Species-specific outcomes of avian gut passage on germination of Melastomataceae seeds

Background and aims - Frugivory and seed dispersal are of major importance for plant recruitment and distribution. However, few studies have addressed the effects of gut passage on seed germination in complex fruit-frugivore systems involving multiple species. Here, we examined whether gut passage by seven bird species affects seed germination of eight Melastomataceae species from the Brazilian Cerrado, a Neotropical savanna. Methods - We take advantage of the generalist dispersal system of melastomes in order to compare the dispersal quality among bird species by contrasting seed germination of hand-cleaned, gut-passed seeds and seeds within intact fruits. We studied gut passage effects on seed germination percentage and mean germination time (MGT) of Clidemia urceolata and seven Miconia species. Key results - Less than 4% germinability was observed for seeds within intact fruits across all plant species, indicating that seed cleaning is required prior to germination. The action of guts on the seeds had non-significant or minor additive effects on germinability compared to hand-cleaned seeds depending on the plant species. Gut treatment had no effect on MGT of two species and minor effects on other three species. However, mechanical/chemical effect significantly decreased MGT of C. urceolata and M albicans while it increased MGT of M ibaguensis. There were significant species-dependent effects depending on both bird and plant species, suggesting that species-specific outcomes arise from Neotropical fruit-frugivore interactions in plants with generalist dispersal systems. Conclusions - Germination enhancement deriving from gut scarification was not observed for all species, but seed cleaning seems to be an important benefit provided by frugivores to Cerrado melastomes. The variable outcomes resulting from complex fruit-frugivore interactions potentially affect the recruitment of Cerrado melastomes.