RESUMO

Fruit availability experienced by different primate species is likely to vary due to species-specific fruit use, even within the same habitat and timeframe. Pitheciines, primates of the subfamily Pitheciinae, particularly favor the seeds of unripe fruits. Researchers consider this dietary characteristic an adaptation to increase access to fruit resources. However, the relative advantages of pitheciines over sympatric non-pitheciine non-seed-eating primates regarding species-specific fruit availability is not well studied. In a 26-ha forest within the city of Manaus, Amazonian Brazil, we assessed the wild-food feeding behavior of free-ranging groups of golden-faced sakis (Pithecia chrysocephala) and sympatric common squirrel monkeys (Saimiri sciureus). We hypothesized that sakis would have greater and more consistent access to wild fruit due to (1) a wider variety of fruit species in their diet, and (2) longer consumption periods per fruit species. We recorded the plant species, part (pulp or seed), and developmental stage (ripe or unripe) of wild fruit consumed by both species. We also conducted monthly fruit censuses of 1000 trees and vines to estimate overall wild fruit abundance. As an indicator of fruit availability, we calculated the proportion of available fruiting trees and vines for each primate species separately based on their observed diet. Throughout the year, the proportion of available trees and vines was significantly higher and more temporally stable for sakis than for squirrel monkeys. This was because sakis used shared fruit species longer than squirrel monkeys by consuming both ripe and unripe fruit. Although sakis had a broader fruit repertoire than squirrel monkeys, it did not contribute to the higher fruit availability. Thus, the fruit feeding system of sakis identifies aspects of a niche that is less restricted in the timing of fruit consumption, which led to a relative advantage in fruit availability.

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Regenerated forests now compose over half of the world's tropical forest cover and are increasingly important as providers of ecosystem services, freshwater, and biodiversity conservation. Much of the value and functionality of regenerating forests depends on the plant diversity they contain. Tropical forest diversity is strongly shaped by mutualistic interactions between plants and fruit-eating animals (frugivores) that disperse seeds. Here we show how seed dispersal by birds can influence the speed and diversity of early successional forests in Puerto Rico. For two years, we monitored the monthly fruit production of bird-dispersed plants on a fragmented landscape, and measured seed dispersal activity of birds and plant establishment in experimental plots located in deforested areas. Two predominantly omnivorous bird species, the Northern Mockingbird (Mimus polyglottos) and the Gray Kingbird (Tyrannus dominicensis), proved critical for speeding up the establishment of woody plants and increasing the species richness and diversity of the seed rain in deforested areas. Seed dispersal by these generalists increased the odds for rare plant species to disperse and establish in experimental forest-regeneration plots. Results indicate that birds that mix fruit and insects in their diets and actively forage across open and forested habitats can play keystone roles in the regeneration of mutualistic plant-animal communities. Furthermore, our analyses reveal that rare-biased (antiapostatic) frugivory and seed dispersal is the mechanism responsible for increasing plant diversity in the early-regenerating community.

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RESUMO

Frugivorous animals may use morphological traits of food items such as size, hardness, shape, color and smell as cues that allow them to assess cost-benefit relationship of foraging activity. Fruit size is an important trait that influences feeding behavior of most frugivores, since there is a functional correlation between fruit size and frugivores' body size. Therefore, size-based preference is fundamental to understand plant-frugivore interactions and seed dispersal. In this sense, we tested the hypothesis of preferential consumption of larger fruits of Piper arboreum by the short-tailed fruit bat Carollia perspicillata in the Brazilian tropical dry forest. Results showed considerable variation in fruit size among and within plants. There was also significant difference in fruit ripening time among plants, which was not related to fruit size. Average size of remaining fruits reduced as they were removed from plants by the bats, which indicates preferential consumption of larger fruits. On the other hand, plant phenology constrained consumption of bigger fruits. Only a small fraction of plant crop was available for consumption each night, regardless of fruit size, which probably coerced bats to feed on smaller fruits as the availability of larger ones decreased. Results suggest that bat preference on fruit size is mediated by plant phenological strategies.

Os frugívoros utilizam as características morfológicas dos frutos tais como tamanho, dureza, forma, cor e cheiro, como pistas para avaliar o custo-benefício da atividade de forrageio. O tamanho dos frutos é uma característica importante que influencia o comportamento alimentar dos frugívoros, já que existe uma correlação funcional entre tamanho do fruto e o do tamanho do frugívoro. Por isso, a seleção do fruto a partir do seu tamanho é um elemento fundamental para a compreensão das interações frugívoro-planta e da dispersão de sementes. Neste sentido, nós testamos a hipótese de consumo preferencial de frutos maiores de Piper arboreum pelo morcego Carollia perspicillata em uma floresta tropical brasileira. Os resultados mostraram ampla variação no tamanho do fruto entre e dentro das plantas parentais. Também houve diferença significativa no tempo de maturação dos frutos entre as plantas, o qual não esteve relacionado com o tamanho do fruto. O tamanho médio dos frutos restantes na planta após a remoção pelos morcegos decresceu, o que indicou o consumo preferencial dos frutos maiores. Por outro lado, a fenologia da planta restringiu o consumo destes frutos. Um número pequeno de frutos maduros esteve disponível para o consumo por noite, independentemente de seu tamanho, o que provavelmente limitou a escolha dos morcegos, obrigando-os a se alimentarem dos frutos menores conforme a disponibilidade dos maiores reduziu-se. Os resultados sugerem que a preferência dos morcegos pelo tamanho dos frutos é mediada pelas estratégias fenológicas das plantas.

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The crab-eating fox (Cerdocyon thous) exhibits a very generalist habit and fruits compose a large proportion of its diet. However, few studies evaluated the importance of this animal as seed disperser. In the Restinga forest, in the Atlantic forest of Brazil, C. thous consumes fruits of Eugenia umbelliflora, a Myrtaceae species, which is dispersed chiefly by birds. This study evaluated the effects of gut transit on seed germination, and size selection of E. umbelliflora fruits by the crab-eating fox. We did not find differences on germination rates between seeds dispersed by foxes and control ones, but seeds dispersed by foxes germinated faster, which may be important for plant recruitment. Seeds consumed by C. thous were smaller than those available on the ground, indicating selection for small fruits. Regardless of the selection of small fruits, C. thous appears to be an important secondary disperser of E. umbelliflora, distributing large quantities of viable seeds of this Myrtaceae in the Restinga forest.

O cachorro do mato (Cerdocyon thous) tem um hábito bastante generalista e frutos compõem uma grande proporção de sua dieta. No entanto, poucos estudos avaliaram a importância deste animal como dispersor de sementes. Na floresta de restinga da Mata Atlântica brasileira C. thous consome frutos de Eugenia umbelliflora, uma espécie de Myrtaceae, que é dispersa principalmente por aves. Este estudo avaliou o efeito da passagem das sementes pelo tubo digestivo na germinação das sementes e a seleção de tamanho de frutos de E. umbelliflora pelo cachorro do mato. Não houve diferença nas taxas de germinação entre as sementes dispersas pelo cachorro do mato e as sementes controle, mas as sementes dispersas pelo cachorro germinaram mais rápido, o que pode ser importante para o recrutamento das plantas. As sementes consumidas pelo cachorro do mato foram menores do que as sementes disponíveis no solo, indicando seleção por frutos menores. Apesar de selecionarem frutos menores, o cachorro do mato parece ser um importante dispersor secundário de E. umbelliflora, distribuindo grandes quantidades de sementes viáveis desta espécie de Myrtaceae na restinga.

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