its distribution in degraded environments. The small size and wing morphology of this species (<6.5g, elongated and narrow wings) would explain its great adaptability and agility.

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