Resumo A dispersão de sementes é um processo fundamental à manutenção de ecossistemas florestais, favorecendo o sucesso germinativo de plantas em locais adequados ao seu crescimento, minimizando a competição, a ação de patógenos e a predação por herbívoros. Variações intra-específicas e sazonais no consumo de frutos por Didelphis albiventris, bem como sua contribuição à dispersão e germinação de sementes endozoocóricas foram avaliados em Floresta Estacional Semidecidual. O estudo foi realizado no Morro do Coco, localizado no município de Viamão, RS às margens do Lago Guaíba (30º16’15”S, 51º02’54”W), entre junho de 2013 a maio de 2014, resultando em um esforço amostral de 2992 armadilhas-noite. Foram capturados 18 indivíduos e coletadas 24 amostras fecais. Frutos estiveram presentes em 96% das amostras e corresponderam a 18 espécies vegetais, pertencentes a 10 famílias. As espécies mais frequentes foram Ficus cestrifolia e Syagrus romanzoffiana, que ocorreram em 66% das amostras, seguidas de Banara parviflora e Cecropia pachystachya, ambas com 25% de ocorrência. Machos e fêmeas não diferiram quanto à riqueza de frutos consumidos (t = 0.083; DF = 32; p = 0.934), o que também não variou sazonalmente (H = 3.165; p = 0.367). A maior amplitude de nicho trófico ocorreu no verão, registrando-se duas vezes mais frutos na dieta do que no outono, estação com a menor amplitude. Tanto a porcentagem quanto a velocidade de germinação das sementes de Ficus cestrifolia e Psidium sp. aumentaram após a passagem pelo trato digestório do animal (a porcentagem de germinação aumentou mais de 40% e a velocidade foi até 7 vezes maior). Didelphis albiventris pode ser considerada uma espécie frugívora-onívora, uma vez que frutos representam um item importante na dieta, e contribui para a dispersão de grande quantidade de sementes endozoocóricas pequenas, aumentando tanto o percentual quanto a velocidade de germinação de algumas espécies.

Abstract Seed dispersal is a process that is fundamental to maintenance of forest ecosystems, enabling plants to successfully germinate in sites that are favorable to their growth, minimizing risks of competition, the action of pathogens and predation by herbivores. Intraspecific and seasonal variations in fruit consumption by Didelphis albiventris, and its contribution to dispersal and germination of endozoochorous seeds were analyzed in a Semideciduous seasonal forest. The study was conducted at Morro do Coco, which is a hilly area in the municipal district of Viamão, RS, Brazil, bordering the shore of Guaíba lake (30º16’15”S, 51º02’54”W), between June 2013 and May 2014, with a total sampling effort of 2992 trap-nights. A total of 18 individuals were captured and 24 fecal samples were collected. Fruits were identified in 96% of the samples, corresponding to 18 plant species, belonging to 10 families. The most common species were Ficus cestrifolia and Syagrus romanzoffiana, which occurred in 66% of the samples, followed by Banara parviflora and Cecropia pachystachya, both with a 25% rate of occurrence. There were no differences between the richness of fruit consumed by males and females (t = 0.083; DF = 32; p = 0.934) and there were no seasonal variations (H = 3.165; p = 0.367). The greatest breadth of dietary niche occurred during the summer, when twice as many fruit species were recorded in the diet than during the autumn, which was the season with the smallest breadth. Both germination percentage and germination velocity of Ficus cestrifolia and Psidium sp. seeds increased after passage through the animals’ digestive tracts (percentage germination increased more than 40% and velocity was up to 7 times highest). Didelphis albiventris can be considered a frugivorous-omnivorous species, since fruit are an important item of its diet, and it contributes to dispersal of a large quantity of small endozoochorous seeds, increasing both germination percentage and germination velocity of some species.

In the state of Rio Grande do Sul, Brazil, yerba mate (Ilex paraguariensis A. St.-Hil.) is an economically and culturally important species. Because of the difficulty in obtaining plantlets from seeds, micropropagation has emerged as an alternative that could increase production. This work aimed to evaluate the effect that treatment with 6-benzyladenine (BA), at concentrations of 2.2, 8.9, and 20 µM and associated with naphthaleneacetic acid (NAA, 0.5 µM), has on the in vitro growth and leaf emission of I. paraguariensis nodal segments cultivated in 0.5 X Murashige and Skoog (MS) medium or 0.5 X Woody Plant Medium (WPM). The most efficient treatment was MS medium with 8.9 µM BA+NAA, in which I. paraguariensis presented greater shoot elongation and higher leaf counts than in the other treatments. Therefore, use of the MS medium with 8.9 µM BA+NAA is recommended in order to increase efficiency in the initial development of I. paraguariensis explants.