We studied variation in flowering phenology, fruit and seed set, and the abundance of the pollinators of four species of night-blooming Sonoran Desert columnar cacti for up to eight years at one site in Mexico and one year at one site in Arizona. We determined how spatiotemporal variation in plant-pollinator interactions affects the evolution of generalized pollination systems. We conducted pollinator exclusion and hand pollination experiments to document annual variability in pollinator reliability and to determine whether pollination systems were redundant (different species are partially or totally substitutable) or complementary (different species have an additive effect on fruit set). The cacti we studied included three species with generalized pollination systems involving bats, birds, and bees (cardon, Pachycereus pringlei; saguaro, Carnegiea gigantea; and organ pipe, Stenocereus thurberi) and one specialized moth-pollinated species (senita, Lophocereus schottii). We predicted that the migratory lesser long-nosed bat, Leptonycteris curasoae, is a less reliable pollinator than birds and bees, and that cacti with generalized pollination systems have more variable flowering phenologies than the specialized species.Annual time of peak flowering and mean size of flower crops were relatively invariant in saguaro and organ pipe. Time of peak flowering in cardon varied by as much as six weeks, and mean flower crop size varied threefold over six years. In senita, peak flowering varied by as much as 5-8 wk among years. Peak numbers of the nectar bat L. curasoae varied among years, and bat density (0.9/ha) was an order of magnitude lower than that of cactus-visiting birds at both study sites. The abundance of migratory hummingbirds was also highly variable among years.Pollinator exclusion experiments indicated that bats were major pollinators of cardon, whereas diurnal visitors accounted for most fruit set in saguaro (except in 1995 when bats were most important) and organ pipe at our Mexican site; honeybees accounted for 64-87% of diurnal fruit set in these species. Annual variation in the contribution to fruit set by bats was substantially higher than that of diurnal pollinators in saguaro and organ pipe, but not in cardon. There was little geographic variation in the relative importance of nocturnal vs. diurnal pollinators in saguaro and senita, but bats were much more important for fruit set in organ pipe in Arizona than in Mexico. We generally detected no effect of different pollinators on number of seeds per fruit in any species.Annual variation in fruit set was lowest in saguaro, the species with the most diurnal pollination system, and highest in organ pipe, the species with the most generalized pollination system. Fruit set was strongly pollen limited only in females of cardon (a trioecious species) and in organ pipe (at both sites). The ''missing'' pollinators in both species are likely Leptonycteris bats. The pollination systems of saguaro and cardon were partially redundant, whereas that of organ pipe was...

We quantitatively assessed rodent dispersal of vesicular—arbuscular mycorrhizal fungi in a lowland tropical rain forest. We examined fecal pellets from seven rodent species of the genera Proechimys, Oryzomys, and Mesomys trapped each month from August 1983 through July 1984 at the Cocha Cash field station in Manu National Park, Peru. We found sporocarps of Sclerocystis coremioides and spores of four Glomus species in 69.3% of fecal samples, with 37.5% of samples containing 2—4 fungus species. There were median numbers of 8.6 S. coremioides sporocarps and 712 Glomus spores/0.1 g feces. S. coremioides and all Glomus species comprised up to 4.1 and 5.4% of fecal mass, respectively. We did not detect differences in fungus consumption by rodent species or sex, but did find significant differences between rodent genera. More than 60% of Proechimys samples contained glomalean fungi in contrast to °37% of Oryzomys samples. Occurrence of the two fungus genera in feces differed seasonally but was generally congruent between Proechimys and Oryzomys. Glomus presence in feces is significantly positively associated with the dry season. Both rodent genera together annually pass 2.96 x 105 S. coremioides sporocarps and 7.30 x 107 Glomus spores/ha at Cocha Cashu. We concluded that Proechimys and Oryzomys are likely to be important agents of vesicular—arbuscular mycorrhizal fungus spore dispersal.

We studied variation in flowering phenology, fruit and seed set, and the abundance of the pollinators of four species of night-blooming Sonoran Desert columnar cacti for up to eight years at one site in Mexico and one year at one site in Arizona. We determined how spatiotemporal variation in plant-pollinator interactions affects the evolution of generalized pollination systems. We conducted pollinator exclusion and hand pollination experiments to document annual variability in pollinator reliability and to determine whether pollination systems were redundant (different species are partially or totally substitutable) or complementary (different species have an additive effect on fruit set). The cacti we studied included three species with generalized pollination systems involving bats, birds, and bees (cardon, Pachycereus pringlei; saguaro, Carnegiea gigantea; and organ pipe, Stenocereus thurberi) and one specialized moth-pollinated species (senita, Lophocereus schottii). We predicted that the migratory lesser long-nosed bat, Leptonycteris curasoae, is a less reliable pollinator than birds and bees, and that cacti with generalized pollination systems have more variable flowering phenologies than the specialized species.Annual time of peak flowering and mean size of flower crops were relatively invariant in saguaro and organ pipe. Time of peak flowering in cardon varied by as much as six weeks, and mean flower crop size varied threefold over six years. In senita, peak flowering varied by as much as 5-8 wk among years. Peak numbers of the nectar bat L. curasoae varied among years, and bat density (0.9/ha) was an order of magnitude lower than that of cactus-visiting birds at both study sites. The abundance of migratory hummingbirds was also highly variable among years.Pollinator exclusion experiments indicated that bats were major pollinators of cardon, whereas diurnal visitors accounted for most fruit set in saguaro (except in 1995 when bats were most important) and organ pipe at our Mexican site; honeybees accounted for 64-87% of diurnal fruit set in these species. Annual variation in the contribution to fruit set by bats was substantially higher than that of diurnal pollinators in saguaro and organ pipe, but not in cardon. There was little geographic variation in the relative importance of nocturnal vs. diurnal pollinators in saguaro and senita, but bats were much more important for fruit set in organ pipe in Arizona than in Mexico. We generally detected no effect of different pollinators on number of seeds per fruit in any species.Annual variation in fruit set was lowest in saguaro, the species with the most diurnal pollination system, and highest in organ pipe, the species with the most generalized pollination system. Fruit set was strongly pollen limited only in females of cardon (a trioecious species) and in organ pipe (at both sites). The ''missing'' pollinators in both species are likely Leptonycteris bats. The pollination systems of saguaro and cardon were partially redundant, whereas that of organ pipe was...

