We investigated pollination biology and breeding systems in hybridizing populations of Pitcairnia albiflos and P. staminea; both species are endemic to rocky outcrops at Rio de Janeiro, Brazil. These species are morphologically distinct and easily recognized by floral color: white in P. albiflos and red in P. staminea. Putative hybrids show a large range of intermediate pink floral colors. The showy hermaphroditic flowers offer pollen and nectar that attract many visitors including bees, butterflies, hawk moths, and bats. Although the flowers of both parental species and hybrids open at night, only P. albiflos had other adaptations for nocturnal pollination. Flowering times overlapped during three consecutive years of observation. Bees visited both species and putative hybrids. Cross-pollinations were performed within and among parental species and hybrids in a greenhouse using plants transplanted from the field. Pitcairnia staminea and hybrids are self-compatible and could be spontaneously self-pollinated, whereas P. albiflos, though self-compatible, needs pollinators' services for self-pollination. Facultative agamospermy was found in the parental species. Prezygotic and postzygotic reproductive barriers between these taxa were weak. Reciprocal hand-pollinations between parental species and with hybrids yielded high fruit sets with viable seeds. Evaluations of fruit set, seed set, seed germination, and pollen viability were undertaken to compare the fitness of the hybrids relative to their parents. The hybrids showed equivalent fitness, except for lower pollen viability. Some conservation implications are noted.

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The phoretic behaviour of ostracods (Elpidium bromeliarum) andannelids (Dero superterrenus) that inhabit tank bromeliads was studied. Our previous field observations had shown that bromeliad ostracods can be found attached to the skin of amphibians and reptiles that move among bromeliads, probably allowing the ostracods to colonise new tanks. In this paper, we present the first record of bromeliad annelids found attached to frogs moving among bromeliads in the field. We have also enlarged the database on bromeliad ostracods engaged in phoretic association with terrestrial vertebrates in three locations in southeastern Brazil. In our laboratory experiments bromeliad annelids show a strong significant tendency to climb onto papers that had been in contact with frog skin when compared with control papers, indicating a kind of chemically oriented behaviour. Bromeliad ostracods, on the other hand, attached themselves to treated and untreated papers with same frequency. When brought into contact with various species of frogs and lizards, the bromeliad annelids and ostracods both presented preference to attach themselves to frogs, but the annelids showed a stronger preference to attach to frogs and to avoid attachment to lizards. Another experiment demonstrated that bromeliad annelids are much more prone to dehydration than are ostracods. We suggest that the chemically oriented behaviour presented by bromeliad annelids toward frogs could diminish the risk of death by dehydration during the transport among bromeliads due to the moist characteristic of frog skins.In the XIX century, the German naturalist Fritz Mu¨ller described the first aquatic organisms, a trichopteran larva (Mu¨ller, 1878) and an ostracod, occurring inside the water impounded among the leaves of tank bromeliads in southern Brazil. Mu¨ller found it easy to explain how the insect larvae have reached the water inside the bromeliad (the adult insect can easily fly and lay the eggs in the plant). But to explain how strictly aquatic ostracods could colonize the interior of terrestrial bromeliads, Mu¨ller formulated the hypothesis that, probably, they are transported from plant to plant by animals (Mu¨ller, 1879).Since Mu¨llerÕs discovery, other researchers have described a diverse aquatic fauna and flora colonizing the tanks formed by bromeliad leaves (Fish, 1983). This community appears to contain a high diversity of endemic organisms, which can be found inside plants under diverse micro-environmental conditions, ranging from the shaded forest Hydrobiologia (2005) 549:15-22 Ó Springer 2005

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Tank bromeliads harbour aquatic microcosms with many endemic species among their leaves. We performed a set of experiments to determine which factors maintain the bromeliad aquatic fauna in isolation from neighbouring ponds. We cultivated three invertebrates species (an ostracod, an annelid and a cladoceran) from a pond surrounded by terrestrial bromeliads in Southeastern Brazil and introduced them inside cleaned bromeliads, using recipients with the same volume as controls. The pH, conductivity and organism densities were monitored in the bromeliad samples and controls for 41 days. The samples introduced inside the cleaned bromeliads showed a significant decrease in pH and conductivity compared to the controls. The pond organism populations introduced in the bromeliads presented a high extinction rate and a significant population decrease when compared to the ones introduced in the controls. We attributed the population decline experienced by the pond organisms to the oligotrophic conditions generated inside the tanks by the bromeliads due to the nutrient absorption. We suggest that the changes in water chemistry induced by the bromeliads could play an important role in isolating their microcosm communities from other freshwater systems. Other mechanisms that could produce the high rates of endemism in bromeliad fauna are discussed.