Potential seed dispersal by Didelphis albiventris (Marsupialia, Didelphidae) in highly disturbed environment

Abstract

Potential seed dispersal by Didelphis albiventris (Marsupialia, Didelphidae) in highly disturbed environment. Biota Neotrop. 10(2): http://www.biotaneotropica. org.br/v10n2/en/abstract?article+bn00610022010.Abstract: Urban forests are usually isolated and highly disturbed, however they are important shelters for tolerant animal species. Their food habits expose the different ecological roles these animals perform in the habitat. We analyzed the contribution of Didelphis albiventris Lund (1840), as a seed disperser, to the vegetation renewal of an urban forest fragment, describing its frugivorous diet and testing the viability of ingested seeds. Both male and female of white-eared opossum included a vast variety of items in their diet, mainly invertebrates and fruits. Fruits were consumed during all year round and seasonality was not observed. The majority of consumed fruits was from pioneer plant species, which is common in disturbed areas, in accordance to the opossum's opportunistic habits. The viability of ingested seeds, evaluated by linear logistic regression models applied to data from germination tests, was different of the seeds collected directly from ripe fruits; it varied among species, maybe due to the intrinsic characteristics of plant species. As a highly generalist species, D. albiventris can inhabit disturbed environments and then disperse seeds from pioneer plants, where the vegetation must be restored. It is crucial that this process does not depend only on the specialist frugivores, which are frequently absent in urban forest fragments. Therefore, the presence of generalist species of secondary environments has its importance emphasized. Resumo: Florestas urbanas são geralmente isoladas e altamente degradadas; contudo são importantes abrigos para espécies de animais tolerantes. Os hábitos alimentares destes animais explicitam os diferentes papéis ecológicos que eles desempenham no hábitat. Nós analisamos a contribuição de Didelphis albiventris Lund (1840) como dispersor de sementes para a regeneração da vegetação de um fragmento florestal urbano. Para isso, descrevemos sua dieta frugívora e testamos a viabilidade das sementes por ele ingeridas. Tanto machos quanto fêmeas de gambá-de-orelha-branca incluiram uma grande variedade de itens alimentares na dieta, principalmente invertebrados e frutos. Frutos foram consumidos durante todo o ano e a sazonalidade não foi observada. A maioria das sementes defecadas era proveniente de plantas pioneiras, comuns em ambientes perturbados, o que concorda com seu hábito oportunista. A viabilidade das sementes ingeridas, verificada mediante modelos de regressão logística linear aplicada a dados de testes de germinação, foi diferente das sementes obtidas de frutos maduros e variou entre espécies, talvez devido a características intrínsecas da planta. Enquanto uma espécie generalista, D. albiventris é capaz de habitar ambientes perturbados, e dispersar as sementes de plantas de estágio inicial de sucessão, onde a vegetação necessita ser restaurada. É essencial q...

Effects of gut passage on the germination of seeds ingested by didelphid marsupials in a neotropical savanna

“…However, despite the fact that changes in the probabilities of seed germination after gut passage comprise an important component of seed dispersal and effectiveness (Traveset & Verdu 2002;Silveira et al 2012b), increased germination is not a general rule for seeds consumed by didelphid dispersers (Cáceres & Lessa 2012, present study). Recent studies indicate that the passage of seeds through the digestive tract of D. albiventris and G. agilis does not always improve seed germinability (see Cantor et al 2010;Camargo et al 2011, respectively). Our germination experiments revealed that, although the CG -control group.…”

“…When didelphids accelerate seed germination (as in the case of C. urceolata), ingested seeds germinate in higher proportions than do non-ingested seeds, probably as a result of seed coat scarification (Robertson et al 2006;Lessa & Cáceres 2012). Many factors related both to the intrinsic plant and disperser traits may influence the outcomes of seed passage through the digestive tract of potential vertebrate dispersers (Traveset & Verdú 2002;Rodrigues-Peréz et al 2005), such as seed size, fruit color, experimental conditions, disperser taxon, habitat structure and vegetation composition, or a combination of such factors (Traveset & Verdu 2002;Cantor et al 2010;Cáceres & Lessa 2012). All these factors, together or alone, can explain the differences observed between the germination of seeds found in the samples and the control group.…”

“…A longer seed retention period reduces germinability (Murray 1994) or germination time, which may explain differences in germinability and germination time of very small seeds, such as C. urceolata (~ 1.0 mm) and P. crassifolium (~ 0.6 mm) eaten by larger species, such as D. albiventris. Therefore, the simple passage through the digestive tract of the disperser is not a prerequisite for increasing the germination of gut-passed seeds (Cantor et al 2010). Finally, it is also important to consider the group of dispersers involved, because small gut-passed seeds are more likely to be eaten and dispersed by a wide range of vertebrates (Fleming & Sosa 1994).…”

“…One of the apparent advantages of seed dispersal is the increase in the rate of germination of the seeds ingested by vertebrate dispersers (Traveset & Verdú 2002). However, recent studies have shown that this increase is not universal and that a myriad of factors intrinsic to the plant or the type of seed disperser may influence the outcome after seed passage through the digestive tract of the disperser (Traveset & Verdú 2002;Cantor et al 2010).…”

“…In the neotropics, the role of didelphids as potential seed dispersers is usually related to the consumption of a wide variety of fruits and the presence of intact seeds in their feces with generally increased germinability (Cáceres & Monteiro-Filho 2007;Raíces & Bergallo 2008;Lessa & Costa 2010;Cáceres & Lessa 2012). However, the process of gut scarification of the seed coat by passage through the digestive tract of didelphid dispersers does not always have positive effects on the germinability and germination time of the ingested seeds (see Cantor et al 2010;Camargo et al 2011;Cáceres & Lessa 2012).…”