Does seed coat structure modulate gut-passage effects on seed germination? Examples from Miconieae DC. (Melastomataceae)

Abstract

Fruits of Melastomataceae constitute a key resource for Neotropical frugivores. However, the mechanisms determining gut-passage effects on seed germination are poorly known. Here, we determine how bird gut-passage affects seed germination in three species of Miconieae by running germination experiments, examining changes in seed coat structure and determining germination inhibition by fruit extracts. Mature fruits of Clidemia urceolata, Leandra aurea and Miconia rubiginosa were sampled in south-eastern Brazil and seeds were submitted to treatments evaluating gut-passage effects and different concentrations of fruit extracts. Light and scanning electron microscopy were used to compare seed coat structure and thickness of control and gut-passed seeds. We found minor effects of gut passage on seed germination. However, changes in seed coat structure of gut-passed seeds of L. aurea may have been related to a decrease in germination. Our data also support the idea that germination inhibitors in fruit pulp may contribute to the inhibition effect. Our study corroborates the idea that changes in the seed coat following gut passage modulate the complex fruit–frugivore interactions, especially between plants and generalist dispersers, and that seed cleaning is a key factor determining seedling establishment in Neotropical Melastomataceae.

Escarificación de endocarpos del jobo (Spondias mombin, Anacardiaceae) debido al paso por el tracto digestivo de monos aulladores de manto (Alouatta palliata mexicana): un vistazo microscópico

“…), was thinner in relation to intact seeds; finding, in addition, differences among animal groups. On the contrary, Ribeiro et al (2016) did not observe differences in seed coat thickness of Clidemia urceolata DC., Miconia rubiginosa (Bonpl.) DC.…”

The effect of gut passage by waterbirds on the seed coat and pericarp of diaspores lacking “external flesh”: Evidence for widespread adaptation to endozoochory in angiosperms

“…The thickness of the “seed coat”, understood in a broad sense to also include the pericarp or other embryo covering structures, was deemed important for the survival of various ingested diaspores by different frugivorous vertebrates [38], and research on granivorous waterbirds also suggests that seed coat thickness is important [39]. However, the defense role played by specific tissues within the seed coat or the pericarp during gut passage has received little attention [40–41]. Nevertheless, given the considerable evidence to suggest that endozoochory is a major dispersal mechanism for many plants not assigned to an "endozoochory syndrome" (including those considered to have “unspecialized” diaspores), the significance of diaspore protective layers for these plants needs to be investigated in more detail.…”

Contrasting patterns of taxonomic, phylogenetic and functional variation along a Costa Rican altitudinal gradient in the plant family Melastomataceae

“…Indeed, wind-dispersed melastome species are restricted to lower altitudes (Renner 1986), whereas melastomes with endozoochoric seeds may have short dispersal distances due to the low gut retention time (~20 min) of their passeriform dispersers (Ribeiro et al . 2016). Alternatively, the integrative functional traits that we measured may obscure some key physiological differences between species that are the targets of abiotic filtering.…”