Keyword: seed predation

The agouti Dasyprocta leporina (Rodentia: Dasyproctidae) as seed disperser of the palm Astrocaryum aculeatissimum

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Some large-seeded plants depend heavily on agoutis for seedling recruitment. The importance of Dasyprocta leporina as seed disperser of the Atlantic Forest palm Astrocaryum aculeatissimum was evaluated using camera-traps and seed removal experiments. Agoutis were registered at 67% of the records obtained through the monitoring of mature fruits; palms were visited from 07:00 to 18:45 h. Dispersal distances ranged from 0.5 to 48.7 m (mean ± sd = 6.8 ± 9.1 m) and most of the removed seeds were buried (57.8%). These results corroborate the importance of agoutis for the seed dispersal of Astrocaryum palms.

A cutia Dasyprocta leporina (Rodentia: Dasyproctidae) como dispersor de sementes da palmeira Astrocaryum aculeatissimum. Algumas plantas de sementes grandes são fortemente dependentes de cutias para o recrutamento de suas plântulas. A importância de Dasyprocta leporina como dispersora de sementes da palmeira da Mata Atlântica Astrocaryum aculeatissimum foi avaliado com o uso de armadilhas fotográficas e experimentos de remoção de sementes. Cutias foram observadas em 67% dos registros obtidos durante o monitoramento de frutos maduros; as palmeiras foram visitadas entre 07:00 e 18:45 h. As distâncias de dispersão variaram de 0.5 a 48.7 m (media ± dp = 6.8 ± 9.1 m) e a maioria das sementes removidas foram enterradas (57.8%). Estes resultados confirmam a importância de cutias para a dispersão de sementes de palmeiras do gênero Astrocaryum.

The role of Cerradomys subflavus (Rodentia, Cricetidae) as seed predator and disperser of the palm Allagoptera arenaria

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Small rodents are among the most abundant vertebrate seed predators in the tropics and palm fruits are a rich source of energy for them. Allagoptera arenaria is a nurse plant species at restinga vegetation in southeastern Brazil. Forty-five adult A. arenaria were marked to estimate fruit crop size and seed predation by rodents. Two trapping sessions were carried out to identify the rodent seed predators. In addition, a fruit removal experiment was conducted to investigate the role of rodents as seed dispersers. Of the 7409 seeds collected, 24% were damaged by rodents. Predation rates ranged from 0 to 64% per plant and the number and the proportion of damaged seeds increased significantly with crop size. In the removal experiments, 64% of the fruits were manipulated by rodents either in situ or away from palms: 16% were preyed in the same place, 29% were preyed following removal, 2% were dispersed and 12% were buried. Seed fate could not be identified for 5% of the seeds. Cerradomys subflavus was the only species caught and this fact together with its abundance in the study area and tooth marks left in the endocarps indicates that this rodent is the main seed predator of this palm. Considering this, C. subflavus should play a key role in A. arenaria population dynamics through the reduction of the total number of seeds that may be recruited. However, seed burial in sites favorable for germination suggests that this rodent can act also as seed disperser of this palm.

El papel de Cerradomys subflavus (Rodentia, Cricetidae) como depredador y dispersor de semillas de la palma Allagoptera arenaria. Algunos pequeños roedores están entre los vertebrados depredadores de semillas más abundantes en los trópicos y las semillas de palmas son una rica fuente de energía para ellos. Allagoptera arenaria es una planta facilitadora de la vegetación en restingas en el sudeste de Brasil. Cuarenta y cinco palmas adultas de A. arenaria fueron marcadas para estimar la producción de frutos y la depredación de semillas por roedores. Dos sesiones de trampeo fueron conducidas para identificar los roedores depredadores de semillas. Adicionalmente, un experimento de remoción de frutos fue conducido para investigar el papel de los roedores como dispersores de semillas. De las 7409 semillas colectadas el 24% fue dañada por roedores. Las tasas de depredación variaron de 0 a 64% por planta y el número y proporción de semillas dañadas aumentó significativamente con la producción de frutos. En los experimentos de remoción, 64% de los frutos fueron manipulados por roedores in situ o distantes de las plantas madres: 16% fueron depredadas in situ, 29% fueron depredadas después de removidas, 2% fueron dispersadas y 12% fueron enterradas. El destino de las semillas no pudo ser identificado para 5% de las semillas. Cerradomys subflavus fue la única especie capturada y este hecho, junto con su abundancia en la área de estudio y las marcas de alimentación dejadas en los endocarpios, indican que sería el principal depredador de semillas en esta palma. C. subflavus puede estar desempeñando un papel clave en la dinámica poblacional de A. arenaria por la reducción del total de semillas que pueden ser reclutadas. Además, el enterramiento de las mismas en situaciones favorables para germinación indica que este roedor puede también actuar como dispersor.

Human use and small mammal communities of Araucaria forests in Neuquén, Argentina

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Small mammals were sampled in five closed, humid, Araucaria araucana forests that differed in the degree of anthropogenic disturbance in southwestern Neuquén Province. Nine species were captured in 3416 trap nights. Abrothrix longipilis and Oligoryzomys longicaudatus made up 88% of all captures. Small mammal relative abundance was 52 times higher where grazing was absent compared to a site with intense grazing pressure. Seed predation, primarily by livestock and feral exotic mammals, varied from 59.7% to 15.1% of marked seeds per day. Small mammal community productivity and composition were correlated with understory structure (Mantel test, r = 0.529, p = 0.04), and with rates of seed predation (r = -0.91, n = 4, p = 0.08). Forests with less complex understories had fewer captures and lower mammal diversity. Exotic large mammals appear to affect native small mammals by simplifying the structure of the forest understory and by competing for seeds. Four native species (Abrothrix longipilis, Oligoryzomys longicaudatus, Chelemys macronyx, and Irenomys tarsalis) ate Araucaria piñones. Anthropogenic changes in small mammal communities indicate that management of feral and domestic mammals needs to be a prominent part of the conservation of these majestic forests.