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I present data on flower morphology, pollination, breeding system, and genetic diversity of the columnar cactus Weber‐bauerocereus weberbaueri at 2500 m elevation in southwestern Peru. Weberbauerocereus weberbaueri is a self‐compatible columnar cactus that is visited and pollinated by one species of rare endemic bat, Platalina genovensium, and two species of hummingbirds, Patagona gigas and Rhodopis vesper. W. weberbaueri exhibits pronounced interplant variation in floral color and size, and flowers exhibit traits corresponding to both bat and hummingbird pollination syndromes. Starch‐gel electrophoresis of flower bud tissue indicated that W. weberbaueri is an autotetraploid and that genetic diversity (Hep = 0.257) of the study population was high relative to diploid plants but similar to other tetraploid species. Initial fruit set from pollinator exclusion experiments conducted in 1991 and 1993, at the onset of and after a drought associated with the El Niño event of 1991–1992, revealed that bats were the most important pollinators in 1991, but that hummingbirds and diurnal insects were most important in 1993. In both years, however, autogamy and lepidopteran larval infestation of fruits reduced differences in mature fruit production among pollinator exclusion treatments so that differences in mature fruit set were not statistically significant. Reduced bat pollination in 1993 is attributed to the reduced abundance of bats at the study site during a drought caused by El Niño. I hypothesize that interaction among several factors, including tetraploidy, autogamy, larval infestation of developing fruits, and variation in pollinator abundance, may not result in strong selection for a bat vs. hummingbird floral morph, thus allowing the persistence of floral variation in this cactus.

Knowledge of feeding habits of small rodents is necessary for understanding food webs, trophic structure, and plant–animal interactions in Neotropical forests. Despite several studies that have investigated community structure and feeding behavior of rodents, large gaps remain in our understanding of their guild occupancy. Our objective was to investigate the diets of 7 species of small (< 100g) sympatric sigmodontine rodents in a high (3,500 m) Andean montane rainforest in Peru. We qualitatively and quantitatively assessed diet items in fecal samples from livetrapped rodents from 2009 to 2012. Frequency data for 4 diet categories indicated that all 7 species of rodents contained 4 diet categories in fecal samples: arthropods (88%), remains of leaves and fibers from plants (61%), intact seeds (with or without fruit pulp; 50%), and mycorrhizal spores (45%). Omnivory was found to be a strategy used by all species, although contingency table analysis revealed significant differences among and within species in diet categories. Cluster analysis showed 2 main groupings: that of the Thomasomys spp. plus Calomys sorellus group which included high amounts of intact seeds and plant parts in their fecal samples, and those of the genera Akodon, Microryzomys, Oligoryzomys, which included a greater proportion of arthropods in their fecal samples, but still consumed substantial amounts of fruit and plant parts. Intact seed remains from at least 17 plant species (9 families) were found in fecal samples. We concluded that this assemblage of sigmodontine rodents is omnivorous but that they likely play an important role as frugivores and in seed dispersal in tropical montane forests in Peru.El conocimiento de los hábitos alimenticios de roedores pequeños es necesario para comprender cadenas alimenticias, estructura trófica, e interacciones planta-animal en los bosques neotropicales. A pesar de que numerosos estudios han investigado la estructura de comunidades y el comportamiento de forrajeo en roedores, aún existen grandes vacíos en nuestra comprensión de sus gremios tróficos. Nuestro objetivo fue investigar las dietas de siete especies de pequeños (< 100 g) roedores sigmodontinos simpátricos en un bosque montano andino a 3.500] m en Perú. Cualitativamente y cuantitativamente evaluamos la dieta en muestras fecales de roedores capturados entre el 2009 y el 2012. Datos de frecuencia para cuatro categorías de dieta indicaron que las siete especies de roedores consumieron cuatro categorías de dieta: artrópodos (88%), pedazos de hojas y fibras de plantas (61%), semillas intactas (con o sin pulpa de frutos; 50%), y esporas de micorrizas (45%). Omnivoría fue la estrategia utilizada por todas las especies, aunque el análisis con tablas de contingencia reveló diferencias significativas entre y dentro de especies en categorías de dieta. El análisis de agrupación presentó 2 grupos principales: el grupo Thomasomys spp. y Calomys sorellus, que incluye una gran proporción de semillas intactas, y partes de plantas en las muestras fecales y el g...

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