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The generalist diet of most frugivores opens a window of opportunity to the invasion of alien plants whit fleshy-fruits. The outcome of the new relationships between alien plants and native frugivores depends both on traits of the invaders and of the mutualist partners in the recipient community. Two contrasting hypotheses attempt to explain the integration of alien species in native communities. "Darwin's naturalization hypothesis" proposes that alien species more different from native species are more likely to integrate in the community. The "similarity hypothesis" proposes the opposite, that alien species more similar to native species are more likely to integrate the native community. By comparing chemical and morphological traits of 12 alien and 48 native fleshy-fruited species, we tested both hypothesis as assembly rules of alien species in subtropical Andean forests. We did not find differences in most chemical or morphological traits between alien and native fruit species. The multidimensional variation of alien fruit traits was nested within that of native species. However, alien fruits tended to score high in the range of variation of native chemical traits. Accordingly, we propose the "fraction similarity hypothesis" as a main force that drive the assembly of alien species in mutualistic networks, i.e. alien species benefit from existing mutualistic interactions that involve fruit species with traits selected by the frugivores to invade native communities. The striking similarity in fruit traits between alien and native species highlights the potential role of seed dispersers as ecological filters to the invasion of alien plants. In turn, this similarity suggests that alien fruits can be functionally equivalent to native ones in terms of their interaction with fruit-eating birds. [ABSTRACT FROM AUTHOR]

In visually driven seed dispersal mutualisms, natural selection should promote plant strategies that maximize fruit visibility to dispersers. Plants might increase seed dispersal profitability by increasing conspicuousness of fruit display, understood as a plant strategy to maximize fruit detectability by seed dispersers., The role of different plant traits in fruit choice and consumption by seed dispersers has been broadly studied. However, there is no clear evidence about the importance of the traits that increase conspicuousness of fruit display. Because strategies to maximize conspicuousness of fruit display are diverse, and usually are expected to be costly, we would expect that individual plant species will produce an efficient combination of traits., We explored this prediction with 62 fleshy fruited plant species of a subtropical Andean forest (Southern Yungas), and using a large dataset of fruit consumption by birds (4476 records). Conspicuousness of fruit display was characterized by both fruit and plant traits including chromatic contrast, size, exposure, aggregation and crop size of fruits. We also considered phylogenetic effects on phenotypic variation., Fruit consumption was explained by fruit chromatic contrast depending on fruit crop size. These traits revealed low phylogenetic effects, with the exception of four plant clades at different levels in the phylogenetic tree. Negative correlations between pairs of traits support our assumption that fruit display traits are costly, suggesting natural selection favours parsimonious evolutionary pathways., Plant species seem to rely on conspicuousness of fruit display by a combination of traits that might minimize costs of fruit display. This appears adaptively relevant to improve communication with mutualistic animals, to increase fruit consumption in a community context and, ultimately, to enhance the profitability of seed dispersal., A is available for this article. [ABSTRACT FROM AUTHOR]

The stability and dynamics of multispecies interactions often rely on a small core of species. We examine whether the Yellow-striped Brush-Finch (Atlapetes citrinellus), the only species of bird endemic to the Argentinean Yungas, is a core species for seed dispersal. Of 30 species of fleshy fruit consumed, 16 were dispersed through endozoochory. The Yellow-striped Brush-Finch mostly used the 'cut or mash' method of handling fruit, in which reasonably large seeds (>0.04 g) were discarded or swallowed equally. Medium-sized and small seeds were more often swallowed than discarded. Although the fruits consumed were mostly understorey species, there was no difference in the consumption of fruit from forest understorey or canopy when total fruit abundance in vertical strata was considered. By using interaction network metrics, we determined that the role of Yellow-striped Brush-Finches in seed dispersal during the rainy season was more important at higher altitudes and in the southern sector of its distribution. Our findings support the idea that the Yellow-striped Brush-Finch must be considered a core seed-disperser of understorey and canopy fruits. Use of network metrics is an effective way to assess the importance of individual species in a network, allowing restoration and conservation efforts to be focussed on environments in which these species occur. [ABSTRACT FROM AUTHOR]

The effect of fruit removal and passage through the digestive tract of frugivorous birds on seed germination has been mostly studied in species that swallow the whole fruit without mandibulating ("gulpers"), and defecate or regurgitate seeds without pulp away from the maternal plant. Functional groups with other fruit-handling methods, while often quantitatively important in removing fruits, are presumed to provide lower quality seed dispersal due to their tendency to damage seeds with the beak or discard seeds with pulp still attached under the maternal plant. We conducted a series of experiments with five bird species that mandibulate fruits with the beak before swallowing ("mashers"). They were fed with fruits of one to five plant species to test the effect of handling on their germination. We compared germination probabilities and times of seeds defecated or dropped from the bill with seeds with pulp removed by hand. Overall, bird processed seeds germinated in equal proportions than manually extracted seeds (69.9 vs 70.2%, respectively). However, depending on the bird-fruit species pair considered, the proportion and germination time of seeds processed by masher birds were equal to or less than those of manually extracted seeds. Most of the retrieved seeds processed by these birds were defecated (94%), and a large percentage of them germinated (70.3%), which confirms that they are important for the seed dispersal process. Our results provide new insights on aspects of the qualitative component of seed dispersal by masher birds. We discuss the possible implications of these findings on seed dispersal in the rest of the Neotropical region. • "Mashers" mandibulate fruits with the bill, and may leave damaged or pulp-surrounded seeds • This decreases the likelihood of seeds germinating, although this has rarely been empirically tested. • Seeds of 5 plant species defecated or dropped by 5 species of masher birds were germinated. • Retrieved seeds were generally defecated, and a large percentage germinated (70.3%) • Mashers can be qualitatively important for the seed dispersal process. [ABSTRACT FROM AUTHOR]